Closed loop nerve conditioning for selective fiber stimulation

Abstract

Systems and techniques to selectively stimulate or attenuate the neural activity of specific nerve fiber types, the system including electrical stimulation circuitry to generate electrical stimulation deliverable to a target nerve via a set of electrodes. System processing circuitry is also configured to determine one or more parameter values that define the electrical stimulation generated by the electrical stimulation circuitry as well as to control the electrical stimulation circuitry to generate a burst of conditioning pulses deliverable to the target nerve. The burst of conditioning pulses is configured to change a state of excitability of target nerve fibers within the target nerve. Finally to control, based on the one or more parameter values, the electrical stimulation circuitry to generate electrical stimulation therapy to the target nerve, wherein the electrical stimulation therapy is configured to treat a condition of the patient.

Description

CLOSED LOOP NERVE CONDITIONING FOR SELECTIVE FIBER STIMULATION

[0001] This application is a PCT application that claims priority to, and the benefit of, U.S. Provisional Patent Application No. 63 / 592,653, filed October 24, 2023, the entire contents of which is incorporated herein by reference.TECHNICAL FIELD

[0002] The disclosure relates to implantable medical devices used for monitoring and delivering electrical stimulation therapy to a patient.BACKGROUND

[0003] Medical devices may be external or implanted and may be used to monitor patient signals such as cardiac activity, biological impedance and 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 or fecal incontinence, sexual dysfunction, obesity, or gastroparesis and other conditions. In some examples, medical devices may include a rechargeable electrical power source, or may be powered directly by transmitting energy through tissue. Nerves in the body contain multiple fiber types that have different innervation thresholds based on factors such as size and myelination. These different fiber types can be motor or sensory, and are responsible for relaying information related to movement and sensations such as pain or touch.SUMMARY

[0004] In general, the disclosure describes systems and techniques to selectively stimulate or attenuate the neural activity of one or more specific nerve fiber types instead of other nerve fiber types. Nerves in the body contain multiple nerve fiber types that have different innervation thresholds (e.g., depolarization threshold or excitation threshold) based on factors such as size, ion channel concentration and decomposition, and myelination of each nerve fiber type. These different fiber types can be motor or sensory (and different types of each), and can be responsible for relaying information related to movement and / or sensations such as pain or touch. Some examples of neuromodulationtherapies focus on stimulating larger areas of the body (e.g., spinal cord) or entire nerves (e.g., sacral / tibial) that may produce unwanted side effects such as unintended movement or uncomfortable sensations. Additionally, for peripheral nerves that ultimately feed into the spinal cord, different fibers within the nerve may feed into different levels of the spinal cord. One example nerve is the tibial nerve with nerve fibers that span from S3 to L4 along the spinal cord.

[0005] The systems and techniques of this disclosure may selectively stimulate and / or attenuate the neural activity of specific fiber types, which may reduce unwanted side effects, as well as deliver differential therapy to targeted anatomical targets through the spinal cord. In this way, this disclosure describes a multiplexed therapy delivered through a single nerve that may result in the modulation of multiple components of the nervous system (e.g., the tibial nerve would enervate the local periphery, plus the lumbar and sacral regions of the spinal cord).

[0006] Nerve conditioning, i.e., shifting one or more fibers of the nerve towards an increased or decreased state of excitability, could enable this stimulation or attenuation of selective nerve fibers via different stimulation patterns. These various stimulation patterns may be configured to effectively raise the activation threshold for certain fibers of the nerve. This selective raising of the activation threshold can enable the generation and propagation of neural activity of some higher threshold fiber types (less sensitive) while other lower threshold fiber types (more sensitive) cannot be activated while their threshold is raised temporarily. The systems of this disclosure may maintain or reverse the excitability effect both during or outside of conventional electrical stimulation therapy delivery and in some examples may be automated using invoked response sensing, accelerometer, or other sensor data for closed loop control.

[0007] In one example, the disclosure is directed to a medical device comprising: electrical stimulation circuitry configured to generate electrical stimulation deliverable to a target nerve via a set of electrodes of a plurality of electrodes; and processing circuitry configured to: determine one or more parameter values that define the electrical stimulation generated by the electrical stimulation circuitry; control the electrical stimulation circuitry to generate a burst of conditioning pulses deliverable to the target nerve, wherein the burst of conditioning pulses is configured to change a state of excitability of target nerve fibers within the target nerve; and control, based on the one or more parameter values, the electrical stimulation circuitry to generate electricalstimulation therapy to the target nerve via the second set of electrodes, wherein the electrical stimulation therapy is configured to treat a condition of the patient.

[0008] In another example, the disclosure is directed to a system comprising: one or more electrodes configured to be located proximal to a target nerve of a patient; a medical device comprising: electrical stimulation circuitry configured to generate electrical stimulation deliverable to a target nerve via a set of electrodes of a plurality of electrodes; processing circuitry configured to: determine one or more parameter values that define the electrical stimulation generated by the electrical stimulation circuitry; control the electrical stimulation circuitry to generate a burst of conditioning pulses deliverable to the target nerve, wherein the burst of conditioning pulses is configured to change a state of excitability of target nerve fibers within the target nerve; and control, based on the one or more parameter values, the electrical stimulation circuitry to generate electrical stimulation therapy to the target nerve via the set of electrodes, wherein the electrical stimulation therapy is configured to treat a condition of the patient.

[0009] In another example, the disclosure is directed to a method comprising: controlling, by processing circuitry of a medical device, electrical stimulation circuitry of the medical device to generate a burst of conditioning pulses deliverable to a target nerve, wherein the target nerve is located proximal to one or more electrodes operatively coupled to the electrical stimulation circuitry; wherein the burst of conditioning pulses is configured to change a state of excitability of target nerve fibers within the target nerve; responsive to completing the burst of conditioning pulses, controlling, by the processing circuitry, the electrical stimulation circuitry to generate electrical stimulation therapy deliverable to the target nerve, wherein the electrical stimulation therapy is configured to treat a condition of the patient.

[0010] The details of one or more examples of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the disclosure will be apparent from the description and drawings, and from the claims.BRIEF DESCRIPTION OF DRAWINGS

[0011] FIG. l is a conceptual diagram illustrating example system that includes an implantable medical device and an external computing device.

[0012] FIG. 2 is a conceptual diagram illustrating example system that includes an implantable medical device (IMD) configured to deliver electrical stimulation to a patient according to an example of the techniques of the disclosure.

[0013] FIGS. 3 A and 3B are conceptual diagrams illustrating an example of sensing and applying electrical stimulation therapy to nerve fibers via a tissue-electrode interface.

[0014] FIGS. 4A and 4B are timing diagrams illustrating examples of conditioning and therapy application according to one or more techniques of this disclosure.

[0015] FIG. 5 is a block diagram illustrating example components of the medical device of FIG. 1.

[0016] FIG. 6 is a block diagram of an example an external computing device of FIGS. 1 and 2.

[0017] FIGS. 7A, 7B and 7C are conceptual diagrams that illustrate human anatomy in relation to peripheral nerves of the lower (inferior) portions of the human body.

[0018] FIG. 8Ais a flow chart illustrating an example closed loop operation of the medical system of this disclosure.

[0019] FIG. 8B is a flow chart illustrating an example of closed loop operation for the systems of this disclosure to control the speed of recovery of conditioned nerves.

[0020] FIGS. 9A, 9B and 9C are timing diagrams illustrating examples of the effects of conditioning bursts on nerve fibers.

[0021] FIG. 10 is a flow chart illustrating an example mode of operation of the medical system according to one or more techniques of this disclosure.DETAILED DESCRIPTION

[0022] The disclosure describes systems and techniques to apply electrical stimulation conditioning bursts to a nerve to selectively increase or decrease excitability of specific nerve fibers within the nerve. This conditioning of the nerve can then enable subsequent electrical stimulation therapy that can target those specific nerve fibers or other nerve fibers within the nerve. In some examples, the conditioner stimulus is a bursting pattern in which each burst has a number of parameters that can be tweaked such as number of bursts, pulses per burst, inter / intra-burst frequency, pulse amplitude, pulse frequency, polarity, recharge type (passive vs active), pulse width, and similar parameters. The conditioner can be set to specific amplitudes to reduce neural excitability, i.e., reduce the activity of specific fiber types. A lower amplitude conditionermay only reduce the activity of nerve fibers that have a low activation threshold (bigger, myelinated fibers), whereas a higher amplitude conditioner may reduce a larger percentage of nerve fibers.

[0023] In some examples, processing circuitry of an implanted medical device (IMD) may regulate the conditioner feature in a closed loop fashion using evoked response sensing (e.g., ECAPs), accelerometer, or other sensor data, including sensing electromyography (EMG), which measures muscle response or electrical activity in response to a nerve's stimulation of the muscle. In this disclosure, an ECAP is an evoked compound action potential. For example, the processing circuitry may adjust the conditioner pulse amplitude based on the sensed ECAP amplitude or based on presence, or absence of an ECAP, or other evoked response. The IMD may turn on or off the conditioner feature based on accelerometer data, e.g., indicating that a patient is in motion or indicating a specific patient posture. In some examples, the IMD may be configured to apply conditioning pulses during or outside of standard therapy delivery. For example, in tibial neuromodulation, electrical stimulation therapy to treat a patient’s condition, e.g., overactive bladder (OAB) , may typically delivered for about 30 minutes every other day. In some examples, the IMD may be configured to apply the conditioner feature during those 30 minutes, directly before or after delivering the stimulation therapy, or apply the conditioner feature on a day when therapy is not scheduled depending on the desired effect and desired patient outcome.

