Managing storage of sensing information

Abstract

The present disclosure relates to devices, systems, and techniques for managing storage of sensing information. In some examples, a system includes a memory and a processing circuit. The processing circuit can be configured to: receive evoked compound action potential (ECAP) information, wherein the ECAP information includes information from a plurality of evoked compound action potential (ECAP) signals; receive a trigger signal requesting long-term storage of at least a portion of the ECAP information in the memory; and in response to receiving the trigger signal, store at least a portion of the ECAP information in the memory.

Description

[0001] This application claims priority to U.S. Application No. 17 / 343,201, filed June 9, 2021, which claims the benefit of U.S. Provisional Patent Application No. 63 / 037,406, filed June 10, 2020, the entire contents of each of which are incorporated herein by reference. Technical Field

[0002] This disclosure relates generally to medical devices, and more specifically to information collected by medical devices. Background Technology

[0003] Medical devices can be external or implanted and can be used to deliver electrical stimulation therapy to patients via various tissue sites to treat a variety of symptoms or conditions, such as chronic pain, tremor, Parkinson's disease, epilepsy, urinary and fecal incontinence, sexual dysfunction, obesity, or gastroparesis. Medical devices can deliver electrical stimulation therapy via one or more leads comprising electrodes positioned near target locations associated with the patient's brain, spinal cord, pelvic nerves, peripheral nerves, or gastrointestinal tract. Stimulation near the spinal cord, sacral nerves, brain, and peripheral nerves is commonly referred to as spinal cord stimulation (SCS), sacral nerve modulation (SNM), deep brain stimulation (DBS), and peripheral nerve stimulation (PNS), respectively.

[0004] Evoked compound action potentials (ECAPs) are synchronous firings of a group of neurons in response to the application of a stimulus (in some cases, including electrical stimulation from a medical device). ECAPs can be detected as separate events from the stimulus itself, and they can reveal the characteristics of the stimulus's effect on nerve fibers. Electrical stimulation can be delivered to the patient by a medical device as a series of electrical pulses, and the parameters of these pulses can include frequency, amplitude, pulse width, and pulse shape. The parameters of the electrical pulses can be altered in response to sensory input, such as ECAPs sensed in response to a series of electrical pulses. Such alterations may affect the patient's perception of the electrical pulses, or render them imperceptible. Summary of the Invention

[0005] In general, this disclosure relates to devices, systems, and techniques for managing the storage of sensed information. Implantable medical devices (IMDs) can sense various patient-related information. For example, an IMD can sense multiple evoked compound action potential (ECAP) signals. These ECAP signals are physiological signals induced in response to the delivery of electrical stimulation (e.g., a stimulation pulse). The IMD can monitor one or more characteristics of the ECAP signals and adjust electrical stimulation based on one or more characteristics. In some examples, more information about the ECAP signals may help in further investigations of patient activity, patient symptoms and / or disease progression, or the efficacy of electrical stimulation therapy.

[0006] An IMD or other device can store ECAP information in memory in response to receiving a trigger signal requesting long-term storage of at least a portion of the ECAP information. The ECAP information can include a plurality of characteristics and / or waveforms representative of a sensed ECAP signal. Additionally or alternatively, the IMD can increase a rate at which the IMD senses the ECAP signal. The IMD can also store a marker indicating a timing of the trigger signal relative to the stored ECAP information. The trigger signal can be a user input indicating a patient event, a characteristic of the ECAP signal exceeding a threshold, a user request for a change to one or more stimulation parameters defining electrical stimulation, or any other type of event.

[0007] In some examples, a system includes a memory and processing circuitry configured to: receive evoked compound action potential (ECAP) information, wherein the ECAP information includes information from a plurality of evoked compound action potential (ECAP) signals; receive a trigger signal requesting long-term storage of at least a portion of the ECAP information in the memory; and store, in response to receiving the trigger signal, at least a portion of the ECAP information in the memory.

[0008] In some examples, a method includes: receiving, by processing circuitry, evoked compound action potential (ECAP) information, wherein the ECAP information includes information from a plurality of evoked compound action potential (ECAP) signals; receiving, by the processing circuitry, a trigger signal requesting long-term storage of at least a portion of the ECAP information in a memory; and storing, by the processing circuitry in response to receiving the trigger signal, at least a portion of the ECAP information in the memory.

[0009] In some examples, a computer-readable medium includes instructions that, when executed by a processor, cause the processor to: receive evoked compound action potential (ECAP) information, wherein the ECAP information includes information from a plurality of evoked compound action potential (ECAP) signals; receive a trigger signal requesting long-term storage of at least a portion of the ECAP information in a memory; and store, in response to receiving the trigger signal, at least a portion of the ECAP information in the memory.

[0010] This summary is intended to provide an overview of the subject matter described in this disclosure. It is not intended to provide an exclusive or exhaustive explanation of the systems, devices, and methods described in detail within the accompanying drawings and description below. Further details of one or more examples are set forth in the accompanying drawings and in the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 is a conceptual diagram illustrating an example system including an implantable medical device (IMD) configured to deliver spinal cord stimulation (SCS) therapy and an external programmer in accordance with one or more techniques of this disclosure.

[0012] Figure 2 is a block diagram illustrating an example configuration of components of an IMD in accordance with one or more techniques of this disclosure.

[0013] Figure 3 is a block diagram illustrating an example configuration of components of an external programmer in accordance with one or more techniques of this disclosure.

[0014] Figure 4 is a graph illustrating an example evoked compound action potential (ECAP) for a respective stimulation pulse sensed in accordance with one or more techniques of this disclosure.

[0015] Figure 5A is a timing diagram illustrating an example of an electrical stimulation pulse, a respective stimulation signal, and a respective sensed ECAP in accordance with one or more techniques of this disclosure.

[0016] Figure 5B is a timing diagram illustrating an example of an electrical stimulation pulse, a respective stimulation signal, and a respective sensed ECAP in accordance with one or more techniques of this disclosure.

[0017] Figure 6A is a timing diagram illustrating an example of an electrical stimulation pulse, a respective stimulation signal, and a respective sensed ECAP in accordance with one or more techniques of this disclosure.

[0018] Figure 6B is a timing diagram illustrating another example of an electrical stimulation pulse, a respective stimulation signal, and a respective sensed ECAP in accordance with one or more techniques of this disclosure.

[0019] Figure 7 is a timing diagram illustrating another example of an electrical stimulation pulse, a respective stimulation signal, and a respective ECAP in accordance with one or more techniques of this disclosure.

[0020] Figure 8 is a timing diagram illustrating another example of an electrical stimulation pulse, a respective stimulation signal, and a respective ECAP in accordance with one or more techniques of this disclosure.

[0021] Figure 9 is a flow diagram illustrating an example operation of controlling stimulation based on one or more sensed ECAPs in accordance with one or more techniques of this disclosure.

[0022] Figure 10Voltage / current / time graphs are exhibited in accordance with one or more techniques of the disclosure that plot control pulse current amplitude, notification pulse current amplitude, ECAP voltage amplitude, and second ECAP voltage amplitude as a function of time.

[0023] Figure 11 is a flowchart that exhibits example operations for controlling storage of ECAP information.

[0024] Figure 12 is a flowchart that exhibits example operations for sensing an ECAP signal and storing ECAP information.

[0025] Figure 13 is a flowchart that exhibits example operations for adjusting a rate at which an ECAP signal is sensed.

[0026] The same reference numbers in different drawings represent the same element. DETAILED DESCRIPTION

[0027] The present disclosure describes examples of medical devices, systems, and techniques for managing storage of sensed information, such as ECAP information. Electrical stimulation therapy is typically delivered to target tissue (e.g., one or more nerves or muscles) of a patient via two or more electrodes. Parameters defining the electrical stimulation therapy (e.g., electrode combination, voltage or current amplitude, pulse width, pulse frequency, duty cycle, etc.) are selected by a clinician and / or patient to alleviate various symptoms, such as pain, muscle disorders, etc.

[0028] However, as the patient moves, the distance between the electrodes and the target tissue changes. Changes in posture or patient activity can cause the electrodes to move closer or further from the target nerve. Migration of the lead over time can also change the distance between the electrodes and the target tissue. In some examples, patient events can include transient patient conditions such as coughing, sneezing, laughing, valsalva maneuver, leg lifting, neck movement, or deep breathing, which can temporarily cause the stimulation electrodes of the medical device to move closer to the target tissue of the patient. When the electrodes move closer to the nerve, the patient’s perception of the electrical stimulation therapy can change.

[0029] Because neural recruitment is a function of stimulation intensity and distance between the target tissue and the electrodes, movement of the electrodes closer to the target tissue can result in increased perception by the patient (e.g., possible uncomfortable, undesirable, or painful sensations) and movement of the electrodes away from the target tissue can result in decreased therapeutic efficacy to the patient. For example, if stimulation is consistent and the stimulation electrodes are moved closer to the target tissue, the patient can perceive the stimulation as more intense, uncomfortable, or even painful. Conversely, when the electrodes are moved away from the target tissue, consistent stimulation can result in the patient perceiving less intense stimulation, which can decrease the therapeutic effect on the patient. Discomfort or pain caused by patient events including transient patient conditions can be referred to herein as “transient overstimulation.” Accordingly, in some examples, it can be beneficial to adjust stimulation parameters in response to patient movement or other conditions that can result in transient overstimulation.

[0030] ECAPs can be evoked by stimulation pulses delivered to a patient’s neural fibers. After being evoked, ECAPs can propagate along the neural fibers away from the initial stimulation. In some cases, the sensing circuitry of a medical device can detect such ECAPs as ECAP signals. Characteristics of the detected ECAP signals can be indicative of changes in distance between the electrodes and the target tissue. For example, a sharp increase in ECAP amplitude over a short period of time (e.g., less than a second) can be indicative of a decrease in distance between the electrodes and the target tissue due to a transient patient action, such as a cough. A gradual increase in ECAP amplitude over a longer period of time (e.g., days, weeks, or months) can be indicative of a decrease in distance between the electrodes and the target tissue due to long-term lead migration after the medical device has been implanted. It can be beneficial to adjust one or more therapy parameter values to prevent the patient from experiencing uncomfortable sensations due to one or both of short-term movement of the electrodes relative to the target tissue and long-term movement of the electrodes relative to the target tissue.

[0031] To facilitate sensing of ECAPs, in some examples, a medical device can deliver pulses that are part of therapy (e.g., notification pulses) and also deliver a plurality of control pulses designed to elicit a detectable ECAP when the notification pulses do not elicit a detectable ECAP. For example, the control pulses can be shorter in duration than the notification pulses to reduce or eliminate signal artifacts caused by the notification pulses that prevent or limit detection of ECAPs received at the sensing electrode(s). In particular embodiments, the control pulses are short enough such that the pulse ends before all or most of the ECAP arrives at the sensing electrode(s). In this way, the medical device can interleave the plurality of control pulses with at least some of the plurality of notification pulses. For example, the medical device can deliver a notification pulse for a period of time, then deliver a control pulse and sense for a corresponding ECAP, if any. The medical device can then resume delivery of notification pulses for another period of time. In some examples, the control pulses have a pulse duration that is less than the pulse duration of the notification pulses, and the pulse duration of the control pulses is short enough such that the medical device can sense a single ECAP within each control pulse. In some examples, the control pulses can provide or contribute to therapy perceived by the patient.

[0032] In some examples, the medical device can use a characteristic value representative of a sensed ECAP signal to adjust one or more parameter values defining the electrical stimulation. The characteristic value can be an amplitude value, a slope of one or more peaks, an area under one or more peak values of the ECAP signal, or any other value that characterizes the amplitude of the sensed ECAP signal. Although the medical device can use the characteristic value of the ECAP signal, the medical device can not store the characteristic of the respective ECAP signal or the ECAP signal itself. Continuous storage of ECAP information can be impractical due to limited data storage capacity within the medical device and / or increased power consumption required to continually process and store ECAP information. Additionally, such a large amount of ECAP information can be too large for a clinician to review for relevant information related to the patient.

[0033] As described herein, devices, systems, and techniques can be configured to manage storage of sensing information. An IMD can monitor one or more characteristics of ECAP signals over time and the IMD can or can not adjust one or more parameters that at least partially define the electrical stimulation. In either case, the IMD can selectively store information representative of the sensed ECAP signals. As some examples, the information can be used to further investigate patient activity, monitor patient symptoms and / or patient disease progression, or determine efficacy of electrical stimulation therapy over time.

[0034] ECAP information representative of the sensed ECAP signals can include one or more different types of information. For example, the ECAP information can include one or more characteristics indicative of an amplitude of the respective ECAP signals. These characteristics can be an amplitude between two peaks in the ECAP signal, an area under one or more peaks of the ECAP signal, a steepness of one or more slopes of the ECAP signal, or other such aspects of the ECAP signal. Additionally or alternatively, the ECAP information can include a waveform representative of the sensed ECAP signals.

[0035] The IMD or another device separate from the IMD can store the ECAP information in memory in response to receiving the trigger signal requesting long-term storage of at least a portion of the ECAP information. This memory can be long-term memory, as opposed to temporary memory that only stores the ECAP information for a short time. For example, the temporary memory can be a first-in-first-out (FIFO) memory or other rolling memory that only stores the ECAP information for a predetermined time period or a predetermined amount of data. Additionally or alternatively, to permanently store the IMD information (e.g., until the ECAP information can be transmitted to another device), the IMD can adjust other ECAP-related collection functions, such as increasing a sampling rate of the ECAP signals and / or increasing a rate at which the IMD senses the ECAP signals.

[0036] In some examples, the IMD can store a marker (e.g., a timestamp) indicative of a timing of the trigger signal relative to the stored ECAP information. In this way, the ECAP information can be analyzed with respect to a timing of an event associated with the trigger signal. The trigger signal can be a user input indicative of a patient event, a characteristic of the ECAP signal exceeding a threshold, a user request for a change to one or more stimulation parameters defining the electrical stimulation, or any other type of event.

[0037] The devices, systems, and techniques described herein can provide one or more advantages. For example, storing ECAP information in response to receiving a trigger signal can store high-fidelity ECAP information that would otherwise not be continuously stored. The marker associated with the trigger signal stored with the ECAP information can also allow the ECAP information to be analyzed with respect to an event that prompted the trigger signal. Additionally, storing and / or capturing higher-fidelity ECAP information (e.g., information from more frequently sensed ECAP signals) in response to a trigger signal can improve the analysis capabilities of the system while conserving battery power when such higher-fidelity ECAP information is not needed for therapy and / or later analysis. In some examples, the system can store such higher-fidelity ECAP information as part of a trial stimulation period in which a clinician and patient can evaluate whether electrical stimulation can provide effective therapy for a patient condition.

[0038] In some examples, the IMD can deliver stimulation including pulses (e.g., control pulses) that contribute to therapy and also elicit detectable ECAP signals. In other examples, the IMD can deliver stimulation pulses to include control pulses and notification pulses. A neural impulse can be detected when an ECAP signal propagates rapidly along a nerve fiber after a delivered stimulation pulse first depolarizes the nerve. Thus, if a stimulation pulse delivered by a first electrode has a pulse width that is too long, a different electrode configured to sense ECAPs will sense the stimulation pulse itself as an artifact that masks a lower amplitude ECAP signal. However, as the potential propagates from the electrical stimulation, the ECAP signal loses fidelity because different nerve fibers propagate the potential at different speeds. Thus, sensing the ECAP at a distance far from the stimulation electrode can avoid artifacts caused by stimulation pulses with long pulse widths, but the ECAP signal can lose the fidelity needed to detect changes in the ECAP signal that occur as the electrode changes distance from the target tissue. In other words, the system can not be able to identify ECAPs from stimulation pulses configured to provide therapy to the patient at any distance from the stimulation electrode. Thus, the IMD can employ control pulses configured to elicit detectable ECAPs and notification pulses that can or can not contribute to the therapeutic effect on the patient, but can not elicit detectable ECAPs.

[0039] In these examples, the IMD is configured to deliver multiple notification pulses configured to provide therapy to the patient and multiple control pulses that can or can not contribute to the therapy. At least some of the control pulses can elicit detectable ECAP signals, but the primary purpose is not to provide therapy to the patient. The control pulses can be interleaved with the delivery of notification pulses. For example, the medical device can alternate delivering notification pulses and control pulses such that a control pulse is delivered and an ECAP signal is sensed between successive notification pulses. In some examples, multiple control pulses are delivered and respective ECAP signals are sensed between the delivery of successive notification pulses. In some examples, multiple notification pulses will be delivered between successive control pulses. In any case, the notification pulses can be delivered according to a selected predetermined pulse frequency such that the notification pulses can produce a therapeutic result for the patient. One or more control pulses are then delivered and respective ECAP signals are sensed within one or more time windows between successive notification pulses delivered according to the predetermined pulse frequency. In this way, the medical device can uninterruptedly deliver notification pulses from the medical device while sensing ECAP signals from control pulses delivered during times when notification pulses are not delivered. In other examples described herein, the medical device senses ECAP signals in response to notification pulses delivered by the medical device, while control pulses are not used to elicit ECAPs.

