Systems, methods, and devices for reduced power consumption while providing stimulation therapy

Abstract

A medical device may reduce power consumption during stimulation therapy during periods when a low power therapy is acceptable. In one instance, a measurement of neural signal at the patient may be used to determine if a low power stimulation therapy is appropriate by detecting if the neural signal has reached a period of low volatility indicated by the amplitude variation settling into a smaller range for a predetermined time. In another instance, one or more parameters may be used to determine if a patient is in a resting state indicating that low power therapy is appropriate, such as by considering neural signal volatility in addition to other parameters that indicate the resting state. Once the implantable medical device begins low power therapy, one or more stimulation parameters may be adjusted to reduce power consumption of a battery of the implantable medical device like amplitude or ON / OFF cycling.

Description

SYSTEMS, METHODS, AND DEVICES FOR REDUCED POWER CONSUMPTION WHILE PROVIDING STIMULATION THERAPY

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 675,794, filed July 26, 2024, the entire content of which is incorporated herein by reference.TECHNICAL FIELD

[0002] Embodiments relate to enhancement of battery longevity of a medical device. More particularly, embodiments relate to enhancement of battery longevity when a patient of the medical device is in a state that allows energy to be reduced by entering a low power mode.BACKGROUND

[0003] Medical devices may be used to deliver electrical stimulation therapy to various tissue sites of a patient to treat a variety of symptoms or conditions such as chronic pain, tremor, Parkinson's disease, other movement disorders, epilepsy, urinary or fecal incontinence, sexual dysfunction, obesity, or gastroparesis. These medical devices may be external to a patient or implanted within a patient. A medical device may deliver electrical stimulation therapy via one or more leads that include electrodes located proximate to target locations associated with the brain, the spinal cord, pelvic nerves, peripheral nerves, or the gastrointestinal tract of a patient. Hence, electrical stimulation may be used in different therapeutic applications, such as deep brain stimulation (DBS), spinal cord stimulation (SCS), pelvic stimulation, gastric stimulation, or peripheral nerve field stimulation (PNFS).

[0004] There may be multiple electrical stimulation modes for a medical device. In an example, in conventional DBS (CDBS), a patient may receive a constant level of stimulation, where various stimulation parameters including amplitude, pulse width, and pulse frequency are held constant. Under certain circumstances, CDBS may not have efficacy when a patient is suffering from a symptom or condition that changes based on patient activity.

[0005] In adaptive DBS (ADBS), stimulation may be adapted based on one or more sensed physiological parameters of a patient, such as a neural signal including either a local field potential (LFP) or evoked resonant neural activity (ERNA). When ADBS uses a single threshold, generally, stimulation is held constant when a physiological parameter of the patient is at the single threshold and altered when the physiological signal value strays from the threshold. For example, when a neural signal amplitude exceeds a threshold, a stimulation amplitude may be increased to force the neural signal amplitude lower toward the threshold. Likewise, when the neural signal amplitude drops below the threshold, the stimulation amplitude may be decreased to force the neural signal amplitude higher toward the threshold.

[0006] Alternatively, ADBS may be performed with two or more thresholds that define a range that the physiological parameter, such as a neural signal including an LFP or ERNA, is desired to be maintained within. The range may be defined by an upper and a lower threshold for the neural signal. As an example, with ADBS applying two or more thresholds, when the neural signal amplitude is below the lower threshold, stimulation amplitude may be decreased until the neural signal amplitude rises and at which time the stimulation parameters may be held constant. Likewise, when the neural signal amplitude is above the range, stimulation amplitude may be increased until the neural signal amplitude is within the range and at which time the stimulation parameters may be held constant. As a result, the stimulation parameters may be held constant while the neural signal amplitude is within the range. Additionally, a stimulation parameter limit window may be defined to limit the stimulation parameter to be within the stimulation parameter limit window. For example, a simulation parameter limit window may, for example, allow a clinician to define a minimum stimulation amplitude to treat the conditions and symptoms of the patient, and the maximum stimulation amplitude is one that can be safely applied to the patient. Typically, the medical device cannot stimulate outside the stimulation parameter limit window.

[0007] A consequence of providing DBS is the consumption of energy which, typically, is provided by a battery of the medical device. When the energy of the battery is depleted to a certain level, the battery must either be recharged or replaced.Thus, DBS therapy may result in the patient being required to initiate frequent device recharges and / or undergo a device replacement procedure.SUMMARY

[0008] Embodiments disclosed herein address issues such as these and others by altering one or more stimulation parameters of a medical device to provide low power DBS when a patient is in a state that allows the medical device to operate in such a manner. The low power DBS expends energy at a slower rate so that device recharges and / or a device replacement are not as frequent. An example of a patient state that would allow the medical device to operate in the low pow DBS mode is a resting state, such as being asleep. In an example, a neural signal may be used to determine if the patient is in the resting state by determining if neural signal amplitude volatility has settled into a smaller window for a predetermined amount of time. In another example, one or more parameters may be used to determine or confirm that a patient is in the resting state, such as considering heart rate, respiration, patient position, time of day, patient movement, and patient input in addition to the neural signal. The low power DBS may then utilize a reduced stimulation parameter such as a reduced amplitude, frequency, or pulse width or may utilize a therapy duty cycle stimulation parameter that causes the stimulation to cycle between periods of being ON and OFF.

[0009] Embodiments provide a method of reducing power consumption of an implantable medical device providing stimulation therapy. The method involves, upon detecting that a neural signal has an amplitude volatility that has decreased from a first range to a second range that is smaller than the first range, sensing a resting state parameter of a patient. The method further involves, when the resting state parameter indicates that the patient is in a resting state, providing low power stimulation therapy by adjusting at least one stimulation parameter to reduce power consumption.

[0010] Embodiments provide a method of reducing power consumption of a stimulation device. The method involves, while providing stimulation therapy by the stimulation device, sensing a neural signal. The method further involves, when the neural signal has an amplitude within a first range, limiting at least one stimulation parameter that controls stimulation delivered by the stimulation device to a first value.The method also involves, when the neural signal has an amplitude volatility within a second range that is smaller than the first range, limiting the at least one stimulation parameter to a second value that is smaller than the first value.

[0011] Embodiments provide an implantable medical device that includes a memory, a processor, a sense circuit, and a stimulation circuit. The memory, the sense circuit, and the stimulation circuit are coupled to the processor, and the memory stores instructions that, when executed by the processor, cause the processor to perform various actions. The processor detects that a neural signal has an amplitude volatility that has decreased from a first range to a second range that is smaller than the first range using the sense circuit. The processor senses a patient resting state parameter after having detected the neural signal amplitude volatility has decreased from the first range to the second range. The processor provides low power stimulation therapy from the stimulation circuit by adjusting at least one stimulation parameter to reduce power consumption when the patient resting state parameter indicates that the patient is in a resting state.

[0012] Embodiments provide an implantable medical device that includes a memory, a processor, a sense circuit, and a stimulation circuit. The memory, the sense circuit, and the stimulation circuit are coupled to the processor, and the memory stores instructions that, when executed by the processor, cause the processor to perform various actions. The processor uses the sense circuit to sense a neural signal. The processor limits at least one stimulation parameter that controls stimulation delivered by the stimulation circuit to a first value when the neural signal has an amplitude volatility that is within a first range. The processor limits the stimulation parameter to a second value that is smaller than the first value when the neural signal amplitude volatility is within a second range that is smaller than the first range.DESCRIPTION OF THE DRAWINGS

[0013] FIG. l is a conceptual diagram illustrating an example system that includes an implantable medical device (IMD) configured to deliver deep brain stimulation to a patient according to an example of the techniques of the disclosure.

[0014] FIG. 2 is a block diagram of the example IMD of FIG. 1 for delivering stimulation therapy according to an example of the techniques of the disclosure.

[0015] FIG. 3 shows an example of logical operations that may be performed by a medical system 100 to operate IMD 106 in a normal DBS mode and a low power DBS mode according to an example of the techniques of the disclosure.

[0016] FIG. 4 shows an example of logical operations that may be performed by a medical system 100 to operate IMD 106 to determine if the low power DBS mode is appropriate according to an example of the techniques of the disclosure.

[0017] FIG. 5 shows another example of logical operations that may be performed by a medical system 100 to determine if the low power DBS mode is appropriate according to an example of the techniques of the disclosure.

[0018] FIG. 6 shows yet another example of logical operations that may be performed by a medical system 100 to determine if the low power DBS mode is appropriate according to an example of the techniques of the disclosure.

[0019] FIG. 7 shows a first example of logical operations that may be performed by a medical system 100 to determine and implement reduced stimulation parameters for the low power DBS mode according to an example of the techniques of the disclosure.