[0024] The systems of this disclosure may also control the duration of recovery of the nerve (e.g., the length of time that some nerve fiber excitability may be selectively suppressed) in a closed loop fashion. As shown by preclinical results, the conditioning effect may be sustained during continuous probe stimulation with a slow nerve recovery time. However, nerve recovery may be faster after conditioning when an IMD of this disclosure applies fixed amplitude single probe pulses delivered (e.g., every few minutes) as opposed to delivering continuous stimulation. Lastly, the conditioning effect may immediately negated by initiating a growth curve (i.e., a series of rapid probe pulses of increasing amplitude). In this way, the systems of this disclosure may control the recovery rate of the nerve, after applying conditioning pulses. This use of burst pulses for conditioning may be applied to any system for neuromodulation therapy that may use electrical energy stimulation via electrodes to interact with nerves. The incorporation of accelerometer or bioelectrical signal sensing (e.g., ECAP) data could enable closed loop conditioning to control duration of conditioning as well as nerve recovery.

[0025] Said another way, in some examples, the recovery period during which some fibers are less excitable (or more excitable) can be changed by providing conditioning pulses continuously, intermittently, or with a growth curve (amplitude stepping) prior to therapy pulses. In other examples, delivering therapy with continuous pulses may prolong the recovery period, e.g., stopping or pausing therapy may allow the recovery from conditioning more quickly that if continuing to apply therapy. In other examples, “probe pulses” may be interleaved with the electrical stimulation therapy to extend, or shorten, the recovery period. In other examples, probe pulses are electrical stimulation configured to elicit an evoked response, such as an ECAP. The system may apply probe pulses to initially determine excitability for target nerve fibers by eliciting and measuring the evoked response. In some examples, probe pulses may be applied periodically after conditioning to monitor the recovery from conditioning by measuring the evoked response from the conditioned fiber. In other words, probe pulses may be electrical stimulation pulses that may not be configured to elicit a therapeutic response. For example, probe pulses may be configured to elicit an ECAP signal, or to adjust a recovery period after the condition stimulation has been delivered, e.g., without measuring an evoked response. In some examples, probe pulses may have an intensity set near or just above the threshold, where the threshold is a level needed to elicit a response by the target nerve fibers. The threshold may be different for different patients, and may change for the same patient depending on changes to blood chemistry, posture, and other factors. In some examples, probe pulses may be lower amplitude than the therapy pulses, and be presented at a lower rate. In some examples, a probe pulse may be narrower in pulse width, and otherwise optimized for sensing (for example, be triphasic). In this disclosure, intensity means parameter settings that affect the amount of charge delivered to the patient’s tissue, e.g., any one or more of amplitude, pulse width, rate, and similar factors.

[0026] In this disclosure, “continuous stimulation” refers to a series of probe pulses in a row, which in some examples have the same or similar amplitude and may be applied for thirty seconds or more. In some examples, continuous stimulation may be applied for five minutes, ten minutes or longer depending on the patient and desired response. For medium recovery, this would be a single probe pulse delivered every few minutes. In some examples, an intermittent application of probe pulses may be applied as a single pulse, or series of pulses, delivered with durations in between the pulse(s) of several minutes, e.g., five minute durations. In some examples, both intermittent probe andcontinuous probe may be delivered with a frequency of less than 50 Hz with a pulse width of less than 300 microseconds (ps).

[0027] The conditioning stimulation of this disclosure refers to the bursting pattern. In some examples a bursting pattern may include two or more pulses together that are relatively higher frequency (e.g.,., greater than 200 Hz). Therapeutic stimulation refers to parameters that are typically supported by clinical evidence. For example, electrical stimulation therapy for the tibial nerve may be applied at 20 Hz with a pulse width of 200 ps. For sacral therapeutic stimulation may be applied at 14 Hz and 210 ps pulse width. For other therapy, e.g., for spinal stimulation therapy, the stimulation parameters may have a greater range than other types of therapy. In other words, in some examples, continuous probe stimulation may be considered therapeutic if the parameters align with clinically therapeutic stimulation therapy parameters.

[0028] FIG. l is a conceptual diagram illustrating example system that includes an implantable medical device and an external computing device. The example of system 100 in FIG. 1 includes an implantable medical device 10, external computing device 110, and one or more servers 112.

[0029] External computing device 110 may include one or more antennae, such as antenna 26. External computing device 110 may be used to program or adjust settings of IMD 10 and may also recharge an electrical energy storage device, such as a battery, of IMD 10. External computing device 110 may also communicate with servers 112. In other examples, an external computing device separate from external computing device 110 may communicate with IMD 10 to adjust therapy and / or sensing parameters, download recorded data, and so on, such as smart phone, tablet or similar computing device. In some examples external computing device may communicate, and inductively deliver electrical energy to IMD 10 via an internal antenna 28. In other examples, external computing device 110 may include an external wand with one or more antennae for communication and electrical energy delivery.

[0030] The example of FIG. 1 is a side view of a patient’s leg showing a leadless neurostimulation device 10 near the ankle adjacent to the tibial nerve 102. Device 10 can be implanted through the patient’s skin and cutaneous fat layer via a small incision 101. The example of FIG. 1 describes a neurostimulation implantable medical device for tibial nerve stimulation. In other examples, the techniques of this disclosure may apply to other medical devices, such as implantable neurostimulation system for use in spinal cordmonitoring and stimulation therapy, pelvic nerve stimulation and deep brain stimulation, as well as to other types of medical devices without limitation.

[0031] Device 10 may be positioned adjacent to the region defined by flexor digitorum longus and soleus in which tibial nerve 102 is contained and implanted adjacent and proximal to a fascia layer. One or more electrodes of device 10 may face toward tibial nerve 102. The example of system 100 includes a leadless device. Though not shown in FIG. 1, device 10 may also connect to one or more leads comprising one or more electrodes (not shown in FIG. 1).

[0032] IMD 10 may be constructed of any polymer, metal, or composite material sufficient to house the components of IMD 10. In this example, IMD 10 may be constructed with a biocompatible housing, such as titanium or stainless steel, or a polymeric material such as silicone or polyurethane, and surgically implanted at a site in patient near the tibial nerve, in some examples. In other examples, IMD 10 implanted in other locations including the arm, knee, and other peripheral locations as well as near the pelvis, abdomen, or buttocks. The housing of IMD 10 may be configured to provide a hermetic seal for components, such as a rechargeable power source. In addition, the housing of IMD 10 may be selected of a material that facilitates receiving energy to charge the rechargeable power source.

[0033] An advantage of the devices and methods described herein can be improved patient safety and therapy efficacy after implant. In contrast to other approaches, leadless neurostimulation device 10 may not require the patient’s fascia layer near the implant site to be disturbed which may reduce risks affiliated with alternative procedures. Further, device 10 is a unitary structure and may be hermetically sealed.

[0034] During operation, an electrical stimulation signal may be transmitted between one or more electrodes through the fascia layer. The electrical signal may be used to stimulate tibial nerve 102 which may be useful in the treatment of overactive bladder (OAB) symptoms of urinary urgency, urinary frequency and / or urge incontinence, fecal incontinence, sexual dysfunction, pain, or other symptoms.

[0035] In some examples, disease, age, and injury may impair physiological functions of a patient. In one example, bladder dysfunction, such as overactive bladder, urgency, or urinary incontinence, is a problem that may afflict people of all ages, genders, and races. Various muscles, nerves, organs, and conduits within the pelvic floor cooperate to collect, store and release urine. A variety of disorders may compromise urinary tract performance, and contribute to an overactive bladder, urgency, or urinary incontinencethat interferes with normal physiological function. System 100 may help relieve some symptoms of some disorders.

[0036] In some examples, the techniques described in this disclosure are directed to delivery of neurostimulation therapy in a non-continuous manner which may include on- cycles and off-cycles. For example, an IMD may deliver neurostimulation therapy for a specified period of time followed by a specified period of time when the IMD does not deliver neurostimulation (e.g., withholds delivery of neurostimulation). A period during which stimulation is delivered (an on-cycle) may include on and off periods (e.g., a duty cycle or bursts of pulses) with short inter-pulse durations of time when pulses are not delivered.

[0037] In the example in which the power source is a rechargeable power source, the power source of IMD 10 may include one or more capacitors, batteries, or other components (e.g., chemical, or electrical energy storage devices). Example batteries may include lithium-based batteries, nickel metal-hydride batteries, or other materials. The rechargeable power source may be replenished, refilled, or otherwise capable of increasing the amount of energy stored after energy has been depleted. The energy received by secondary coil 16 may be conditioned and / or transformed by a charging circuit of IMD 10. The charging circuit may then send an electrical signal used to charge the rechargeable power source. In other examples, the power source may be a non- rechargeable battery, e.g., a primary battery, as well as other types of power sources including mechanical energy harvesting devices (not shown in FIG. 1).

[0038] External computing device 110 may be used to recharge the rechargeable power source within IMD 10 implanted in the patient. External computing device 110 may be a hand-held device, a portable device, or a stationary charging system. External computing device 110 may also be referred to as charging device 110 in this disclosure. External computing device 110 may include components necessary to charge IMD 10 through tissue of the patient. External computing device 110 may include an internal energy transfer coil 28 and external energy transfer coil 26, also referred to as primary coil 26 or primary coil 28. In other examples, external computing device may only include internal primary coil 28 and omit the use of external primary coil 26, or only include external primary coil 26 and omit the use of internal primary coil 28.

[0039] External computing device 110 may include a housing to enclose operational components such as a processor, memory, user interface, telemetry module, power source, and charging circuit configured to transmit energy to secondary coil 16 via energytransfer coil 26 and / or 28. Although a user may control the recharging process with a user interface of external computing device 110, external computing device 110 may alternatively be controlled by another device, e.g., an external programmer, a computing device of servers 112 such as a tablet computer, laptop or other similar computing device. The second external computing device of servers 112 may include a computing device with a touch-screen user interface. In other examples, external computing device 110 may be integrated with an external programmer, such as a patient programmer carried by the patient.