[0040] Although electrical stimulation is generally described herein in the form of electrical stimulation pulses, electrical stimulation can be delivered in non-pulsatile form in other examples. For example, electrical stimulation can be delivered as a signal having various waveform shapes, frequencies, and amplitudes. Thus, electrical stimulation in non-pulsatile signal form can be a continuous signal, possibly having a sinusoidal waveform or other continuous waveform.

[0041] Figure 1 is a conceptual diagram illustrating an example system 100 in accordance with one or more techniques of the present disclosure, including an implantable medical device (IMD) 110 configured to deliver spinal cord stimulation (SCS) therapy, processing circuitry 140, and an external programmer 150. Although the techniques described in this disclosure are generally applicable to a variety of medical devices including external devices and IMDs, for illustrative purposes, applications of such techniques to IMDs, and more specifically, to implantable electrical stimulators (e.g., neurostimulators) will be described. More specifically, for illustrative purposes, the present disclosure will refer to implantable SCS systems, but is not limited to other types of medical devices or other therapeutic applications of medical devices.

[0042] As shown in Figure 1 System 100 includes IMD 110, leads 130A and 130B, and external programmer 150 shown with patient 105, which is typically a human patient. In Figure 1 example, IMD 110 is an implantable electrical stimulator configured to generate and deliver electrical stimulation therapy to patient 105 via one or more electrodes of leads 130A and / or 130B (collectively, “leads 130”), e.g., for relief of chronic pain or other symptoms. In other examples, IMD 110 can be coupled to a single lead carrying a plurality of electrodes or to more than two leads each carrying a plurality of electrodes. As part of stimulation pulses that deliver electrical stimulation therapy, IMD 110 can be configured to generate and deliver control pulses configured to elicit ECAP signals. In some examples, control pulses can provide therapy. In other examples, IMD 110 can deliver notification pulses that facilitate patient therapy but do not elicit detectable ECAPs. IMD 110 can be a chronic electrical stimulator that remains implanted in patient 105 for weeks, months, or even years. In other examples, IMD 110 can be a temporary or trial stimulator used to screen or evaluate the efficacy of electrical stimulation for chronic therapy. In one example, IMD 110 is implanted in patient 105, while in another example, IMD 110 is an external device coupled to a percutaneously implanted lead. In some examples, IMD 110 uses one or more leads, while in other examples, IMD 110 is leadless.

[0043] IMD 110 can be powered by a power source 120 sufficient to power components of IMD 110 (e.g., processing circuitry 140, telemetry circuitry 160, therapy delivery circuitry 170, and / or other components of IMD 110) for a desired period of time. In some examples, power source 120 is a rechargeable battery. In other examples, power source 120 is a non-rechargeable battery. In some examples, power source 120 is a supercapacitor. In other examples, power source 120 is a combination of a battery and a supercapacitor. In some examples, power source 120 is a combination of a rechargeable battery and a supercapacitor. In other examples, power source 120 is a combination of a non-rechargeable battery and a supercapacitor. In some examples, power source 120 is a combination of a rechargeable battery and a non-rechargeable battery. In other examples, power source 120 is a combination of a supercapacitor and a rechargeable battery. In other examples, power source 120 is a combination of a supercapacitor and a non-rechargeable battery. In some examples, power source 120 is a combination of a supercapacitor and a rechargeable battery and a non-rechargeable battery. In other examples, power source 120 is a combination of a supercapacitor and a rechargeable battery and a non-rechargeable battery. In some examples, power source 120 is a combination of a rechargeable battery, a non-rechargeable battery, and a supercapacitor. In other examples, power source 120 is a combination of a rechargeable battery, a non-rechargeable battery, and a supercapacitor.Figure 2 The components shown are constructed of any polymer, metal, or composite material housed within the body of patient 105. In this example, IMD 110 can be constructed with a biocompatible housing, such as titanium or stainless steel, or a polymeric material, such as silicone, polyurethane, or liquid crystal polymer, and implanted in a patient 105 by surgery at a site near the pelvis, abdomen, or hip of the patient 105. In other examples, IMD 110 can be implanted within other suitable sites within the body of patient 105, which can depend, for example, on a target site within the body of patient 105 that needs to be delivered electrical stimulation therapy. The housing of IMD 110 can be configured to provide a hermetic seal for components such as a rechargeable or non-rechargeable power source. Additionally, in some examples, the housing of IMD 110 is selected from materials that facilitate receiving energy in order to charge a rechargeable power source.

[0044] For example, electrical stimulation energy, which can be pulses based on constant current or constant voltage, is delivered from IMD 110 to one or more target tissue sites of patient 105 via one or more electrodes (not shown) of implantable lead 130. In this example, lead 130 carries electrodes that are placed proximate to target tissue spinal cord 120. The one or more electrodes can be disposed at a distal end of lead 130 and / or other locations along an intermediate point of the lead. Lead 130 can be implanted and coupled to IMD 110. The electrodes can convey electrical stimulation generated by an electrical stimulation generator in IMD 110 to tissue of patient 105. Although leads 130 can each be a single lead, leads 130 can include lead extensions or other segments that can facilitate implantation or positioning of leads 130. In some other examples, IMD 110 can be a leadless stimulator with one or more electrode arrays arranged on the stimulator housing rather than on a lead extending from the housing. Additionally, in some other examples, system 100 can include one lead or more than two leads, each coupled to IMD 110 and directed to similar or different target tissue sites. Figure 1

[0045] Electrodes of lead 130 can be electrode pads on a paddle lead, circular (e.g., ring) electrodes around a lead body, conformable electrodes, cuff electrodes, segmented electrodes (e.g., electrodes disposed at different circumferential locations on a lead rather than a continuous ring electrode), any combination thereof (e.g., ring electrodes and segmented electrodes), or any other type of electrode capable of forming monopolar, bipolar, or multipolar electrode combinations for therapy. Ring electrodes disposed at different axial locations at a distal end of lead 130 will be described for purposes of illustration.

[0046] ​Electrodes are described as being deployed via lead 130 for illustrative purposes, but electrode arrays can be deployed in different ways. For example, a housing associated with a leadless stimulator can carry an electrode array, e.g., in the form of rows and / or columns (or other patterns), to which shift operations can be applied. Such electrodes can be arranged as surface electrodes, ring electrodes, or protrusions. As another option, an electrode array can be formed of electrode rows and / or columns on one or more paddle leads. In some examples, an electrode array includes electrode segments arranged at respective locations on a periphery of a lead, e.g., in the form of one or more segmented rings on a circumference of a cylindrical lead. In other examples, one or more leads 130 are linear leads with 8 ring electrodes along an axial length of the lead. In another example, the electrodes are segmented rings arranged in a linear fashion along an axial length of the lead and at a periphery of the lead.

[0047] Stimulation parameters defining a therapy stimulation program of stimulation pulses of electrical stimulation therapy by IMD 110 through electrodes of lead 130 can include information identifying which electrodes have been selected for delivery of stimulation according to the stimulation program, polarity of the selected electrodes (i.e., electrode combination of the program), and voltage or current amplitude, pulse frequency, pulse width, pulse shape of the stimulation delivered by the electrodes. These stimulation parameters of the stimulation pulses (e.g., control pulses and / or notification pulses) are typically predetermined parameter values determined (e.g., set according to the stimulation program) prior to delivery of the stimulation pulses. In some examples, however, the system 100 automatically changes one or more parameter values based on one or more factors or based on user input.

[0048] ECAP test stimulation programs can define stimulation parameter values defining control pulses delivered by IMD 110 through at least some electrodes of lead 130. These stimulation parameter values can include information identifying which electrodes have been selected for delivery of control pulses, polarity of the selected electrodes (i.e., electrode combination of the program), and voltage or current amplitude, pulse frequency, pulse width, pulse shape of the stimulation delivered by the electrodes. The stimulation signals (e.g., one or more stimulation pulses or continuous stimulation waveform) defined by the parameters of each ECAP test stimulation program are configured to evoke a compound action potential from a nerve. In some examples, when notification pulses are also delivered, the ECAP test stimulation program defines when control pulses are delivered to the patient based on a frequency and / or pulse width of the notification pulses. In some examples, the stimulation defined by each ECAP test stimulation program is not intended to provide or contribute to therapy of the patient. In other examples, the stimulation defined by each ECAP test stimulation program can contribute to therapy when the control pulses elicit a detectable ECAP signal and contribute to therapy. In this way, the ECAP test stimulation programs can define stimulation parameters that are the same or similar to stimulation parameters of a therapy stimulation program.

[0049] Although Figure 1 SCS therapy for treating pain, in other examples, the system 100 can be configured to treat any other condition that can benefit from electrical stimulation therapy. For example, the system 100 can be used to treat tremor, Parkinson’s disease, epilepsy, pelvic floor disorders (e.g., urinary incontinence or other bladder dysfunction, fecal incontinence, pelvic pain, intestinal dysfunction, or sexual dysfunction), obesity, gastroparesis, or psychiatric disorders (e.g., depression, mania, obsessive-compulsive disorder, anxiety, etc.). In this way, the system 100 can be configured to provide therapy in the form of deep brain stimulation (DBS), peripheral nerve stimulation (PNS), peripheral nerve field stimulation (PNFS), cortical stimulation (CS), pelvic floor stimulation, gastrointestinal stimulation, or any other stimulation therapy capable of treating a condition of the patient 105.

[0050] In some examples, the lead 130 includes one or more sensors configured to allow the IMD 110 to monitor one or more parameters of the patient 105, such as patient activity, pressure, temperature, or other characteristics. The one or more sensors can be provided in addition to or in lieu of therapy delivery by the lead 130.

[0051] The IMD 110 is configured to deliver electrical stimulation therapy to the patient 105 via a selected combination of electrodes carried by one or both of the leads 130, alone or in combination with electrodes carried or defined by the housing of the IMD 110. The target tissue of the electrical stimulation therapy can be any tissue affected by electrical stimulation, which can be in the form of electrical stimulation pulses or continuous waveforms. In some examples, the target tissue includes a nerve, smooth muscle, or skeletal muscle. In Figure 1 In the illustrated example, the target tissue is tissue proximate to the spinal cord 120, such as within the intrathecal space or epidural space of the spinal cord 120, or in some examples, a neighboring nerve branching off of the spinal cord 120. The lead 130 can be introduced to the spinal cord 120 via any suitable region, such as the thoracic, cervical, or lumbar region. Stimulation of the spinal cord 120, for example, can prevent pain signals from propagating through the spinal cord 120 and to the brain of the patient 105. The patient 105 can perceive the interruption of the pain signals as a reduction in pain, and thus as an effective therapy outcome. In other examples, stimulation of the spinal cord 120 can produce paresthesia, which can reduce the perception of pain by the patient 105, and thus provide an effective therapy outcome.

[0052] IMD 110 generates and delivers electrical stimulation therapy to a target stimulation site in patient 105 via electrodes of lead 130 to patient 105 in accordance with one or more therapy stimulation programs. A therapy stimulation program defines values for one or more parameters that define an aspect of therapy that IMD 110 delivers in accordance with the program. For example, a therapy stimulation program that controls IMD 110 to deliver stimulation in the form of pulses can define values for voltage or current pulse amplitude, pulse width, and pulse rate (e.g., pulse frequency) of stimulation pulses that IMD 110 delivers in accordance with the program.

[0053] In some examples in which an ECAP signal cannot be detected from the type of pulses intended to be delivered to provide therapy to a patient, control pulses and informing pulses can be delivered. For example, IMD 110 is configured to deliver control stimulation to patient 105 via electrode combinations of lead 130, alone or in combination with electrode combinations carried or defined by the housing of IMD 110. The tissue targeted by the control stimulation can be the same tissue targeted by the electrical stimulation therapy, but IMD 110 can deliver the control stimulation pulses via the same electrodes, at least some of the same electrodes, or different electrodes. Because the control stimulation pulses are delivered in an interleaved manner with the informing pulses, the clinician and / or user can select any desired electrode combination for the informing pulses. As with the electrical stimulation therapy, the control stimulation can be in the form of electrical stimulation pulses or continuous waveforms. In one example, each control stimulation pulse can include a balanced biphasic square wave pulse that employs an active charging phase. However, in other examples, the control stimulation pulses can include a monophasic pulse followed by a passive charging phase. In other examples, the control pulses can include an unbalanced biphasic portion and a passive charging portion. Although not required, the biphasic control pulses can include an interphase interval between the positive and negative phases to facilitate neural impulse propagation in response to the first phase of the biphasic pulse. The control stimulation can be delivered without interrupting the delivery of the electrical stimulation informing pulses, such as during a window between consecutive informing pulses. The control pulses can elicit an ECAP signal from the tissue, and IMD 110 can sense the ECAP signal via two or more electrodes on lead 130. In the case that the control stimulation pulses are applied to spinal cord 120, IMD 110 can sense the signal from spinal cord 120.

[0054] IMD 110 can deliver control stimulation to a target stimulation site in patient 105 via electrodes of lead 130 in accordance with one or more ECAP test stimulation programs. The one or more ECAP test stimulation programs can be stored in a memory device of IMD 110. Each of the one or more ECAP test programs includes values for one or more parameters defining an aspect of control stimulation delivered by IMD 110 in accordance with the program, such as current or voltage amplitude, pulse width, pulse frequency, electrode combination, and in some examples, timing based on an informative pulse to be delivered to patient 105. In some examples, IMD 110 delivers control stimulation to patient 105 in accordance with multiple ECAP test stimulation programs.

[0055] A user, such as a clinician or patient 105, can interact with a user interface of external programmer 150 to program IMD 110. Programming IMD 110 can generally refer to generating and communicating commands, programs, or other information used to control the operation of IMD 110. In this way, IMD 110 can receive communicated commands and programs from external programmer 150 to control electrical stimulation therapy (e.g., informative pulses) and control stimulation (e.g., control pulses). For example, external programmer 150 can transmit therapy stimulation programs, ECAP test stimulation programs, stimulation parameter adjustments, therapy stimulation program selections, ECAP test program selections, user inputs, or other information used to control the operation of IMD 110, e.g., by wireless telemetry or wired connection. As described herein, stimulation delivered to a patient can include control pulses, and in some examples, stimulation can include control pulses and informative pulses.

[0056] In some cases, if external programmer 150 is primarily intended for use by a physician or clinician, it can be characterized as a physician or clinician programmer. In other cases, if external programmer 150 is primarily intended for use by a patient, it can be characterized as a patient programmer. A patient programmer is generally accessible to patient 105, and in many cases, it can be a portable device that can accompany patient 105 throughout his or her daily routine. For example, a patient programmer can receive input from patient 105 when the patient wishes to terminate or change electrical stimulation therapy. Generally, a physician or clinician programmer can support a clinician in selecting and generating programs for use by IMD 110, while a patient programmer can support a patient in adjusting and selecting these programs during normal use. In other examples, external programmer 150 can include or be part of an external charging device that charges a power source of IMD 110. In this way, a user can program and charge IMD 110 using one device or multiple devices.

[0057] As described herein, information can be transmitted between external programmer 150 and IMD 110. Accordingly, IMD 110 and external programmer 150 can communicate via wireless communication using any of the techniques known in the art. Examples of communication techniques can include, for example, radiofrequency (RF) telemetry and inductive coupling, although other techniques are also contemplated. In some examples, external programmer 150 includes a communication head that can be placed near the patient’s body proximate to the IMD 110 implant site to improve the quality or security of communication between IMD 110 and external programmer 150. Communication between external programmer 150 and IMD 110 can occur during or separate from power transmission.

[0058] In some examples, in response to a command from external programmer 150, IMD 110 delivers electrical stimulation therapy to a target tissue site of spinal cord 120 of patient 105 according to a plurality of therapy stimulation programs via electrodes (not depicted) on lead 130. In some examples, IMD 110 can modify the therapy stimulation programs as the treatment needs of patient 105 evolve over time. For example, modification of the therapy stimulation programs can result in an adjustment to at least one parameter of the plurality of notification pulses. As patient 105 receives the same therapy over an extended period of time, the efficacy of the therapy can decrease. In some cases, the parameters of the plurality of notification pulses can be updated automatically.

