Therapy scheduling for deep brain stimulation

Abstract

A system for therapy scheduling includes one or more memories configured to store a therapy schedule; and processing circuitry coupled to the one or more memories and configured to: prior to a scheduled transition from a first therapy of the therapy schedule to a second therapy of the therapy schedule, cause delivery of one or more ping stimulation pulses configured to evoke an evoked signal in a brain of a patient; determine, based on the evoked signal, whether to deviate from or change the therapy schedule; and control delivery of electrical stimulation therapy based on the determination.

Description

THERAPY SCHEDULING FOR DEEP BRAIN STIMULATION

[0001] This application is a PCT application that claims priority to and the benefit of U.S. Provisional Patent Application No. 63 / 623,021, filed January 19, 2024, the entire contents of which is incorporated herein by reference.TECHNICAL FIELD

[0002] This disclosure generally relates to electrical stimulation therapy.BACKGROUND

[0003] Medical devices may be external or implanted, and may be used to deliver electrical stimulation therapy to various tissue sites of a patient to treat a variety of symptoms or conditions such as chronic pain, tremor, Parkinson’s disease, other movement disorders, epilepsy, urinary or fecal incontinence, sexual dysfunction, obesity, or gastroparesis. A medical device delivers electrical stimulation therapy via one or more leads that include electrodes located proximate to target locations associated with the brain, the spinal cord, pelvic nerves, peripheral nerves, or the gastrointestinal tract of a patent. For bipolar stimulation, the electrodes used for stimulation may be on one or more leads. For unipolar stimulation, the electrodes may be on one or more leads, and an electrode on a stimulator housing located remotely from the target site (e.g., near clavicle). It may be possible to use leadless stimulation using electrodes mounted on the stimulation housing. Hence, electrical stimulation is used in different therapeutic applications, such as deep brain stimulation (DBS), spinal cord stimulation (SCS), pelvic stimulation, gastric stimulation, or peripheral nerve field stimulation (PNFS).

[0004] A clinician may select values for a number of programmable parameters in order to define the electrical stimulation therapy to be delivered by the implantable stimulator to a patient. For example, the clinician may select one or more electrodes for delivery of the stimulation, a polarity of each selected electrode, a voltage or current pulse amplitude, a pulse width, and a pulse frequency as parameters. A set of parameters, such as a set including electrode combination, electrode polarity, amplitude, pulse width, and pulse rate, may be referred to as a program in the sense that they define the electrical stimulation therapy to be delivered to the patient.SUMMARY

[0005] This disclosure describes example techniques for processing circuitry to determine therapy scheduling for deep brain stimulation (DBS), such as to determine therapy scheduling based on evoked signals and / or local field potential (LFP) signals. One example of the evoked signal is an evoked resonant neural activity (ERNA) signal, that is evoked from delivery from stimulation signals. An LFP may be from an intrinsic signal generated within a brain of a patient. That is, the LFP is intrinsic because it can be present without being evoked by delivery of an electrical stimulation; however, characteristics of the LFP may be influenced (e.g., modified) by delivered stimulation. In some examples, the LFP is generated due to a signal source (e.g., oscillatory signal source) within the brain of the patient. An evoked signal, on the other hand, is a signal that the brain generates (e.g., evokes) in response to an electrical stimulation signal. That is, the evoked signal is not present until after electrical stimulation has been delivered.

[0006] A medical device may be configured to deliver therapy in accordance with a therapy schedule. The therapy schedule may define a plurality of therapies, with each therapy associated with a respective set of parameters (e.g., amplitude, frequency, pulse width, electrode selection, etc.). The therapy schedule may also define a stimulation on / off time (also called cycle time). In this disclosure, no stimulation being delivered (e.g., stimulation off) is also considered as one of the therapies defined in the therapy schedule. That is, the therapy schedule may define a first therapy in which no stimulation is being delivered and a second therapy in which therapeutic stimulation is being delivered. In some examples, the first therapy may also include therapeutic stimulation but with parameters different than those of the second therapy.

[0007] This disclosure describes example techniques for the processing circuitry to determine whether deviation from the therapy schedule, and possibly longer-term changes to the therapy schedule is appropriate based on the evoked signal and / or LFP signal. In some cases, there may be benefits to deviate from or change the therapy schedule to account for patient activity, medication, disease progression, etc. Accordingly, in one or more examples, prior to a scheduled transition from a first therapy of the therapy schedule to a second therapy of the therapy schedule, the processing circuitry may cause delivery of one or more subtherapeutic stimulation pulses configured to evoke an evoked signal in a brain of a patient. The stimulation pulses configured to evoke the evoked signal may not be subtherapeutic in all examples. The processing circuitry may determine, based on the evoked signal, whether toremain with the first therapy, transition to the second therapy having a set of one or more parameters, or update the set of one or more parameters for the second therapy and then transition to the second therapy based on the updated set of one or more parameters.

[0008] In one example, the disclosure describes a system for therapy scheduling, the system comprising: one or more memories configured to store a therapy schedule; and processing circuitry coupled to the one or more memories and configured to: prior to a scheduled transition from a first therapy of the therapy schedule to a second therapy of the therapy schedule, cause delivery of one or more ping stimulation pulses configured to evoke an evoked signal in a brain of a patient; determine, based on the evoked signal, whether to deviate from or change the therapy schedule; and control delivery of electrical stimulation therapy based on the determination.

[0009] In one example, the disclosure describes a method for therapy scheduling, the method comprising: prior to a scheduled transition from a first therapy of a therapy schedule to a second therapy of the therapy schedule, causing delivery of one or more ping stimulation pulses configured to evoke an evoked signal in a brain of a patient; determining, based on the evoked signal, whether to deviate from or change the therapy schedule; and controlling delivery of electrical stimulation therapy based on the determination.

[0010] In one example, the disclosure describes a computer-readable storage medium storing instructions thereon that when executed cause one or more processors to: prior to a scheduled transition from a first therapy of a therapy schedule to a second therapy of the therapy schedule, cause delivery of one or more ping stimulation pulses configured to evoke an evoked signal in a brain of a patient; determine, based on the evoked signal, whether to deviate from or change the therapy schedule; and control delivery of electrical stimulation therapy based on the determination.

[0011] In one example, the disclosure describes a system for therapy scheduling, the system comprising: means for causing delivery of one or more ping stimulation pulses configured to evoke an evoked signal in a brain of a patient prior to a scheduled transition from a first therapy of a therapy schedule to a second therapy of the therapy schedule; means for determining, based on the evoked signal, whether to deviate from or change the therapy schedule; and means for controlling delivery of electrical stimulation therapy based on the determination.