[0020] FIG. 8 shows a second example of logical operations that may be performed by a medical system 100 to determine and implement ON / OFF stimulation parameters for the low power DBS mode according to an example of the techniques of the disclosure.

[0021] FIG. 9 shows an example of logical operations that may be performed by a medical system 100 to incorporate patient feedback according to an example of the techniques of the disclosure.

[0022] FIG. 10 shows a graph of stimulation from the normal DBS zone to the low power DBS zone and back to the normal DBS zone along with various patient state information according to an example of the techniques of the disclosure.DETAILED DESCRIPTION

[0023] With certain symptoms or conditions, a patient in certain states such as a resting state may require less stimulation. As some patients with tremor disorder, such as Essential Tremor, experience less symptoms at night, patients may discontinue nighttime stimulation. With traditional dual threshold ADBS, during a resting state the stimulation parameters such as amplitude, frequency, and pulse width may be held relatively constant since the physiological parameter of interest, namely a neural signal containing local field potentials (LFP) or evoked resonant neural activity (ERNA) has an amplitude that may not fluctuate outside of pre-defined limits. However, these stimulation parameters may be at a level that consumes more power than is necessary for the patient during that period of time. Therefore, by monitoring the patient’s state and adjusting the stimulation parameters to a level that consumes less power while a patient is in the particular state, such as reducing parameters or setting parameters to cycle stimulation between ON and OFF states, battery power is conserved. If an implantable medical device has a rechargeable battery, this power conservation may allow the patient to go longer between recharges. If the implantable medical device has a non-rechargeable battery that must be replaced in a medical procedure, this power conservation may allow for longer periods of time between those medical procedures. Additional benefits beyond reduced power consumption may also occur in some cases by adjusting the stimulation parameters to a low power mode when appropriate, such as reducing habituation so that the patient’s body does not become too accustomed to the therapy and the therapy continues to be effective.

[0024] FIG. 1 is a conceptual diagram illustrating an example system 100 that includes an implantable medical device (IMD) 106 configured to deliver stimulation therapy such as deep brain stimulation (DBS) to a patient 112. While the discussion that follows is with reference to DBS, the embodiments disclosed herein may apply to other forms of stimulation therapy and therefore the reference to DBS should be taken as an example.

[0025] A brief overview of DBS is provided where DBS has multiple types. DBS may be conventional where the stimulation parameter values are fixed or may be adaptive in the sense that IMD 106 may adjust, increase, or decrease the magnitude of one or more of the stimulation parameters of the DBS in response to changes in patientactivity or movement, a severity of one or more symptoms of a disease of the patient, a presence of one or more side effects due to the DBS, or one or more sensed signals of the patient, etc. For example, one or more sensed signals of the patient may be used as a control signal such that the IMD 106 correlates the magnitude of the one or more parameters of the electrical stimulation to the magnitude of the one or more sensed signals. According to the techniques of the disclosure, system 100, via IMD 106, delivers electrical stimulation therapy having one or more stimulation parameters, such as voltage or current amplitude, pulse width, and signal frequency, that may be fixed or adjusted during a normal DBS mode and may be adjusted to lower levels for lower power consumption during a low power DBS mode.

[0026] The IMD 106 may deliver electrical stimulation therapy having one or more stimulation parameters that are adjusted in response to sensing characteristics of the patient during adaptive DBS. For example, when the patient enters a period of low volatility of a sensed amplitude of neural signal such as a low LFP and / or ERNA amplitude volatility and / or when the patient exhibits other sensed characteristics indicative of being in a resting state, the one or more stimulation parameters of the stimulation therapy may be reduced to provide the low power DBS mode such that the power consumed from a battery of the IMD 106 is reduced. The ability to switch between the normal DBS mode and the lower power DBS mode is discussed in more detail below with reference to FIGS. 2-9.

[0027] Further details regarding the more general operation of the devices of system 100 are discussed in relation to FIG. 1. System 100 may be configured to provide the stimulation to treat a patient condition, such as a movement disorder, neurodegenerative impairment, a mood disorder, or a seizure disorder of patient 112. Patient 112 ordinarily is a human patient. In some cases, however, therapy system 100 may be applied to other mammalian or non-mammalian, non-human patients. While movement disorders and neurodegenerative impairment are primarily referred to herein, in other examples, therapy system 100 may provide therapy to manage symptoms of other patient conditions, such as, but not limited to, seizure disorders (e.g., epilepsy) or mood (or psychological) disorders (e.g., major depressive disorder (MDD), bipolar disorder, anxiety disorders, post-traumatic stress disorder, dysthymic disorder, and obsessive-compulsive disorder (OCD)). At least some of these disordersmay be manifested in one or more patient movement behaviors. As described herein, a movement disorder or other neurodegenerative impairment may include symptoms such as, for example, muscle control impairment, motion impairment or other movement problems, such as rigidity, spasticity, bradykinesia, rhythmic hyperkinesia, nonrhythmic hyperkinesia, and akinesia. In some cases, the movement disorder may be a symptom of Parkinson's disease. However, the movement disorder may be attributable to other patient conditions.

[0028] Example therapy system 100 includes medical device programmer 104, implantable medical device (IMD) 106, lead extension 110, and leads 114A and 114B with respective sets of electrodes 116, 118. In the example shown in FIG. 1, electrodes 116, 118 of leads 114A, 114B are positioned to deliver electrical stimulation to a tissue site within brain 120, such as a deep brain site under the dura mater of brain 120 of patient 112. In some examples, delivery of stimulation to one or more regions of brain 120, such as the subthalamic nucleus, globus pallidus or thalamus, may be an effective treatment to manage movement disorders, such as Parkinson's disease. Some or all of electrodes 116, 118 also may be positioned to sense neural signals within brain 120 of patient 112. In some examples, some of electrodes 116, 118 may be configured to sense neural signals and others of electrodes 116, 118 may be configured to deliver electrical stimulation to brain 120. In other examples, all of electrodes 116, 118 are configured to both sense neural signals and deliver electrical stimulation to brain 120.

[0029] IMD 106 includes a therapy module (e.g., which may include processing circuitry, signal generation circuitry or other electrical circuitry configured to perform the functions attributed to IMD 106) that includes a stimulation generator configured to generate and deliver electrical stimulation therapy to patient 112 via a subset of electrodes 116, 118 of leads 114A and 114B, respectively. The subset of electrodes 116, 118 that are used to deliver electrical stimulation to patient 112, and, in some cases, the polarity of the subset of electrodes 116, 118, may be referred to as a stimulation electrode combination. The stimulation electrode combination can be selected for a particular patient 112 and target tissue site (e.g., selected based on the patient condition). The group of electrodes 116, 118 includes at least one electrode and can include a plurality of electrodes. In some examples, the plurality of electrodes 116and / or 118 may have a complex electrode geometry such that two or more electrodes are located at different positions around the perimeter of the respective lead.

[0030] In some examples, the neural signals sensed within brain 120 may reflect changes in electrical current produced by the sum of electrical potential differences across brain tissue. Examples of neural signals include, but are not limited to, electrical signals generated from LFPs or ERNAs sensed within one or more regions or hemispheres of brain 120, such as an electroencephalogram (EEG) signal, or an electrocorti cogram (ECoG) signal. Neural signals including LFPs and ERNAs, however, may include a broader genus of electrical signals within brain 120 of patient 112, where the neural signals being sensed from the one or more regions or hemispheres may be from various frequencies such as alpha-beta, theta, gamma, delta, sigma, etc. Each region or hemisphere may be sensed independently for the neural signals at these various frequencies.

[0031] In some examples, the neural signals that are used to select a stimulation electrode combination may be sensed within the same region of brain 120 as the target tissue site for the electrical stimulation. These tissue sites may include tissue sites within anatomical structures such as the thalamus, subthalamic nucleus or globus pallidus of brain 120, as well as other target tissue sites. The specific target tissue sites and / or regions within brain 120 may be selected based on the patient’s condition.Thus, in some examples, both a stimulation electrode combination and sense electrode combinations may be selected from the same set of electrodes 116, 118. In other examples, the electrodes used for delivering electrical stimulation may be different than the electrodes used for sensing neural signals.