[0059] One or more characteristics of the action potential (e.g., amplitude of one or more peaks or amplitude between one or more peaks or area under the curve of one or more peaks) evoked by the stimulation pulses delivered by the IMD 110 (i.e., characteristics of the ECAP signal) can be indicative of efficacy of the electrical stimulation therapy. The electrical stimulation therapy delivered by the lead 130 of the IMD 110 can cause neurons within the target tissue to evoke a compound action potential that propagates up and down from the target tissue, eventually reaching the sensing electrodes of the IMD 110. In addition, the control stimulation can also elicit at least one ECAP, and the ECAP in response to the control stimulation can also be a surrogate indicator of therapeutic efficacy. The amount of action potential evoked (e.g., number of neurons propagating the action potential signal) can be based on various parameters of the electrical stimulation pulses, such as amplitude, pulse width, frequency, pulse shape (e.g., rate of change at the beginning and / or end of the pulse), etc. The rate of change can be defined as the rate of change of the voltage and / or current amplitude of the pulse at the beginning and / or end of each pulse or phase within a pulse. For example, a very high rate of change represents a sharp edge of the pulse that is nearly vertical, while a low rate of change represents a longer ramp up (or ramp down) of the pulse amplitude. In some examples, these parameters contribute to the strength of the electrical stimulation. Additionally, the characteristics (e.g., amplitude) of the ECAP signal can vary based on the distance between the stimulation electrode and the nerves affected by the electric field produced by the delivered control stimulation pulses.

[0060] In one example, each therapy pulse can have a pulse width greater than about 300 μβ, such as between about 300 μβ and 1000 μβ (i.e., 1 millisecond) in some examples. At these pulse widths, IMD 110 can not adequately detect the ECAP signal because the therapy pulse is also detected as an artifact that masks the ECAP signal. If the ECAP is not adequately recorded, the ECAP that reaches IMD 110 cannot be compared to a target ECAP characteristic (e.g., a target ECAP amplitude) and therapy stimulation cannot be altered in response to the responsive ECAP. When the informing pulses have these longer pulse widths, IMD 110 can deliver control stimulation in the form of control pulses. The control pulses can have a pulse width less than about 300 μβ, such as biphasic pulses having a duration of about 100 μβ per phase for each phase. Because the control pulses can have a shorter pulse width than the informing pulses, ECAP signals can be sensed and identified after each control pulse and used to inform IMD 110 of any changes that should be made to the informing pulses (and control pulses in some examples). Generally, the term "pulse width" refers to the total duration of each phase of a single pulse and, where appropriate, the interphase interval. A single pulse includes a single phase in some examples (i.e., a monophasic pulse) or two or more phases in other examples (e.g., a biphasic pulse or a triphasic pulse). The pulse width defines the time period from the start time of the first phase of the pulse to the end time of the last phase of the pulse (e.g., a biphasic pulse having a positive phase with a duration of 100 μβ, a negative phase with a duration of 100 μβ, and an interphase interval with a duration of 30 μβ defines a pulse width of 230 μβ). In another example, a control pulse can include a positive phase with a duration of 90 μβ, a negative phase with a duration of 90 μβ, and an interphase interval with a duration of 30 μβ to define a pulse width of 210 μβ. In another example, a control pulse can include a positive phase with a duration of 120 μβ, a negative phase with a duration of 120 μβ, and an interphase interval with a duration of 30 μβ to define a pulse width of 270 μβ.

[0061] During delivery of the control stimulation pulses defined by the one or more ECAP test stimulation programs, IMD 110 senses the electrical potential of the tissue of the spinal cord 120 of patient 105 via two or more electrodes placed on lead 130 to measure electrical activity of the tissue. IMD 110, for example, utilizes electrodes and associated sensing circuitry on one or more leads 130 to sense ECAPs from the target tissue of patient 105. In some examples, IMD 110 receives signals indicative of ECAPs from one or more sensors (e.g., one or more electrodes and circuitry) internal or external to patient 105. Such example signals can include signals indicative of ECAPs of the tissue of patient 105. Examples of the one or more sensors include one or more sensors configured to measure or be indicative of physiological effects of a compound action potential of patient 105. For example, to measure physiological effects indicative of a compound action potential, the one or more sensors can be an accelerometer, a pressure sensor, a flex sensor, a sensor configured to detect a posture of patient 105, or a sensor configured to detect a respiratory function of patient 105. In this way, while ECAPs can be indicative of a change in posture or other patient action, other sensors can also detect similar changes in posture or movement using modalities separate from ECAPs. In other examples, however, external programmer 150 receives signals indicative of compound action potentials in the target tissue of patient 105 and transmits notifications to IMD 110.

[0062] The control stimulation parameters and the target ECAP characteristic values can be initially set at a clinic, but can be set and / or adjusted by patient 105 at home. Once the target ECAP characteristic values are set, example techniques allow for automatic adjustment of the therapy stimulation parameters to maintain a consistent amount of neural activation and a consistent perception of therapy for the patient as the distance of the electrodes from the neurons changes. The ability to change stimulation parameter values can also allow for therapy to have long term efficacy, being able to maintain a consistent strength of stimulation (e.g., as indicated by ECAPs) by comparing measured ECAP values to the target ECAP characteristic values. IMD 110 can perform these changes without intervention by a physician or patient 105.

[0063] In some examples, the system varies the target ECAP characteristic value over a period of time. The system can be programmed to vary the target ECAP characteristic in order to adjust the intensity of the informed pulses to provide different sensations to the patient (e.g., to increase or decrease the amount of neural activation). In one example, the system can be programmed to oscillate the target ECAP characteristic value between a maximum target ECAP characteristic value and a minimum target ECAP characteristic value at a predetermined frequency to provide a sensation to the patient that can be perceived as a wave or other sensation that can provide therapeutic relief to the patient. The maximum target ECAP characteristic value, the minimum target ECAP characteristic value, and the predetermined frequency can be stored in a storage device of the IMD 110 and can be updated in response to a signal from the external programmer 150 (e.g., a user request to change the values stored in the storage device of the IMD 110). In other examples, the target ECAP characteristic value can be programmed to steadily increase or steadily decrease to a baseline target ECAP characteristic value over a period of time. In other examples, the external programmer 150 can program the target ECAP characteristic value to automatically vary over time according to other predetermined functions or patterns. In other words, the target ECAP characteristic value can be programmed to change incrementally by a predetermined amount or a predetermined percentage that is selected according to a predetermined function (e.g., a sinusoidal function, a ramp function, an exponential function, a logarithmic function, etc.). The increment by which the target ECAP characteristic value is changed can vary for every particular number of pulses or particular units of time. Although the system can vary the target ECAP characteristic value, the received ECAP signals can still be used by the system to adjust one or more parameter values of the informed pulses and / or the control pulses to meet the target ECAP characteristic value.

[0064] In some examples, IMD 110 includes stimulation generation circuitry configured to deliver electrical stimulation therapy to patient, where the electrical stimulation therapy includes a plurality of notification pulses. Additionally, the stimulation generation circuitry of IMD 110 can be configured to deliver a plurality of control pulses, where the plurality of control pulses are interleaved with at least some of the plurality of notification pulses. In some examples, IMD 110 includes sensing circuitry configured to detect a plurality of ECAPs, where the sensing circuitry is configured to detect each of the plurality of ECAPs after one of the plurality of control pulses and before a subsequent therapy pulse of the plurality of notification pulses. Although IMD 110 can receive the plurality of ECAPs based on IMD 110 delivering the plurality of control pulses (e.g., the plurality of control pulses can evoke the plurality of ECAPs received by IMD 110), the plurality of ECAPs can be indicative of efficacy of the plurality of notification pulses. In other words, although in some cases the plurality of ECAPs can not be evoked by the plurality of notification pulses themselves, the plurality of ECAPs can still reveal one or more characteristics of the plurality of notification pulses or one or more effects of the plurality of notification pulses on patient 105. In some examples, IMD 110 delivers the plurality of notification pulses above a perception threshold, where patient 105 is able to perceive the plurality of notification pulses delivered above the perception threshold. In other examples, IMD 110 delivers the plurality of notification pulses below a perception threshold, where patient 105 is not able to perceive the plurality of notification pulses delivered below the perception threshold.

[0065] IMD 110 can include processing circuitry configured to, in some examples, process the plurality of ECAPs received by the sensing circuitry of IMD 110. For example, the processing circuitry of IMD 110 is configured to determine whether a parameter of a first ECAP is greater than a threshold parameter value. The processing circuitry can monitor a characteristic value of each of the plurality of ECAPs, and the first ECAP can be the first of the plurality of ECAPs recorded by IMD 110 to exceed the threshold characteristic value. In some examples, the characteristic monitored by IMD 110 can be ECAP amplitude. In some examples, the ECAP amplitude can be given by the voltage difference between the Nl ECAP peak and the P2 ECAP peak. Further description related to the Nl ECAP peak, the N2 ECAP peak, and other ECAP peaks can be found below in the description of FIG. 6. Figure 4In other examples, IMD 110 can monitor another characteristic or more than one characteristic of the plurality of ECAPs, such as current amplitude, slope, slew rate, ECAP frequency, ECAP duration, or any combination thereof. In some examples where the characteristic includes ECAP amplitude, the threshold ECAP characteristic value can be selected from a range of about 5 microvolts (pV) to about 30 pV. These characteristics can be stored in temporary memory as ECAP information and can be stored in long-term memory by IMD 110 for later analysis and / or transmission to another device in response to receiving the trigger signal.

[0066] If the processing circuit of IMD 110 determines that the characteristic of the first ECAP is greater than the threshold ECAP characteristic value, the processing circuit can decrement (or reduce) a parameter of the set of informed pulses delivered by the stimulation generation circuit after the first ECAP. In some examples, to decrement the parameter of the set of informed pulses, IMD 110 can reduce the current amplitude of each therapy pulse in each successive therapy pulse of the set of informed pulses by a certain current amplitude value. In other examples, to decrement the parameter of the set of informed pulses, IMD 110 can reduce the amplitude of a parameter other than current (e.g., voltage). Because the plurality of ECAPs can indicate some effect of the therapy delivered by IMD 110 on patient 105, IMD 110 can decrement the parameter of the set of informed pulses in order to improve the therapy delivered to patient 105. In some cases, an ECAP received by IMD 110 exceeding the threshold ECAP characteristic value can indicate to IMD 110 that one or more of leads 130 has moved closer to the target tissue of patient 105 (e.g., spinal cord 120). In these cases, if the therapy delivered to spinal cord 120 is maintained at the current level, patient 105 can experience transient overstimulation because the distance between leads 130 and the target tissue of patient 105 is a factor in determining the effect of the electrical stimulation therapy on patient 105. Thus, decrementing the first set of informed pulses based on determining that the first ECAP exceeds the threshold ECAP characteristic value can prevent patient 105 from experiencing transient overstimulation due to the electrical stimulation therapy delivered by IMD 110.

[0067] After determining that the first ECAP exceeds the threshold ECAP characteristic value, the processing circuit of IMD 110 can continue to monitor the plurality of ECAPs detected by the sensing circuit. In some examples, the processing circuit of IMD 110 can identify a second ECAP that occurs after the first ECAP, where a characteristic of the second ECAP is less than the threshold ECAP characteristic value. In some cases, the second ECAP can be the first ECAP that occurs after the first ECAP whose characteristic value is less than the threshold ECAP characteristic value. In other words, the characteristic value of each ECAP that occurs between the first ECAP and the second ECAP can be greater than or equal to the threshold ECAP characteristic value. In this way, because IMD 110 can decrement the notification pulses delivered to patient 105 between the first ECAP and the second ECAP, the risk of patient 105 experiencing transient overstimulation during the period of time extending between receipt of the first ECAP and receipt of the second ECAP can be reduced. Based on the characteristic of the second ECAP being less than the threshold ECAP characteristic value, the processing circuit of IMD 110 can increment the parameter of the second set of notification pulses delivered by the stimulation generation circuit after the second ECAP.

[0068] As described herein, system 100 can include memory and processing circuitry. For example, IMD 110 and / or external programmer 150 can include some or all processing circuitry configured to perform various functions. System 100 can be configured to receive ECAP information, where the ECAP information includes information from a plurality of ECAP signals, receive a trigger signal requesting long-term storage of at least a portion of the ECAP information in memory, and store at least a portion of the ECAP information in memory in response to receiving the trigger signal. Stimulation generation circuitry of IMD 110 can be configured to deliver electrical stimulation to a patient, where the electrical stimulation therapy includes a plurality of stimulation pulses, and sensing circuitry of IMD 110 or another device can be configured to sense a plurality of ECAP signals. Sensing circuitry can be configured to sense each ECAP signal of the plurality of ECAP signals evoked by a respective stimulation pulse of the plurality of stimulation pulses, and processing circuitry can be configured to receive the ECAP signals from the sensing circuitry as the ECAP information.

[0069] The ECAP information can include at least one characteristic value representative of a respective ECAP signal of the plurality of ECAP signals. The characteristic value can be at least one of an amplitude value, a slope value, or an area under a peak value indicative of the respective ECAP signal. Since the ECAP signals are representative of action potentials from a plurality of nerves, with stronger ECAP signals indicating a greater number of nerves activated, the characteristic value can similarly be indicative of the number of nerves activated as a result of the delivery of the stimulation pulse. Additionally or alternatively, the ECAP information can include a plurality of waveforms representative of a respective ECAP signal of the plurality of ECAP signals. The waveforms can be analog or digitized representations of the analog waveforms of each ECAP signal. In this way, the stored waveforms can be representative of the time-varying ECAP signals sensed from the tissue, rather than values computed from the waveforms, such as the amplitude between two peaks of an ECAP waveform. In this way, the ECAP information can include any type of information or data representative of one or more sensed ECAP signals. Storing waveform information can be a more high-fidelity type of information compared to other characteristic values representative of the ECAP signals.

[0070] The system 100 can take different actions in response to receiving the trigger signal requesting long-term storage of at least a portion of the ECAP information. For example, the system 100 can initially store the received ECAP information in a temporary memory. In response to receiving the trigger signal, the system 100 can store the ECAP information initially stored in the temporary memory in a long-term memory. The system 100 can thus transfer the ECAP information to the long-term memory. In this way, the temporary memory can behave like a buffer, such that the system 100 can store the ECAP information received prior to the trigger signal in the long-term memory when needed. In some examples, the system 100 can be configured to delete the ECAP information stored in the temporary memory in response to a predetermined period of time elapsing. For example, the predetermined period of time can be selected to be between a fraction of a second (e.g., one millisecond or one microsecond) to several hours. In one example, the predetermined period of time can be between 20 seconds and 5 minutes. In other words, the temporary memory can have a buffer length of approximately 20 seconds to 5 minutes. For example, the buffer length can be 30 seconds or 60 seconds. In another example, the buffer can be less than or equal to two minutes. Other buffer lengths can be used in other examples, which can be shorter or longer. The time can have elapsed prior to receiving the trigger signal. The system 100 can thus delete the ECAP information from the temporary memory when not needed. These types of temporary memories can be similar to first-in, first-out types of memories or buffers.

[0071] In other examples, the system 100 can be configured to control the sensing circuit to increase a rate at which the sensing circuit senses subsequent ECAP signals in response to receiving the trigger signal and store subsequent ECAP information including the subsequent ECAP signals in the memory. In this way, the system 100 can also increase a rate at which the stimulation generation circuit generates stimulation pulses from which the increased rate ECAP signals are sensed, as typically one ECAP signal is sensed from one corresponding stimulation pulse. By increasing the rate at which ECAP signals are detected, the system 100 can increase fidelity of the ECAP information in response to receiving the trigger signal.

[0072] The trigger signal can take a variety of forms. For example, the trigger signal can include a request from an external device (e.g., external programmer 150, such as a patient programmer or clinician programmer) to store ECAP information. A user can interact with the external device and request the external device transmit a request to the IMD 110 to store ECAP information for long-term storage. In this way, the IMD 110 can receive the trigger signal from the external device. In other examples, the IMD 110 can receive a user request directly from the user, such as a housing tap, where the patient taps the housing of the IMD 110 through the patient’s skin. The IMD 110 can include one or more accelerometers or other motion detection or presence detection devices configured to detect taps on the housing. Accordingly, the IMD 110 can be configured to receive or detect a housing tap by receiving accelerometer data from an accelerometer within the housing of the IMD 110 and determining that the accelerometer data indicates that the user tapped the IMD 110. The IMD 110 can employ a particular tap algorithm to distinguish the tap from other movement or motion. For example, the IMD 110 can need to detect a particular tap pattern, a number of taps, a magnitude of the tap or taps, or any other type of housing tap that is different from other routine collisions and movements with the IMD 110.

[0073] In other examples, the trigger signal includes an indication that a characteristic of one of the plurality of ECAP signals exceeds a threshold. The threshold can indicate that a particular motion of the patient 105 (e.g., a cough, a sneeze, a laugh, a bend, etc.) can have caused the stimulation to produce an undesired sensation, at which point further analysis of the ECAP signals can be desirable. In some examples, the trigger signal can include an indication that the user changed one or more stimulation parameter values that define the electrical stimulation deliverable to the patient. The user changing the stimulation parameters can indicate that the patient 105 felt ineffective therapy and / or an undesired sensation, and thus ECAP information related to such an event can be beneficial for further analysis of the cause that can have caused the patient to change the stimulation parameter values.