[0012] The details of one or more examples of the techniques of this disclosure are set forth in the accompanying drawings and the description below. Other features, objects, andadvantages of the techniques will be apparent from the description and drawings, and from the claims.BRIEF DESCRIPTION OF DRAWINGS

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

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

[0015] FIG. 3 is a block diagram of the external programmer of FIG. 1 for controlling delivery of DBS therapy according to an example of the techniques of the disclosure.

[0016] FIG. 4 is a block diagram illustrating an example of a sensing circuitry of FIG. 2 in further detail.

[0017] FIG. 5 is a graph illustrating an example of an evoked signal.

[0018] FIG. 6 is a flowchart illustrating an example operation in accordance with techniques of the disclosure.

[0019] FIG. 7 is another flowchart illustrating an example operation in accordance with techniques of the disclosure.DETAILED DESCRIPTION

[0020] This disclosure describes example techniques to dynamically determine deviations or updates to a therapy schedule based on evoked signals and / or local field potential (LFP) signals. The example techniques are described with respect to deep brain stimulation (DBS), but the example techniques are not so limited and may be applied to other types of therapies and / or other anatomical locations. DBS may provide relief for many different patient conditions such as essential tremors (ETs), Parkinson’s, obsessive compulsive disorder (OCD), depression, and others. For DBS, a surgeon implants one or more leads within the brain of the patient for outputting therapeutic electrical stimulation signals at depth within the brain. The one or more leads are coupled to an implantable medical device (IMD) that generates the therapeutic electrical stimulation signals for delivery through the one or more leads.

[0021] After implantation, the surgeon / clinician may be tasked with determining what the parameters should be for the therapeutic electrical stimulation signals. The IMD may thengenerate the therapeutic electrical stimulation signals in accordance with the determined parameters. For example, the clinician may determine a therapy schedule that defines a plurality of therapies, each having different parameters. The therapy schedule may define cycling between different therapies, such as on / off (referred to as duty cycle), different amplitudes, different pulse widths, different frequencies, different electrode combinations, etc. As described above, no stimulation being delivered (e.g., stimulation off) is also considered as one of the therapies defined in the therapy schedule. That is, the therapy schedule may define a first therapy in which no stimulation is being delivered and a second therapy in which therapeutic stimulation is being delivered. In some examples, the first therapy may also include therapeutic stimulation but with parameters different than those of the second therapy.

[0022] The clinician may determine the therapy schedule based on various factors. For instance, the clinician may determine the therapy schedule (e.g., when and for how long a particular therapy is delivered) to optimize therapeutic effectiveness, maximize device longevity, and / or reduce stimulation habituation. In some examples, the duty cycle or dynamics of cycling would be pre-defined during an in-clinic visit.

[0023] However, over time the efficacy of the therapeutic electrical stimulation signals may change. For instance, if there is lead migration, the therapeutic electrical stimulation signals may be insufficient to provide adequate therapeutic relief. If the patient condition worsens, such as due to disease progression or therapy accommodation, the therapeutic electrical stimulation signals may become insufficient to provide adequate therapeutic relief. That is, having a therapy schedule is beneficial for various reasons, but the therapy schedule may not account for differences in therapy that are desirable due to changes in patient activity, disease progression, medication state, etc.

[0024] There may be other examples for why the therapeutic electrical stimulation signals may be insufficient to provide adequate therapeutic relief. Also, there may be instances where a patient condition may improve (e.g., due to medication supplementing the stimulation therapy). In such cases, the intensity of the therapeutic electrical stimulation signals may be greater than needed to provide effective therapy.

[0025] This disclosure describes example techniques where, with sensing both LFP and evoked signals, the processing circuitry may modify the dynamics of cycling stimulation to customize and optimize on a patient-by-patient, day-by-day, and hour-by-hour basis. The processing circuitry may be part of the IMD, an external programmer, a cloud computingenvironment, or any combination thereof. For instance, the processing circuitry configured to perform one or more example techniques described in this disclosure may include the processing circuitry of just the IMD, the programmer, or the cloud computing environment, or any combination of the processing circuitry of the IMD, the programmer, and the cloud computing environment.

[0026] In one or more examples described in this disclosure, the therapy schedule may define when to transition (e.g., the IMD or the processing circuitry) from the first therapy to the second therapy. The first therapy may include delivery of no stimulation pulses (e.g., off- time of the duty cycle). However, in some examples, the first therapy may define a first set of one or more parameters for the first therapy, where the first therapy is therapeutic.

[0027] Prior to a scheduled transition from the first therapy of the therapy schedule to the second therapy of the therapy schedule, the processing circuitry may cause delivery of one or more ping stimulation pulses configured to evoke an evoked signal in a brain of a patient. The parameters (e.g., amplitude, frequency, and pulse width) for the ping stimulation pulses may be subtherapeutic. That is, the one or more ping stimulation pulses may be configured to deliver subtherapeutic intensity below a therapeutic threshold. The subtherapeutic intensity may refer to one or combination of amplitude, pulse width, or frequency of the ping stimulation pulses, and the therapeutic threshold may refer to a threshold at which the stimulation pulses generate therapeutic impact.

[0028] For instance, the parameters for the ping stimulation pulses may be different than the parameters for electrical stimulation that is used for therapeutic results. In some examples, the ping stimulation pulses may provide some therapeutic results, but the efficacy may be less than the efficacy of therapeutic electrical stimulation (e.g., below therapeutic threshold). As an example, to reduce power consumption, an amplitude or frequency of the ping stimulation pulses may be at or near the minimum amplitude or frequency needed to evoke an evoked signal that can be sensed, and there may be little to no therapeutic benefit of electrical stimulation at such amplitude or frequency. In some examples, it may be possible for the ping stimulation pulses to provide therapeutic benefit as well.

[0029] The processing circuitry may determine, based on the evoked signal, whether to deviate from or change (e.g., longer-term update) the therapy schedule. As one example, the processing circuitry may determine, based on the evoked signal, whether to remain with the first therapy, transition to the second therapy having a set of one or more parameters, or update the set of one or more parameters for the second therapy and then transition to thesecond therapy based on the updated set of one or more parameters. In some examples, the processing circuitry may also receive information indicative of a local field potential (LFP) signal, where the LFP signal is an intrinsic signal (e.g., generated without delivery of stimulation pulses, but could be affected by stimulation signals). The processing circuitry may be configured to determine, based on the evoked signal and the LFP signal, whether to deviate from or change the therapy schedule.