[0040] External computing device 110 and IMD 10 may utilize any wireless power transfer techniques that are capable of recharging the power source of IMD 10 when IMD 10 is implanted within the patient. In some examples, system 10 may utilize inductive coupling between primary coils (e.g., energy transfer coil 28) and secondary coils (e.g., secondary coil 16) of external computing device 110 and IMD 10. In inductive coupling, energy transfer coil 28 is placed near implanted IMD 10 such that energy transfer coil 28 is aligned with secondary coil 16 of IMD 10. External computing device 110 may then generate an electrical current in energy transfer coil 28 based on a selected power level for charging the rechargeable power source of IMD 10. When the primary and secondary coils are aligned, the electrical current in the primary coil may magnetically induce an electrical current in secondary coil 16 within IMD 10. Since the secondary coil is associated with and electrically coupled to the rechargeable power source, the induced electrical current may be used to increase the voltage, or charge level, of the rechargeable power source. Although inductive coupling is generally described herein, any type of wireless energy transfer may be used to transfer energy between external computing device 110 and IMD 10.

[0041] Either primary coil 26 and / or 28 of system 100 may include a heat sink device (not shown in FIG. 1). In the example of system 100, external computing device 110 is the power transmitting unit and IMD 10 is the power receiving unit. IMD 10 may be in a flipped or non-flipped position.

[0042] As noted above, in this disclosure external computing device 110 may also be referred to as recharger 110. Recharger 110 may include a user interface to receive control inputs from a user, such as the patient, medical professional or other caregiver. The user interface of recharger 110 may also provide information to a user. For example, recharger 110 may include a control configured to receive user input (not shown in FIG. 1) with as well as a set of indicator lights. In some examples the indicator lights may beconfigured to illuminate the control. The indicator lights may also be configured to output information regarding an operational state of external computing device 110, such as a communication status and wireless power transfer status. Processing circuitry of recharger 110 may receive an indication from the control when the control is activated, which may, for example cause the processing circuitry to turn on and turn off one or more functions of recharger 110. In some examples, the control may include a button, a switch, knobs, a touch sensitive screen or any similar component that may be manipulated by a user and signal the processing circuitry. In some examples, the indicator lights are configured to illuminate the control.

[0043] In operation, electrodes for IMD 10 of system 100 (located on the back side of IMD 10 and not shown in FIG. 1) may be located proximal to the target nerve, such as tibial nerve 102. Processing circuitry of IMD 10, or some combination of the processing circuitry of IMD 10, external computing device 110 and server 112, may be configured to control one or more parameters of electrical stimulation that is output by electrical stimulation circuitry of IMD 10. The electrical stimulation circuitry may output the electrical stimulation via the electrodes of IMD 10, and may be conducted via an electrode tissue interface to tibial nerve 102.

[0044] The processing circuitry (not shown in FIG. 1) may be configured to cause the electrical stimulation circuitry to output a burst of conditioning pulses directed at the target nerve, or at least a portion of the target nerve. The burst of conditioning pulses may be configured to change a state of excitability of target nerve fibers within the target nerve. In contrast to other types of nerve conditioning, the nerve conditioning stimulation of this disclosure is output as a burst of a plurality of pulses, where the burst of pulses may be repeated for a predetermined period of time, a number of pulses, a number of bursts, etc. The burst may be defined by a number of different parameters, as described above, e.g., frequency, pulse amplitude, number of pulses in a burst, groups of pulses in a burst, and similar characteristics. The frequency of the conditioning pulses within each burst may be in the range of 100 to 1,000 Hz in one example, 200 to 500 Hz in another example, and in some examples may be approximately 300 Hz. In this disclosure, “approximately” means with five to ten percent of the specified value.

[0045] The conditioning burst stimulation of this disclosure, e.g., within the identified ranges which include approximately 300 Hz, provides is a surprising result when compared to other types of nerve conditioning. For example, transcutaneous electrical nerve stimulation (TENS) is a therapy that uses low voltage electrical current that deliverselectrical impulses through electrodes placed on the surface of the skin. TENS units may operate in the range of 10 - 100 Hz, and with skin surface electrodes may have less effective coupling to nerve fibers, when compared to implanted electrodes described in this disclosure. Other examples of transcutaneous and percutaneous nerve block strategies may provide pules at frequencies much greater than 1000 Hz, such as 10,000 Hz in some examples.

[0046] The techniques of this disclosure may be effective when applied to complex nerves with mixed nerve fibers, such as the tibial nerve, sacral nerve, the vagus nerve and similar complex nerves. Also, the conditioning techniques of this disclosure may be effective for electrodes in a relatively fixed location in relation to the target nerve, when compared to other systems in which the electrodes may move relative to the target nerve, e.g., based on patient posture or patient movement.

[0047] FIG. 2 is a conceptual diagram illustrating example system that includes an implantable medical device (IMD) configured to deliver electrical stimulation to a patient according to an example of the techniques of the disclosure. In the example of FIG. IB, system 200 may be similar to system 100A and includes an implantable medical device (IMD) 130 which may be similar to IMD 106. IMD 130 may be configured to deliver therapy to and / or sense physiological signals from target tissue. The target tissue may include or be near spinal cord 128 and / or pelvic nerves 136 (e.g., a pudendal nerve or sacral nerve), or any other nervous or muscle tissue that may be stimulated or from which physiological signals may be sensed of patient 112 through lead 134 (coupled to IMD 130 via connector 132). Lead 134 may carry a plurality of electrodes 138 at the distal end of lead 134. IMD 130 may provide neurostimulation to treat symptoms of patient 112, such as pain, fecal or urinary incontinence, erectile dysfunction, or other sexual dysfunction. IMD 130 may thus be configured to provide sacral nerve stimulation in one example.

[0048] In other examples, IMD 130 may be configured to deliver electrical stimulation to other nerves that may alleviate symptoms related to pelvic floor disorders. In one example, IMD 130 may be configured to deliver electrical stimulation to the tibial nerve (e.g., tibial nerve stimulation). Electrodes 138 may be implanted near a desired portion of the tibial nerve, which may be located in a leg and / or ankle of patient 112.

[0049] As described above in relation to FIG. 1, processing circuitry (not shown in FIG. 2) of IMD 130 may cause the electrical stimulation circuitry to output a burst of conditioning pulses via electrodes 138, or other electrodes of system 200 directed at the target nerves, e.g., pelvic nerve tissue, sacral nerve, pudendal nerve and other nerves. Theburst of conditioning pulses is configured to change a state of excitability of target nerve fibers within the target nerve. In some examples, the conditioning pulses may change the state of excitability from a first state to a less excitable state. That is, when in the less excitable state, the target nerve fibers are less likely to respond to electrical stimulation. When these target nerve fibers are less excitable, stimulation applied at this time can cause other nerve fibers to benefit from the stimulation without affecting the target nerve fibers in which excitation is suppressed. In other examples, the condition pulses may change the state of the nerve to a more excitable state, which may reduce the stimulation intensity needed to depolarize the target nerve fibers.

[0050] In some examples, the processing circuitry may control the conditioning pulses based on a closed loop process. Sensing circuitry of medical device 130 may receive bioelectrical signals from electrodes proximal to the target nerves, e.g., ECAP signals, or electrodes proximal to muscle tissue, e.g., EMG signals. The processing circuitry of system 200 may determine, from sensed signals, thresholds for different nerve fiber types in the target nerve. In some examples, the sensing circuitry may determine these thresholds. The processing circuitry, e.g., processing circuitry of medical device 216, or other processing circuitry of system 200, may monitor characteristics of sensed evoked response signals and determine whether one or more of the characteristics of the sensed signals are within a desired range for the characteristics. For example, the processing circuitry may determine that an ECAP amplitude is within a desired range. In response to the determination, the processing circuitry may adjust the parameters of the conditioning signal, or may leave the conditioning signal characteristics unchanged. In this manner, the processing circuitry may be able to adjust the level of conditioning in order to achieve a desired level of excitability of certain nerve fibers that can enable effective therapeutic results from therapeutic stimulation.

[0051] The conditioning pulses may also serve to let the patient know their device is working correctly. As described above in relation to FIG. 1, in some examples, external computing device 104 may be implemented as a patient programmer. Patient 112 may adjust one or more parameters of the delivered electrical stimulation therapy based on the perceived needs of patient 112. In some examples, patient 112 may be acclimated to the prescribed intensity level of the sensation of stimulus from the delivered electrical stimulation therapy. Patient 112 may associate loss of sensation of therapy, caused by becoming acclimated to the stimulus, with decreased therapy efficacy. As a result, over the lifetime of IMD 130, patient 112 may feel it necessary to incrementally adjust thestimulation intensity upwards repeatedly as the sensation associated with their stimulation lessens, even though the electrical stimulation therapy is performing the prescribed function, e.g., pain management, bladder control, and similar functions. These incremental increases to stimulation amplitude may use more electrical power and therefore may significantly reduce the lifetime of IMD 130, particularly for non- rechargeable devices. The conditioning pulses may eliminate the patient’s desire to increase the stimulation amplitude, thereby reducing the risk of unnecessarily draining the battery and reducing its lifetime.

[0052] For example, the medical device of this disclosure, e.g., IMD 130, and other medical devices described herein, may receive a signal from patient 112, e.g., via external device 104 to increase the stimulation intensity, where increasing the intensity may include increasing amplitude, pulse width, burst length or other stimulation parameters. The medical device of this disclosure may temporarily increase the stimulation intensity above the sensory threshold for patient 112. After a short period of time where the implant is delivering stimulation at an intensity that is perceptible to the patient, the processing circuitry for the medical device may return the stimulation parameters to the original, e.g., reduced, level without any user intervention. In this manner, the medical device may provide feedback to the patient that their therapy is still being delivered, enhancing perception of efficacy, while mitigating the impact to device longevity associated with incremental therapy intensity increases over the medical device lifetime. However, the conditioning pulses may provide feedback to the patient that their therapy is still being delivered, or otherwise enhance the patient’s perception of efficacy, thereby eliminating the patient’s desire to increase stimulation intensity.