[0074] In some examples, the system 100 can select a particular portion of the ECAP information in accordance with the trigger signal. For example, in response to receiving the trigger signal, the system 100 can select at least a portion of the ECAP information representative of one or more ECAP signals sensed between an initial time and a final time of the plurality of ECAP signals. The initial time can occur a first period of time before receiving the trigger signal, and the final time can occur a second period of time after receiving the trigger signal. In this way, the system 100 can store ECAP information recorded and received prior to the triggering event and ECAP information after the triggering event in long-term memory. The ECAP information stored thereby can include information representative of ECAP signals sensed before and after the event that resulted in the generation of the trigger signal. In this way, the system can capture ECAP information prior to the identified trigger signal. To the user, this can result in the patient being able to record ECAP information captured before the sensation that caused the patient to desire to store the ECAP information and / or before the patient was able to provide an input request to the programmer. Additionally, this process makes it impossible for the system or user to predict which ECAP information can be relevant prior to certain events occurring.

[0075] In some examples, the system 100 can move the ECAP information stored in the temporary memory prior to receiving the trigger signal to the long-term memory and then store ECAP information received after the trigger signal directly to the long-term memory. In other examples, the system 100 can first store all received ECAP information in the temporary memory and then move ECAP information representative of ECAP signals sensed between an initial time and a final time to the long-term memory. In some examples, the system 100 can add a marker representative of the trigger signal to at least a portion of the ECAP information stored in the memory. The marker can indicate a time of the trigger signal relative to the sensed ECAP signals of the ECAP information. Additionally or alternatively, the marker can include information identifying a type of event that resulted in the trigger signal (e.g., a user request, an ECAP characteristic value above a threshold, etc.). In this way, the system 100 can be configured to or enable a user to categorize trigger signals or associated data based on a time at which the trigger signal occurred (e.g., trigger signals within a period of time of a specified time or within a specified range of times). In some examples, the system 100 can be configured to store data based on the type of trigger signal that caused the data to be stored (e.g., provide data associated with a user or system specified type of trigger signal).

[0076] In some examples, IMD 110 can analyze ECAP information stored in long-term memory. In other examples, IMD 110 may include communication circuitry configured to transmit the stored ECAP information to an external device, such as programmer 150. IMD 110 may transmit any ECAP information stored in long-term memory during a communication session with the external device or upon request from the external device. External devices, such as programmer 150, may include a display, such that the external device is configured to present one or more representations of the stored ECAP information via the display. For example, the external device may display a waveform graph of the ECAP information over time, a characteristic value over time, a marker associated with a trigger signal, or any other such representation of the ECAP information.

[0077] Figure 2 This is a block diagram illustrating an example configuration of components of the IMD 200 according to one or more techniques disclosed herein. The IMD 200 can be... Figure 1 An example of IMD 110. In Figure 2 In the example shown, IMD 200 includes a stimulus generation circuit 202, a switching circuit 204, a sensing circuit 206, a communication circuit 208, a processing circuit 210, a storage device 212, multiple sensors 222, and a power supply 224.

[0078] exist Figure 2 In the example shown, storage device 212 stores therapeutic stimulation program 214 and ECAP storage instructions 216 in a separate memory or a separate area within storage device 212. Storage device 212 also includes temporary memory 218 (e.g., a rolling buffer) and long-term memory 220, which may be on the same memory or physically separate memory. Each stored therapeutic stimulation program in therapeutic stimulation program 214 defines values ​​for a set of electrical stimulation parameters (e.g., a set of stimulation parameters), such as stimulation electrode combination, electrode polarity, current or voltage amplitude, pulse width, pulse rate, and pulse shape. ECAP storage instructions 216 include instructions regarding receiving and storing ECAP information, such as how long to store ECAP information, when to store ECAP information in temporary memory 218, when to store ECAP information in long-term memory 220, when to change the ECAP sensing rate, or any other aspects related to the sensing and storage of ECAP information. Temporary memory 218 may include a rolling buffer (e.g., first-in-first-out) memory that stores all ECAP information received from sensing circuitry 206. Long-term memory 220 may include ECAP information that processing circuitry 210 has selected for long-term storage and / or eventual transfer to another device (e.g., programmer 150) based on criteria such as when a trigger signal is received.

[0079] Therefore, in some examples, the stimulation generation circuit 202 generates an electrical stimulation signal according to the described electrical stimulation parameters. Other ranges of stimulation parameter values ​​may also be used, depending on the target stimulation site within the patient 105. Although stimulation pulses are described, the stimulation signal can be of any form, such as a continuous-time signal (e.g., a sine wave). The switching circuit 204 may include one or more switch arrays, one or more multiplexers, one or more switches (e.g., a switch matrix or other set of switches), or other circuitry configured to direct stimulation signals from the stimulation generation circuit 202 to one or more of electrodes 232 and 234 or to direct sensing signals from one or more of electrodes 232 and 234 to sensing circuit 206. In other examples, the stimulation generation circuit 202 and / or sensing circuit 206 may include sensing circuitry that directs signals to and / or from one or more of electrodes 232 and 234, which may or may not include the switching circuit 204.

[0080] Sensing circuit 206 monitors signals from any combination of electrodes 232, 234. In some examples, sensing circuit 206 includes one or more amplifiers, filters, and analog-to-digital converters. Sensing circuit 206 can be used to sense physiological signals, such as ECAP. In some examples, sensing circuit 206 detects ECAP from a specific combination of electrodes 232, 234. In some cases, the specific combination of electrodes used to sense ECAP includes electrodes different from the set of electrodes 232, 234 used to deliver stimulation pulses. Alternatively, in other cases, the specific combination of electrodes used to sense ECAP includes at least one of the same set of electrodes used to deliver stimulation pulses to patient 105. Sensing circuit 206 can provide signals to analog-to-digital converters for conversion into digital signals for processing, analysis, storage, or output by processing circuit 210.

[0081] Under the control of the processing circuit 210, the communication circuit 208 supports communication between the IMD 200 and an external programmer. Figure 2 Wireless communication between the IMD 200 (not shown) or another computing device. The processing circuitry 210 of the IMD 200 can receive values ​​of various stimulation parameters (e.g., amplitude and electrode combinations) from an external programmer via the communication circuitry 208 as updates to the program. Updates to the therapeutic stimulation program 214 and the ECAP test stimulation program 216 can be stored in the storage device 212. The communication circuitry 208 in the IMD 200, as well as telemetry circuitry (e.g., external programmers) in other devices and systems described herein, can communicate via radio frequency (RF) communication technology. Additionally, the communication circuitry 208 can interact with an external medical device programmer (IMD 200) via proximity sensing interaction between the IMD 200 and the external programmer.Figure 2 (Not shown in the image) Communication. An external programmer can be... Figure 1 An example of an external programmer 150. Therefore, the communication circuit 208 can continuously, at periodic intervals, or upon request from the IMD 110 or the external programmer.

[0082] Processing circuitry 210 may include any one or more of the following: a microprocessor, a controller, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), discrete logic circuitry, or any other processing circuitry configured to provide functionality attributable to processing circuitry 210, which may be embodied herein as firmware, hardware, software, or any combination thereof. Processing circuitry 210 controls stimulation generation circuitry 202 to generate stimulation signals according to therapeutic stimulation program 214 and ECAP test stimulation program 216 stored in storage device 212, applying stimulation parameter values ​​specified by one or more programs, such as the amplitude, pulse width, pulse rate, and pulse shape of each stimulation signal.

[0083] exist Figure 2 In the example shown, the set of electrodes 232 includes electrodes 232A, 232B, 232C, and 232D, and the set of electrodes 234 includes electrodes 234A, 234B, 234C, and 234D. In other examples, a single lead may include all eight electrodes 232 and 234 along a single axial length of the lead. The processing circuit 210 also controls the stimulation generation circuit 202 to generate stimulation signals and apply them to selected combinations of electrodes 232, 234. In some examples, the stimulation generation circuit 202 includes switching circuitry (as an alternative to or complement to switching circuitry 204) that can couple stimulation signals to selected conductors within the lead 230, which in turn deliver stimulation signals across the selected electrodes 232, 234. Such switching circuitry may be a switch array, switch matrix, multiplexer, or configured to selectively couple stimulation energy to selected electrodes 232, 234 and selectively utilize the selected electrodes 232, 234 to sense bioelectric nerve signals in the patient's spinal cord. Figure 2 (not shown) any other type of switching circuit.

[0084] In other examples, however, the stimulation generation circuit 202 does not include a switching circuit, and the switching circuit 204 does not interface between the stimulation generation circuit 202 and the electrodes 232, 234. In these examples, the stimulation generation circuit 202 includes pairs of voltage sources, current sources, voltage sinks, or current sinks connected to each electrode 232, 234, such that each pair of electrodes has a unique signal circuit. In other words, in these examples, each of the electrodes 232, 234 is independently controlled via its own signal circuit (e.g., via a combination of regulated voltage sources and sinks or regulated current sources and sinks), as opposed to a switching signal between the electrodes 232, 234.

[0085] The electrodes 232, 234 on the respective lead 230 can be configured in a variety of different designs. For example, one or both leads 230 can include one or more electrodes at each longitudinal position along the length of the lead, such as one electrode at each of the different perimeter positions A, B, C, D on the perimeter of the lead. In one example, the electrodes can be electrically coupled to the stimulation generation circuit 202 via respective conductive wires that are straight or coiled within the housing of the lead and extend to a connector at the proximal end of the lead. In another example, each electrode on the lead can be an electrode disposed on a thin film. The thin film can include a conductive trace for each electrode that extends the length of the thin film to the proximal connector. The thin film can then be wrapped (e.g., in a spiral) around an inner member to form the lead 230. These and other configurations can be used to construct leads with complex electrode geometries.

[0086] Although the sensing circuit 206 is embedded in a common housing with the stimulation generation circuit 202 and the processing circuit 210 in Figure 2 other examples, the sensing circuit 206 can be in a different housing from the IMD 200 and can communicate with the processing circuit 210 via wired or wireless communication techniques.

[0087] In some examples, one or more of the electrodes 232 and 234 are adapted to sense ECAPs. For example, the electrodes 232 and 234 can sense a voltage amplitude of a portion of the ECAP signal, where the sensed voltage amplitude is a characteristic of the ECAP signal.

[0088] The storage device 212 can be configured to store information within the IMD 200 during operation. The storage device 212 can comprise a computer-readable storage medium or computer-readable storage device. In some examples, the storage device 212 includes one or more of a short-term memory (e.g., the temporary memory 218) or a long-term memory (e.g., the long-term memory 220). The storage device 212 can include, for example, random access memory (RAM), dynamic random access memory (DRAM), static random access memory (SRAM), ferroelectric random access memory (FRAM), magnetic disk, optical disk, flash memory, or forms of electrically programmable memory (EPROM) or electrically erasable and programmable memory (EEPROM). In some examples, the storage device 212 is used to store data indicative of instructions for execution by the processing circuit 210. As discussed above, the storage device 212 is configured to store the therapy stimulation programs 214 and the ECAP storage instructions 216.

[0089] In some examples, the stimulation generation circuit 202 can be configured to deliver electrical stimulation therapy to the patient 105. In some cases, the electrical stimulation therapy can include a plurality of informing pulses. Additionally, the stimulation generation circuit 202 can be configured to deliver a plurality of control pulses, where the plurality of control pulses are interleaved with at least some of the plurality of informing pulses. The stimulation generation circuit can deliver the plurality of informing pulses and the plurality of control pulses to a target tissue (e.g., the spinal cord 120) of the patient 105 via the electrodes 232, 234 of the lead 230. By delivering such informing pulses and control pulses, the stimulation generation circuit 202 can induce responsive ECAPs in the target tissue, which propagate through the target tissue and then return to the electrodes 232, 234. In some examples, a different combination of electrodes 232, 234 can sense the responsive ECAPs than the combination of electrodes 232, 234 that deliver the informing pulses and the combination of electrodes 232, 234 that deliver the control pulses. The sensing circuit 206 can be configured to detect the responsive ECAPs via the electrodes 232, 234 and the lead 230. In other examples, the stimulation generation circuit 202 can be configured to deliver the plurality of control pulses without delivering any informing pulses, when the control pulses also provide a therapeutic effect for the patient.

[0090] In some cases, processing circuitry 210 can instruct sensing circuitry 206 to continuously monitor ECAPs. In other cases, processing circuitry 210 can instruct sensing circuitry 206 to monitor ECAPs based on signals from sensor(s) 222. For example, processing circuitry 210 can activate sensing circuitry 206 based on a patient 105 activity level exceeding an activity level threshold (e.g., an accelerometer signal of acceleration sensor 225 rising above a threshold). In some examples, activating and deactivating sensing circuitry 206 can extend battery life of power source 224. In other examples, processing circuitry 210 can determine and store acceleration data derived from acceleration sensor 225 that is representative of a patient’s posture state and / or activity. Processing circuitry 210 can associate the acceleration data with ECAP information for temporary storage or long-term storage in response to receiving a trigger signal herein. In this way, the acceleration data can be representative of a patient’s posture state and / or activity corresponding to the same time at which ECAP information is collected for the patient. Thus, the acceleration data and ECAP information can be time-aligned to represent aspects of the patient at the same time. Additionally, processing circuitry 210 can store a timestamp or other indication data with the ECAP information and / or acceleration data to time-align the ECAP information and acceleration data and / or other events. The combination of ECAP information and acceleration data can help a clinician or patient identify movements that result in uncomfortable stimulation or ineffective therapy.

[0091] In some examples, processing circuitry 210 determines whether a characteristic of the first ECAP is greater than a threshold ECAP characteristic value. The threshold ECAP characteristic value can be stored in storage device 212. In some examples, the characteristic of the first ECAP is a voltage amplitude of the first ECAP. In some such examples, the threshold ECAP characteristic value is selected from a range of about 10 microvolts (pV) to about 20 pV. In other examples, processing circuitry 210 determines whether another characteristic of the first ECAP (e.g., ECAP current amplitude, ECAP slew rate, area under the ECAP, ECAP slope, or ECAP duration) is greater than a threshold ECAP characteristic value.

[0092] If processing circuit 210 determines that the characteristic of the first ECAP is greater than the threshold ECAP characteristic value, processing circuit 210 is configured to activate a decrementing mode, altering at least one parameter of each therapy pulse in the set of notification pulses delivered by IMD 200 after sensing circuit 206 senses the first ECAP. Additionally, when the decrementing mode is activated, processing circuit 210 can change at least one parameter of each control pulse in the set of control pulses delivered by IMD 200 after sensing circuit 206 senses the first ECAP. In some examples, the at least one parameter of the notification pulses and the at least one parameter of the control pulses adjusted by processing circuit 210 during the decrementing mode includes a stimulation current amplitude. In some such examples, during the decrementing mode, processing circuit 210 decreases the current amplitude of each successive stimulation pulse (e.g., each therapy pulse and each control pulse) delivered by IMD 200. In other examples, the at least one parameter of the stimulation pulses adjusted by processing circuit 210 during the decrementing mode includes any combination of a current amplitude, a voltage amplitude, a slew rate, a pulse shape, a pulse frequency, or a pulse duration.

[0093] In Figure 2 In the illustrated example, the decrementing mode is stored in storage device 212 as part of control strategy 213. The decrementing mode can include a list of instructions that enable processing circuit 210 to adjust a parameter of a stimulation pulse according to a function. In some examples, when the decrementing mode is activated, processing circuit 210 decreases the parameter (e.g., current) of each successive therapy pulse and each successive control pulse according to a linear function. In other examples, when the decrementing mode is activated, processing circuit 210 decreases the parameter (e.g., current) of each successive therapy pulse and each successive control pulse according to an exponential function, a logarithmic function, or a piecewise function. Sensing circuit 206 can continue to monitor for responsive ECAPs while the decrementing mode is activated. In turn, sensing circuit 206 can detect ECAPs in response to control pulses delivered by IMD 200.

[0094] Throughout the decremental mode, the processing circuitry can monitor ECAPs in response to the stimulation pulses. The processing circuitry 210 can determine whether a characteristic of a second ECAP is less than the threshold ECAP characteristic value. In some cases, the second ECAP can be the first ECAP that occurs after the first ECAP that is less than the threshold ECAP characteristic value. In other words, every ECAP recorded by the sensing circuitry 206 between the first ECAP and the second ECAP is greater than or equal to the threshold ECAP characteristic value. Based on the characteristic of the second ECAP being less than the threshold ECAP characteristic value, the processing circuitry 210 can deactivate the decremental mode and activate the incremental mode, thereby altering at least one parameter of each therapy pulse in the set of informed pulses delivered by the IMD 200 after the sensing circuitry 206 senses the second ECAP. Additionally, when the incremental mode is activated, the processing circuitry 210 can change at least one parameter of each control pulse in the set of control pulses delivered by the IMD 200 after the sensing circuitry 206 senses the second ECAP.