[0030] In this way, the example techniques described herein may enable a dynamic determination of patient condition, and determine whether deviation or changes to the therapy schedule are appropriate to improve therapeutic effectiveness, increase IMD longevity, or address accommodation. For example, if the processing circuitry relied solely or mainly on the therapy schedule, changes in patient condition due to patient activity, disease progression, medication state, etc. may not be accounted for. The evoked signals and / or LFP signals may indicate patient activity, disease progression, medication state, etc. With the example techniques, the processing circuitry can use the evoked signal and / or LFP signal to determine whether deviation or changes to the therapy schedule is appropriate, which in turn can account for changes to patient activity, disease progression, medication state changes, etc. that may otherwise reduce therapy efficacy.

[0031] FIG. 1 is a conceptual diagram illustrating an example system 100 that includes an implantable medical device (IMD) 106 configured to deliver deep brain stimulation to a patient 112. In some examples, the DBS may be closed-loop in the sense that IMD 106, as one example, may adjust, increase, or decrease the magnitude of one or more parameters of the DBS in response to changes in patient activity or movement, a severity of one or more symptoms of a disease of the patient, medication state, a presence of one or more side effects due to the DBS, or one or more sensed signals of the patient. In some examples, DBS may include therapy delivered through the venus or arterial system.

[0032] For instance, one example of system 100 is a bi-directional DBS system with capabilities to both deliver stimulation, sense intrinsic neuronal signals, and sense neural signals that are evoked in response to delivery of stimulation. System 100 may be configured to treat a patient condition, such as a movement disorder (e.g., essential tremor (ET) or Parkinson’s), neurodegenerative impairment, a mood disorder, or a seizure disorder of patient 112. Patient 112 ordinarily is a human patient. In some cases, however, therapy system 100 may be applied to other mammalian or non-mammalian, non-human patients. While movement disorders and neurodegenerative impairment are primarily referred to herein, inother examples, therapy system 100 may provide therapy to manage symptoms of other patient conditions, such as, but not limited to, seizure disorders (e.g., epilepsy) or mood (or psychological) disorders (e.g., major depressive disorder (MDD), bipolar disorder, anxiety disorders, post-traumatic stress disorder, dysthymic disorder, and obsessive-compulsive disorder (OCD)). At least some of these disorders may be manifested in one or more patient movement behaviors. As described herein, a movement disorder or other neurodegenerative impairment may include symptoms such as, for example, muscle control impairment, motion impairment or other movement problems, such as rigidity, spasticity, bradykinesia, rhythmic hyperkinesia, nonrhythmic hyperkinesia, and akinesia. In some cases, the movement disorder may be a symptom of Parkinson’s disease or essential tremor (ET). However, the movement disorder may be attributable to other patient conditions.

[0033] Example therapy system 100 includes medical device programmer 104, implantable medical device (IMD) 106, lead extension 110, and leads 114A and 114B with respective sets of electrodes 116, 118. In the example shown in FIG. 1, electrodes 116, 118 of leads 114A, 114B are positioned to deliver electrical stimulation to a tissue site within brain 120, such as a deep brain site under the dura mater of brain 120 of patient 112. In some examples, delivery of stimulation to one or more regions of brain 120, such as the subthalamic nucleus (STN), globus pallidus or thalamus, ventralus intermediate (VIM), anterior nucleus (ANT), ventral internal capsule / ventral striatum (VCVS), cortico-basal ganglia-thalamocortical circuit, or anterior insular cortex (AIC), may be an effective treatment to manage disorders, such as Parkinson’s disease. Some or all of electrodes 116, 118 also may be positioned to sense neurological brain signals within brain 120 of patient 112. In some examples, some of electrodes 116, 118 may be configured to sense neurological brain signals and others of electrodes 116, 118 may be configured to deliver electrical stimulation to brain 120. In other examples, all of electrodes 116, 118 are configured to both sense neurological brain signals and deliver electrical stimulation to brain 120. In some examples, unipolar stimulation may be possible where one electrode is on the housing of IMD 106.

[0034] IMD 106 includes a therapy module (e.g., which may include processing circuitry or other electrical circuitry configured to perform the functions attributed to IMD 106) that includes stimulation generation circuitry configured to generate and deliver electrical stimulation therapy to patient 112 via a subset of electrodes 116, 118 of leads 114A and 114B, respectively. The subset of electrodes 116, 118 that are used to deliver electricalstimulation to patient 112, and, in some cases, the polarity of the subset of electrodes 116, 118, may be referred to as a stimulation electrode combination. The stimulation electrode combination can be selected for a particular patient 112 and target tissue site (e.g., selected based on the patient condition). The group of electrodes 116, 118 includes at least one electrode and can include a plurality of electrodes. In some examples, the plurality of electrodes 116 and / or 118 may have a complex electrode geometry such that two or more electrodes are located at different positions around the perimeter of the respective lead.

[0035] In some examples, the neurological signals sensed within brain 120 may reflect changes in electrical current produced by the sum of electrical potential differences across brain tissue. There may be various examples of neurological brain signals that electrodes 116, 118 may be configured to sense. One example of a neurological brain signal is a local field potential (LFP) signal. An LFP signal may be an intrinsic signal within brain 120 of patient 112 that is generated by a signal source within brain 120 of patient 112. Another example of a neurological brain signal is an evoked signal, such as an evoked resonant neural activity (ERNA) signal. For ease of illustration, the example techniques are described with respect to an ERNA signal as an evoked signal, but the example techniques should not be considered limited to an ERNA signal. Delivery of electrical stimulation within brain 120 may evoke an ERNA signal, and the ERNA signal may not be an intrinsic signal. The electrical stimulation delivered within brain 120 to evoke the ERNA signal need not necessarily provide therapeutic benefit, but therapeutic benefit from the electrical stimulation used to evoke the ERNA signal is possible.

[0036] Electroencephalogram (EEG) signal or an electrocorticogram (ECoG) signal are also examples of neurological signals. For example, neurons generate the neurological signals, and if measured at depth, it is LFP or ERNA (if evoked), if measured on the dura, it is ECoG, and if on scalp, it is EEG.

[0037] In some examples, the delivery of therapeutic electrical stimulation signals may be based on a feature of interest (e.g., biomarker). One example of the feature of interest (e.g., biomarker) within the LFPs is synchronized beta frequency band (8-33Hz) LFP activity recorded within the sensorimotor region of the subthalamic nucleus (STN) in Parkinson’s disease or essential tremor patients. The source of the LFP activity can be considered as a signal source, within the brain of the patient, that outputs an oscillatory electrical voltage signal that is sensed by one or more of electrodes 116 and / or 118. The suppression of pathological beta activity (e.g., suppression or squelching of the signal component of thebioelectric signals generated from the LFP source that is within the beta frequency band) by both medication and DBS may correlate with improvements in the motor symptoms of patients who have Parkinson’s disease or essential tremor.