[0053] FIGS. 3 A and 3B are conceptual diagrams illustrating an example of sensing physiological signals (e.g., ECAPs or EMGs) and applying electrical stimulation therapy to nerve fibers via a tissue-electrode interface. FIG. 3 A illustrates IMD 242 with electrodes 244 positioned proximal to a complex peripheral nerve 240 (e.g., a tibial nerve) containing multiple different types of nerve fibers. In this disclosure, a “peripheral nerve” is any nerve not part of the spinal cord or brain.

[0054] FIG. 3B illustrates a cross sectional view of nerve 240 and the nerve fibers that are within nerve 240 and proximal to one of the electrodes 244 of IMD 242. In some examples, IMD 242 may deliver electrical stimulation therapy that may affect sensitive proximal nerve fibers 250 of nerve 240. Sensitive nerve fibers may have lower activation thresholds than other less sensitive nerve fibers. In some examples, IMD 242 may outputone or more conditioning bursts of pulses that may decrease the excitability of nerve fibers 250 followed by delivery of electrical stimulation therapy configured to activate (e.g., depolarize) smaller nerve fibers 252 and / or nerve fibers 254 without activating desensitized fibers 250. Nerve fibers 254 may be more distant from electrode 244 than nerve fibers 250. In some examples, IMD 242 may output conditioning bursts that may be configured to increase the excitability of nerve fibers 252 and / or nerve fibers 254, followed by electrical stimulation therapy for either or both of nerve fibers 252 and 254.

[0055] In some examples, IMD 242 may apply conditioning bursts to decrease excitability of the more proximal nerve fibers 250, and encourage a slow recovery of nerve fibers 250 (e.g., causing nerve fibers 250 to remain desensitized, or have a higher activation threshold, for a longer time) by immediately and continuously delivering electrical stimulation for either or both of nerve fibers 252 and 254 after the conditioning burst(s) are delivered. Central masking of perception may be more effective with burst stimulation. Fixed stimulation at intermediate rates may be beneficial for therapy with S2 / S3 targeted stimulation.

[0056] In some examples, in response to completing the conditioning protocol, IMD 242 may deliver electrical stimulation, e.g., deliver electrical stimulation “immediately” after completing the nerve fiber conditioning. In other examples, “immediately” may refer to starting follow-on electrical stimulation within 1 second, within 100 milliseconds (ms), within 10 ms, within 1 ms, or some similar duration following the completion of the nerve fiber conditioning.

[0057] FIGS. 4A and 4B are timing diagrams illustrating examples of conditioning and therapy application according to one or more techniques of this disclosure. FIG. 4A illustrates an example of applying a first therapy sequence 402 targeting sensitive nerve fibers, e.g., nerve fibers 250 that are proximal to an electrode and that have lower activation thresholds, as described above in relation to FIG. 3B. In some examples, the application of the first therapy sequence 402 may include one or more conditioning bursts of pulses configured to decrease the excitability of the sensitive nerve fibers. Although two pulses in each burst is shown in first therapy sequency 402, three or more pulses may be provided in each burst. The example of FIG. 4 A shows application of a second therapy sequence 404 in response to terminating first therapy sequence 402 (e.g., immediately after or relatively soon after) and that is configured to target more distant nerve fibers, e.g., nerve fibers 254 of FIG. 3B. The example of FIG. 4A illustrates inducing a slow recovery for the sensitive nerve fibers after decreasing the excitability ofthe sensitive nerve fibers by delivering therapy sequence 404 with little or no delay after the conditioning sequence, e.g., a near immediate application of sequence 404. In some examples, the conditioning burst may elevate the threshold of sensitive fibers as long as therapy 404 is maintained. Withholding of stimulation, e.g., stimulation break 406, may allow the nerve fibers to recover to previous excitation state. In the example of FIG. 4 A, the IMD repeats the sequence by applying therapy 1 again as therapy sequence 408.

[0058] As described above, a therapy sequence, and a conditioning sequence, may be defined by stimulation parameters that may include a voltage amplitude, a current amplitude, a pulse rate, a pulse width, a duty cycle, or the combination of electrodes. In this disclosure, a conditioning sequence may be defined by one or more burst parameters, such as number of bursts, pulses per burst, inter / intra-burst frequency, burst duration, conditioning duration, pulse amplitude, pulse frequency and similar parameters. The conditioner output by the systems of this disclosure may be set to specific amplitudes to reduce neural excitability, i.e., reduce the activity of specific fiber types or to increase excitability. In some examples, lower amplitude conditioning pulses may reduce the activity of nerve fibers that have a low activation threshold, such as bigger, myelinated fibers. In other examples, a higher amplitude conditioning pulses may reduce a larger percentage of nerve fibers.

[0059] Similarly, FIG. 4B illustrates an example of a therapy switch-over concept. In the example of FIG. 4B, a system of this disclosure may apply a first therapy sequence 410 targeting sensitive nerve fibers. The system may next apply one or more conditioning bursts 412 configured to reduce excitability of the sensitive fibers and / or increase excitability of other target nerve fibers. The system may next apply a second therapy sequence 414 directed at more distant nerve fibers. As described above, a stimulation break 416 may allow recovery and the nerve fibers may return to the unconditioned state, e.g., from increased excitability or from reduced excitability. The example of FIG. 4B shows repeating therapy sequence 418, directed at sensitive fibers, but the system may apply any other therapy sequence, or a pause in therapy for an extended period.

[0060] FIG. 5 is a block diagram illustrating example components of the medical device of FIG. 1. Implantable medical device 514 is an example of IMD 10 described above in relation to FIG. 1 and medical device 216 described above in relation to FIG. 2. In the example illustrated in FIG. 5, IMD 514 includes temperature sensor 539, coil 516, processing circuitry 530, therapy and sensing circuitry 534, recharge circuitry 538,memory 532, telemetry circuitry 536, power source 518, and one or more sensors 537, such as an accelerometer. In other examples, IMD 514 may include a greater or a fewer number of components, e.g., in some examples, IMD 514 may not include temperature sensor 539 or sensors 537. In general, IMD 514 may comprise any suitable arrangement of hardware, alone or in combination with software and / or firmware, to perform the various techniques described herein attributed to IMD 514 and processing circuitry 530, and any equivalents thereof.

[0061] As described above in relation to FIGS. 1 - 4B, processing circuitry 530 may cause therapy and sensing circuitry 534 to output conditioning pulse bursts, as well as electrical stimulation therapy configured to treat a condition of a patient. The conditioning pulse bursts may increase or decrease excitability of nerve fibers within a target nerve. In some examples, a conditioning pulse burst may also be referred to as a conditioning burst in this disclosure.

[0062] Processing circuitry 530 of IMD 514 may include one or more processors, such as one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or any other equivalent integrated or discrete logic circuitry, as well as any combinations of such components. IMD 514 may include a memory 532, such as random access memory (RAM), read only memory (ROM), programmable read only memory (PROM), erasable programmable read only memory (EPROM), electronically erasable programmable read only memory (EEPROM), flash memory, comprising executable instructions for causing the processing circuitry 530 to perform the actions attributed to this circuitry. Moreover, although processing circuitry 530, therapy and sensing circuitry 534, recharge circuitry 538, telemetry circuitry 536, and temperature sensor 539 are described as separate modules, in some examples, some combination of processing circuitry 530, therapy and sensing circuitry 534, recharge circuitry 538, telemetry circuitry 536 and temperature sensor 539 are functionally integrated. In some examples, processing circuitry 530, therapy and sensing circuitry 534, recharge circuitry 538, telemetry circuitry 536, and temperature sensor 539 correspond to individual hardware units, such as ASICs, DSPs, FPGAs, or other hardware units. In this disclosure, therapy and sensing circuitry 534 may be referred to as therapy circuitry 534, for simplicity.

[0063] Memory 532 may store therapy programs or other instructions that specify therapy parameter values for the therapy provided by therapy circuitry 534 and IMD 514. In some examples, memory 532 may also store temperature data from temperature sensor539, instructions for recharging rechargeable power source 518, thresholds, instructions for communication between IMD 514 and an external computing device, or any other instructions required to perform tasks attributed to IMD 514. Memory 532 may be configured to store instructions for communication with and / or controlling one or more temperature sensors of temperature sensor 539. In various examples, memory 532 stores information related to determining the temperature of housing 19 and / or exterior surface(s) of housing 19 of IMD 514 based on temperatures sensed by one or more temperature sensors, such as temperature sensor 539, located within IMD 514.

[0064] For example, memory 532 may store programming settings such as electrical stimulation therapy output magnitude, pulse width, and so on. Memory 532 may store sensed bioelectrical signals, such as an ECAP or other sensed signal, or other data. Memory 532 may store programming instructions that when executed by processing circuitry 530 cause processing circuitry 530 to cause electrical stimulation circuitry therapy circuitry 534 to deliver electrical stimulation therapy to a target nerve of a patient.

[0065] Therapy and sensing circuitry 534 may generate and deliver electrical stimulation under the control of processing circuitry 530. In some examples, processing circuitry 530 controls therapy circuitry 534 by accessing memory 532 to selectively access and load at least one of the stimulation programs to therapy circuitry 534. For example, in operation, processing circuitry 530 may access memory 532 to load one of the stimulation programs to therapy circuitry 534. In such examples, relevant stimulation parameters may include a voltage amplitude, a current amplitude, a pulse rate, a pulse width, a duty cycle, or the combination of electrodes 517A, 517B, 517C, and 517D (collectively “electrodes 517”) that therapy circuitry 534 may use to deliver the electrical stimulation signal as well as sense biological signals. In other examples, IMD 514 may have more or fewer electrodes than the four shown in the example of FIG. 5. In some examples electrodes 517 may be part of or attached to a housing of IMD 514, e.g., a leadless electrode, as described above in relation to FIG. 1. In other examples, one or more of electrodes 517 may be part of a lead implanted in or attached to a patient to sense biological signals and / or deliver electrical stimulation, as described above in relation to FIG. 2.