[0095] In some examples, the at least one parameter of the informed pulses and the at least one parameter of the control pulses adjusted by the processing circuitry 210 during the incremental mode includes a stimulation current amplitude. In some such examples, during the incremental mode, the processing circuitry 210 increases the current amplitude of each successive stimulation pulse (e.g., each therapy pulse and each control pulse) delivered by the IMD 200. In other examples, the at least one parameter of the stimulation pulses adjusted by the processing circuitry 210 during the incremental mode includes any combination of current amplitude, voltage amplitude, slew rate, pulse shape, pulse frequency, or pulse duration.

[0096] In Figure 2 In the illustrated example, the incremental mode is stored in the storage device 212 as part of the control strategy 213. The incremental mode can include a list of instructions that enable the processing circuitry 210 to adjust parameters of the stimulation pulses according to a function. In some examples, when the incremental mode is activated, the processing circuitry 210 increases the parameters (e.g., current) of each successive therapy pulse and each successive control pulse according to a linear function. In other examples, when the incremental mode is activated, the processing circuitry 210 increases the parameters (e.g., current) of each successive therapy pulse and each successive control pulse according to a non-linear function, such as an exponential function, a logarithmic function, or a piecewise function. When the incremental mode is activated, the sensing circuitry 206 can continue to monitor for responsive ECAPs. In turn, the sensing circuitry 206 can detect ECAPs in response to the control pulses delivered by the IMD 200.

[0097] Processing circuitry 210 can complete the incrementing mode such that the one or more parameters of the stimulation pulses return to the baseline parameter values of the stimulation pulses delivered prior to processing circuitry 210 activating the decrementing mode (e.g., prior to sensing circuitry 206 detecting the first ECAP). By first decrementing and then incrementing the stimulation pulses in response to the ECAP exceeding the threshold ECAP characteristic value, processing circuitry 210 can prevent the patient 105 from experiencing transient overstimulation or reduce the severity of transient overstimulation experienced by the patient 105.

[0098] Although in some examples, sensing circuitry 206 senses ECAPs occurring in response to control pulses delivered according to the ECAP test stimulation program 216, in other examples, sensing circuitry 206 senses ECAPs occurring in response to notification pulses delivered according to the therapy stimulation program 214. The techniques of this disclosure can enable IMD 200 to switch between the decrementing mode and the incrementing mode using any combination of ECAPs corresponding to notification pulses and ECAPs corresponding to control pulses.

[0099] The sensor(s) 222 can include one or more sensing elements that sense values of respective patient parameters. As described, the electrodes 232 and 234 can be electrodes that sense characteristic values of ECAPs. The sensor(s) 222 can include one or more accelerometers (such as the acceleration sensor 225), optical sensors, chemical sensors, temperature sensors, pressure sensors, or any other type of sensor. The sensor(s) 222 can output patient parameter values that can be used as feedback to control delivery of therapy. For example, the sensor(s) 222 can indicate patient activity, and the processing circuit 210 can increase a frequency of control pulses and ECAP sensing in response to detecting an increase in patient activity. In one example, the processing circuit 210 can initiate control pulses and corresponding ECAP sensing in response to a signal from the sensor(s) 222 indicating that patient activity has exceeded an activity threshold. Conversely, the processing circuit 210 can decrease a frequency of control pulses and ECAP sensing in response to detecting a decrease in patient activity. For example, in response to the sensor(s) 222 no longer indicating that sensed patient activity exceeds a threshold, the processing circuit 210 can pause or cease delivery of control pulses and ECAP sensing. In this way, the processing circuit 210 can dynamically deliver control pulses and sense ECAP signals based on patient activity to reduce power consumption of the system when the distance of the electrodes from neurons is unlikely to change and to increase the system’s responsiveness to changes in ECAPs when the distance of the electrodes from neurons is likely to change. The IMD 200 can include additional sensors that are within the housing of the IMD 200 and / or coupled via the lead 130 or one of the other leads. Additionally, the IMD 200 can wirelessly receive sensor signals from remote sensors, e.g., via the communication circuit 208. In some examples, one or more of these remote sensors can be located outside the patient’s body (e.g., carried on an external surface of the skin, attached to clothing, or otherwise positioned outside the patient 105). In some examples, the signals from the sensor(s) 222 indicate a position or body state (e.g., sleeping, awake, sitting, standing, etc.), and the processing circuit 210 can select a target ECAP characteristic value according to the indicated position or body state.

[0100] The power source 224 is configured to deliver operating power to the components of the IMD 200. The power source 224 can include a battery and power generation circuitry to produce the operating power. In some examples, the battery is rechargeable to allow longer operation. In some examples, recharging is accomplished through inductive interactions between an external charger and an inductive charging coil within the IMD 200. The power source 224 can include any one or more of a variety of different battery types such as nickel cadmium, and lithium ion.

[0101] Figure 3is a block diagram illustrating an example configuration of components of an external programmer 300 in accordance with one or more techniques of this disclosure. The external programmer 300 can be an example of the external programmer 150 of Figure 1 Although the external programmer 300 can generally be described as a handheld device, the external programmer 300 can be a larger portable device or a more fixed device. Additionally, in other examples, the external programmer 300 can be included as part of, or include the functionality of, an external charging device. As Figure 3 As illustrated in FIG. 3, the external programmer 300 can include a processing circuit 352, a storage device 354, a user interface 356, a communication circuit 358, and a power source 360. The storage device 354 can store instructions that, when executed by the processing circuit 352, cause the processing circuit 352 and the external programmer 300 to provide the functionality attributed to the external programmer 300 in this disclosure. Each of these components, circuits, or modules can include circuitry configured to perform some or all of the functions described herein. For example, the processing circuit 352 can include processing circuitry configured to perform the processes discussed with respect to the processing circuit 352.

[0102] Generally, the external programmer 300 includes any suitable hardware arrangement, alone or in combination with software and / or firmware, to perform the techniques attributed to the external programmer 300, as well as the processing circuit 352, the user interface 356, and the communication circuit 358 of the external programmer 300. In various examples, the external programmer 300 can include one or more processors, such as one or more microprocessors, DSPs, ASICs, FPGAs, or any other equivalent integrated or discrete logic circuitry, as well as any combinations of such components. In various examples, the external programmer 300 can also include a storage device 354, such as RAM, ROM, PROM, EPROM, EEPROM, flash memory, hard disks, CD-ROMs, including executable instructions to cause the one or more processors to perform the actions attributed to the processors. Additionally, although the processing circuit 352 and the communication circuit 358 are described as separate modules, in some examples, the processing circuit 352 and the communication circuit 358 are functionally integrated. In some examples, the processing circuit 352 and the communication circuit 358 correspond to separate hardware units, such as ASICs, DSPs, FPGAs, or other hardware units.

[0103] The storage device 354 (e.g., a memory device) can store instructions that, when executed by the processing circuit 352, cause the processing circuit 352 and the external programmer 300 to provide the functionality attributed to the external programmer 300 in this disclosure. For example, the storage device 354 can include instructions that cause the processing circuit 352 to obtain a parameter set from a memory, select a spatial electrode movement pattern, or receive a user input and send a corresponding command to the IMD 200, or instructions for any other functionality. Additionally, the storage device 354 can include a plurality of programs, where each program includes a parameter set defining a stimulation pulse, such as a control pulse and / or an informative pulse. The storage device 354 can also store data received from a medical device, such as the IMD 110. For example, the storage device 354 can store ECAP-related data recorded at a sensing module of the medical device, and the storage device 354 can also store data from one or more sensors of the medical device. The ECAP-related data can include ECAP information transmitted from an implantable medical device, such as the IMD 110.

[0104] The user interface 356 can include buttons or a keypad, lights, voice commands speakers, a display such as a liquid crystal (LCD), light emitting diode (LED), or organic light emitting diode (OLED). In some examples, the display includes a touch screen. The user interface 356 can be configured to display any information related to the delivery of electrical stimulation, a recognized patient behavior, a sensed patient parameter value, a patient behavior criterion, or any other such information. Additionally, as described herein, the processing circuit 352 can control the user interface 356 to present a graphical representation of ECAP information transmitted by the IMD 110. The user interface 356 can also receive user input via the user interface 356. The input can be in the form of, for example, pressing a button on a keypad or selecting an icon from a touch screen. The input can request that electrical stimulation be started or stopped, the input can request a new spatial electrode movement pattern or a change to an existing spatial electrode movement pattern, the input can request some other change to the delivery of electrical stimulation.

[0105] The communication circuit 358 can support wireless communication between the medical device and the external programmer 300 under the control of the processing circuit 352. The communication circuit 358 can also be configured to communicate with another computing device via a wireless communication technique or directly through a wired connection. In some examples, the communication circuit 358 provides wireless communication via RF or proximity inductive media. In some examples, the communication circuit 358 includes an antenna, which can take a variety of forms, such as an internal or external antenna.

[0106] Examples of local wireless communication techniques that can be employed to facilitate communication between the external programmer 300 and the IMD 110 include RF communication according to the 802.11 or Bluetooth® standard, including any a set of specifications, or other standard or proprietary telemetry protocol. In this way, other external devices can be able to communicate with external programmer 300 without the need to establish a secure wireless connection. As described herein, communication circuitry 358 can be configured to transmit the spatial electrode movement pattern or other stimulation parameter values to IMD 110 for use in delivering electrical stimulation therapy.

[0107] In some examples, the selection of the stimulation parameter or therapy stimulation program is transmitted to a medical device for delivery to a patient (e.g., patient 105). In other examples, the therapy can include a medication, activity, or other instruction that patient 105 must perform themselves or that a caregiver performs for patient 105. In some examples, external programmer 300 provides a visual, audible, and / or tactile notification indicating that there is a new instruction. In some examples, external programmer 300 requires receiving user input confirming that the instruction has been completed. Figure 1

[0108] According to the techniques of this disclosure, user interface 356 of external programmer 300 can also receive user input associated with a trigger signal to be transmitted to IMD 110 to store ECAP information in long-term memory. For example, the user input can explicitly request ECAP information that is being recorded at the time. In other examples, the user input can indicate that an event has occurred, such as a patient motion (e.g., a sneeze, a cough, a laugh, a change in posture, etc.) that results in an unwanted stimulation sensation or loss of therapy or any other situation related to the stimulation therapy (e.g., any sensation or loss of therapy that the patient or clinician can be interested in). In this way, the patient can provide the user input at any time that the patient feels an unwanted, "funny," or sensation that the patient can be interested in in any way. Processing circuitry 352 can cause communication circuitry 358 to transmit the trigger signal to IMD 110. Processing circuitry 352 can then receive the stored ECAP information from IMD 110 via communication circuitry 358.

[0109] Power source 360 is configured to deliver operating power to the components of external programmer 300. Power source 360 can include a battery and power generation circuitry to produce the operating power. In some examples, the battery is rechargeable to allow prolonged operation. Charging can come about through an external rechargeable cradle or docking station that is connected to an alternating current (AC) outlet, cordless battery charging in which an external charger generates an induction field that enables external programmer 300 to receive power for charging its batteries without being physically connected to the charger, or a combination thereof. Additionally, power source 360 can be directly coupled to an alternating current (AC) outlet.

[0110] Figure 3 ​The architecture of the external programmer 300 shown in the illustration is for illustrative purposes only. The technologies described in this disclosure can be used in… Figure 3 The example external programmer 300 is implemented, but it can also be implemented in other types of systems not specifically described herein. Nothing in this disclosure should be construed as limiting these techniques to... Figure 3 The example architecture shown.

[0111] Figure 4 This is an example evoked compound action potential (ECAP) curve 402 for sensing a corresponding stimulus impulse according to one or more techniques of this disclosure. Figure 4 As shown, graph 402 illustrates example ECAP signals 404 (dashed line) and 406 (solid line). In some examples, each of ECAP signals 404 and 406 is sensed from a control pulse delivered from the protective cathode, wherein the control pulse is a biphase pulse comprising the phase-to-phase interval between each positive and negative phase of the pulse. In some such examples, the protective cathode comprises an 8-electrode lead (e.g., ...). Figure 1 The stimulation electrode is located at the end of lead 130, while two sensing electrodes are provided at the other end of the 8-electrode lead. The ECAP signal 404 represents the sensed voltage amplitude as a result of a sub-detection threshold stimulation pulse or a stimulation pulse that results in an undetectable ECAP. A peak 408 is detected in the ECAP signal 404, and this peak represents an artifact of the delivered control pulse. However, no propagating signal is detected after the artifact in the ECAP signal 404 because the control pulse is a sub-detection threshold stimulation pulse.

[0112] In contrast to ECAP signal 404, ECAP signal 406 (e.g., a waveform) represents the voltage amplitude detected from a supra-detection stimulation threshold control pulse. A peak 408 of ECAP signal 406 is detected, and represents an artifact of the delivered control pulse. ECAP signal 406 also includes peaks PI, Nl, and P2 after peak 408, which are three representative peaks of a propagating action potential from an ECAP. The example duration of the artifact and peaks PI, Nl, and P2 is about 1 millisecond (ms). When an ECAP of ECAP signal 406 is detected, different characteristics can be identified. For example, a characteristic of the ECAP can be the amplitude between Nl and P2. The Nl-P2 amplitude can be easily detected even though the artifact can affect the relatively larger signal of PI, and the Nl-P2 amplitude can be least affected by electronic drift in the signal. In other examples, a characteristic of the ECAP used to control a subsequent control pulse and / or informed pulse can be the amplitude of PI, Nl, or P2 relative to a neutral or zero voltage. In some examples, a characteristic of the ECAP used to control a subsequent control pulse or informed pulse is a sum of two or more of peaks PI, Nl, or P2. In other examples, a characteristic of ECAP signal 406 can be an area under one or more of peaks PI, Nl, and / or P2. In other examples, a characteristic of the ECAP can be a ratio of one of peaks PI, Nl, or P2 to another of these peaks. In some examples, a characteristic of the ECAP is a slope between two points in the ECAP signal, such as the slope between Nl and P2. In other examples, a characteristic of the ECAP can be a time between two points of the ECAP, such as the time between Nl and P2. The time between the time of delivery of a stimulation pulse and a point in the ECAP signal can be referred to as a latency of the ECAP, and can be indicative of the type of fiber captured by the stimulation pulse (e.g., control pulse). An ECAP signal with a lower latency (i.e., a smaller latency value) indicates a higher percentage of neural fibers with a higher signal propagation speed, while an ECAP signal with a higher latency (i.e., a larger latency value) indicates a higher percentage of neural fibers with a slower signal propagation speed. Latency can also refer to the time between detecting an electrical feature at one electrode and then detecting the electrical feature again at a different electrode. This time or latency is inversely proportional to the conduction velocity of the neural fiber. Other characteristics of the ECAP signal can be used in other examples.

[0113] The amplitude of the ECAP signal will increase with an increase in the amplitude of the control pulse, so long as the pulse amplitude is greater than a threshold value, thereby depolarizing the nerve and propagating the signal. When a notification pulse is determined to be delivered to the patient 105 as an effective therapy, a target ECAP characteristic (e.g., a target ECAP amplitude) can be determined from the ECAP signal detected from the control pulse. Thus, the ECAP signal is representative of the distance between the stimulation electrode and the nerve, which is appropriate for the stimulation parameter values of the notification pulse delivered at the time. Accordingly, the IMD 110 can attempt to use the detected change in the measured ECAP characteristic value to change the therapy pulse parameter values and maintain the target ECAP characteristic value during therapy pulse delivery.

[0114] Figure 5A A timing diagram 500A illustrating examples of electrical stimulation pulses, corresponding stimulation signals, and corresponding sensed ECAPs in accordance with one or more techniques of this disclosure. For convenience, reference is made to the IMD 200 of Figure 2 is described. Figure 5A As shown, the timing diagram 500A includes a first channel 502, a plurality of stimulation pulses 504A-504N (collectively, “stimulation pulses 504”), a second channel 506, a plurality of corresponding ECAPs 508A-508N (collectively, “ECAPs 508”), and a plurality of stimulation signals 509A-509N (collectively, “stimulation signals 509”). In some examples, the stimulation pulses 504 can represent control pulses configured to elicit ECAPs 508 that can be detected by the IMD 200, but this is not required. The stimulation pulses 504 can represent any type of pulse deliverable by the IMD 200. In examples where the IMD 200 delivers therapy with control pulses instead of or without notification pulses, the stimulation pulses 504 can represent therapy pulses. Figure 5A

[0115] ​The first channel 502 is a time / voltage (and / or current) graph indicating the voltage (or current) of at least one of the electrodes 232, 234. In one example, the stimulation electrodes of the first channel 502 can be located on an opposite side of the lead from the sensing electrodes of the second channel 506. The stimulation pulses 504 can be electrical pulses delivered to the patient’s spinal cord by at least one of the electrodes 232, 234, and the stimulation pulses 504 can be balanced biphasic square wave pulses with an interphase interval. In other words, each stimulation pulse 504 is shown as having a negative phase and a positive phase separated by an interphase interval. For example, the amount of time and the magnitude of the negative voltage of the stimulation pulse 504 can be the same as its positive voltage. Note that the negative voltage phase can precede or follow the positive voltage phase. The stimulation pulses 504 can be delivered according to a test stimulation program 216 stored in the storage device 212 of the IMD 200, and the ECAP test stimulation program can be updated according to user input via an external programmer and / or can be updated according to signals from the sensor(s) 222. In one example, the stimulation pulses 504 can have a pulse width (e.g., the total time of the positive phase, negative phase, and interphase interval) of less than about 300 microseconds. In another example, the stimulation pulses 504 can have a pulse width of about 100 ps for each phase of the biphasic pulse. As Figure 5A shown, the stimulation pulses 504 can be delivered via the channel 502. The delivery of the stimulation pulses 504 can be delivered by the lead 230 in a protected cathode electrode combination. For example, if the lead 230 is a linear 8 electrode lead, the protected cathode combination is the central cathode electrode and the anode electrode immediately adjacent to the cathode electrode.