[0038] For example, one or more of electrodes 116 and / or 118 may sense the LFP activity. Accordingly, there may be a plurality of LFP measurements of an LFP, where each of the LFP measurements may be measured with different electrodes 116 and / or 118 on leads 114A, 114B or by the same electrodes 116 and / or 118 on leads 114A, 114B. As described, the LFP is intrinsically generated by a signal source (e.g., oscillatory electrical voltage source) within brain 120 of patient 122.

[0039] In some examples, the neurological brain signals that are used to select a stimulation electrode combination may be sensed within the same region of brain 120 as the target tissue site for the electrical stimulation. As previously indicated, these tissue sites may include tissue sites within anatomical structures such as the thalamus, subthalamic nucleus or globus pallidus of brain 120, as well as other target tissue sites. The specific target tissue sites and / or regions within brain 120 may be selected based on the patient condition. Thus, in some examples, both a stimulation electrode combination and sense electrode combinations may be selected from the same set of electrodes 116, 118. In other examples, the electrodes used for delivering electrical stimulation may be different than the electrodes used for sensing neurological brain signals.

[0040] Therapeutic electrical stimulation generated by IMD 106 may be configured to manage a variety of disorders and conditions. In some examples, the stimulation generation circuitry of IMD 106 is configured to generate and deliver therapeutic electrical stimulation pulses to patient 112 via electrodes of a selected stimulation electrode combination. However, in other examples, the stimulation generation circuitry of IMD 106 may be configured to generate and deliver a continuous wave signal, e.g., a sine wave or triangle wave. In either case, stimulation generation circuitry within IMD 106 may generate the electrical stimulation therapy for DBS according to a selected therapy program. In examples in which IMD 106 delivers therapeutic electrical stimulation in the form of stimulation pulses, a therapy program may include a set of therapy parameter values (e.g., parameters), such as a stimulation electrode combination for delivering stimulation to patient 112, pulse frequency, pulse width, and a current or voltage amplitude of the pulses. As previously indicated, the electrode combination may indicate the specific electrodes 116, 118 that areselected to deliver therapeutic stimulation signals to tissue of patient 112 and the respective polarities of the selected electrodes.

[0041] In accordance with one or more examples described in this disclosure, the stimulation generation circuitry of IMD 106 is configured to generate and deliver therapeutic electrical stimulation pulses to patient 112 in accordance with a therapy schedule. For instance, the therapy schedule may define which therapy program is to be executed at what time and for how long. As one example, the therapy schedule may define a cycle period. In the cycle period, for a first amount of time, the stimulation generation circuitry of IMD 106 may deliver electrical stimulation in accordance with a first therapy, and for a second amount of time, the stimulation generation circuitry of IMD 106 may deliver electrical stimulation in accordance with a second therapy.

[0042] In some examples, the first therapy or the second therapy may indicate delivery of no stimulation pulses (e.g., off-time of the cycle period), and the other of the first therapy or second therapy may define a set of one or more parameters that provide effective therapy (e.g., on-time of the cycle period). During the on-time of the cycle period, there may be instances, such as between two stimulation pulses within the on-time when stimulation is not being delivered. In some examples, the first therapy may define a first set of one or more parameters that provide effective therapy, and the second therapy may define a second set of one or more parameters that provide effective therapy.

[0043] The therapy schedule may define that the stimulation generation circuitry of IMD 106 is configured to deliver electrical stimulation in accordance with the first therapy (e.g., including examples where the first therapy includes delivery of no electrical stimulation), and then deliver electrical stimulation in accordance with the second therapy, and repeat. In some examples, there may be more therapies than the first therapy and the second therapy in the therapy schedule, and the stimulation generation circuitry of IMD 106 may be configured to deliver electrical stimulation cycling through the first therapy, second therapy, and other therapies, or may be configured to select one of the therapies. The first therapy, second therapy, and other therapies are examples of the therapy programs, where each of the therapies may define a different set of one or more parameters.

[0044] In some examples, electrodes 116, 118 may be circumferentially-segmented DBS arrays of electrodes, and include some non-segmented electrodes as well, such as ring electrodes. Circumferentially-segmented DBS arrays refer to electrodes that are segmented circumferentially along the lead. As one example, leads 114A and 114B may include a firstset of electrodes arranged circumferentially around leads 114A and 114B that are all at the same height level on leads 114A and 114B. Each of the electrodes in the first set of electrodes is a separate segmented electrode and form a level of circumferentially-segmented array of electrodes. Leads 114A and 114B may include a second set of electrodes arranged circumferentially around leads 114A and 114B that are all at the same height level on leads 114A and 114B. Each of the electrodes in the first set of electrodes is a separate segmented electrode and form a level of circumferentially-segmented array of electrodes. The electrodes may be beneficial by enabling directional stimulation and sensing.

[0045] With the electrodes, IMD 106 may be configured to perform both directional stimulation and sensing, thereby enhancing the ability to target the source of the LFP activities (also referred to as pathological neuronal activities). For example, IMD 106 may be configured to perform directional sensing to determine a direction and / or orientation of the LFP source (e.g., signal source that generates the LFP) having the signal component in the beta frequency band. IMD 106 may direct the electrical stimulation toward the signal source to suppress (e.g., squelch) the signal component produced by the signal source in the beta frequency band, as one example. This disclosure describes example techniques to utilize evoked signals to determine the parameters of the therapeutic electrical stimulation signals used to suppress the signal component produced by the signal source in the beta frequency band.

[0046] The signal component in the beta frequency band is described as one example, and the techniques are applicable to other types of LFP activity. Also, the example techniques should not be considered as being limited to suppressing signal components produced by the signal source. The example techniques may be used generally for DBS, or other types of therapy where a combination of LFP signal measurements and evoked signals are used as part of closed-loop therapy.

[0047] Furthermore, the example techniques are not limited to examples where one or more of electrodes 116, 118 are circumferentially-segmented electrodes. The example of using circumferentially-segmented electrodes is described as a way of directional stimulation and sensing. However, the example techniques are also useable in examples where directional stimulation and sensing are not available or are not used. Moreover, there may be other ways of performing directional stimulation and sensing that do not require the use of circumferentially-segmented electrodes.

[0048] As an example, to suppress the signal component having the beta frequency band from the LFP source (e.g., the signal source of the LFP), IMD 106 may output an electrical stimulation signal that alters the way in which neurons of the LFP source produce signals. For example, the electrical stimulation either directly inhibits a certain neuronal population that includes the LFP source or excites one group of neurons which in turn suppresses another group of neurons (e.g., network effect). The stimulation may act on the neurons directly, and not necessarily on the signals the neurons (e.g., LFP source) produces.