[0066] In some examples, one or more electrodes connected to therapy circuitry 534 may connect to one or more sensing electrodes, e.g., attached to housing of IMD 514. In some examples the electrodes may be configured to detect an evoked motor response caused by the electrical stimulation event, or other bioelectrical signals such as ECAPs,impedance and so on. In some examples, sensing circuitry may also be configured to sense spontaneous activity, e.g., activity not related to electrical stimulation, such as an EMG or other bioelectrical signal from patient movement.

[0067] IMD 514 also includes components to receive power to recharge rechargeable power source 518 when rechargeable power source 518 has been at least partially depleted. As shown in FIG. 5, IMD 514 includes coil 516 and recharge circuitry 538 coupled to rechargeable power source 518. Recharge circuitry 538 may be configured to charge rechargeable power source 518 with the selected power level determined by either processing circuitry 530 or an external charging device, such as external computing device 110 described above in relation to FIG. 1. Recharge circuitry 538 may include any of a variety of charging and / or control circuitry configured to process or convert current induced in coil 516 into charging current to charge power source 518.

[0068] Secondary coil 516 may include a coil of wire or other device capable of inductive coupling with a primary coil disposed external to patient 12. Although secondary coil 516 is illustrated as a simple loop in the example of in FIG. 5, secondary coil 516 may include multiple turns of conductive wire. Secondary coil 516 may include a winding of wire configured such that an electrical current can be induced within secondary coil 516 from a magnetic field. The induced electrical current may then be used to recharge rechargeable power source 518, or communicate between an external computing device and IMD 5514.

[0069] Recharge circuitry 538 may include one or more circuits that process, filter, convert and / or transform the electrical signal induced in the secondary coil to an electrical signal capable of recharging rechargeable power source 518. For example, in alternating current induction, recharge circuitry 538 may include a half-wave rectifier circuit and / or a full-wave rectifier circuit configured to convert alternating current from the induction to a direct current for rechargeable power source 518. The full-wave rectifier circuit may be more efficient at converting the induced energy for rechargeable power source 518. However, a half-wave rectifier circuit may be used to store energy in rechargeable power source 518 at a slower rate. In some examples, recharge circuitry 538 may include both a full-wave rectifier circuit and a half-wave rectifier circuit such that recharge circuitry 538 may switch between each circuit to control the charging rate of rechargeable power source 518 and temperature of IMD 514.

[0070] Rechargeable power source 518 may include one or more capacitors, batteries, and / or other energy storage devices. Rechargeable power source 518 may deliveroperating power to the components of IMD 514. In some examples, rechargeable power source 518 may include a power generation circuit to produce the operating power. Rechargeable power source 518 may be configured to operate through many discharge and recharge cycles. Rechargeable power source 518 may also be configured to provide operational power to IMD 514 during the recharge process. In some examples, rechargeable power source 518 may be constructed with materials to reduce the amount of heat generated during charging. In other examples, IMD 514 may be constructed of materials and / or using structures that may help dissipate generated heat at rechargeable power source 518, recharge circuitry 538, and / or secondary coil 516 over a larger surface area of the housing of IMD 514.

[0071] Although rechargeable power source 518, recharge circuitry 538, and secondary coil 516 are shown as contained within the housing of IMD 514, in alternative implementations, at least one of these components may be disposed outside of the housing. For example, in some implementations, secondary coil 516 may be disposed outside of the housing of IMD 514 to facilitate better coupling between secondary coil 516 and the primary coil of external charging device. In other examples, power source 518 may be a primary power cell and IMD 514 may not include recharge circuitry 538 and recharge coil 516.

[0072] Processing circuitry 530 may also control the exchange of information with an external computing device using telemetry circuitry 536. Telemetry circuitry 536 may be configured for wireless communication using radio frequency protocols, such as BLUETOOTH, MICS or similar RF protocols, as well as using inductive communication protocols. Telemetry circuitry 536 may include one or more antennas 537 configured to communicate with external charging device, for example. Processing circuitry 5530 may transmit operational information and receive therapy programs or therapy parameter adjustments via telemetry circuitry 536. Also, in some examples, IMD 514 may communicate with other implanted devices, such as stimulators, control devices, or sensors, via telemetry circuitry 536. In addition, telemetry circuitry 536 may be configured to control the exchange of information related to sensed and / or determined temperature data, for example temperatures sensed by and / or determined from temperatures sensed using temperature sensor 5539. In some examples, telemetry circuitry 536 may communicate using inductive communication, and in other examples, telemetry circuitry 536 may communicate using RF frequencies separate from the frequencies used for inductive charging.

[0073] FIG. 6 is a block diagram of an example an external computing device of FIGS. 1 and 2. External computing device 622 in of FIG. 6 is an example of external computing device 110 and external device 224 described above in relation to FIG. 1 and 2. In some examples, external computing device 622 may be described as a hand-held device, in other examples, external computing device 622 may be a larger or a nonportable device. In addition, in other examples external computing device 622 may be included as part of an external programmer or include functionality of an external programmer. As shown in the example of FIG. 6, external computing device 622 includes two separate components. Housing 624 encloses components such as a processing circuitry 650, memory 652, user interface 654, telemetry circuitry 656, control 662, one or more sets of indicator lights 664, audio output circuitry 670, and power source 660. In some examples, charging head 626, also called charging wand 626, may include charging circuitry 658, temperature sensor 659, and coil 648. Housing 624 may be electrically coupled to charging head 626 via charging cable 628. As described above in relation to FIG. 1, in some examples external computing device 622 may omit charging head 626. Housing 624 may also include charging circuitry 668 and coil 628, which is an example of coil 628 described above in relation to FIG. 1.

[0074] In some examples, separate charging wand 626 may facilitate positioning of coil 648 over coil 16 of IMD 14. In some examples, charging circuitry 668 and / or coil 628 may be integrated within housing 624, as described above in relation to FIG. 1. Memory 652 may store instructions that, when executed by processing circuitry 650, causes processing circuitry 650 and external computing device 622 to provide the functionality ascribed to external computing device 622 throughout this disclosure, and / or any equivalents thereof. Coil 648 and coil 628 may also be referred to as an antenna. External computing device 622 may also include one or more temperature sensors, illustrated as temperature sensor 659, similar to temperature sensor 39 of FIG. 2.

[0075] In general, external computing device 622 comprises any suitable arrangement of hardware, alone or in combination with software and / or firmware, to perform the techniques ascribed to external computing device 622, and processing circuitry 650, user interface 654, telemetry circuitry 656, and charging circuitry 658 of external computing device 622, and / or any equivalents thereof. In various examples, external computing device 622 may 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. External computing device 622 also, invarious examples, may include a memory 652, such as RAM, ROM, PROM, EPROM, EEPROM, flash memory, a hard disk, a CD-ROM, comprising executable instructions for causing the one or more processors to perform the actions attributed to them. Moreover, although processing circuitry 650, telemetry circuitry 656, charging circuitry 658, and temperature sensor 659 are described as separate modules, in some examples, processing circuitry 650, telemetry circuitry 656, charging circuitry 658, and / or temperature sensor 659 are functionally integrated. In some examples, processing circuitry 650, telemetry circuitry 656, charging circuitry 658, and / or temperature sensor 659 correspond to individual hardware units, such as ASICs, DSPs, FPGAs, or other hardware units.

[0076] Memory 652 may store instructions that, when executed by processing circuitry 650, cause processing circuitry 650 and external computing device 622 to provide the functionality ascribed to external computing device 622 throughout this disclosure, and / or any equivalents thereof. For example, memory 652 may include instructions that cause processing circuitry 650 to control the power level used to charge IMD 14 in response to the determined temperatures for the housing / external surface(s) of IMD 14, as communicated from IMD 14, or instructions for any other functionality. Memory 652 may include a record of selected power levels, sensed temperatures, determined temperatures, or any other data related to charging rechargeable power source 18, described above in relation to FIG. 2. Memory 652 may store instructions that when executed by processing circuitry 650 may control the operation of indicator lights 664 as described above in relation to FIG. 1.

[0077] Processing circuitry 650 may, when requested, cause telemetry circuitry 656 to transmit stored data in memory 652 to another computing device for review or further processing, such as to server 112 depicted in FIG. 1. Processing circuitry 650 may be configured to access memory, such as memory 32 of IMD 14 and / or memory 652 of external computing device 622, to retrieve information comprising instructions, formulas, and determined values for one or more constants.

[0078] User interface 654 may include buttons, such as control 662 or a keypad, lights, such as indicator lights 664, a speaker for voice commands, a display, such as a liquid crystal (LCD), light-emitting diode (LED), or cathode ray tube (CRT). In some examples, the display may be a touch screen. Control 662 may be implemented as any type of component that may receive user input and provide an indication of the user input to processing circuitry 650.

[0079] Charging circuitry 658 may include one or more circuits that generate an electrical signal, and an electrical current, within primary coil 648. Charging circuitry 658 may generate an alternating current of specified amplitude and frequency in some examples. In other examples, charging circuitry 658 may generate a direct current. In any case, charging circuitry 658 may be capable of generating electrical signals, and subsequent magnetic fields, to transmit various levels of power to IMD 14. In this manner, charging circuitry 658 may be configured to charge a rechargeable power source, such as power source 518 of IMD 514 described above in relation to FIG. 5.