[0116] The second channel 506 is a time / voltage (and / or current) graph indicating the voltage (or current) of at least one of the electrodes 232, 234. In one example, the electrodes of the second channel 506 can be located on an opposite side of the lead from the electrodes of the first channel 502. In response to the stimulation pulses 504, ECAPs 508 can be sensed from the patient’s spinal cord at the electrodes 232, 234. The ECAPs 508 are electrical signals that can propagate along the nerve away from the origin of the stimulation pulses 504. In one example, the ECAPs 508 are sensed by a different electrode than the electrode used to deliver the stimulation pulses 504. As Figure 5A shown, the ECAPs 508 can be recorded on the second channel 506.

[0117] Stimulation signals 509A, 509B, and 509N can be sensed by lead 230 and sensing circuitry 206 and can be sensed during the same time period as the delivery of stimulation pulses 504. Because the stimulation signals can have a greater amplitude and strength than ECAPs 508, any ECAPs reaching IMD 200 during the occurrence of stimulation signals 509 can not be sufficiently sensed by sensing circuitry 206 of IMD 200. However, because each ECAP 508 or at least a portion of ECAP 508 used as feedback for stimulation pulses 504 drops after each stimulation pulse 504 is completed, ECAPs 508 can be sufficiently sensed by sensing circuitry 206. As shown in Figure 5A stimulation signals 509 and ECAPs 508 can be recorded on channel 506. In some examples, ECAPs 508 can not follow the corresponding stimulation signals 509 when the ECAPs are not elicited by stimulation pulses 504 or the amplitude of the ECAPs is too low (e.g., below a detection threshold) to be detected.

[0118] Figure 5B is a timing diagram 500B illustrating one example of electrical stimulation pulses, corresponding stimulation signals, and corresponding sensed ECAPs in accordance with one or more techniques of this disclosure. For convenience, IMD 200 of Figure 2 is described with reference to IMD 200 of Figure 5B . As shown, timing diagram 500B includes a first channel 510, a plurality of control pulses 512A-512N (collectively, “control pulses 512”), a second channel 520, a plurality of notification pulses 524A-524N (collectively, “notification pulses 524”) including passive charging phases 526A-526N (collectively, “passive charging phases 526”), a third channel 530, a plurality of corresponding ECAPs 536A-536N (collectively, “ECAPs 536”), and a plurality of stimulation signals 538A-538N (collectively, “stimulation signals 538”).

[0119] The first channel 510 is a time / voltage (and / or current) graph indicating the voltage (or current) of at least one of the electrodes 232, 234. In one example, the stimulation electrodes of the first channel 510 can be located on the opposite side of the lead from the sensing electrodes of the third channel 530. The control pulses 512 can be electrical pulses delivered to the patient’s spinal cord by at least one of the electrodes 232, 234, and the control pulses 512 can be balanced biphasic square wave pulses with an interphase gap. In other words, each control pulse 512 is shown as having a negative phase and a positive phase separated by an interphase gap. For example, the amount of time of the negative voltage of the control pulse 512 can be the same as its positive voltage. Note that the negative voltage phase can precede or follow the positive voltage phase. The control pulses 512 can be delivered according to an ECAP test stimulation program stored in the storage device 212 of the IMD 200, and the ECAP test stimulation program can be updated according to user input via an external programmer and / or can be updated according to signals from the sensor(s) 222. In one example, the control pulses 512 can have a pulse width of 300 microseconds (e.g., the total time of the positive phase, negative phase, and interphase gap is 300 microseconds). In another example, the control pulses 512 can have a pulse width of approximately 100 ps for each phase of the biphasic pulse. As Figure 5B shown, the control pulses 512 can be delivered via the first channel 510. The delivery of the control pulses 512 can be delivered by the lead 230 in a protected cathode electrode combination. For example, if the lead 230 is a linear 8 electrode lead, the protected cathode combination is the central cathode electrode and the anode electrode immediately adjacent to the cathode electrode.

[0120] The second channel 520 is a time / voltage (and / or current) graph indicating the voltage (or current) of at least one of the electrodes 232, 234 used for the informing pulses. In one example, the electrodes of the second channel 520 can partially or completely share common electrodes with the electrodes of the first channel 510 and the third channel 530. The informing pulses 524 can also be delivered by the same lead 230 configured to deliver the control pulses 512. The informing pulses 524 can be interleaved with the control pulses 512 such that the two types of pulses are not delivered during overlapping time periods. However, the informing pulses 524 can or can not be delivered by the exact same electrodes as the control pulses 512. The informing pulses 524 can be monophasic pulses having a pulse width greater than about 300 ps and less than about 1000 ps. In fact, the informing pulses 524 can be configured to have a longer pulse width than the control pulses 512. As Figure 5B shown, the informing pulses 524 can be delivered on the second channel 520.

[0121] The notification pulses 524 can be configured to be passive charging. For example, each notification pulse 524 can be followed by a passive charging phase 526 to equalize the charge on the stimulation electrodes. Unlike pulses configured for active charging where residual charge on the tissue after a stimulation pulse is immediately removed from the tissue by oppositely applied charge, passive charging allows the tissue to naturally discharge to some reference voltage (e.g., ground voltage or rail voltage) after the therapy pulse terminates. In some examples, the electrodes of the medical device can be grounded at the medical device body. In this case, after the notification pulse 524 terminates, the charge on the tissue surrounding the electrodes can dissipate to the medical device, resulting in a rapid decay of the residual charge on the tissue after the pulse terminates. This rapid decay is illustrated in the passive charging phase 526. The passive charging phase 526 can have a duration in addition to the pulse width of the preceding notification pulse 524. In other examples (not depicted in FIG. 5), the notification pulse 524 can be a biphasic pulse with a positive phase and a negative phase (and in some examples, with an interphase interval between each phase), which can be referred to as a pulse that includes active charging. The notification pulse as a biphasic pulse can or can not be followed by a passive charging phase. Figure 5B

[0122] The third channel 530 is a time / voltage (and / or current) graph indicating the voltage (or current) of at least one of the electrodes 232, 234. In one example, the electrode of the third channel 530 can be on an opposite side of the lead from the electrode of the first channel 510. In response to the control pulse 512, an ECAP 536 can be sensed at the electrodes 232, 234 from the patient’s spinal cord. The ECAP 536 is an electrical signal that can propagate along the nerve away from the origin of the control pulse 512. In one example, the ECAP 536 is sensed by a different electrode than the electrode used to deliver the control pulse 512. As shown, the ECAP 536 can be recorded on the third channel 530. Figure 5B

[0123] The stimulation signals 538A, 538B, and 538N can be sensed by the lead 230 and can be sensed during the same time period as the delivery of the control pulses 512 and the notification pulses 524. Because the stimulation signals can have a greater amplitude and strength than the ECAP 536, any ECAP reaching the IMD 200 during the occurrence of the stimulation signals 538 can not be sufficiently sensed by the sensing circuit 206 of the IMD 200. However, because each ECAP 536 falls after each control pulse 512 completes and before the delivery of the next notification pulse 524, the ECAP 536 can be sufficiently sensed by the sensing circuit 206. As shown, the stimulation signals 538 and the ECAP 536 can be recorded on the channel 530. Figure 5B ​​​

[0124] Figure 6A A timing diagram 600A illustrates an example of an electrical stimulation pulse, a corresponding stimulation signal, and a corresponding sensed ECAP, according to one or more techniques of this disclosure. For convenience, refer to... Figure 2 IMD 200 description Figure 6A As shown in the figure, timing diagram 600A includes a first channel 602, multiple stimulation pulses 604A-604N (collectively referred to as "stimulation pulses 604"), a second channel 606, multiple corresponding ECAPs 608A-608N (collectively referred to as "ECAPs 608"), and multiple stimulation signals 609A-609N (collectively referred to as "stimulation signals 609"). In some examples, stimulation pulse 604 may represent a control pulse configured to elicit ECAPs 608 that can be detected by IMD 200, but this is not necessary. Stimulation pulse 604 can represent any type of pulse that can be delivered by IMD 200. Figure 6A In the example, the IMD 200 can deliver treatment using a control pulse instead of a notification pulse or without using a notification pulse.

[0125] Figure 6A The timing diagram 600A can be used with Figure 5A The timing diagram 500A is basically the same, the difference being that stimulation pulses 604A and 604N did not induce ECAPs detectable by the IMD 200. Although stimulation pulse 604B emitted ECAP 608B detectable by the IMD 200, Figure 6A In some examples, there may be situations where the IMD 200 does not sense enough detectable ECAP for treatment determination. In such cases, the IMD 200 can determine one or more characteristics of the stimulation signal 609 to determine one or more parameters of the upcoming stimulation pulse following the stimulation pulse 604N. For example, the IMD 200 can determine the amplitude of at least a portion of each stimulation signal of the stimulation signal 609 and determine one or more parameters of the upcoming stimulation pulse based on the determined amplitude. Although the stimulation signal 609 is shown as a square pulse, in some examples, the stimulation signal 609 may include other shapes and / or waveforms. In some examples, each stimulation signal in the stimulation signal 509 may include two or more phases. The processing circuitry 210 of the IMD 200 can analyze two or more phases of the stimulation signal 509 to determine the treatment.

[0126] Figure 6B Timing diagram 600B illustrates another example of an electrical stimulation pulse, a corresponding stimulation signal, and a corresponding sensed ECAP, according to one or more techniques disclosed herein. For convenience, refer to... Figure 2 IMD 200 description Figure 6BAs shown, timing diagram 600B includes a first channel 610, a plurality of control pulses 612A-612N (collectively, "control pulses 612"), a second channel 620, a plurality of notification pulses 624A-624N (collectively, "notification pulses 624") including passive charging phases 626A-626N (collectively, "passive charging phases 626"), a third channel 630, a plurality of corresponding ECAPs 636A-636N (collectively, "ECAPs 636"), and a plurality of stimulation signals 638A-638N (collectively, "stimulation signals 638").

[0127] Figure 6B Timing diagram 600B can be substantially the same as timing diagram 500B of Figure 5B , with the exception that control pulse 612A and control pulse 612N do not elicit an ECAP that is detectable by IMD 200. Although control pulse 612B emits an ECAP 636B that is detectable by IMD 200, in the example of Figure 6B , there can be instances in which IMD 200 does not sense enough detectable ECAPs for therapy determination. As such, IMD 200 can determine one or more characteristics of stimulation signals 638 in order to determine one or more parameters of a stimulation pulse that is forthcoming after control pulse 612N. For example, IMD 200 can determine an amplitude of at least a portion of each of stimulation signals 638 and determine one or more parameters of the forthcoming stimulation pulse based on the determined amplitudes. Although stimulation signals 638 are illustrated as square pulses, in some examples, stimulation signals 639 can include other shapes and / or waveforms. In some examples, each of stimulation signals 638 can include two or more phases. Processing circuitry 210 of IMD 200 can analyze the two or more phases of stimulation signals 638 to determine therapy.

[0128] Figure 7 Timing diagram 700 illustrates another example of electrical stimulation pulses, corresponding stimulation signals, and corresponding ECAPs in accordance with one or more techniques of this disclosure. For convenience, IMD 200 of Figure 2 is described with reference to Figure 7 . As shown, timing diagram 700 includes a first channel 710, a plurality of control pulses 712A-712N (collectively, "control pulses 712"), a second channel 720, a plurality of notification pulses 724A-724B (collectively, "notification pulses 724") including passive charging phases 726A-726B (collectively, "passive charging phases 726"), a third channel 730, a plurality of corresponding ECAPs 736A-736N (collectively, "ECAPs 736"), and a plurality of stimulation interference signals 738A-738N (collectively, "stimulation interference signals 738").Figure 7 may be substantially similar to Figure 5B , except for the differences detailed below.

[0129] Two or more (e.g., two) control pulses 712 can be delivered during each of a plurality of time events (e.g., windows), and each time event represents a time between two consecutive notification pulses 724. For example, during each time event, a first control pulse can be followed by a first respective ECAP, and after the first respective ECAP is complete, a second control pulse can be followed by a second respective ECAP. A notification pulse can begin after the second respective ECAP. In other examples, not shown here, three or more control pulses 712 can be delivered during each of a plurality of time events, and respective ECAP signals are sensed.

[0130] Figure 8 is a timing diagram 800 illustrating another example of electrical stimulation pulses, respective stimulation signals, and respective ECAPs in accordance with one or more techniques of this disclosure. For convenience, reference is made to Figure 2 IMD 200. Figure 8 As shown, timing diagram 800 includes a first channel 810, a plurality of control pulses 812A-812N (collectively, “control pulses 812”), a second channel 820, a plurality of notification pulses 824A-824B (collectively, “notification pulses 824”) including passive charging phases 826A-826B (collectively, “passive charging phases 826”), a third channel 830, respective ECAPs 836B (collectively, “ECAPs 836”), and a plurality of stimulation interference signals 838A-838N (collectively, “stimulation interference signals 838”). Figure 8 Timing diagram 800 can be substantially the same as timing diagram 700 of Figure 7 with the exception that control pulses 812A and control pulses 812N do not evoke ECAPs that are detectable by IMD 200. Although control pulse 812B emits an ECAP 836B that is detectable by IMD 200, in the example of Figure 8 there can be instances in which IMD 200 does not sense sufficient detectable ECAPs for therapy determination. As such, IMD 200 can determine one or more characteristics of stimulation signals 838 in order to determine one or more parameters of a stimulation pulse forthcoming after control pulse 812N.

[0131] Figure 9 is a flowchart illustrating example operations for controlling stimulation based on one or more sensed ECAPs in accordance with one or more techniques of this disclosure. For convenience, reference is made to Figure 2 IMD 200. Figure 9.However, Figure 9 The technology can be performed by different components of the IMD 200 or by additional or alternative medical devices.

[0132] The stimulation generation circuit 202 of the IMD 200 can deliver electrical stimulation therapy to a patient (e.g., patient 105). To control the electrical stimulation therapy, the processing circuit 210 can guide the delivery of at least some stimulation pulses according to a treatment stimulation program 214 stored in the storage device 212, wherein the electrical stimulation therapy may include multiple control pulses and / or notification pulses. In some cases, the notification pulses may generate an ECAP that can be detected by the IMD 200. However, in other cases, the polarization of the notification pulses may interfere with the sensing of the ECAP in response to the notification pulses. In some examples, to induce an ECAP that can be detected by the IMD 200, the stimulation generation circuit 202 delivers multiple control pulses, which are interleaved with at least some of the notification pulses. The processing circuit 210 can control the delivery of the control pulses according to an ECAP testing stimulation program or an ECAP storage instruction 216. Because the control pulses can be interleaved with the notification pulses, the sensing circuit 206 of the IMD 200 can detect multiple ECAPs. The sensing circuit 206 is configured to detect each of the multiple ECAPs after one of the control pulses and before a subsequent notification pulse of the multiple notification pulses. In this way, the IMD 200 can induce multiple ECAPs in the target tissue by delivering control pulses, without the notification pulses interfering with the IMD 200's sensing of the ECAPs.

[0133] like Figure 9 As shown, processing circuit 210 instructs stimulation generation circuit 202 to deliver control pulses (902). Stimulation generation circuit 202 can deliver control pulses to target tissue of patient 105 via any combination of electrodes 232, 234 of lead 230. In some examples, the control pulse may include a balanced biphasic square wave pulse employing an active charging phase. However, in other examples, the control pulse may include a monophasic pulse followed by a passive charging phase. In other examples, the control pulse may include an unbalanced biphasic portion and a passive charging portion. Although not required, the biphasic control pulse may include an interphase interval between the positive and negative phases to facilitate nerve impulse propagation in response to the first phase of the biphasic pulse. The control pulse may have a pulse width of 300 μs, such as a biphasic pulse with a duration of approximately 100 μs per phase.