[0032] Electrical stimulation generated by IMD 106 may be configured to manage a variety of disorders and conditions. In some examples, the stimulation generator of IMD 106 is configured to generate and deliver electrical stimulation pulses to patient 112 via electrodes of a selected stimulation electrode combination. However, in other examples, the stimulation generator of IMD 106 may be configured to generate and deliver a continuous wave signal, e.g., a sine wave or triangle wave. In either case, a stimulation generator within IMD 106 may generate the electrical stimulation therapy for DBS according to a therapy program that is selected at that given time in therapy. In examples in which IMD 106 delivers electrical stimulation in the form ofstimulation pulses, a therapy program may include a set of therapy parameter values (e.g., stimulation parameters), such as a stimulation electrode combination for delivering stimulation to patient 112, pulse frequency, pulse width, and a current or voltage stimulation amplitude of the pulses. The electrode combination may indicate the specific electrodes 116, 118 that are selected to deliver stimulation signals to tissue of patient 112 and the respective polarities of the selected electrodes.

[0033] IMD 106 may be implanted within a subcutaneous pocket above the clavicle, or, alternatively, on or within cranium 122 or at any other suitable site within patient 112. Generally, IMD 106 is constructed of a biocompatible material that resists corrosion and degradation from bodily fluids. IMD 106 may comprise a hermetic housing to substantially enclose components, such as a processor, therapy module, and memory.

[0034] As shown in FIG. 1, implanted lead extension 110 is coupled to IMD 106 via connector 108 (also referred to as a connector block or a header of IMD 106). In the example of FIG. 1, lead extension 110 traverses from the implant site of IMD 106 and along the neck of patient 112 to cranium 122 of patient 112 to access brain 120. In the example shown in FIG. 1, leads 114A and 114B (collectively “leads 114”) are implanted within the right and left hemispheres, respectively, of patient 112 in order to deliver electrical stimulation to one or more regions of brain 120, which may be selected based on the patient condition or disorder controlled by therapy system 100. The specific target tissue site and the stimulation electrodes used to deliver stimulation to the target tissue site, however, may be selected, e.g., according to the identified patient behaviors and / or other sensed patient parameters. Other lead 114 and IMD 106 implant sites are contemplated. For example, IMD 106 may be implanted on or within cranium 122, in some examples. Or leads 114 may be implanted within the same hemisphere or IMD 106 may be coupled to a single lead implanted in a single hemisphere.

[0035] Existing lead sets include axial leads carrying ring electrodes disposed at different axial positions and so-called “paddle” leads carrying planar arrays of electrodes. In some examples, more complex lead array geometries may be used.

[0036] Although leads 114 are shown in FIG. 1 as being coupled to a common lead extension 110, in other examples, leads 114 may be coupled to IMD 106 via separatelead extensions or directly to connector 108. Leads 114 may be positioned to deliver electrical stimulation to one or more target tissue sites within brain 120 to manage patient symptoms associated with a movement disorder of patient 112. Leads 114 may be implanted to position electrodes 116, 118 at desired locations of brain 120 through respective holes in cranium 122. Leads 114 may be placed at any location within brain 120 such that electrodes 116, 118 are capable of providing electrical stimulation to target tissue sites within brain 120 during treatment. For example, electrodes 116, 118 may be surgically implanted under the dura mater of brain 120 or within the cerebral cortex of brain 120 via a burr hole in cranium 122 of patient 112, and electrically coupled to IMD 106 via one or more leads 114.

[0037] In the example shown in FIG. 1, electrodes 116, 118 of leads 114 are shown as ring electrodes. Ring electrodes may be used in DBS applications because they are relatively simple to program and are capable of delivering an electrical field to any tissue adjacent to electrodes 116, 118. In other examples, electrodes 116, 118 may have different configurations. For example, in some examples, at least some of the electrodes 116, 118 of leads 114 may have a complex electrode array geometry that is capable of producing shaped electrical fields. The complex electrode array geometry may include multiple electrodes (e.g., partial ring or segmented electrodes) around the outer perimeter of each lead 114, rather than one ring electrode. In this manner, electrical stimulation may be directed in a specific direction from leads 114 to enhance therapy efficacy and reduce possible adverse side effects from stimulating a large volume of tissue. In some examples, a housing of IMD 106 may include one or more stimulation and / or sensing electrodes. In alternative examples, leads 114 may have shapes other than elongated cylinders as shown in FIG. 1. For example, leads 114 may be paddle leads, spherical leads, bendable leads, or any other type of shape effective in treating patient 112 and / or minimizing invasiveness of leads 114.

[0038] In the example shown in FIG. 1, IMD 106 includes a memory to store a plurality of therapy programs that each define a set of therapy parameter values. In some examples, IMD 106 may select a therapy program from the memory based on various parameters, such as sensed patient parameters and the identified patient behaviors. IMD 106 may generate electrical stimulation based on the selected therapy program to manage the patient symptoms associated with a movement disorder.

[0039] External programmer 104 wirelessly communicates with IMD 106 as needed to provide or retrieve therapy information. Programmer 104 is an external computing device that the user, e.g., a clinician and / or patient 112, may use to communicate with IMD 106. For example, programmer 104 may be a clinician programmer that the clinician uses to communicate with IMD 106 and program one or more therapy programs for IMD 106. Alternatively, programmer 104 may be a patient programmer that allows patient 112 to select programs and / or view and modify therapy parameters. The clinician programmer may include more programming features than the patient programmer. In other words, more complex or sensitive tasks may only be allowed by the clinician programmer to prevent an untrained patient from making undesirable changes to IMD 106.

[0040] When programmer 104 is configured for use by the clinician, programmer 104 may be used to transmit initial programming information to IMD 106. This initial information may include hardware information, such as the type of leads 114 and the electrode arrangement, the position of leads 114 within brain 120, the configuration of electrode array 116, 118, initial programs defining therapy parameter values, and any other information the clinician desires to program into IMD 106. Programmer 104 may also be capable of completing functional tests (e.g., measuring the impedance of electrodes 116, 118 of leads 114).

[0041] The clinician may also store therapy programs within IMD 106 with the aid of programmer 104. During a programming session, the clinician may determine one or more therapy programs that may provide efficacious therapy to patient 112 to address symptoms associated with the patient condition, and, in some cases, specific to one or more different patient states, such as a resting state or movement / activity state. For example, the clinician may select one or more stimulation electrode combination with which stimulation is delivered to brain 120. During the programming session, the clinician may evaluate the efficacy of the specific program being evaluated based on feedback provided by patient 112 or based on one or more physiological parameters of patient 112 (e.g., muscle activity, muscle tone, rigidity, tremor, etc.). Alternatively, identified patient behavior from video information may be used as feedback during the initial and subsequent programming sessions. Programmer 104 may assist the clinicianin the creation / identification of therapy programs by providing a methodical system for identifying potentially beneficial therapy parameter values.

[0042] Programmer 104 may also be configured for use by patient 112. When configured as a patient programmer, programmer 104 may have limited functionality (compared to a clinician programmer) in order to prevent patient 112 from altering critical functions of IMD 106 or applications that may be detrimental to patient 112. In this manner, programmer 104 may only allow patient 112 to adjust values for certain therapy parameters or set an available range of values for a particular therapy parameter.

[0043] Programmer 104 may also provide an indication to patient 112 when therapy is being delivered, when patient input has triggered a change in therapy or when the power source within programmer 104 or IMD 106 needs to be replaced or recharged. For example, programmer 104 may include an alert LED, may flash a message to patient 112 via a programmer display, generate an audible sound or somatosensory cue to confirm patient input was received, e.g., to indicate a patient state or to manually modify a therapy parameter.

[0044] Therapy system 100 may be implemented to provide chronic stimulation therapy to patient 112 over the course of several months or years. However, system 100 may also be employed on a trial basis to evaluate therapy before committing to full implantation. If implemented temporarily, some components of system 100 may not be implanted within patient 112. For example, patient 112 may be fitted with an external medical device, such as a trial stimulator, rather than IMD 106. The external medical device may be coupled to percutaneous leads or to implanted leads via a percutaneous extension. If the trial stimulator indicates DBS system 100 provides effective treatment to patient 112, the clinician may implant a chronic stimulator within patient 112 for relatively long-term treatment.

[0045] Although IMD 106 is described as delivering electrical stimulation therapy to brain 120, IMD 106 may be configured to direct electrical stimulation to other anatomical regions of patient 112. For example, an IMD may provide other electrical stimulation such as spinal cord stimulation to treat a movement disorder.

[0046] In one example, external programmer 104 issues commands to IMD 106 causing IMD 106 to deliver electrical stimulation therapy via electrodes 116, 118 vialeads 114. The one or more stimulation parameters may include a current amplitude (for a current-controlled system) or a voltage amplitude (for a voltage-controlled system), a pulse rate or frequency, and a pulse width. In examples where the electrical stimulation is delivered according to a “burst” of pulses, or a series of electrical pulses defined by an “on-time” and an “off-time,” the one or more stimulation parameters may further define one or more of a number of pulses per burst, an on-time, and an off- time. In one example, the therapeutic window defines an upper bound and a lower bound for one or more parameters, such as upper and lower bounds for a current amplitude of the electrical stimulation therapy (in current-controlled systems) or upper and lower bounds of a voltage amplitude of the electrical stimulation therapy (in voltage-controlled systems). While the examples herein are typically given with respect to adjusting a voltage amplitude or a current amplitude, the techniques herein may equally be applied using other parameters, such as, e.g., pulse rate or pulse width.