[0049] In an example, for DBS, IMD 106 may be configured to deliver therapeutic electrical stimulation signals based on one or more parameters such as amplitude, pulse width, and frequency. In some examples, shortly after implantation or during the implantation surgery for IMD 106 and / or leads 114A, 114B, a clinician / surgeon may determine a therapy schedule that cycles between a plurality of therapies (e.g., different therapy programs includes examples of no delivery of stimulation). However, the effectiveness of the therapy schedule may change overtime. For instance, due to lead migration, accommodation of the neural substrate to stimulation, worsening of patient condition, changes in patient activity, changes in medication state, the therapy schedule may be insufficient to provide effective therapy or may provide effective therapy in an inefficient manner (e.g., providing electrical stimulation even when delivery of electrical stimulation is not needed). That is, if patient condition improves, the intensity of the first set of one or more therapeutic electrical stimulation signals may be greater than needed to provide effective therapy.

[0050] Accordingly, there may be benefit in periodically, or possibly continuously, determining the effectiveness of the therapy schedule. One way to update the therapy schedule for therapeutic electrical stimulation signals may be for patient 112 to periodically schedule an appointment with a clinician to update the parameters. Another way to update the parameters for therapeutic electrical stimulation signals may be for patient 112 to manually adjust the parameters himself / herself. In both such examples, there may be burden on patient 112 to have to schedule appointments for parameter adjustment or self-titrate the parameters. This may also lead to delay in updates to parameters.

[0051] This disclosure describes example techniques for determining, based on an evoked signal (e.g., ERNA), whether to deviate from or change the therapy schedule. For instance, the therapy schedule may schedule a time for transitioning from a first therapy of the therapy schedule to a second therapy of the therapy schedule. In accordance with one or moreexamples, the processing circuitry of IMD 106 may, prior to a scheduled transition from the first therapy of the therapy schedule to the second therapy of the therapy schedule, cause delivery of one or more ping stimulation pulses configured to evoke an evoked signal in brain 120 of patient 112. In one or more examples, the ping stimulation pulses may be subtherapeutic, but may be therapeutic in other examples. For instance, the one or more ping stimulation pulses may be configured to deliver subtherapeutic intensity below a therapeutic threshold. The subtherapeutic intensity may refer to one or combination of amplitude, pulse width, or frequency of the ping stimulation pulses, and the therapeutic threshold may refer to a threshold at which the stimulation pulses generate therapeutic impact.

[0052] That is, the parameters of the ping stimulation pulses may be different than parameters of electrical stimulation known to provide therapeutic benefit. As described above, the ping stimulation pulses may provide some therapeutic results, but the efficacy may be less than the efficacy of therapeutic electrical stimulation. As an example, to reduce power consumption, an amplitude or frequency of the ping stimulation pulses may be at or near the minimum amplitude or frequency needed to evoke an evoked signal that can be sensed, and there may be little to no therapeutic benefit of electrical stimulation at such amplitude or frequency.

[0053] The processing circuitry of IMD 106 may analyze the evoked signal to determine whether to deviate from or change the therapy schedule. As one example, the processing circuitry of IMD 106 may be configured to determine, based on the evoked signal, whether to remain with the first therapy, transition to the second therapy having a set of one or more parameters, or update the set of one or more parameters for the second therapy and then transition to the second therapy based on the updated set of one or more parameters.

[0054] The processing circuitry of IMD 106 may utilize both LFP measurements and the evoked (e.g., ERNA) signals to determine whether to deviate from or change the therapy schedule. For example, the processing circuitry of IMD 106 may be configured to determine one or more LFP measurements of an LFP, with each of the LFP measurements being measured with different electrodes 116, 118 on leads 114 A, 114B or same electrodes 116, 118 on leads 114A, 114B. As one example, one of electrodes 118 may be a reference electrode (e.g., ground), and the processing circuitry may receive a first LFP measurement that is sensed by a first one of electrodes 116 relative to the reference electrode of electrodes 118. The processing circuitry may receive a second LFP measurement that is sensed by asecond one of electrodes 116 relative to the reference electrode of electrodes 118, and so forth.

[0055] Although the above examples describe the reference electrode being one of electrodes 118, and receiving the LFP measurements through electrodes 116, the techniques are not so limited. In some examples, the reference electrode may be one of electrodes 116, and the processing circuitry may receive the LFP measurements through electrodes 118. In some examples, the reference electrode need not be one of electrodes 116 or 118, and may be another electrode, such as an electrode on the housing of IMD 106.

[0056] Examples where the reference electrode is on one of leads 114A or 114B, and the other electrode used for sensing the LFP (e.g., determining the LFP measurement) is on the other of leads 114A or 114B or on the housing of IMD 106 is referred to as a monopolar sensing. In some examples, to determine the LFP measurements, the processing circuitry may receive bipolar sensing measurements. In bipolar sensing measurements, electrodes 116, 118 for sensing are on the same one of leads 114 A, 114B.

[0057] For ease of description, this disclosure describes monopolar sensing, but the example techniques are applicable to bipolar sensing as well. Also, for ease of description, for monopolar sensing, the example techniques are described with respect to the reference electrode being one of electrodes 118, and other electrode used for sensing being one of electrodes 116.

[0058] As an example, assume that the time to transition from the first therapy to the second therapy is reached. The processing circuitry may cause delivery of one or more ping stimulation pulses configured to evoke an evoked signal, and evaluate the evoked signal, and possibly the LFP, to determine whether there is a change in a characteristic of the evoked signal or LFP. interictal spiking. If there is no change, the processing circuitry may determine that there is no immediate need to transition to the second therapy. In this example, the processing circuitry may deviate from the therapy schedule and delay the time when transitioning to the second therapy.

[0059] As another example, assume that the time to transition from the first therapy to the second therapy is reached. The processing circuitry may cause delivery of one or more ping stimulation pulses configured to evoke an evoked signal, and evaluate the evoked signal, and possibly the LFP, to determine whether there is interictal spiking. If there is large change in the evoked signal, the processing circuitry may determine that the parameters of the second therapy should be updated (e.g., higher amplitude, pulse width, or frequency of the electricalstimulation). In this example, the processing circuitry may update the parameters of the second therapy, and then transition to the second therapy based on the updated set of one or more parameters.

[0060] In examples where the processing circuitry of IMD 106 deviates from the therapy schedule may refer to examples where for the next immediate transition from first therapy to second therapy, or back from second therapy to first therapy, the processing circuitry of IMD 106 may delay or otherwise deviate from the therapy schedule. However, the processing circuitry of IMD 106 may revert back to the therapy schedule for the following transition. In some examples, before transitioning back, the processing circuitry of IMD 106 may again evoke an evoked signal, and determine whether to transition back based on the evoked signal.