[0134] After delivering the control pulse, IMD 200 attempts to detect an ECAP (904). For example, sensing circuitry 206 can monitor signals from any combination of electrodes 232, 234 of lead 230. In some examples, sensing circuitry 206 detects an ECAP from a particular combination of electrodes 232, 234. In some cases, the particular combination of electrodes used to sense the ECAP includes different electrodes than the set of electrodes 232, 234 used to deliver the stimulation pulse. Alternatively, in other cases, the particular combination of electrodes used to sense the ECAP includes at least one of the same electrodes as the set of electrodes used to deliver the stimulation pulse to patient 105. In some examples, the particular combination of electrodes used to sense the ECAP can be on an opposite side of lead 230 from the particular combination of electrodes used to deliver the stimulation pulse. IMD 200 can detect an ECAP in response to the control pulse. IMD 200 can measure one or more characteristics of the responsive ECAP, such as an ECAP amplitude, an ECAP duration, a peak-to-peak duration, or any combination thereof. For example, to measure an amplitude of an ECAP, IMD 200 can determine a voltage difference between the Nl ECAP peak and the P2 ECAP peak. Processing circuitry 210 can store the ECAP signal, characteristic values, or any other relevant data as ECAP information.

[0135] At block 906, processing circuitry 210 determines whether the ECAP amplitude of the responsive ECAP is greater than the ECAP amplitude threshold. If the ECAP amplitude is greater than the ECAP amplitude threshold (“YES” branch of block 906), processing circuitry 210 activates / continues a decrementing mode in IMD 200 (908). For example, if the decrementing mode is already “on” in IMD 200 when processing circuitry determines that the ECAP amplitude is greater than the ECAP amplitude threshold, processing circuitry 210 maintains IMD 200 in the decrementing mode. If the decrementing mode is “off’ in IMD 200 when processing circuitry determines that the ECAP amplitude is greater than the ECAP amplitude threshold, processing circuitry 210 activates the decrementing mode. In some examples, the decrementing mode can be stored in storage device 212 as part of control strategy 213. The decrementing mode can be a set of instructions that cause IMD 200 to decrease one or more parameter values of each successive notification pulse from a respective predetermined value (e.g., a value determined by a stimulation program) and decrease one or more parameter values of each successive control pulse from a respective predetermined value (e.g., a value determined by a stimulation program). In other words, the parameter values can be decreased from the values that would be used by IMD 200 to define the respective pulses if the ECAP amplitude did not exceed the threshold ECAP amplitude. For example, when the decrementing mode is activated, processing circuitry 210 can decrease the current amplitude of each successive notification pulse delivered by IMD 200 and decrease the current amplitude of each successive control pulse delivered by IMD 200. After processing circuitry 210 activates / continues the decrementing mode, example operations can return to block 902 and IMD 200 can deliver another control pulse.

[0136] If the ECAP amplitude is not greater than the ECAP amplitude threshold (“NO” branch of block 906), processing circuitry 210 determines whether the decrementing mode is activated in IMD 200 (910). If the decrementing mode is activated in IMD 200 (“YES” branch of block 910), processing circuitry 210 deactivates the decrementing mode and activates an incrementing mode in IMD 200 (912). In some examples, the incrementing mode can be stored in storage device 212 as part of control strategy 213. The incrementing mode can be a set of instructions that cause IMD 200 to increase one or more parameter values of each successive notification pulse and increase one or more parameter values of each successive control pulse. For example, when the incrementing mode is activated, processing circuitry 210 can increase the current amplitude of each successive notification pulse delivered by IMD 200 and increase the current amplitude of each successive control pulse delivered by IMD 200. After processing circuitry 210 deactivates the decrementing mode and activates the incrementing mode, example operations can return to block 902 and IMD 200 can deliver another control pulse.

[0137] When Figure 9When the example operation reaches box 910 and the decrementing mode is not activated in IMD 200 (the "No" branch of box 910), processing circuitry 210 determines whether an incrementing mode is activated in IMD 200 (914). If the incrementing mode is activated in IMD 200 (the "Yes" branch of box 914), processing circuitry 210 can complete the incrementing mode in IMD 200 (916). In some examples, to complete the incrementing mode, processing circuitry 210 may increase the current amplitude of each successive notification pulse delivered by IMD 200 and increase the current amplitude of each successive control pulse delivered by IMD 200 until the pulse amplitude of the stimulation pulse reaches the current amplitude of the stimulation pulse delivered by IMD 200 before the decrementing mode was activated (e.g., a predetermined value that may be set by the stimulation program selected for treatment). In this way, the process may not be referred to as a fully closed-loop system. In other words, IMD 200 can monitor the high end (ECAP amplitude threshold) to adjust the stimulation pulse, without monitoring any low end of the sensed ECAP amplitude. For example, IMD 200 can continue to increase the current amplitude of successive notification pulses without any feedback from the sensed ECAP, unless the sensed ECAP value exceeds the ECAP amplitude threshold again. After processing circuitry 210 completes the incrementing mode, the example operation can return to block 902, and IMD 200 can deliver another control pulse. When Figure 9 When the example operation reaches box 914 and the incremental mode is not activated in IMD 200 (the "No" branch of box 914), the processing circuit 210 holds the stimulus (918) in IMD 200. Although Figure 9 The description covers both notification and control pulses, but it also addresses situations where the IMD200 only delivers control pulses to the patient (e.g., no notification pulses) for treatment. Figure 9 The technology is also applicable.

[0138] Figure 10 According to one or more techniques disclosed herein, a voltage / current / time graph 1000 is shown, which plots the control pulse current amplitude 1002, the notification pulse current amplitude 1004, the ECAP voltage amplitude 1008, and the second ECAP voltage amplitude 1010 as a function of time. Additionally, Figure 10 The threshold ECAP amplitude of 1006 is shown. For convenience, please refer to... Figure 2 IMD 200 description Figure 10 .However, Figure 10 The technology can be performed by different components of the IMD 200 or by additional or alternative medical devices.

[0139] Voltage / current / time plot 1000 illustrates the relationship between the sensed ECAP voltage amplitude and the stimulation current amplitude. For example, the control pulse current amplitude 1002 and the notification pulse current amplitude 1004 are plotted together with the ECAP voltage amplitude 1008 as a function of time, thus showing how the stimulation current amplitude varies relative to the ECAP voltage amplitude. In some examples, IMD 200 delivers multiple control pulses and multiple notification pulses, respectively, with control pulse current amplitude 1002 and notification pulse current amplitude 1004. Initially, IMD 200 may deliver a first set of control pulses, wherein IMD 200 delivers the first set of control pulses with a current amplitude I2. Additionally, IMD 200 may deliver a first set of notification pulses, wherein IMD 200 delivers the first set of control pulses with a current amplitude I1. I1 and I2 may be referred to as predetermined values ​​for the amplitudes of the corresponding control pulses and notification pulses. This predetermined value can be a programmed value or a value selected in another way, chosen by the stimulation procedure to at least partially define the stimulation pulse for the patient in the absence of transient conditions (e.g., when the ECAP amplitude is below a threshold ECAP value). The first set of control pulses and the first set of notification pulses can be delivered before time T1. In some examples, I1 is 8 mA and I2 is 4 mA. Although the control pulse current amplitude 1002 is shown as greater than the notification pulse current amplitude 1004, in other examples, the control pulse current amplitude 1002 may be less than or equal to the notification pulse current amplitude 1004.

[0140] During the delivery of the first set of control pulses and the first set of notification pulses, the IMD 200 can record the ECAP voltage amplitude 1008. During dynamic and transient conditions occurring in patient 105 (such as coughing, sneezing, laughing, Valsalva maneuver, leg raising, neck movement, or deep breathing), if the control pulse current amplitude 1002 and the notification pulse current amplitude 1004 remain constant, the ECAP voltage amplitude 1008 may increase. This increase in the ECAP voltage amplitude 1008 may be due to a decrease in the distance between the electrode and the nerve. For example, as... Figure 10 As shown, when the stimulation current amplitude remains constant, the ECAP voltage amplitude 1008 can increase before time T1. The increased ECAP voltage amplitude 1008 may indicate that the patient 105 is at risk of experiencing transient overstimulation due to the control pulses and notification pulses delivered by the IMD 200. To prevent the patient 105 from experiencing transient overstimulation, the IMD 200 can decrease the control pulse current amplitude 1002 and the notification pulse current amplitude 1004 in response to the ECAP voltage amplitude 1008 exceeding the threshold ECAP amplitude 1006. For example, if the IMD 200 senses that the ECAP voltage amplitude 1008 of the ECAP reaches or exceeds the threshold ECAP amplitude 1006, as... Figure 10If the ECAP voltage amplitude 1008 exceeds the threshold ECAP amplitude 1006, as shown at time Tl, then the IMD 200 can enter a decremental mode in which the control pulse current amplitude 1002 and the informed pulse current amplitude 1004 are reduced. In some examples, the threshold ECAP amplitude 1006 is selected from a range of about 5 microvolts (pV) to about 30 pV, or from a range of about 10 microvolts (pV) to about 20 pV. For example, the threshold ECAP amplitude 1006 is 15 pV. In other examples, the threshold ECAP amplitude 1006 is less than or equal to 5 pV or greater than or equal to 30 pV.

[0141] The IMD 200 can respond relatively quickly to an ECAP voltage amplitude 1008 that exceeds the threshold ECAP amplitude 1006. For example, the IMD can be configured to detect an ECAP amplitude that exceeds the threshold within 20 milliseconds (ms). If the IMD 200 delivers control pulses at a frequency of 50 Hz, then the time period including delivery of a control pulse and detection of a single sample of the resulting ECAP signal can be 20 ms or less. However, because the ECAP signal can occur within one or two milliseconds after delivery of a control pulse, the IMD 200 can be configured to detect an ECAP signal that exceeds the threshold ECAP amplitude within less than 10 ms. For transient conditions, such as a patient coughing or sneezing, these sampling periods are sufficient to identify an ECAP amplitude that exceeds the threshold and responsively reduce the amplitude of subsequent pulses before the ECAP amplitude reaches a higher level that can cause the patient discomfort.

[0142] In some cases, the decremental mode can be stored in the storage device 212 of the IMD 200 as part of the control strategy 213. In Figure 10In the illustrated example, the decrementing pattern is performed by the IMD 200 on a second set of control pulses and a second set of notification pulses occurring between time Tl to time T2. In some examples, to perform the decrementing pattern, the IMD 200 decreases the control pulse current amplitude 1002 of each control pulse in the second set of control pulses according to a first function with respect to time. In other words, the IMD 200 decreases each successive control pulse in the second set of control pulses in proportion to the amount of time that has elapsed since the previous control pulse. Additionally, during the decrementing pattern, the IMD 200 can decrease the notification pulse current amplitude 1004 of each notification pulse in the second set of notification pulses according to a second function with respect to time. Although linear first and second functions are illustrated, in other examples, the first and / or second functions can be non-linear, such as a logarithmic function (e.g., a rate of change that decreases over time), an exponential function (e.g., a rate of change that increases over time), a parabolic function, a step function, a plurality of different functions, etc. During the time period (e.g., time interval T2-Tl) in which the IMD 200 operates in the decrementing pattern, the ECAP voltage amplitude 1008 of an ECAP sensed by the IMD 200 can be greater than or equal to the threshold ECAP amplitude 1006.

[0143] In Figure 2 In the illustrated example, the IMD 200 can sense an ECAP at time T2, where the ECAP has an ECAP voltage amplitude 1008 that is less than the threshold ECAP amplitude 1006. In some cases, the ECAP sensed at time T2 can be the first ECAP sensed by the IMD 200 since the IMD 200 started the decrementing pattern at time Tl that has a lower threshold amplitude. Based on sensing the ECAP at time T2, the IMD 200 can deactivate the decrementing pattern and activate an incrementing pattern. In some cases, the incrementing pattern can be stored in the storage device 212 of the IMD 200 as part of the control strategy 213. The IMD 200 can perform the incrementing pattern on a third set of control pulses and a third set of notification pulses occurring between time T2 to time T3. In some examples, to perform the incrementing pattern, the IMD 200 increases the control pulse current amplitude 1002 of each control pulse in the third set of control pulses according to a third function with respect to time. In other words, the IMD 200 increases each successive control pulse in the third set of control pulses in proportion to the amount of time that has elapsed since the previous control pulse. Additionally, during the incrementing pattern, the IMD 200 can increase the notification pulse current amplitude 1004 of each notification pulse in the third set of notification pulses according to a fourth function with respect to time.

[0144] As Figure 10As shown, IMD 200 is configured to decrease the amplitude at a faster rate than the amplitude is increased after the ECAP voltage amplitude 1008 falls below the threshold ECAP amplitude 1006. In other examples, the rate of change during the decrementing and incrementing modes can be similar. In other examples, IMD 200 can be configured to increase the amplitude of the notification pulses and the control pulses at a faster rate than the amplitude is decreased. In other examples, the rate of change of the pulse amplitudes can be relatively instantaneous (e.g., very fast rates). For example, in response to the ECAP voltage amplitude 1008 exceeding the threshold ECAP amplitude 1006, IMD 200 can immediately reduce the amplitude of one or both of the control pulse current amplitude 1002 or the notification pulse current amplitude 1004 to a predetermined or calculated value. Then, in response to the ECAP voltage amplitude 1008 falling below the threshold ECAP amplitude 1006, IMD 200 can enter the incrementing mode as described above.

[0145] When the control pulse current amplitude 1002 and the notification pulse current amplitude 1004 return to the current amplitude I2 and the current amplitude II, respectively, IMD 200 can deactivate the incrementing mode and deliver stimulation pulses at a constant current amplitude. By decreasing stimulation in response to the ECAP amplitude exceeding a threshold and subsequently increasing stimulation in response to the ECAP amplitude falling below the threshold, IMD 200 can prevent or reduce the severity of transient overstimulation experienced by patient 105, whether by reducing the length, the relative intensity, or both, of the experienced transient overstimulation.

[0146] Figure 10 The techniques described are described in the context of IMD 200 delivering both control pulses and notification pulses. However, IMD 200 can apply the techniques of Figure 10 to situations in which IMD 200 delivers only control pulses to provide therapy to a patient. In this way, IMD 200 will similarly enter a decrementing mode or an incrementing mode for the control pulse current amplitude 1002 based on the detected ECAP voltage amplitude 1008 without adjusting the amplitude or other parameters of any other type of stimulation pulse.

[0147] Figure 11 is a flowchart illustrating example operations for controlling storage of ECAP information. With respect to IMD 200, processing circuit 210, and long-term memory 220, Figure 2 is described. However, Figure 11 the techniques of Figure 11 may be performed by different components of IMD 200, IMD 110, external programmer 150, or by additional or alternative medical devices.

[0148] As Figure 11As shown in the example, processing circuit 210 receives ECAP information (1100). Processing circuit 210 may receive ECAP information from sensing circuit 206. In some examples, processing circuit 210 may generate some or all of the ECAP information based on the ECAP signal received from sensing circuit 206. Typically, processing circuit 210 may store the ECAP information in temporary memory 218. If processing circuit 210 does not receive a trigger signal (the "No" branch of block 1102), processing circuit 210 may continue to receive ECAP information and continue normal functioning, such as adjusting stimulation parameters based on ECAP characteristic values.

[0149] If processing circuitry 210 does receive a trigger signal (the "Yes" branch of block 1102), then processing circuitry 210 stores at least a portion of the ECAP information in memory (1104). For example, processing circuitry 210 may move at least a portion of the ECAP information from temporary memory 218 to long-term memory 220. In some examples, processing circuitry 210 may store information other than ECAP information. For example, processing circuitry 210 may also store acceleration data (e.g., attitude state and / or activity information) along with ECAP information. For example, processing circuitry 210 may also store timestamps or other data along with ECAP information and any other information to associate said information with concurrently occurring events.

[0150] Figure 12 This is a flowchart illustrating an example operation for sensing ECAP signals and storing ECAP information. About Figure 2 The IMD 200, processing circuitry 210, and long-term memory 220 are described Figure 12 .However, Figure 12 The technology can be performed by different components of the IMD 200, IMD 110, external programmer 150, or by additional or alternative medical devices.

[0151] like Figure 12 As shown in the example, processing circuit 210 controls stimulation generation circuit 202 to deliver stimulation pulses (1200). The stimulation pulses may or may not be configured to aid treatment, but an ECAP signal can be detected as a result of the stimulation pulses. Sensing circuit 206 senses the generated ECAP signal (1202). Processing circuit 210 then receives ECAP information (1204) from sensing circuit 206. The ECAP information may be a digitized waveform or include pre-determined ECAP characteristic values. Processing circuit 210 then stores the received ECAP information in temporary memory 2018 (1206).