[0047] In some examples where system 100 adjusts multiple parameters of the electrical stimulation, system 100 may adjust at least one of a voltage amplitude or current amplitude, a stimulation frequency, a pulse width, or a selection of electrodes, and the like. In such an example, the clinician may set an order or sequence for adjustment of the parameters (e.g., adjust voltage amplitude or current amplitude, then adjust stimulation frequency, and then adjust the selection of electrodes). In other examples, system 100 may randomly select a sequence of adjustments to the multiple parameters. In either example, system 100 may adjust a value of a first parameter of the parameters of the electrical stimulation. If the signal does not exhibit a response to the adjustment of the first parameter, system 100 may adjust a value of a second parameter of the parameters of the electrical stimulation.

[0048] The system 100 may capture information from sensors either included within the IMD 106 or external to but in communication with the IMD 106. In some examples, each of sensors 109 is an accelerometer, a bonded piezoelectric crystal, a mercury switch, or a gyro. In some examples, sensors 109 may provide a signal that indicates a physiological parameter of the patient, which in turn varies as a function of patient activity. For example, the device may monitor a signal that indicates the heart rate, electrocardiogram (ECG) morphology, electroencephalogram (EEG) morphology,respiration rate, respiratory volume, core temperature, subcutaneous temperature, or muscular activity of the patient.

[0049] In some examples, sensors 109 generate a signal both as a function of patient activity and patient posture, and this information may provide an indication of a particular patient state. For example, accelerometers, gyros, or magnetometers may generate signals that indicate both the activity and the posture of a patient 112. External programmer 104 may be provided with this information that is used to determine whether external programmer 104 should perform adjustments to the stimulation therapy being provided. Likewise, IMD 106 may utilize such information to make adjustments to the stimulation therapy without further input from the external programmer 104.

[0050] For example, in order to identify posture, sensors 109 such as accelerometers may be oriented substantially orthogonally with respect to each other. In addition to being oriented orthogonally with respect to each other, each of sensors 109 used to detect the posture of a patient 112 may be substantially aligned with an axis of the body of a patient 112. When accelerometers, for example, are aligned in this manner, the magnitude and polarity of DC components of the signals generate by the accelerometers indicate the orientation of the patient relative to the Earth's gravity, e.g., the posture of a patient 112.

[0051] Other sensors 109 that may generate a signal that indicates the posture of a patient 112 include electrodes that generate a signal as a function of electrical activity within muscles of a patient 112, e.g., an electromyogram (EMG) signal, or a bonded piezoelectric crystal that generates a signal as a function of contraction of muscles. Electrodes or bonded piezoelectric crystals may be implanted in the legs, buttocks, chest, abdomen, or back of a patient 112, and coupled to one or more of external programmer 104 and IMD 106 wirelessly or via one or more leads. Alternatively, electrodes may be integrated in a housing of the IMD 106 or piezoelectric crystals may be bonded to the housing when IMD 106 is implanted in the buttocks, chest, abdomen, or back of a patient 112. The signals generated by such sensors when implanted in these locations may vary based on the posture of a patient 112, e.g., may vary based on whether the patient is standing, sitting, or lying down.

[0052] Further, the posture of a patient 112 may affect the thoracic impedance of the patient. Consequently, sensors 109 may include an electrode pair, including one electrode integrated with the housing of IMDs 106 and one of electrodes 116, 118, that generate a signal as a function of the thoracic impedance of a patient 112, and IMD 106 may detect the posture or posture changes of a patient 112 based on the signal. In one example (not depicted), the electrodes of the pair may be located on opposite sides of the patient's thorax. For example, the electrode pair may include electrodes located proximate to the spine of a patient for delivery of SCS therapy, and IMD 106 with an electrode integrated in its housing may be implanted in the abdomen or chest of patient 112. As another example, IMD 106 may include electrodes implanted to detect thoracic impedance in addition to leads 114 implanted within the brain of patient 112. The posture or posture changes may affect the delivery of DBS or SCS therapy to patient 112 for the treatment of any type of neurological disorder, and may also be used to detect patient sleep, as described herein.

[0053] Additionally, changes of the posture of a patient 112 may cause pressure changes with the cerebrospinal fluid (CSF) of the patient. Consequently, sensors 109 may include pressure sensors coupled to one or more intrathecal or intracerebroventricular catheters, or pressure sensors coupled to HMDs 106 wirelessly or via one of leads 114. CSF pressure changes associated with posture changes may be particularly evident within the brain of the patient, e.g., may be particularly apparent in an intracranial pressure (ICP) waveform.

[0054] Accordingly, in some examples, instead of or in addition to monitoring a neural signal of the patient, the system 100 monitors one or more signals from sensors 109 indicative of a magnitude of a physiological parameter of patient 112. Such information may be used to determine a patient state, such as whether the patient is in a resting state where a low power DBS mode may be appropriate to allow for reduced battery consumption during that period of time when the patient remains in the resting state.

[0055] Further, such a system 100 may use external sensors, such as accelerometers, instead of or in addition to internal sensors, such as electrodes, to detect symptoms of the disease of the patient and control adjustments to the magnitude of one or more parameters of the therapy. For example, the system 100 may use a wristsensor to detect wrist flexion or tremor of a patient suffering from Parkinson's disease. Thus, such an IMD the monitoring of a physiological parameter may be less invasive than other IMD systems because the system of the present disclosure may not require sensing electrodes to be implanted in the brain of the patient 112.

[0056] The architecture of system 100 illustrated in FIG. 1 is shown as an example. The techniques as set forth in this disclosure may be implemented in the example system 100 of FIG. 1, as well as other types of systems not described specifically herein. Furthermore, either external programmer 104 or IMD 106 may receive the signal representative of the signal of patient 112 and determine an adjustment to one or more parameters defining the electrical stimulation therapy that IMD 106 delivers to patient 112. Nothing in this disclosure should be construed so as to limit the techniques of this disclosure to the example illustrated by FIG. 1.

[0057] FIG. 2 shows a block diagram of one example of medical system 100. Medical system 100 may include a programmer 104 like that shown in FIG. 1. Programmer 104 may include processor 230, memory 232, transmit circuit 236, and receive circuit 238. Memory 232 may store instructions executed by processor 230. The processor 230 may be in the form of a general purpose programmable processor, an application specific processor, hardwired digital logic, combinations thereof, and the like. The memory 232, transmit circuit 236, and receive circuit 238 are communicatively coupled to the processor 230. Transmit circuit 236 and receive circuit 238 of programmer 104 may be used to facilitate communication between programmer 104 and IMD 106 also using signal 210 and signal 220. These features of the programmer 104 may exist as independent components may be included as a features of one or more components. For instance, the transmit circuit 236 and receive circuit 238 may be included as a single transceiver component.

[0058] The medical system 100 of FIG. 2 also includes the IMD 106. IMD 106 may include processor 246, memory 248, transmit circuit 250, receive circuit 252, stimulation generator 260, and sensing module 270. The processor 246 may be in the form of a general purpose programmable processor, an application specific processor, hardwired digital logic, combinations thereof, and the like. Memory 248 may store instructions executed by processor 246. Sensing module 270 may sense one or more physiological parameters of patient 112 via electrodes electrically coupled thereto.Transmit circuit 250 and receive circuit 252 of IMD 106 may be used to facilitate communication between programmer 104 and IMD 106 also using signal 210 and signal 220.

[0059] Stimulation generator 260 may deliver stimulation to patient 112. Stimulation generator 260 may be controlled by one or more stimulation parameters. Stimulation parameters may control any aspect of the stimulation, such as, voltage stimulation amplitude, current stimulation amplitude, pulse width, pulse frequency, pulse rate, as well as a therapy duty cycle including an ON time for the delivery of stimulation and an OFF time when stimulation is stopped for a period, such as multiple seconds or minutes, that is significantly greater than the time between pulses during the ON time, and the like. The waveform stimulation may be any kind of waveform, such as continuous time signals (e.g., sine waves) or burst of signals.