[0061] In examples where the processing circuitry of IMD 106 changes the therapy schedule, such changes may be a longer-term modification to the therapy schedule. That is, the processing circuitry of IMD 106 may rewrite the therapy schedule. For example, the evoked signal and / or the LFP may change as there is disease progression, wash in or wash out of medication, etc. The processing circuitry of IMD 106 may access the evoked signals and / or LFP when the patient was first implanted with IMD 106, and compare more recently measured evoked signals and / or LFP to determine whether there is a change in disease progression. The processing circuitry may then make more long-term changes to the therapy schedule as the disease progresses.

[0062] In some examples, the clinician may utilize the evoked signals and / or LFP measurements to determine medication efficacy. For example, the processing circuitry of IMD 106 may receive information indicative of a medication schedule, and may generate association information that associates the evoked signal and / or LFP information with the medication schedule. As an example, the association information may indicate the evoked signal and / or LFP information that corresponds to the time when the patient took medication and / or evoked signal and / or LFP information that corresponds to certain times after the patient took medication. The processing circuitry may output the generated association information. A clinician may review the association information to determine whether changes in medication type, frequency, dosage, etc. is advisable.

[0063] Times when the patient took medication may be indicated by patient 112 via programmer 104, or medication schedule may be stored in IMD 106. There may be other ways to determine that patient 112 took medication, such as based on sensed signals.

[0064] The clinician may also use the association information to determine efficacy of the medication alone (e.g., if the evoked signal and LFP are during stimulation off-cycle), efficacy of stimulation alone (e.g., if the evoked signal and LFP are from time when there is no medication in the patient), or combined efficacy of stimulation and medication. For instance, in addition to sensing evoked signals from the one or more ping stimulation pulses, the processing circuitry may be configured to sense evoked signals from delivery of therapeutic electrical stimulation. The clinician may evaluate the evoked signals evoked from delivery of therapeutic electrical stimulation that are associated with times when medication is present in patient 112 to determine the combined efficacy of stimulation and medication. The clinician may use such information to better understand medication compliance, as well as to inform patients when to take more medication. In some examples, IMD 106 may output to programmer 104 information to notify patient 112 to take more medication.

[0065] In some examples, the processing circuitry may be configured to use the generated association information to determine whether to change (e.g., a longer-term modification) the therapy schedule, rather than make a more immediate deviation from the therapy schedule. For example, if the evoked signal when patient 112 is taking medication, as indicated by the association information, corresponds to low likelihood of patient experiencing negative symptoms, the processing circuitry may change the time when IMD 106 is to transition from the first therapy to the second therapy.

[0066] As described, the processing circuitry may use evoked signals, LFP measurements, or both for determining whether to deviate from or change the therapy schedule. In examples where there is no delivery of stimulation pulses (e.g., off-cycle), electrodes 116, 118 that are normally used for delivery of stimulation may be available for sensing. Accordingly, in such times, the processing circuitry may record the LFP measurements. Also, electrical stimulation, such as therapeutic electrical stimulation may cause artifacts in the LFP measurements. Therefore, recording LFP measurements during the off-cycle may be beneficial.

[0067] The processing circuitry may then determine the evoked signal using the one or more ping stimulation pulses. The processing circuitry may use the LFP measurements measured only during the off-cycle, and then the evoked signals measured from the one or more ping stimulation pulses to determine whether to deviate from or change the therapy schedule.

[0068] However, in some states, it may be possible for the processing circuitry to use both evoked signals and LFP measurements together. For instance, if the one or more ping stimulation pulses configured to evoke the evoked signal have sufficiently low amplitude, pulse width, and / or frequency, the one or more ping stimulation pulses may not suppress or otherwise cause artifacts on the LFP measurements. In such cases, the processing circuitry may receive both LFP measurements and evoked signals, and determine whether to deviate from or change the therapy schedule.

[0069] There may be various characteristics of the evoked signals that the processing circuitry may evaluate to determine whether to deviate from or change the therapy schedule. As one example, the processing circuitry may determine a latency of the evoked signal or determine a decay interval of the evoked signal. The latency of the evoked signal may be a measure of how long after the delivery of the one or more ping stimulation pulses that the peak of the evoked signal occurs.. The evoked signal tends to oscillate in a damped manner. The decay interval of the evoked signal may be a measure of how long the evoked signal takes to decay to zero. There may be various examples of latency and delay interval, as described in more detail with respect to FIG. 5. The example techniques should not be considered limited to these examples.

[0070] The latency and the decay interval tend to be patient specific. Accordingly, in some examples, the processing circuitry may determine whether the latency or the decay interval are different than a baseline latency or decay interval of the evoked signal that is specific to patient 112. If the latency or decay interval are different than the baseline (e.g., by some threshold), the processing circuitry may determine to deviate from or change the therapy schedule (e.g., update the parameters of the second therapy). If, however, the latency or decay interval are not different than the baseline, the processing circuitry may determine not to deviate from the therapy schedule, and may transition to the second therapy as scheduled.

[0071] Other examples of characteristics of the evoked signals that the processing circuitry may evaluate to determine whether to deviate from or change the therapy schedule include amplitude and frequency of the evoked signals. For example, if the amplitude or frequency of the evoked signal is greater than a baseline amplitude or frequency of the evoked signal, the processing circuitry may deviate from or change the therapy schedule. However, if the amplitude or frequency of the evoked signal is not greater than a baselineamplitude or frequency of the evoked signal, the processing circuitry may not deviate from or change the therapy schedule, and transition to the second therapy as scheduled.

[0072] Although not required, in some examples, the processing circuitry of IMD 106 may be configured to determine one or more electrodes 116 on lead 114A for delivering therapeutic electrical stimulation signal based on the LFP measurements. However, the example techniques are not so limited. In some examples, a clinician may manually select which electrodes 116 on lead 114A are configured to deliver therapeutic electrical stimulation signals.

[0073] As shown in FIG. 1, implanted lead extension 110 is coupled to IMD 106 via connector 108 (also referred to as a connector block or a header of IMD 106). In the example of FIG. 1, lead extension 110 traverses from the implant site of IMD 106 and along the neck of patient 112 to cranium 122 of patient 112 to access brain 120. In the example shown in FIG. 1, leads 114A and 114B (collectively “leads 114”) are implanted within the right and left hemispheres (or in just one hemisphere in some examples), respectively, of patient 112 in order to deliver electrical stimulation to one or more regions of brain 120, which may be selected based on the patient condition or disorder controlled by therapy system 100. The specific target tissue site and the stimulation electrodes used to deliver stimulation to the target tissue site, however, may be selected, e.g., according to the identified patient behaviors and / or other sensed patient parameters. For example, the target tissue site may be the location of the signal source that generates the LFP having a signal component in the beta frequency band. The stimulation electrodes used to deliver stimulation to the target tissue site may be those that are most proximal to the signal source, e.g., as determined by the electrodes having the highest CSD, RMS, peak value, rectified average value, etc. Other lead 114 and IMD 106 implant sites are contemplated. For example, IMD 106 may be implanted on or within cranium 122, in some examples. Leads 114A and 114B may be implanted within the same hemisphere or IMD 106 may be coupled to a single lead implanted in a single hemisphere, in some examples.