[0080] Power source 660 may deliver operating power to the components of external computing device 622. Power source 660 may also deliver the operating power to drive primary coil 648 during the charging process. Power source 660 may include a battery and a power generation circuit to produce the operating power. In some examples, a battery of power source 660 may be rechargeable to allow extended portable operation. In other examples, power source 660 may draw power from a wired voltage source such as a consumer or commercial power outlet.

[0081] Telemetry circuitry 656 supports wireless communication between IMD 14 and external computing device 622 under the control of processing circuitry 650.Telemetry circuitry 656 may also be configured to communicate with another computing device via wireless communication techniques, or direct communication through a wired connection. In some examples, telemetry circuitry 656 may be substantially similar to telemetry circuitry 536 of IMD 514 described herein, providing wireless communication via an RF or proximal inductive medium. In some examples, telemetry circuitry 656 may include an antenna 657, which may take on a variety of forms, such as an internal or external antenna. Although telemetry modules 656 and 36 may each include dedicated antennas for communications between these devices, telemetry modules 656 and 36 may instead, or additionally, be configured to utilize inductive coupling from coils 16 and 648 to transfer data.

[0082] Examples of local wireless communication techniques that may be employed to facilitate communication between external computing device 622 and IMD 14 include radio frequency and / or inductive communication according to any of a variety of standard or proprietary telemetry protocols, or according to other telemetry protocols such as the IEEE 802.1 lx, MICS or Bluetooth specification sets. In this manner, other external devices may be capable of communicating with external computing device 622 without needing to establish a secure wireless connection.

[0083] FIGS. 7A, 7B and 7C are conceptual diagrams that illustrate human anatomy in relation to peripheral nerves of the lower (inferior) portions of the human body. FIG. 7A is a conceptual diagram of a human spine that lists, for example the sacral and lumbar vertebrae numbering. Nerves that exit the spine between vertebrae may also be referred to by the associated vertebrae numbers.

[0084] FIG. 7B is a conceptual diagram illustrating regions of a human leg associated with motor and sensor nerves. As shown in FIG. 7B, nerve fibers in the legs may travel to various lumbar and sacral vertebrae of the spine.

[0085] FIG. 7C is a conceptual diagram illustrating various nerves and their entry points on the spine. For example, pudendal nerve 726 may have fibers in nerve branches that span S2 - S4. Superior gluteal nerve 720 and inferior gluteal nerve 722 may join sciatic nerve 730 before entering the spinal cord.

[0086] Sciatic nerve 730 may include nerve fibers in fibular portion 732 and in tibial portion 734. Tibial portion 734 has branches that span L4 to S3. Based on clinical studies, there may be a central and peripheral nervous system component to tibial mechanism of action, most likely associate with S2 and S3. Electrical stimulation therapy applied to the tibial nerve may impact affective components such as urge perception, likely with SI and L5. A sensation, such as pain has both a sensory component (intensity) and an affective component (e.g., unpleasantness). As described above, e.g., in relation to FIGS. 1 - 6, the systems of this disclosure may be able to selectively activate the different spinal levels based on conditioned stimulation that is configured to target different fiber types of the nerve and spatially distant fibers. Put another way, selectively changing activation thresholds (or excitability) of certain nerve fibers within a nerve may enable the system to direct stimulation to targeted nerve fibers associated with respective spinal levels.

[0087] FIG. 8Ais a flow chart illustrating an example closed loop operation of the medical system of this disclosure. Processing circuitry of medical device of this disclosure, such as IMD 10, medical device 216 and IMD 514 described above in relation to FIGS. 1, 2 and 5, may cause therapy and sensing circuitry 534 to apply probe pulses via electrodes 517 to the target nerve to determine the thresholds of different fiber types within the target nerve (740).

[0088] Based on the determination, the processing circuitry, e.g., processing circuitry 530 of FIG. 5, may apply one or more bursts of conditioning stimulation (741), then monitor the evoked response, including monitoring ECAPs, or other response, ofconditioned nerve fibers (742). In some examples, the processing circuitry may monitor the amplitudes of the ECAPS evoked by an application of a control pulse from the IMD (742). In some examples, the IMD may also apply electrical stimulation therapy pulses to treat the condition of the patient. The therapy pulses may have interleaved control pulses, where control pulses are configured to elicit an evoked response. In some examples, the processing circuitry of the system may use the measured evoked response from the control pulses to monitor the evoked response amplitude (742). In other examples, the parameters of the therapy pulses may also elicit an evoked response and the processing circuitry of the system use the amplitudes of the evoked response from the therapy pulses, e.g., received via sensing circuitry of the IMD, to monitor the evoked response amplitude (742). Though not shown in FIG. 8A, the IMD may adjust amplitudes of control pulses and / or therapy pulses in response to the sensed evoked responses, as described above in relation to FIG. 1. In some examples the parameters, e.g., amplitude, pulse width and other parameters, of probe pulses may be the same or similar to the parameters for the control pulses.

[0089] In response to the measured ECAP being either too high or too low (Yes branch of 746), the processing circuitry may adjust the amplitude, or other parameters, of the conditioning burst sequence (744). For example, a conditioning burst sequence may be configured to increase the excitability of a target nerve fiber. However, the processing circuitry may determine that the expected response, which in the example of FIG. 8 A is an amplitude of the measured ECAP, is less than an expected amplitude threshold, e.g., the ECAP amplitude is too low. Therefore, the processing circuitry may adjust one or more parameters of the conditioning pulse burst, e.g., pulse amplitude, number of pulses, or some other parameters (744).

[0090] In other examples, if the measured ECAP amplitude is within an expected range (No branch of 746), then the processing circuitry may maintain the parameters of the conditioning burst sequence (745).

[0091] FIG. 8B is a flow chart illustrating an example of closed loop operation for the systems of this disclosure to control the speed of recovery of conditioned nerves. As described above in relation to FIG. 8A, processing circuitry of this disclosure, e.g., processing circuitry 530 of FIG. 5, may monitor the effects of applying a conditioning burst sequence based on measured ECAP. A “recovery” as described above, is when a conditioned nerve returns to an original excitability state after receiving a conditioning burst, according to one or more techniques of this disclosure.

[0092] In some examples, the electrical stimulation following the application of the conditioning burst may be referred to as conditioning maintenance stimulation. In some examples, the conditioning maintenance stimulation may be specific to maintaining the recovery time for the selected conditioning, e.g., medium, slow or fast recovery. In other examples, the conditioning maintenance stimulation may include therapy stimulation, along with some combination of other stimulation, e.g., interleaved with the therapy stimulation, as noted above.

[0093] Based on criteria or commands stored at a memory associated with the processing circuitry, the processing circuitry may determine desired recovery time 750. As shown in the example of FIG. 8B, the selected recovery time may be slow recovery 756, medium recovery 754 or fast recovery 752, as described above.

[0094] In some examples, as described above in relation to FIG. 3B and 4A, to ensure a slow recovery by applying conditioning with a continuous probe stimulation 756, the processing circuitry may apply the predetermined conditioning burst sequence 764 for the desired response in the target nerve fibers. Then for slow recovery, immediately apply continuous probe stimulation following the completion of the conditioning bursts 770. In other examples, as described above in relation to FIG. 4A, the IMD may apply some combination of electrical stimulation therapy and other stimulation.

[0095] In other words, the processing circuitry may cause the therapy delivery circuitry to output a conditioning burst, followed by a continuous application of an electrical stimulation therapy sequence, which may result in a slow recovery of the conditioned nerve fibers. For example, in tibial neuromodulation, the processing circuitry may apply electrical stimulation therapy to treat a patient’s condition for about 30 minutes every other day. In some examples, the processing circuitry for IMD may be configured to apply the conditioner feature before applying the electrical stimulation therapy, e.g., to decrease excitability of sensitive nerve fibers, or to increase excitability of target nerve fibers. The processing circuitry may then continuously apply the electrical stimulation therapy directed to treating the condition of the patient during those 30 minutes, which may result in a slow recovery of the conditioned nerve fibers. That is, either the more excitable nerve fibers remain more excitable, or the suppressed nerve fibers remain suppressed while receiving the electrical stimulation therapy. In some examples, the slow recovery duration may be up to approximately twenty to thirty or more minutes, as long as the continuous electrical stimulation therapy is being delivered.

[0096] In other examples, the processing circuitry may cause a fast recovery 752 to the original excitability state by applying a growth curve 766 after the conditioner application, e.g., application of a conditioning burst 760 . In some examples a growth curve may include application of a burst with an increasing pulse amplitude for the pulses in the burst over the duration of the burst. In other examples, a growth curve may be applied using probe pulses, e.g., increasing the probe amplitude up to a predetermined amplitude limit within a predetermined amount of time. Example situations for causing a fast recovery may include that the electrical stimulation therapy session is complete, or that a therapy session needs to be interrupted. For example, during a therapy session for which the patient should remain seated, the patient may need to get up in the middle of the session. Therefore, applying a growth curve to the conditioned nerve fibers may cause a fast recovery and return the conditioned nerve fibers to the original state. In some examples, a fast recovery may include a recovery duration of one minute or less, or up to about five minutes.

[0097] To cause a recovery duration between a fast recovery 752 and slow recovery 756, e.g., a medium duration recovery 754, the processing circuitry may apply the conditioning burst 762, followed by intermittent probe stimulation 768. In other words, the processing circuitry may apply the conditioning burst, then apply electrical stimulation therapy, interleaved with some stimulation breaks, as described above in relation to FIGS. 4 A and 4B, which may result in a recovery duration of medium duration. In some examples, a medium duration recovery may be approximately five, ten to about twenty minutes. The processing circuitry may also monitor the recovery of the nerve fiber, and results of other stimulation, such as therapy stimulation 772, as described above in relation to FIG. 8A.