[0060] Stimulation from the stimulation generator 260 may include two or more modes where each mode operates in a different manner. For example, stimulation may include a normal DBS mode where normal stimulation parameter values are implemented and a low power DBS mode where stimulation parameters are adjusted in some manner to reduce power consumption, such as by reducing a stimulation parameter like amplitude, pulse width, or frequency or by defining an ON / OFF cycling of the stimulation. Stimulation parameters of each mode may have limits to set maximum and / or minimum limits for the stimulation parameter values. For example, a larger simulation limit window may be defined for normal power DBS mode and a smaller stimulation limit window may be defined for low power DBS mode. The use of the normal power DBS mode and low power DBS mode are discussed in greater detail below with reference to FIGS. 3-10.

[0061] Sensing module 270 and sensors 109 may be used to determine which mode to operate stimulation generator 260. For example, LFP and / or ERNA volatility alone as detected by sensing module 270 and / or a patient resting state determined from LFP and / or ERNA from the sensing module 270 and / or additional factors determined by sensor 109 may be used to determine which mode to operate stimulation generator 260.

[0062] FIG. 3 shows an example of logical operations that may be performed by a medical system 100, and the processor 246 in particular, to operate IMD 106 in anormal power DBS mode and a low power DBS mode. IMD 106 may begin operation in the normal power DBS stimulation mode at operation 310. In the normal power DBS stimulation mode, DBS may be performed using stimulation parameters that are not directed to reduced power consumption but instead are directed to therapy capable of addressing a typical LFP and / or ERNA volatility that a patient may experience throughout the typical activities of the day. In some examples, the patient state during the normal power DBS mode may be a typical daily state such as the patient being awake, eating a meal, shopping, exercising, and the like. The normal power DBS stimulation mode may include such stimulations as CDBS, single threshold ADBS, dual threshold ADBS, and other stimulation methods appropriate for when a patient is in a normal non-resting state.

[0063] A determination may be made if the low power DBS mode is appropriate at operation 320. The determination may be made based on one or more parameters, such as any combination of one or more physiological parameters of the patient, sensor values, time of day, current stimulation parameters, patient input, previous information learned about the patient, information gathered from other patients, input from a clinician, input from a person involved with patient care, and the like. For example, when a patient is in a resting state over a predetermined amount of time, it may be determined that the low power DBS mode is appropriate. On the other hand, if the sensors 109 determine a patient is currently active, it may be determined that the low power DBS mode is not appropriate. For another example, when a patient’s LFP and / or ERNA amplitude volatility becomes low, where the changes in LFP / ERNA amplitude are confined to a smaller range than is typically the case during a normal active state of the patient for a predetermined amount of time, it may be determined that the low power DBS mode is appropriate. Additionally, the determination of whether the low power DBS mode is appropriate may be based in part on previously collected data, such as data collected for this particular patient or data collected for a population of patients receiving the same therapy. An artificial intelligence / machine learning model may be trained on the previous data to provide the determination for the currently collected data. This model may be specific to the patient and / or include a grouping of other patients.

[0064] When determining if low power DBS mode is appropriate, consideration may be given to neural signals from each hemisphere of the brain and for one or more of the frequency bands of the neural signals. Thus, the determination of whether low power mode is appropriate may be made for each hemisphere of the brain separately or collectively. Likewise, the adjustment of stimulation parameters to provide the low power DBS mode as discussed below may also be done separately for each hemisphere based on the determination of whether low power DBS mode is appropriate for each hemisphere or may be done collectively. Determining whether low power DBS mode is appropriate for each hemisphere separately and then adjusting stimulation parameters to provide the low power DBS mode for each hemisphere separately is beneficial particularly where a patient has different disease states for each hemisphere.

[0065] When it is determined that the low power DBS mode is not appropriate at operation 320, normal DBS may be continued at operation 310. When it is determined that the low power DBS mode is appropriate at operation 320, low power DBS may be performed at operation 330.

[0066] IMD 106 may begin operation in the low power DBS mode at operation 330 by adjusting one or more stimulation parameters so that the power consumed from the battery of IMD 106 is reduced. For example, the amplitude of a voltage or current, a pulse width, and / or a frequency may be reduced. Additionally, the stimulation parameters may be reduced until a negative impact on the patient is determined and the stimulation parameters may be increased until before the negative impact is detected so as to optimize the stimulation parameters for the low power stimulation mode. Examples of negative impact may be determined based on a physiological signal changing, such as LFP amplitude increasing. Likewise, a negative impact may be determined based on input from the patient, such as an indication of poor quality of sleep. As another example, the stimulation parameters defining an ON / OFF cycling mode of the stimulation therapy may be adjusted so as to activate and optimize the ON / OFF cycling for the current patient state. Details of these examples of providing the low power mode are discussed in more detail below with reference to FIGS. 7 and 8.

[0067] When transitioning to and from the low power DBS mode, the transition may be delayed by a predetermined amount of time. For example, one hour afterdetermining that a patient has entered a resting state, the DBS therapy may transition to the low power DBS mode. Likewise, one hour before the patient is expected to awaken, the DBS therapy may transition to the normal power DBS mode. A ramp time from when the stimulation transitions to and from the normal power DBS mode and the low power DBS mode may be specified. Also, the change in stimulation may be a factor of the patient’s condition. For example, when the therapy is for treating pain, the frequency may be increased at a faster rate. Also, to determine the aspects such as ramp time, heart rate and other patient state parameters may be monitored. While ramping stimulation, if the LFP or heart rate increases, stimulation parameters may be held constant at this stimulation level. The stimulation parameters may be set based on previous stimulations, such as a baseline in the normal power DBS mode. For example, when the lowest effective stimulation parameters were previously found, IMD 106 may change to these stimulation parameters at a faster rate as compared to when the IMD 106 is titrating for the lowest effective stimulation parameters.

[0068] Although FIG. 3 illustrates the two stimulation therapy modes being the normal power DBS mode and the low power DBS mode, any number of modes may be used. For example, a normal power mode may be used during a zone of time defined between when a patient awakes at 6:01am until 6pm, a resting low power mode during a zone from 6:01pm to 11pm, and a sleeping low power mode during a zone between 11 :01pm and 6am. Each transition to a mode and corresponding stimulation parameters may be distinct for each zone of time. For example, the acceptable LFP / ERNA amplitude volatility range for the lower power evening resting mode may be larger than for the low power sleeping mode, and the stimulation parameters for the low power evening resting mode may be larger than for the low power sleeping mode.

[0069] FIG. 4 shows an example of logical operations 320a that correspond to operation 320 from FIG. 3 and that may be performed by a medical system 100 to operate IMD 106 to determine if the low power DBS mode is appropriate because the patient is in a resting state. One or more factors may be considered to determine if the patient is in the resting state where low power stimulation therapy is appropriate. For instance, LPF and / or ERNA volatility may first be considered and then when the LFP and / or ERNA volatility is low, thus suggesting that the patient is in a resting statewhere low power DBS mode is acceptable. Other factors may be considered as a manner of verification that the patient is in a resting state where low power DBS is appropriate. Examples of these additional factors that can be considered include sensed data 421, such as LFP / ERNA volatility over an extended period of time, heart rate (HR) and respiration, patient position data 422, time of day data 430, patient movement data 440, stimulation parameters data 450, and patient input data 460. Patient input data 460 may include input from the patient as well as any other person involved in the care of the patient, such as a clinician, a caregiver, etc.

[0070] In this particular example, the operations 320a begin by first detecting if the LFP and / or ERNA amplitudes being sensed are within a first range indicative of a normal patient state or are at a low volatility by being within a smaller range indicative of a resting patient state at operation 410. In one example, only LFP volatility is considered, while in another example only ERNA volatility is considered. In a third example, both the LFP volatility and the ERNA volatility are considered. The smaller range for LFP / ERNA may be a range that has been determined by prior observation of the current patient or of information aggregated for a population of patients with similar conditions and therapy as the current patient. If the LFP and / or ERNA amplitude fluctuations are not within the smaller range indicative of low volatility, then control returns to operation 310 of FIG. 3 where normal power DBS therapy continues. If the LFP and / or ERNA amplitude fluctuations are within the smaller range indicative of low volatility, then control proceeds to operation 420 where verification that the low power DBS is appropriate may be performed.