[0152] If processing circuitry 210 does not receive a trigger signal ("No" branch of block 1208), processing circuitry 210 can continue delivering stimulation pulses (1200) and receiving ECAP information and continue normal functions such as adjusting stimulation parameters based on ECAP characteristic values. If processing circuitry 210 does receive a trigger signal ("Yes" branch of block 1208), processing circuitry 210 selects a portion of the ECAP information from temporary memory 218 (1210). For example, processing circuitry 210 can select ECAP information representative of ECAP signals sensed or a predetermined number of ECAP signals over a predetermined period of time (e.g., seconds, minutes, or longer). Processing circuitry 210 then stores the selected portion of the ECAP information in long-term memory 220 (1212). For example, processing circuitry 210 can move at least a portion of the ECAP information from temporary memory 218 to long-term memory 220. In some examples, processing circuitry 210 can continue to select ECAP information received within a predetermined period of time after receiving the trigger signal and store this new ECAP information in long-term memory 220. The ECAP information before and after the trigger signal can be tagged as associated with a single event. Processing circuitry 210 can then continue delivering another stimulation pulse (1200). In some examples, storing the selected portion of the ECAP information in long-term memory enables the system to determine and / or display data proximate in time to the trigger signal, which can be representative of the patient's condition before and / or after the trigger signal. In some examples, processing circuitry 210 can store other information in addition to the ECAP information in temporary and long-term memory upon request. For example, processing circuitry 210 can also store acceleration data (e.g., posture state and / or activity information) with the ECAP information. For example, processing circuitry 210 can also store timestamps or other data with the ECAP information and any other information to associate the information with a contemporaneous event.

[0153] Figure 13 is a flowchart illustrating example operations for adjusting a rate at which to sense ECAP signals. With respect to Figure 2 IMD 200, processing circuitry 210, and long-term memory 220 are described Figure 13 However, Figure 13 the techniques of

[0154] As Figure 12As shown by the example of FIG. 13, processing circuitry 210 controls stimulation generation circuitry 202 to deliver stimulation pulses (1300). The stimulation pulses can or can not be configured to facilitate therapy, but an ECAP signal can be detected as a result of the stimulation pulses. Sensing circuitry 206 senses the resulting ECAP signal (1302). Processing circuitry 210 then receives ECAP information from sensing circuitry 206 (1304). The ECAP information can be a digitized waveform or include ECAP characteristic values that have been determined.

[0155] If processing circuitry 210 does not receive a trigger signal (the "No" branch of block 1208), processing circuitry 210 can continue to deliver stimulation pulses (1300) and receive ECAP information and continue normal functions such as adjusting stimulation parameters based on ECAP characteristic values. If processing circuitry 210 does receive a trigger signal (the "Yes" branch of block 1306), processing circuitry 210 stores the ECAP information in memory, such as in long-term memory 202 (1308). In addition to storing the ECAP information, processing circuitry 210 increases the rate at which ECAP signals are sensed (1310). This increase in the rate of sensing can include increasing the rate at which processing circuitry 210 controls stimulation generation circuitry 202 to deliver stimulation pulses and the rate at which sensing circuitry 206 captures ECAP signals elicited from each delivered stimulation pulse. In this way, processing circuitry 210 can increase the fidelity of the ECAP information, which can increase the frequency with which ECAP signals are captured. It should be noted that, Figure 11 、 Figure 12 and Figure 13 Some or all of the techniques described in FIGS. 12-13 can be used together. For example, processing circuitry 210 can store ECAP information in long-term memory and increase the rate at which ECAP signals are sensed to obtain higher fidelity ECAP information for later analysis. In some examples, processing circuitry 210 can store other information in addition to ECAP information in temporary memory and long-term memory upon request. For example, processing circuitry 210 can also store acceleration data (e.g., posture state and / or activity information) with the ECAP information. For example, processing circuitry 210 can also store timestamps or other data with the ECAP information and any other information to relate the information to contemporaneous events.

[0156] This application generally describes storing ECAP information in long-term storage in response to receiving a trigger signal. However, in response to receiving a trigger signal, the system can store additional or alternative information. For example, in addition to or in lieu of ECAP information described herein, the system can store local field potential (LFP) information. The system can store LFP information representative of LFP signals sensed by one or more electrode combinations. The LFP signals can be sensed by one or more electrode combinations located near the spinal cord and / or in the brain. The system can store LFP information and ECAP information in temporary storage, and store both LFP information and ECAP information in long-term storage in response to a trigger signal. In some examples, the system can sample LFP signals at a higher, lower, or the same rate as ECAP signals. The system can store LFP information in the frequency domain. The system can be configured to control a display to present ECAP information and LFP information (and / or other types of sensed physiological information) together in temporal overlap to illustrate a correlation between ECAP information and LFP information. In other examples, the system can correlate ECAP information with LFP information to identify and / or confirm one or more patient events that occurred.

[0157] The following examples are described herein. Example 1 : A system comprising a memory; and processing circuitry configured to: receive evoked compound action potential (ECAP) information, wherein the ECAP information comprises information from a plurality of evoked compound action potential (ECAP) signals; receive a trigger signal requesting long-term storage of at least a portion of the ECAP information in the memory; and in response to receiving the trigger signal, store the at least a portion of the ECAP information in the memory.

[0158] Example 2: The system of example 1, further comprising stimulation generation circuitry configured to deliver electrical stimulation to a patient, wherein the electrical stimulation therapy comprises a plurality of stimulation pulses; and sensing circuitry configured to sense the plurality of ECAP signals, wherein the sensing circuitry is configured to sense each of the plurality of ECAP signals elicited by a respective stimulation pulse of the plurality of stimulation pulses, wherein the processing circuitry is configured to receive the ECAP signals from the sensing circuitry as the ECAP information.

[0159] Example 3 : The system of example 2, wherein the processing circuitry is configured to: in response to receiving the trigger signal, control the sensing circuitry to increase a rate at which the sensing circuitry senses subsequent ECAP signals; and store subsequent ECAP information comprising the subsequent ECAP signals in the memory.

[0160] Example 4: The system of any of examples 1-3, wherein the ECAP information includes at least one characteristic value representative of a respective ECAP signal of the plurality of ECAP signals, wherein the characteristic value includes at least one of an amplitude value, a slope value, or an area under a peak value.

[0161] Example 5: The system of any of examples 1-4, wherein the ECAP information includes a plurality of waveforms representative of a respective ECAP signal of the plurality of ECAP signals.

[0162] Example 6: The system of any of examples 1-5, wherein the memory includes long-term memory, and wherein the processing circuit is configured to store the received ECAP information in temporary memory, and wherein the processing circuit is configured to delete the ECAP information stored in the temporary memory in response to a predetermined time period elapsing.

[0163] Example 7: The system of any of examples 1-6, further comprising a communication circuit configured to transmit the stored ECAP information to an external device.

[0164] Example 8: The system of example 7, further comprising: an external device including a display; and an implantable medical device including the memory, the processing circuit, and the communication circuit configured to transmit the stored ECAP information to the external device, wherein the external device is configured to present one or more representations of the stored ECAP information via the display.

[0165] Example 9: The system of any of examples 1-8, wherein the trigger signal includes a request from an external device to store ECAP information.

[0166] Example 10: The system of any of examples 1-9, wherein the trigger signal includes a housing tap from a user, and wherein the processing circuit is configured to receive the housing tap by: receiving accelerometer data from an accelerometer within a housing of the implantable medical device; and determining that the accelerometer data indicates that a user tapped the implantable medical device.

[0167] Example 11: The system of any of examples 1-10, wherein the trigger signal includes an indication that a characteristic of one ECAP signal of the plurality of ECAP signals exceeds a threshold value.

[0168] Example 12: The system of any of examples 1-11, wherein the trigger signal includes an indication that a user changed one or more stimulation parameter values defining electrical stimulation deliverable to a patient.

[0169] Example 13: The system of any of examples 1 to 12, wherein the processing circuit is configured to, in response to receiving the trigger signal, select at least a portion of the ECAP information representative of one or more ECAP signals of the plurality of ECAP signals sensed between an initial time and a final time, the initial time occurring a first time period before receiving the trigger signal and the final time occurring a second time period after receiving the trigger signal.

[0170] Example 14: The system of any of examples 1 to 13, wherein the processing circuit adds a marker representative of the trigger signal to at least a portion of the ECAP information stored in the memory, wherein the marker indicates a time of the trigger signal relative to sensed ECAP signals of the ECAP information.

[0171] Example 15: The system of any of examples 1 to 14, wherein the processing circuit is configured to, in response to receiving the trigger signal, store acceleration data representative of at least one of a posture state or an activity of a patient corresponding to a same time as generation of the ECAP signals.

[0172] Example 16: The system of any of examples 1 to 15, further comprising an implantable medical device including the memory and the processing circuit.

[0173] Example 17: A method comprising: receiving, by a processing circuit, evoked compound action potential (ECAP) information, wherein the ECAP information includes information from a plurality of evoked compound action potential (ECAP) signals; receiving, by the processing circuit, a trigger signal requesting long-term storage of at least a portion of the ECAP information in a memory; and in response to receiving the trigger signal, storing, by the processing circuit, the at least a portion of the ECAP information in the memory.

[0174] Example 18: The method of example 17, further comprising: delivering, by stimulation generation circuitry, electrical stimulation to a patient, wherein the electrical stimulation therapy includes a plurality of stimulation pulses; sensing, by sensing circuitry, the plurality of ECAP signals by sensing each ECAP signal of the plurality of ECAP signals elicited by a respective stimulation pulse of the plurality of stimulation pulses, and receiving, by the processing circuit, the ECAP signals from the sensing circuitry as the ECAP information.

[0175] Example 19: The method of example 18, further comprising, in response to receiving the trigger signal, controlling the sensing circuit to increase a rate at which the sensing circuit senses subsequent ECAP signals; and storing subsequent ECAP information including the subsequent ECAP signals in the memory.

[0176] Example 20: The method of any of examples 17-19, wherein the ECAP information includes at least one characteristic value representative of a respective ECAP signal of the plurality of ECAP signals, wherein the characteristic value includes at least one of an amplitude value, a slope value, or an area under a peak.

[0177] Example 21 : The method of any of examples 17-20, wherein the ECAP information includes a plurality of waveforms representative of a respective ECAP signal of the plurality of ECAP signals.

[0178] Example 22: The method of any of examples 17-21, wherein the memory includes long-term memory, and wherein the method further comprises storing received ECAP information in temporary memory; and deleting ECAP information stored in the temporary memory in response to a predetermined period of time elapsing.

[0179] Example 23: The method of any of examples 17-22, further comprising transmitting the stored ECAP information to an external device via a communication circuit.

[0180] Example 24: The method of example 23, further comprising presenting one or more representations of the stored ECAP information via a display of the external device.

[0181] Example 25: The method of any of examples 17-24, wherein the trigger signal includes a request from an external device to store ECAP information.

[0182] Example 26: The system of any of examples 17-25, wherein the trigger signal includes a housing tap from a user, and wherein receiving the housing tap includes receiving accelerometer data from an accelerometer within a housing of the implantable medical device; and determining that the accelerometer data indicates that a user tapped the implantable medical device.

[0183] Example 27: The method of any of examples 17-26, wherein the trigger signal includes an indication that a characteristic of one ECAP signal of the plurality of ECAP signals exceeds a threshold value.

[0184] Example 28: The method of any of examples 17 to 27, wherein the trigger signal comprises an indication that a user changed one or more stimulation parameter values defining electrical stimulation deliverable to the patient.

[0185] Example 29: The method of any of examples 17 to 28, further comprising, in response to receiving the trigger signal, selecting at least a portion of the ECAP information representative of one or more ECAP signals of the plurality of ECAP signals sensed between an initial time and a final time, the initial time occurring a first time period before receiving the trigger signal and the final time occurring a second time period after receiving the trigger signal.

[0186] Example 30: The method of any of examples 17 to 29, further comprising adding a marker representative of the trigger signal to at least a portion of the ECAP information stored in the memory, wherein the marker indicates a time of a sensed ECAP signal of the ECAP information relative to the trigger signal.

[0187] Example 31 : A computer-readable medium comprising instructions that, when executed by a processor, cause the processor to receive evoked compound action potential (ECAP) information, wherein the ECAP information comprises information from a plurality of evoked compound action potential (ECAP) signals; receive a trigger signal requesting long-term storage of at least a portion of the ECAP information in a memory; and in response to receiving the trigger signal, store the at least a portion of the ECAP information in the memory.

[0188] The techniques described in this disclosure can be implemented, at least in part, in hardware, software, firmware or any combination thereof. For example, various aspects of the techniques can be implemented within one or more microprocessors, DSPs, ASICs, FPGAs or any other equivalent integrated or discrete logic circuitry, as well as any combinations of such components, embodied in external devices, such as physician or patient programmers, stimulators, or other devices. The terms "processor" and "processing circuitry" can generally refer to any of the foregoing logic circuitry, alone or in combination with other logic circuitry, or any other equivalent electrical circuitry.

[0189] For aspects implemented in software, at least some of the functionality attributed to the systems and devices described in this disclosure can be embodied as instructions on a computer-readable storage medium such as RAM, DRAM, SRAM, FRAM, magnetic disks, optical disks, flash memory, or forms of EPROM or EEPROM. Such instructions can be executed to support one or more aspects of the functionality described in this disclosure.

[0190] Moreover, in some aspects, the functionality described herein can be provided within dedicated hardware and / or software modules. Different embodiments are depicted with different features to emphasize different implementations, and it can be that different features are utilized for both depicted and non-depicted embodiments, and specific scenes can not be depicted for selected embodiments in order to not obscure aspects of the embodiments. The different embodiments are not necessarily mutually exclusive, as some embodiments can be combined with each other into other embodiments not specifically depicted.

Claims

1. A system for managing the storage of sensed information, the system comprising: Memory; as well as Processing circuit, the processing circuit being configured to: Receive evoked compound action potential (ECAP) information, wherein the ECAP information includes information from multiple evoked compound action potential (ECAP) signals; Receive a trigger signal requesting that at least a portion of the ECAP information be permanently stored in the memory; and In response to receiving the trigger signal, at least a portion of the ECAP information is stored in the memory, wherein the at least a portion of the ECAP information represents one or more ECAP signals sensed between a first time period before the trigger signal is received and a second time period after the trigger signal is received.

2. The system of claim 1, further comprising: A stimulation generating circuit configured to deliver electrical stimulation to a patient, wherein the electrical stimulation therapy includes multiple stimulation pulses; and A sensing circuit configured to sense the plurality of ECAP signals, wherein the sensing circuit is configured to sense each of the plurality of ECAP signals triggered by a corresponding stimulus pulse among the plurality of stimulus pulses, wherein the processing circuit is configured to receive the ECAP signal from the sensing circuit as the ECAP information.

3. The system of claim 2, wherein, The processing circuit is configured as follows: In response to receiving the trigger signal, the sensing circuit is controlled to increase the rate at which the sensing circuit senses subsequent ECAP signals; and The subsequent ECAP information, including the subsequent ECAP signal, is stored in the memory.

4. The system of any one of claims 1 to 3, wherein, The ECAP information includes at least one characteristic value representing a corresponding ECAP signal among the plurality of ECAP signals, wherein the characteristic value includes at least one of an amplitude value, a slope value, or an area under the peak.

5. The system of claim 1, wherein, The ECAP information includes multiple waveforms representing the corresponding ECAP signal among the plurality of ECAP signals.

6. The system of claim 1, wherein, The memory includes a long-term memory, and the processing circuitry is configured to store the received ECAP information in a temporary memory, and the processing circuitry is configured to delete the ECAP information stored in the temporary memory in response to the elapsed time period.

7. The system of claim 1, further comprising: External devices including displays; as well as An implantable medical device includes the memory, the processing circuitry, and communication circuitry configured to transmit stored ECAP information to an external device, wherein the external device is configured to present one or more representations of the stored ECAP information via the display.

8. The system of claim 1, wherein, The trigger signal includes a request from an external device for storing ECAP information.

9. The system as claimed in claim 1, wherein, The trigger signal includes a knock from the user's casing, and the processing circuitry is configured to receive the knock in such a way that: Receive accelerometer data from the accelerometer inside the casing of the implantable medical device; and The accelerometer data indicates that the user tapped the implanted medical device.

10. The system of claim 1, wherein, The trigger signal includes an indication that a characteristic of one of the plurality of ECAP signals exceeds a threshold.

11. The system of claim 1, wherein, The trigger signal includes an indication that the user has changed one or more stimulation parameter values ​​that define the electrical stimulation that can be delivered to the patient.

12. The system of claim 1, wherein, The processing circuit is configured to, in response to receiving the trigger signal, select at least a portion of the ECAP information representing one or more ECAP signals sensed between an initial time and a final time, wherein the initial time occurs during a first time period prior to receiving the trigger signal and the final time occurs during a second time period after receiving the trigger signal.

13. The system of claim 1, wherein, The processing circuit adds a marker representing the trigger signal to at least a portion of the ECAP information stored in the memory, wherein the marker indicates the time of the trigger signal relative to the sensed ECAP signal in the ECAP information.

14. The system of claim 1, wherein, The processing circuitry is configured to store acceleration data in response to receiving the trigger signal, the acceleration data representing at least one of the patient's postural state or activity corresponding to the same time the ECAP signal is generated.

15. The system of claim 1, further comprising an implantable medical device including the memory and the processing circuitry.

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