[0074] Existing lead sets include axial leads carrying ring electrodes disposed at different axial positions and so-called "paddle" leads carrying planar arrays of electrodes. In some examples, more complex lead array geometries may be used.

[0075] Although leads 114 are shown in FIG. 1 as being coupled to a common lead extension 110, in other examples, leads 114 may be coupled to IMD 106 via separate lead extensions or directly to connector 108. Leads 114 may be positioned to deliver electricalstimulation to one or more target tissue sites within brain 120 to manage patient symptoms associated with a movement disorder of patient 112. Leads 114 may be implanted to position electrodes 116, 118 at desired locations of brain 120 through respective holes in cranium 122. Leads 114 may be placed at any location within brain 120 such that electrodes 116, 118 are capable of providing electrical stimulation to target tissue sites within brain 120 during treatment. For example, electrodes 116, 118 may be surgically implanted under the dura mater of brain 120 or within the cerebral cortex of brain 120 via a burr hole in cranium 122 of patient 112, and electrically coupled to IMD 106 via one or more leads 114.

[0076] In the example shown in FIG. 1, electrodes 116, 118 of leads 114 are shown as ring electrodes. Ring electrodes may be used in DBS applications because ring electrodes are relatively simple to program and are capable of delivering an electrical field to any tissue adjacent to electrodes 116, 118. In other examples, electrodes 116, 118 may have different configurations. For example, at least some of the electrodes 116, 118 of leads 114 may have a complex electrode array geometry that is capable of producing shaped electrical fields. The complex electrode array geometry may include multiple electrodes (e.g., partial ring or segmented electrodes) around the outer perimeter of each lead 114, rather than one ring electrode. In this manner, electrical stimulation may be directed in a specific direction from leads 114 to enhance therapy efficacy and reduce possible adverse side effects from stimulating a large volume of tissue. For example, one or more electrodes 116, 118 may be circumferentially-segmented DBS arrays of electrodes, and one or more electrodes 116, 118 may be non-segmented electrodes such as ring electrodes, as described above. In some examples, electrodes 116, 118 may only be circumferentially-segmented DBS arrays of electrodes, and in some examples, electrodes 116, 118 may only be non-segmented electrodes, such as ring electrodes.

[0077] In some examples, a housing of IMD 106 may include one or more stimulation and / or sensing electrodes. In some examples, leads 114 may have shapes other than elongated cylinders as shown in FIG. 1. For example, leads 114 may be paddle leads, spherical leads, bendable leads, or any other type of shape effective in treating patient 112 and / or minimizing invasiveness of leads 114.

[0078] IMD 106 includes a memory to store the therapy schedule that defines a plurality of therapy programs (e.g., therapies) that each define a set of therapy parameter values. As described, in some examples, the processing circuitry may change the therapy schedule or update therapy parameters. In some examples, a clinician may approve such changes, such asin examples where IMD 106 is configured for remote programming. However, in some examples, clinician approval may not be necessary, such as in examples where the determined parameters for the electrical stimulation signal are within a “safe-range” as assigned by the surgeon / clinician. In such examples, the processing circuitry of IMD 106 may output information indicative of the determined parameters for storage as a deviation from or change in the therapy schedule, and the stimulation generation circuitry may deliver the therapeutic electrical stimulation signal based on the determined parameters. In this way, IMD 106 may generate therapeutic electrical stimulation therapy based on the parameters of the therapies to manage the patient symptoms associated with the patient disorder.

[0079] Rather than or in addition to using therapy programs, in some examples, it may be possible for the processing circuitry to directly output the information indicative of the determined parameters to the stimulation generation circuitry. Accordingly, there may be various ways in which the processing circuitry may output information indicative of the determined parameters, such as to an external device like external programmer 104, described, below, to a therapy program, or to the stimulation generation circuitry.

[0080] External programmer 104 wirelessly communicates with IMD 106 as needed to provide or retrieve therapy information. Programmer 104 is an external computing device that the user, e.g., a clinician and / or patient 112, may use to communicate with IMD 106. For example, programmer 104 may be a clinician programmer that the clinician uses to communicate with IMD 106 and program one or more therapy programs for IMD 106.Alternatively, programmer 104 may be a patient programmer that allows patient 112 to select programs and / or view and modify therapy parameters. The clinician programmer may include more programming features than the patient programmer. In other words, more complex or sensitive tasks may only be allowed by the clinician programmer to prevent an untrained patient from making undesirable changes to IMD 106.

[0081] When programmer 104 is configured for use by the clinician, programmer 104 may be used to transmit initial programming information to IMD 106. This initial information may include hardware information, such as the type of leads 114 and the electrode arrangement, the position of leads 114 within brain 120, the configuration of electrode array 116, 118, initial programs defining therapy parameter values, and any other information the clinician desires to program into IMD 106. Programmer 104 may also be capable of completing functional tests (e.g., measuring the impedance of electrodes 116, 118 of leads 114).

[0082] The clinician may also store therapy programs within IMD 106 with the aid of programmer 104. During a programming session, the clinician may determine one or more therapy programs that may provide efficacious therapy to patient 112 to address symptoms associated with the patient condition, and, in some cases, specific to one or more different patient states, such as a sleep state, movement state or rest state. For example, the clinician may select one or more stimulation electrode combinations with which stimulation is delivered to brain 120. During the programming session, the clinician may evaluate the efficacy of the specific program being evaluated based on feedback provided by patient 112 or based on one or more physiological parameters of patient 112 (e.g., muscle activity, muscle tone, rigidity, tremor, etc.). In some examples, ERNA signals may be used to evaluate the efficacy of the specific program being evaluated (e.g., certain resonant activity in the ERNA signal may be indicative of efficacious therapy). Alternatively, identified patient behavior may be used as feedback during the initial and subsequent programming sessions. Programmer 104 may assist the clinician in the creation / identification of therapy programs by providing a methodical system for identifying potentially beneficial therapy parameter values.