[0071] Operation 420 may use one or more categories of the various additional data discussed above. For example, if during a resting state, it is expected the LFP volatility, ERNA volatility, HR, and respiration of a patient decrease. Although the LFP, ERNA, and HR have decreased in this example, the respiration is higher than a resting state, and it may be determined that the patient is not in the resting state. Patient position data 420 may be used to either determine or help to support if the patient is in a resting state. For example, if the patient is standing, the patient may be determined not to be in a resting state. The time of day data 430 may be used to either determine or help to support if the patient is in a resting state. For example, if the patient normally sleeps between 11pm and 6am, when the time of day is 3pm, it maybe determined that a patient is not in a resting state. Patient movement data 440 may be used to either determine or help to support if the patient is in a resting state. Patient movement may be determined using an accelerometer of sensor 109. For example, if the patient has a high level of activity, it may be determined that a patient is not in a resting state. Patient movement can be adjusted to account for the patient having a movement disorder, such as a tremor, and the normal sleep movement of the patient. Stimulation parameters may be used to either determine or help to support if the patient is in a resting state. For example, when IMD 106 is actively modifying one or more stimulation parameters to obtain steady state stimulation, it may be determined that the patient is not in the resting state. Patient input data 460 may be used to either determine or help to support if the patient is in a resting state. For example, when the patient goes to bed, they may provide an indication to programmer 104 that the patient is going to bed which in turn can be transmitted to IMD 106 to be considered in determining the patient’s state. For another example, a patient, clinician, or another authorized person may enter the patient’s sleep schedule into programmer 104. Other parameters may be used to determine resting state, such as stress and if the patient is in a bedroom as determined by proximity to a bedside monitor.

[0072] If it is determined by operation 420 that the patient is not in the resting state, then control returns to operation 310 of FIG. 3 where normal power DBS therapy continues. If it is determined that the patient is in the resting state, then control proceeds to operation 330 of FIG. 3 where low power DBS is implemented.

[0073] FIG. 5 shows operations 320b that are another example of operation 320 of FIG. 3 that may be performed by a medical system 100, and particularly the processor 246, to operate IMD 106 to determine if the low power DBS mode is appropriate. Initially, it is determined if the LFP and / or ERNA amplitude fluctuations are in a range for low power DBS mode at operation 510. The determination of whether the LFP and / or ERNA amplitudes are in a range for low power DBS may be made over an initial predetermined amount of time. Similar to operation 410 of FIG. 4, here it may be initially determined if the LFP and / or ERNA amplitudes are within a smaller range than is defined for a normal state of this patient. For instance, in an adaptive DBS system, this smaller range may be smaller than the target range for the LFP and / or ERNA being used to control stimulation during normal power DBS mode. When theLFP and / or ERNA is initially detected as being in the smaller range that suggests low power DBS mode is appropriate, operation 520 may be performed where the LFP and / or ERNA continues to be monitored relative to this smaller range over an extended period of time that establishes a time threshold. If the LFP and / or ERNA signal amplitudes exceed the smaller range before reaching the time threshold, normal power DBS is continued at operation 310 of FIG. 3. If the LFP and / or ERNA signal amplitudes remain within the smaller range beyond reaching the time threshold, then the low power DBS mode may be implemented at the operation 330 of FIG. 3.

[0074] FIG. 6 shows operations 320c that are another example of operation 320 of FIG. 3 that may be performed by a medical system 100, and particularly the processor 246, to operate IMD 106 to determine if the low power DBS mode is appropriate. While monitoring the LFP and / or ERNA while the LFP and / or ERNA signal amplitudes are in the larger range for normal power DBS mode, it may be established that the normal DBS stimulation parameters are in a steady state at operation 610, thus suggesting that the LFP and / or ERNA volatility may be low and that the low power DBS is appropriate. The LFP and / or ERNA range may be measured over a first predefined amount of time in order to establish that the normal DBS stimulation parameters have continued to be steady state during that time to suggest lower power DBS mode is appropriate, which is particularly useful in an adaptive DBS system where stimulation parameters may are adaptive in order to control relatively large LFP and / or ERNA amplitude fluctuations. An LFP and / or ERNA range for the low power DBS mode may then be established based on the LFP and / or ERNA range for the normal power DBS mode at an operation 620 where the LFP and / or ERNA range for the low power DBS mode is smaller than the LFP and / or ERNA range for the normal power DBS mode.

[0075] A determination may be made if the monitored LFP and / or ERNA is within the LFP and / or ERNA amplitude range for the low power DBS mode at an operation 630. The determination that the monitored LFP and / or ERNA amplitude is within the LFP and / or ERNA range for the low power DBS mode may be based on a predetermined time as previously discussed. For example, the LFP and / or ERNA amplitude may be required to be within the low power DBS range for a predetermined amount of time for the determination to be made that the monitored LFP and / or ERNAis within the range for the low power DBS mode. If the monitored LFP and / or ERNA is not within the range for the low power DBS mode, normal power DBS mode may be continued at operation 310 of FIG. 3. If the monitored LFP and / or ERNA is within the range for the low power DBS mode, a transition to the low power DBS mode occurs at operation 330 of FIG. 3.

[0076] FIG. 7 shows operations 330a that are an example of operation 330 of FIG. 3 that may be performed by a medical system 100, and particularly the processor 246, to operate IMD 106 to implement the low power DBS mode. In particular, low power therapy mode stimulation parameters may be determined by the operations 330a while the patient is in a state where low power therapy mode is appropriate. Initially, a starting point for low power stimulation parameters may be set for stimulation generator 260 at an operation 710. Here, the results from previous stimulations may be used to set the starting point for the stimulation parameters. For example, if it was previously determined a patient could tolerate a specific set of stimulation parameters during a period of time when low power therapy mode was appropriate and was used, the stimulation parameters may be set to the previous stimulation parameters. For another example, results collected from a group of patients receiving the same therapy may be used to set the stimulation parameters at operation 710.

[0077] One or more stimulation parameters may be reduced to a lower power consuming level at an operation 720 in order to attempt a further optimization of the stimulation parameters for the low power therapy mode. For example, when the stimulation parameters include a controlled voltage amplitude, the amplitude of the stimulation voltage may be reduced. Other examples include a reduced pulse width and / or a reduced pulse frequency. As an example, the amount of the reduction may be based on previous stimulation adjustments from both the patient and / or a group of patients receiving the same therapy or based on a smallest increment available.

[0078] A determination may be made if a physiological parameter of the patient is increased at operation 730 as a result of the reduced stimulation parameter(s). For example, the determination may be made if the LFP or ERNA amplitude increases over a threshold from the previous stimulation. For another example, the determination may be made if the patient’s movement disorder increases over a threshold from the previous stimulation. Other physiological parameters may beconsidered including parameters that decrease as the stimulation parameter(s) reduce. Reducing stimulation for low power therapy mode may be performed over a predetermined amount of time and over multiple instances of periods when entering low power therapy mode has been deemed appropriate, such as over a period of 1-2 months to slowly titrate the reduced stimulation parameters. Additionally, a predefined amount of time delay may occur during the period when the patient is in a state where low power therapy mode is appropriate. The time delay may occur between when the stimulation is initially reduced at operation 720 and when a determination is made if a physiological parameter increases at operation 730. When the physiological parameter is not increased, the stimulation parameter(s) may be further decreased by repeating operation 720. Furthermore, the reduction of stimulation may include a delay. For example, a one hour delay may occur after a transition to the low power therapy mode to account for a time it is expected for the patient to go to sleep. The repetition of operations 720 and 730 ultimately finds a lower bound for optimizing the stimulation therapy parameter(s).

[0079] When the physiological parameter is increased as detected at operation 730 such that the lower bound of stimulation parameter reduction is found, the one or more stimulation parameter(s) may be increased until the physiological parameter decreases at operation 740 so as to return the low power therapy to an acceptable level. At this point, the low power therapy mode may proceed with the stimulation parameter(s) being limited by either being held constant at the lower level for at least a period of time or otherwise limited to a reduced range at an operation 750. Limiting the stimulation param eter(s) to the reduced range during the low power DBS mode allows the therapy to remain adaptive while also reducing power consumption.

[0080] This limit on the stimulation parameter for low power DBS mode being applied at operation 750 can be set by the IMD or by the programmer either automatically via programmed data or by input from a clinician. Furthermore, the limit may be learned from machine learning and artificial intelligence techniques from training based on collected data. This limit could be set via a percentage of the daily limit of the normal power therapy mode or may be a hard defined level, such as 1.0-3.0 mA for a current amplitude controlled stimulation. The limit may also be dependent on disease state. For instance, in the case of essential tremor, the stimulationamplitude could go all the way to 0.0mA as it is active tremor but clinicians may want the lowest allowed power to be a small residual stim to be applied, i.e., 0.2mA.

[0081] The low power therapy mode continues while a determination is made as to whether low power DBS mode is still appropriate at an operation 760. Conditions that cause the low power DBS mode to no longer be appropriate may include the opposite of conditions that were used to determine that the low power DBS mode was appropriate. For example, if the LFP and / or ERNA signal amplitudes of the patient increase outside a resting state range, it may be appropriate to exit the low power DBS mode and return to the normal power DBS mode. Additionally, it may be appropriate to exit the low power DBS mode for other reasons including those used to determine a resting state as discussed above for FIG. 4, and also based on expected events. For example, it may be appropriate to exit the low power DBS mode one hour before the patient is expected to awaken from sleep. When it is appropriate to remain in the low power DBS mode, operation 750 continues until operation 770 eventually finds it is no longer appropriate. Control then returns to operation 310 of FIG. 3 where normal power therapy mode resumes.