[0098] FIGS. 9A, 9B, and 9C are timing diagrams illustrating examples of the effects of conditioning bursts on nerve fibers. The system increases then decreases amplitude for the conditioning burst pulses, e.g., the governed amplitude during the time span for each timing diagram. The system may deliver the conditioning pulses at a high rate, e.g. 300 Hz (30 Hz - 10 kHz) arranged in one long burst (e.g. several seconds of stimulation) or in several bursts (e.g. 3-20 pulses followed by a pause of 5 msec), for FIG. 9A, or a low rate (e.g. 10 Hz (1 Hz - 30 Hz), e.g., for FIGS. 9B and 9C. The conditioning bursts may be in the same polarity as the ping pulses, also called control pulses in this disclosure, e.g., for FIG. 9C, or may be an opposite or inverted polarity with respect to the control pulses, such as for FIGS. 9 A and 9B. The control pulses are configured to generate an ECAP,which may be measured by sensing circuitry of the system of this disclosure. The measured data shown by FIGS. 9 A, 9B and 9C show unexpected results from the specific conditioning techniques of this disclosure, when compared to other types of nerve conditioning. For example, the applied polarity of the conditioning burst impacted whether the target nerve fibers become more excitable, or became less excitable.

[0099] In the example of FIG. 9 A, as the amplitude 810 for the conditioning burst increases, the measured ECAPS, 802, 804 and 806 for the various amplitudes of control pulse, decrease. At the peak conditioning pulse amplitude, e.g.,., at about 70 seconds, the ECAPs are at their lowest amplitude, and then increase as the conditioning pulse amplitude 810 decreases, which in the example of FIG. 9A is at a reduced amplitude compared to before applying the conditioning burst. In other words, after the peak amplitude, the nerve fibers may be in a less excitable state than the state of excitability before the application of the conditioning pulse burst. Also, in the example of FIG. 9A, a high rate conditioner may elicit ECAPs, as shown by the peak in the conditioning response 808 between 60 and 80 seconds.

[0100] In some examples, conditioning pulses in a conditioning pulse burst may be sub-threshold or supra-threshold, where sub-threshold pulses are below the threshold perceptible to a patient. Each patient is different, so parameters for conditioning pulses may be sub-threshold for one patient and the same parameters may be supra-threshold for a different patient. In some examples, conditioning pulses may start sub-threshold and adjust parameters until the conditioning is effective at target nerves. In some embodiments, where patient response is not easily available, sub-threshold stimulation can also be determined by a lack of physiologic response to the conditioning pulses, e.g.,. ECAP or CMAP or another response that is measurable.

[0101] Similar to the example of FIG. 9A, in the example of FIG. 9B, as the amplitude 820 for the conditioning burst increases, the measured ECAPS, 822, 824 and 826 for the various amplitudes of control pulse, decrease. The measured ECAPS for 822 show little change across the time span. At the peak conditioning pulse amplitude, e.g.,., at about 140 seconds, the ECAPs are at their lowest amplitude, and then increase as the conditioning pulse amplitude 820 decreases. The conditioning response 828 also shows little change across the time span.

[0102] In the example of FIG. 9C, the low-rate conditioner may increase ECAP, e.g.,., increase the target nerve fiber excitability, when the polarity of the conditioner is the same as the polarity for the control pulses. As the amplitude 830 for the conditioningburst increases, the measured ECAPS, 832, 834 and 836 for the various amplitudes of control pulse, increase, then decrease. The conditioning response 838 shows little change across the time span.

[0103] In other examples, not shown in FIG. 9C, may include a feedback based “closed loop” response from the patient. For example, in a clinical setting, an example methodology may include be to apply conditioning bursts after application of therapy, then turn off the conditioning stimulation. The clinician may then cause the IMD to reapply the therapy and check if the conditioning stimulation changed "perception" of therapy (e.g. patient feels the stimulation in a different place) as indication that it changed the neural response.

[0104] FIG. 10 is a flow chart illustrating an example mode of operation of the medical system according to one or more techniques of this disclosure. The steps of FIG. 10 may be executed by any of the processing circuitry of system 100 or of 200, such as by medical device 130, external device 104 or server 126.

[0105] In some examples, the processing circuitry of a medical device, e.g., medical device 10, may control electrical stimulation circuitry of the medical device to generate a burst of conditioning pulses deliverable to a target nerve, such as tibial nerve 102 (92). In the example of FIG. 1, tibial nerve 102 is located proximal to one or more electrodes of medical device 10 (not shown in FIG. 1) operatively coupled to the electrical stimulation circuitry.

[0106] As described above in relation to FIGS. 1 - 9C, the burst of conditioning pulses is configured to change a state of excitability of target nerve fibers within the target nerve, e.g., to make the nerves more or less excitable. Responsive to completing the burst of conditioning pulses, the processing circuitry, may control the electrical stimulation circuitry to generate electrical stimulation therapy deliverable to the target nerve. In contrast to the conditioning pulse burst, the electrical stimulation therapy is may be configured to treat a condition of the patient, e.g., as described above in relation to FIG. 1.

[0107] The techniques of this disclosure may also be described in the following examples.

[0108] Example 1. A medical device comprising: electrical stimulation circuitry configured to generate electrical stimulation deliverable to a target nerve via a set of electrodes of a plurality of electrodes; and processing circuitry configured to: determine one or more parameter values that define the electrical stimulation generated by the electrical stimulation circuitry; control the electrical stimulation circuitry to generate aburst of conditioning pulses deliverable to the target nerve, wherein the burst of conditioning pulses is configured to change a state of excitability of target nerve fibers within the target nerve; and control, based on the one or more parameter values, the electrical stimulation circuitry to generate electrical stimulation therapy to the target nerve, wherein the electrical stimulation therapy is configured to treat a condition of the patient.

[0109] Example 2. The medical device of example 1, wherein the burst of conditioning pulses is configured to change the state of excitability from a first state to a less excitable state, and wherein the target nerve fibers are less likely to respond to electrical stimulation in the less excitable state.

[0110] Example 3. The medical device of any of examples 1 or 2, further comprising sensing circuitry, wherein the processing circuitry is further configured to: control the electrical stimulation circuitry to deliver probe pulses to the target nerve, receive, from the sensing circuitry, information representative of one or more sensed signals responsive to the probe pulses; determine, based on the information representative of the one or more sensed signals, one or more thresholds for different respective nerve fiber types in the target nerve; control the electrical stimulation circuitry to detect at least one evoked compound action potential (ECAP) signal in response to subsequent electrical stimulation; compare one or more characteristics of the at least one ECAP signal to a target range for the one or more characteristics; responsive to determining that at least one of the one or more characteristics are outside the target range, adjust at least one parameter value that defines the burst of conditioning pulses; and control the electrical stimulation circuitry to deliver subsequent bursts of conditioning pulses according to the updated at least one parameter value.

[0111] Example 4. The medical device of example 3, wherein one of the one or more characteristics of the sensed at least one ECAP signal comprises an amplitude of the at least one ECAP signal.

[0112] Example 5. The medical device of any of examples 3 or 4, wherein the processing circuitry is configured to adjust the at least one parameter value that defines the burst of conditioning pulses by at least adjusting an amplitude of one or more pulses of the burst of conditioning pulses.

[0113] Example 6. The medical device of any of examples 1 through 5, wherein the processing circuitry is further configured to maintain the change in the state of excitability of the target nerve fibers for a short duration of time by at least: controllingthe electrical stimulation circuitry to generate the burst of conditioning pulses having continuous pulses for a first duration of time; and responsive to the first duration of time elapsing, controlling the electrical stimulation circuitry to generate the electrical stimulation therapy for the short duration of time.

[0114] Example 7. The medical device of any of examples 1 through 5, wherein the processing circuitry is further configured to maintain the change in the state of excitability of the target nerve fibers for a long duration of time by at least: controlling the electrical stimulation circuitry to generate the burst of conditioning pulses having intermittent pulses for a first duration of time; and responsive to the first duration of time elapsing, controlling the electrical stimulation circuitry to generate electrical stimulation therapy for the long duration of time.

[0115] Example 8. The medical device of any of examples 1 through 7, wherein the one or more parameters of the burst of conditioning pulses comprises a frequency of approximately 200 Hz to 500 Hz.

[0116] Example 9. The medical device of any of examples 1 through 8, wherein the medical device is an implantable medical device configured to deliver the electrical stimulation to the target nerve comprising at least one of a sacral nerve or a tibial nerve of the patient.

[0117] Example 10. A system comprising: one or more electrodes configured to be located proximal to a target nerve of a patient; a medical device comprising: electrical stimulation circuitry configured to generate electrical stimulation deliverable to a target nerve via a set of electrodes of a plurality of electrodes; processing circuitry configured to: determine one or more parameter values that define the electrical stimulation generated by the electrical stimulation circuitry; control the electrical stimulation circuitry to generate a burst of conditioning pulses deliverable to the target nerve, wherein the burst of conditioning pulses is configured to change a state of excitability of target nerve fibers within the target nerve; and control, based on the one or more parameter values, the electrical stimulation circuitry to generate electrical stimulation therapy to the target nerve via the set of electrodes, wherein the electrical stimulation therapy is configured to treat a condition of the patient.

[0118] Example 11. The system of example 10, wherein the burst of conditioning pulses is configured to change the state of excitability from a first state to a less excitable state, and wherein the target nerve fibers are less likely to respond to electrical stimulation in the less excitable state.

[0119] Example 12. The system of any of examples 10 or 11, wherein the one or more parameters of the burst of conditioning pulses comprises a frequency of approximately 200 - 500 Hz.