[0082] At any point in operations 710-760, the low power therapy mode may be exited. For example, while reducing stimulation in step 720 and determining if the physiological parameter increases in step 730, if LFP and / or ERNA signal amplitudes increase or if there are indications that the patient is no longer in a resting state, the low power mode may be exited via operation 760. For another example, the user may select on the programmer 104 to return to the normal power DBS mode. For yet another example, when the patient awakens during the night and leaves the bedroom, IMD 106 may transition to the normal DBS zone. The IMD 106 may recognize the patient is no longer in a resting state based on parameters such as LFP, ERNA, respiration, blood pressure, patient movement increasing, and position changing.

[0083] FIG. 8 shows another example of operations 330b that may be performed to implement and optimize the ON / OFF therapy duty cycle for the low power DBS mode. In addition to the operations 330b, FIG. 8 shows an operation 810 where monitoring of patient-specific parameters may be performed over time in the background by the IMD 106 to learn the characteristics of various resting states of the patient. For instance, the patient may have a resting state where lightly asleep wherelow power DBS mode may be appropriate but at a less aggressive ON / OFF cycling, while the patient may have a resting state that is deep sleep where a more aggressive ON / OFF cycling may be available for the low power DBS mode. Rather than learned parameters for the ON / OFF cycling, the IMD 106 may store a library of pre- established patterns for controlling the ON / OFF cycling. Furthermore, the IMD 106 may be programmed to start and stop the ON / OFF cycling, or certain configurations of the ON / OFF cycling, at certain times of the day.

[0084] After it has been determined that the low power DBS mode is appropriate at operation 320 of FIG. 3, the low power mode stimulation parameters providing the ON / OFF cycling is done at operation 820. These parameters of the ON / OFF cycling, such as the length of the ON time and the length of the OFF time, may be set based on the current patient state, such as whether the patient is lightly asleep or in a deep sleep. The patient state may be determined in the manners previously described including those of FIG. 4 regarding considerations of the resting state, including data from internal and external sensors of the IMD 106. The stimulation is set to ON at the operation 330 where the stimulation proceeds with the specific amplitude, pulse width, frequency and so forth. Operation 840 detects whether the OFF time of the cycle has been reached for the therapy. If not, then the stimulation continues at operation 830.

[0085] Once the operation 840 detects that the OFF time of the cycle has been reached, operation 850 determines if the low power DBS mode is still appropriate. If it is not, low power DBS mode ends and normal power DBS mode begins at operation 310 of FIG. 3. If the low power DBS mode is still appropriate, then the stimulation is set to OFF at operation 860. Operation 870 then detects whether the ON time has been reached. Operation 850 may continue to detect whether low power DBS remains appropriate during the OFF time. For instance, should the patient suddenly awaken during the OFF time, operation 850 may detect the awakened patient state and return stimulation to the normal power DBS mode.

[0086] Once operation 870 detects that the ON time has been reached, then the stimulation parameters for the ON / OFF cycling may be updated for the current patient state at operation 820 prior to the stimulation being turned back on at operation 830. For instance, the patient may have entered a deeper sleep that allows for the more aggressive ON / OFF cycling where the ON time is shorter and the OFF time is longer.The ON / OFF cycling then continues. At any time during these operations 330b, the ON / OFF cycling may be manually disabled via the external programmer so that the normal power DBS mode resumes.

[0087] As an example of the ON / OFF cycling of the low power DBS mode and the adjustments to the stimulation parameters providing the ON / OFF cycling, the ON / OFF cycling may initially be defined with stimulation parameters specifying an ON time three minutes and an OFF time of 30 seconds. Upon the patient entering a deeper sleep, the ON time may be adjusted to a shorter time, such as one minute, while the OFF time is adjusted to a longer time, such as one minute, where these settings are learned and do not interrupt the sleep of the patient. Upon the patient returning to a lighter sleep, the ON time may return to three minutes and the OFF time returns to 30 seconds.

[0088] FIG. 9 shows an example of logical operations that may be performed by a medical system 100 to incorporate user feedback. Low power DBS mode may be performed at operation 910. In an example, operation 910 may be the same as operation 330 of FIG. 3. Feedback may be received regarding low power DBS at an operation 920. The feedback may be from the patient, a clinician, a caregiver, or anyone else involved in the patient’s care. The patient may specify a quality of sleep, such as restlessness during sleep. The patient also may specify if they noticed the transition between states, such as from the transition between the normal power DBS mode and the low power DBS mode. Additionally, the patient may specify if their symptoms were controlled during the low power DBS mode. Furthermore, the patient can specify changes such as disable low power DBS mode, change the amplitude of stimulation, such as 50 percent less amplitude reduction, revert to previous settings, and the like.

[0089] Feedback may be provided in additional ways. A clinician may provide feedback based on data recorded during the low power DBS mode and / or during the normal power DBS mode. The clinician may use the patient feedback and / or recorded data to provide the clinician’s feedback. The clinician may also change a range of stimulation parameters the patient may adjust. An artificial intelligence / machine learning model may be used to provide feedback based on the experience of the patients or a group of other patients.

[0090] The low power therapy mode stimulation parameters may be adjusted based on the received feedback at operation 930. The stimulation parameters that may be adjusted and the amount of the adjustment may be related to the source of the feedback. For example, the feedback from a clinician may be unconstrained for stimulation parameters while patient feedback may only change the stimulation parameters within a range defined by the clinician.

[0091] Functionality described in relation to the IMD 106 with respect to FIGS. 3- 9 may be shared with programmer 104. For example, programmer 104 may determine stimulation parameters for low power therapy mode and send these stimulation parameters to IMD 106. As another example, the programmer 104 may receive data from the IMD 106 in order to make the determination of whether to enter the low power therapy mode.

[0092] FIG. 10 shows a graph demonstrating the change of therapy from the normal power DBS mode to the low power DBS mode and back to the normal power DBS mode along with various patient state information. LFP signal 1010 begins to have lower volatility around 8pm indicating the patient is potentially entering a resting state. As the LFP signal amplitude volatility 1010 decreases, IMD 106 is starting to transition to the low power DBS mode which may cause the amplitude of stimulation 1020 to decrease. Other parameters, such as heart rate 1030, patient movement 1040, and patient position 1050 may be used to confirm that the patient is in the resting state. Patient input 1060 may be used to confirm if the patient is or is not in the resting state and / or to assist in setting the stimulation parameters during the low power therapy mode. Around 7am as the patient is starting to awaken, the patient state parameters are rising toward normal levels and the stimulation amplitude 1020 returns to the normal power DBS mode. FIG. 10 shows the adjustment to the stimulation amplitude to enter and exit low power DBS mode as an example. The adjustment could be to one or more other stimulation parameters. For instance, the ON / OFF cycling of stimulation therapy could be activated during the period of time where FIG. 10 shows the stimulation amplitude being low instead of the stimulation amplitude being reduced during that time.

[0093] The invention may further be described by reference to the following numbered Examples.

[0094] Example 1. A method of reducing power consumption of an implantable medical device providing stimulation therapy, comprising: upon detecting that a neural signal has an amplitude volatility that has decreased from a first range to a second range that is smaller than the first range, sensing a resting state parameter of a patient; and when the resting state parameter indicates that the patient is in a resting state, providing low power stimulation therapy by adjusting at least one stimulation parameter to reduce power consumption.

[0095] Example 2. The method of Example 1, wherein the neural signal comprises a local field potential.

[0096] Example 3. The method of Example 1, wherein the neural signal comprises an evoked resonant neural activity.

[0097] Example 4. The method of any of Examples 1-3, wherein the stimulation parameter comprises an amplitude and wherein the amplitude is reduced when providing low power stimulation therapy.

[0098] Example 5. The method of any of Examples 1-3, wherein the stimulation parameter comprises an ON / OFF cycling and wherein the ON / OFF cycling is implemented when providing low power stimulation therapy.

[0099] Example 6. The method of any of Examples 1-5, wherein the stimulation therapy is deep brain stimulation.

[0100] Example 7. The method of Example 6, wherein the deep brain stimulation is adaptive deep brain stimulation.

[0101] Example 8. The method of any of Examples 1-7, wherein the resting state parameter comprises at least one of heart rate, respiration, patient position, time of day, patient movement, electrical stimulation delivered by the implantable medical device, and patient input.

[0102] Example 9. The method of any of Examples 1-8, wherein the resting state comprises a sleep state.

[0103] Example 10. The method of any of Examples 1-9, further comprising when the patient is in a normal state where the neural signal has an amplitude volatility in the first range, performing a normal power stimulation therapy.

[0104] Example 11. The method of Example 10, wherein the stimulation parameter during normal power therapy stimulation while the patient is in the normalstate is larger than during low power therapy stimulation when the patient is in the resting state.

[0105] Example 12. The method of any of Examples 1-11, wherein the stimulation therapy is adaptive during the normal power stimulation therapy where the stimulation parameter varies within a parameter range, and wherein the stimulation parameter is held to a fixed value during the low power stimulation therapy.

[0106] Example 13. A method of reducing power consumption of a stimulation device, comprising: while providing stimulation therapy by the stimulation device, sensing a neural signal; when the neural signal has an amplitude volatility within a first range, limiting at least one stimulation parameter that controls stimulation delivered by the stimulation device to a first value; and when the neural signal has an amplitude volatility within a second range that is smaller than the first range, limiting the at least one stimulation parameter to a second value that is smaller than the first value.

[0107] Example 14. The method of Example 13, wherein the second range is indicative of a resting state of a patient and the first range is indicative of a normal state of the patient.

[0108] Example 15. The method of any of Examples 13-14, wherein the stimulation parameter is held to the second value once the neural signal amplitude volatility has remained within the second range for a period of time.

[0109] Example 16. The method of any of Examples 13-15, wherein the stimulation therapy is deep brain stimulation.

[0110] Example 17. The method of Example 16, wherein the deep brain stimulation is adaptive deep brain stimulation.

[0111] Example 18. The method of any of Examples 13-17, wherein the neural signal comprises a local field potential.

[0112] Example 19. The method of any of Examples 13-17, wherein the neural signal comprises an evoked resonant neural activity.

[0113] Example 20. An implantable medical device comprising: a memory; a processor; a sense circuit; and a stimulation circuit, wherein the memory, the sense circuit, and the stimulation circuit are coupled to the processor and wherein the memory stores instructions that, when executed by the processor, cause the processor to: detect that a neural signal has an amplitude volatility that has decreased from a firstrange to a second range that is smaller than the first range using the sense circuit, sense a resting state parameter of a patient after having detected the neural signal amplitude volatility has decreased from the first range to the second range, and provide low power stimulation therapy from the stimulation circuit by adjusting at least one stimulation parameter to reduce power consumption when the resting state parameter indicates that the patient is in a resting state.

[0114] Example 21. The implantable medical device of Example 20, wherein the neural signal comprises a local field potential.

[0115] Example 22. The implantable medical device of Example 20, wherein the neural signal comprises an evoked resonant neural activity.

[0116] Example 23. The implantable medical device of any of Examples 20-22, wherein the stimulation parameter comprises an amplitude and wherein the amplitude is reduced when providing low power stimulation therapy.

[0117] Example 24. The implantable medical device of any of Examples 20-22, wherein the stimulation parameter comprises an ON / OFF cycling and wherein the ON / OFF cycling is implemented when providing low power stimulation therapy.

[0118] Example 25. The implantable medical device of any of Examples 20-24, wherein the stimulation therapy is deep brain stimulation.

[0119] Example 26. The implantable medical device of Example 25, wherein the deep brain stimulation is adaptive deep brain stimulation.

[0120] Example 27. The implantable medical device of any of Examples 20-26, wherein the resting state parameters comprises at least one of heart rate, respiration, patient position, time of day, patient movement, electrical stimulation delivered by the implantable medical device, and patient input.

[0121] Example 28. The implantable medical device of any of Examples 20-27, wherein the resting state comprises a sleep state.

[0122] Example 29. The implantable medical device of any of Examples 20-28, further comprising when the patient is a normal state where the neural signal has an amplitude volatility in the first range, the processor performs normal power stimulation therapy.

[0123] Example 30. The implantable medical device of Example 29, wherein the processor provides stimulation therapy that is adaptive during the normal state wherethe stimulation varies within a parameter range and provides lower pow stimulation by holding the stimulation parameter to a fixed value.

[0124] Example 31. An implantable medical device comprising: a memory; a processor; a sense circuit; and a stimulation circuit, wherein the memory, the sense circuit, and the stimulation circuit are coupled to the processor, and wherein the memory stores instructions that, when executed by the processor, cause the processor to: sensing a neural signal at the sense circuit; limit at least one stimulation parameter that controls stimulation delivered by the stimulation circuit to a first value when the neural signal has an amplitude volatility that is within a first range; and limit the stimulation parameter to a second value that is smaller than the first value when the neural signal amplitude volatility is within a second range that is smaller than the first range.

[0125] Example 32. The implantable medical device of Example 31, wherein the second range is indicative of a resting state of a patient and the first range is indicative of a normal state of the patient.

[0126] Example 33. The implantable medical device of any of Examples 31-32, wherein the processor holds the stimulation parameter to the second value once the neural signal amplitude volatility has remained within the second range for a period of time.

[0127] Example 34. The implantable medical device of any of Examples 31-34, wherein the stimulation therapy is deep brain stimulation.

[0128] Example 35. The implantable medical device of Example 34, wherein the deep brain stimulation is adaptive deep brain stimulation.

[0129] Example 36. The implantable medical device of any of Examples 31-35, wherein the neural signal comprises a local field potential.

[0130] Example 37. The implantable medical device of any of Examples 31-35, wherein the neural signal comprises an evoked resonant neural activity.

[0131] While embodiments have been particularly shown and described, it will be understood by those skilled in the art that various other changes in the form and details may be made therein without departing from the spirit and scope of the invention.

Claims

What is claimed is:

1. An implantable medical device (106) comprising: a memory (248); a processor (246); a sense circuit (270); and a stimulation circuit (260), wherein the memory, the sense circuit, and the stimulation circuit are coupled to the processor and wherein the memory stores instructions that, when executed by the processor, cause the processor to: detect that a neural signal has an amplitude volatility that has decreased from a first range to a second range that is smaller than the first range using the sense circuit, sense a resting state parameter of a patient after having detected the neural signal amplitude volatility has decreased from the first range to the second range, and provide low power stimulation therapy from the stimulation circuit by adjusting at least one stimulation parameter to reduce power consumption when the resting state parameter indicates that the patient is in a resting state.

2. The implantable medical device of claim 1, wherein the neural signal comprises a local field potential.

3. The implantable medical device of claim 1, wherein the neural signal comprises an evoked resonant neural activity.

4. The implantable medical device of any of claims 1-3, wherein the stimulation parameter comprises an amplitude and wherein the amplitude is reduced when providing low power stimulation therapy.

5. The implantable medical device of any of claims 1-3, wherein the stimulation parameter comprises an ON / OFF cycling and wherein the ON / OFF cycling is implemented when providing low power stimulation therapy.

6. The implantable medical device of any of claims 1-5, wherein the stimulation therapy is deep brain stimulation.

7. The implantable medical device of claim 6, wherein the deep brain stimulation is adaptive deep brain stimulation.

8. The implantable medical device of any of claims 1-7, wherein the resting state parameters comprises at least one of heart rate, respiration, patient position, time of day, patient movement, electrical stimulation delivered by the implantable medical device, and patient input.

9. The implantable medical device of any of claims 1-8, wherein the resting state comprises a sleep state.

10. The implantable medical device of any of claims 1-9, further comprising when the patient is a normal state where the neural signal has an amplitude volatility in the first range, the processor (246) performs normal power stimulation therapy.

11. The implantable medical device of claim 10, wherein the processor (246) provides stimulation therapy that is adaptive during the normal state where the stimulation varies within a parameter range and provides low power stimulation by holding the stimulation parameter to a fixed value.

12. An implantable medical device (106) comprising: a memory (248); a processor (246); a sense circuit (270); and a stimulation circuit (260), wherein the memory, the sense circuit, and the stimulation circuit are coupled to the processor, and wherein the memory stores instructions that, when executed by the processor, cause the processor to: sensing a neural signal at the sense circuit;limit at least one stimulation parameter that controls stimulation delivered by the stimulation circuit to a first value when the neural signal has an amplitude volatility that is within a first range; and limit the stimulation parameter to a second value that is smaller than the first value when the neural signal amplitude volatility is within a second range that is smaller than the first range.

13. The implantable medical device of claim 12, wherein the second range is indicative of a resting state of a patient and the first range is indicative of a normal state of the patient.

14. The implantable medical device of any of claims 12-13, wherein the processor (246) holds the stimulation parameter to the second value once the neural signal amplitude volatility has remained within the second range for a period of time.

15. The implantable medical device of any of claims 12-14, wherein the stimulation therapy is deep brain stimulation.

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