[0120] Example 13. The system of any of examples 10 through 12, wherein the processing circuitry is further configured to: control the electrical stimulation circuitry to deliver probe pulses to the target nerve, receive, from the sensing circuitry, information representative of one or more sensed signals responsive to the probe pulses; determine, based on the information representative of the one or more sensed signals, one or more thresholds for different respective nerve fiber types in the target nerve; control the electrical stimulation circuitry to detect at least one evoked compound action potential (ECAP) signal in response to subsequent electrical stimulation; compare one or more characteristics of the at least one ECAP signal to a target range for the one or more characteristics; responsive to determining that at least one of the one or more characteristics are outside the target range, adjust at least one parameter value that defines the burst of conditioning pulses; and control the electrical stimulation circuitry to deliver subsequent bursts of conditioning pulses according to the updated at least one parameter value.

[0121] Example 14. The system of example 13, wherein one of the characteristics of the sensed at least one ECAP signal comprises an amplitude of the at least one ECAP signal.

[0122] Example 15. The system of any of examples 10 through 14, wherein the processing circuitry is further configured to maintain the change in the state of excitability of the target nerve fibers for a short duration of time by at least: controlling the electrical stimulation circuitry to generate the burst of conditioning pulses having continuous pulses for a first duration of time; and responsive to the first duration of time elapsing, controlling the electrical stimulation circuitry to generate the electrical stimulation therapy for the short duration of time.

[0123] Example 16. The system of any of examples 10 through 15, wherein the processing circuitry is further configured to maintain the change in the state of excitability of the target nerve fibers for a long duration of time by at least: controlling the electrical stimulation circuitry to generate the burst of conditioning pulses having intermittent pulses for a first duration of time; and responsive to the first duration of time elapsing, controlling the electrical stimulation circuitry to generate electrical stimulation therapy for the long duration of time.

[0124] Example 17. A method comprising: controlling, by processing circuitry of a medical device, electrical stimulation circuitry of the medical device to generate a burst of conditioning pulses deliverable to a target nerve, wherein the target nerve is located proximal to one or more electrodes operatively coupled to the electrical stimulation circuitry; wherein the burst of conditioning pulses is configured to change a state of excitability of target nerve fibers within the target nerve; responsive to completing the burst of conditioning pulses, controlling, by the processing circuitry, the electrical stimulation circuitry to generate electrical stimulation therapy deliverable to the target nerve, wherein the electrical stimulation therapy is configured to treat a condition of the patient.

[0125] Example 18. The method of example 17, wherein the burst of conditioning pulses is configured to change the state of excitability comprises to change the state of excitability from a first state to a less excitable state, and wherein the target nerve fibers are less likely to respond to electrical stimulation in the less excitable state.

[0126] Example 19. The method of any of examples 17 or 18, wherein the one or more parameters of the burst of conditioning pulses comprises a frequency of approximately 200 - 500 Hz.

[0127] Example 20. The method of any of examples 17 through 19, wherein the processing circuitry is further configured to: controlling, by the processing circuitry, the electrical stimulation circuitry to deliver probe pulses to the target nerve, receiving, from sensing circuitry of the medical device, information representative of one or more sensed signals responsive to the probe pulses; determining, based on the information representative of the one or more sensed signals, one or more thresholds for different respective nerve fiber types in the target nerve; controlling the electrical stimulation circuitry to detect at least one evoked compound action potential (ECAP) signal in response to subsequent electrical stimulation; comparing one or more characteristics of the at least one ECAP signal to a target range for the one or more characteristics; responsive to determining that at least one of the one or more characteristics are outside the target range, adjusting at least one parameter value that defines the burst of conditioning pulses; and controlling the electrical stimulation circuitry to deliver subsequent bursts of conditioning pulses according to the updated at least one parameter value.

[0128] In one or more examples, the functions described above may be implemented in hardware, software, firmware, or any combination thereof. For example, the variouscomponents of FIGS. 1, 2, such as IMD 10, external computing device 110, servers 112, IMD 130, External device 104, and servers 126 may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over, as one or more instructions or code, a computer-readable medium and executed by a hardware-based processing unit. Computer-readable media may include computer-readable storage media, which corresponds to a tangible medium such as data storage media, or communication media including any medium that facilitates transfer of a computer program from one place to another, e.g., according to a communication protocol. In this manner, computer-readable media generally may correspond to (1) tangible computer-readable storage media which is non-transitory or (2) a communication medium such as a signal or carrier wave. Data storage media may be any available media that can be accessed by one or more computers or one or more processors to retrieve instructions, code and / or data structures for implementation of the techniques described in this disclosure. A computer program product may include a computer-readable medium.

[0129] The term “non-transitory” may indicate that the storage medium is not embodied in a carrier wave or a propagated signal. In certain examples, a non-transitory storage medium may store data that can, over time, change (e.g., in RAM or cache). By way of example, and not limitation, such computer-readable storage media, may include random access memory (RAM), read only memory (ROM), programmable read only memory (PROM), erasable programmable read only memory (EPROM), electronically erasable programmable read only memory (EEPROM), flash memory, a hard disk, a compact disc ROM (CD-ROM), a floppy disk, a cassette, magnetic media, optical media, or other computer readable media. In some examples, an article of manufacture may include one or more computer-readable storage media.

[0130] Also, any connection is properly termed a computer-readable medium. For example, if instructions are transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. It should be understood, however, that computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other transient media, but are instead directed to non-transient,tangible storage media. Combinations of the above should also be included within the scope of computer-readable media.

[0131] Instructions may be executed by one or more processors, such as one or more DSPs, general purpose microprocessors, ASICs, FPGAs, or other equivalent integrated or discrete logic circuitry. Accordingly, the term “processor” and “processing circuitry,” as used herein may refer to any of the foregoing structure or any other structure suitable for implementation of the techniques described herein. Also, the techniques could be fully implemented in one or more circuits or logic elements.

[0132] The techniques of this disclosure may be implemented in a wide variety of devices or apparatuses, including, an integrated circuit (IC) or a set of ICs (e.g., a chip set). Various components, modules, or units are described in this disclosure to emphasize functional aspects of devices configured to perform the disclosed techniques, but do not necessarily require realization by different hardware units. Rather, as described above, various units may be combined in a hardware unit or provided by a collection of interoperative hardware units, including one or more processors as described above, in conjunction with suitable software and / or firmware.

[0133] Various examples of the disclosure have been described. These and other examples are within the scope of the following claims.

Claims

WHAT IS CLAIMED IS:

1. A medical device comprising: electrical stimulation circuitry configured to generate electrical stimulation deliverable to a target nerve via a set of electrodes of a plurality of electrodes; and processing circuitry configured to: determine one or more parameter values that define the electrical stimulation generated by the electrical stimulation circuitry; control the electrical stimulation circuitry to generate a burst of conditioning pulses deliverable to the target nerve, wherein the burst of conditioning pulses is configured to change a state of excitability of target nerve fibers within the target nerve; and control, based on the one or more parameter values, the electrical stimulation circuitry to generate electrical stimulation therapy to the target nerve, wherein the electrical stimulation therapy is configured to treat a condition of the patient.

2. The medical device of claim 1, wherein the burst of conditioning pulses is configured to change the state of excitability from a first state to a less excitable state, and wherein the target nerve fibers are less likely to respond to electrical stimulation in the less excitable state.

3. The medical device of any of claims 1 or 2, further comprising sensing circuitry, wherein the processing circuitry is further configured to: control the electrical stimulation circuitry to deliver probe pulses to the target nerve, receive, from the sensing circuitry, information representative of one or more sensed signals responsive to the probe pulses; determine, based on the information representative of the one or more sensed signals, one or more thresholds for different respective nerve fiber types in the target nerve; control the electrical stimulation circuitry to detect at least one evoked compound action potential (ECAP) signal in response to subsequent electrical stimulation;compare one or more characteristics of the at least one ECAP signal to a target range for the one or more characteristics; responsive to determining that at least one of the one or more characteristics are outside the target range, adjust at least one parameter value that defines the burst of conditioning pulses; and control the electrical stimulation circuitry to deliver subsequent bursts of conditioning pulses according to the updated at least one parameter value.

4. The medical device of claim 3, wherein one of the one or more characteristics of the sensed at least one ECAP signal comprises an amplitude of the at least one ECAP signal.

5. The medical device of any of claims 3 or 4, wherein the processing circuitry is configured to adjust the at least one parameter value that defines the burst of conditioning pulses by at least adjusting an amplitude of one or more pulses of the burst of conditioning pulses.

6. The medical device of any of claims 1 through 5, wherein the processing circuitry is further configured to maintain the change in the state of excitability of the target nerve fibers for a short duration of time by at least: controlling the electrical stimulation circuitry to generate the burst of conditioning pulses having continuous pulses for a first duration of time; and responsive to the first duration of time elapsing, controlling the electrical stimulation circuitry to generate the electrical stimulation therapy for the short duration of time.

7. The medical device of any of claims 1 through 5, wherein the processing circuitry is further configured to maintain the change in the state of excitability of the target nerve fibers for a long duration of time by at least: controlling the electrical stimulation circuitry to generate the burst of conditioning pulses having intermittent pulses for a first duration of time; and responsive to the first duration of time elapsing, controlling the electrical stimulation circuitry to generate electrical stimulation therapy for the long duration of time.

8. The medical device of any of claims 1 through 7, wherein the one or more parameters of the burst of conditioning pulses comprises a frequency of approximately 200 Hz to 500 Hz.

9. The medical device of any of claims 1 through 8, wherein the medical device is an implantable medical device configured to deliver the electrical stimulation.

10. The medical device of any of claims 1 through 9, wherein the electrical stimulation is configured to be delivered to the target nerve comprising a sacral nerve of the patient.

11. The medical device of any of claims 1 through 10, wherein the electrical stimulation is configured to be delivered to the target nerve comprising a tibial nerve of the patient.

12. A system comprising: the medical device of any of claims 1 through 11, and one or more electrodes configured to be coupled to the medical device and configured to be located proximal to the target nerve of the patient.

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