[0083] Programmer 104 may also be configured for use by patient 112. When configured as a patient programmer, programmer 104 may have limited functionality (compared to a clinician programmer) in order to prevent patient 112 from altering critical functions of IMD 106 or applications that may be detrimental to patient 112. In this manner, programmer 104 may only allow patient 112 to adjust values for certain therapy parameters or set an available range of values for a particular therapy parameter.

[0084] Programmer 104 may also provide an indication to patient 112 when therapy is being delivered, when patient input has triggered a change in therapy or when the power source within programmer 104 or IMD 106 needs to be replaced or recharged. For example, programmer 104 may include an alert LED, may flash a message to patient 112 via a programmer display, generate an audible sound or somatosensory cue to confirm patient input was received, e.g., to indicate a patient state or to manually modify a therapy parameter.

[0085] The above examples for determining whether to update parameters for therapeutic electrical stimulation, and if so, by how much were described with respect to the processing circuitry of IMD 106. In some examples, the processing circuitry of external programmer 104 may perform various techniques described above with respect to the processing circuitry of IMD 106.

[0086] Moreover, in some examples, the example techniques may be performed in the “cloud.” For example, IMD 106 and / or programmer 104 may upload the LFP measurements and ERNA signals to one or more servers that form a cloud computing environment. Processing circuitry of the cloud computing environment may perform the example techniques described in this disclosure. Accordingly, in this disclosure, the processing circuitry that is configured to perform the example techniques may be any one or combination of the processing circuitry of IMD 106, the processing circuitry of programmer 104, and / or processing circuitry of a cloud computing environment.

[0087] Therapy system 100 may be implemented to provide chronic stimulation therapy to patient 112 over the course of several months or years. However, system 100 may also be employed on a trial basis to evaluate therapy before committing to full implantation. If implemented temporarily, some components of system 100 may not be implanted within patient 112. For example, patient 112 may be fitted with an external medical device, such as a trial stimulator, rather than IMD 106. The external medical device may be coupled to percutaneous leads or to implanted leads via a percutaneous extension. If the trial stimulator indicates DBS system 100 provides effective treatment to patient 112, the clinician may implant a chronic stimulator within patient 112 for relatively long-term treatment.

[0088] Although IMD 106 is described as delivering electrical stimulation therapy to brain 120, IMD 106 may be configured to direct electrical stimulation to other anatomical regions of patient 112. Further, an IMD may provide other electrical stimulation such as spinal cord stimulation to treat a movement disorder.

[0089] FIG. 2 is a block diagram of the example IMD 106 of FIG. 1 for delivering deep brain stimulation therapy. In the example shown in FIG. 2, IMD 106 includes processing circuitry 210, memory 212, stimulation generation circuitry 202, sensing circuitry 204, telemetry circuitry 208, and power source 220. Each of these circuits may be or include electrical circuitry configured to perform the functions attributed to each respective circuit. Memory 212 may include any volatile or non-volatile media, such as a random-access memory (RAM), read only memory (ROM), non-volatile RAM (NVRAM), electrically erasable programmable ROM (EEPROM), flash memory, and the like. Memory 212 may store computer-readable instructions that, when executed by processing circuitry 210, cause IMD 106 to perform various functions. Memory 212 may be a storage device or other non- transitory medium.

[0090] In the example shown in FIG. 2, memory 212 stores LFP measurements 214, evoked signals 216, and therapy schedule 218. LFP measurements 214 may be the plurality of local field potential LFP measurements of an LFP that processing circuitry 210 receives. In some examples, evoked signals 216 may be ERNA signals. As described, the LFP is intrinsically generated by a signal source within brain 120 of patient 122. Evoked signals 216 may be information indicative of the evoked signals that are evoked by delivery of the respective plurality of stimulation signals that IMD 106 delivers for evoking the respective evoked signals. In one or more examples, processing circuitry 210 may utilize both LFP measurements 214 and evoked signals 216 to determine whether to deviate from or change therapy schedule 218.

[0091] For example, assume that stimulation generation circuitry 202 is delivering stimulation in accordance with a first therapy. Processing circuitry 210 may evaluate therapy schedule 218 to determine when to transition from the first therapy to the second therapy. In some examples, the first therapy includes no delivery of stimulation pulses (e.g., off-time of cycle period), or the second therapy includes no delivery of stimulation pulses. In some examples, the first therapy defines a first set of one or more parameters. For example, processing circuitry 210 may cause delivery (e.g., via stimulation generation circuitry 202) of a first electrical stimulation in accordance with the first set of one or more parameters for the first therapy.

[0092] Processing circuitry 210 may evaluate evoked signals 216 and / or LFP measurements 214, and determine whether to deviate from or change therapy schedule 218. For example, prior to a scheduled transition from the first therapy of the therapy schedule 218 to the second therapy of the therapy schedule 218, processing circuitry 210 may cause delivery (e.g., via stimulation generation circuitry 202) of one or more ping stimulation pulses configured to evoke an evoked signal in a brain 120 of a patient 112.

[0093] Deviation from therapy schedule 218 may refer to a one-time or a relatively few times that processing circuitry 210 performs actions different than those defined by therapy schedule 218. For example, processing circuitry 210 may determine, based on the evoked signal 216 or LFP measurement 214, whether to remain with the first therapy, even when therapy schedule 218 indicates to transition to the second therapy, transition to the second therapy having a set of one or more parameters, as defined in therapy schedule 218, or update the set of one or more parameters, as defined in therapy schedule 218, for the second therapy and then transition to the second therapy based on the updated set of one or more parameters.

[0094] A change in therapy schedule 218 may refer to a more long-term change in therapy schedule 218. For example, processing circuitry 210 may change values of the therapy schedule 218 so that next time, and multiple times after that, when processing circuitry 210 is to transition to the second therapy, processing circuitry 210 may transition to the second therapy having the updated set of one or more parameters.

[0095] Stimulation generation circuitry 202, under the control of processing circuitry 210, generates stimulation signals (e.g., ping stimulation pulses for evoking the evoked signals and / or therapeutic electrical stimulation signals for delivering therapy) for delivery to patient 112 via selected combinations of electrodes 116, 118. An example range of electrical parameters believed to be effective in DBS to manage a movement disorder of patient include:1. Pulse Rate, i.e., Frequency: between approximately 5 Hertz and approximately 500 Hertz, such as between approximately 5 to 220 Hertz or such as approximately 130 Hertz.2. In the case of a voltage controlled system, Voltage Amplitude: between approximately 0.1 volts and approximately 50 volts, such as between approximately 2 volts and approximately 3 volts.3. In the case of a current controlled system, Current Amplitude: between approximately 0.1 milliamps to approximately 50 milliamps, such as between approximately 1.0 milliamps and approximately 1.75 milliamps.4. Pulse Width: between approximately 20 microseconds and approximately 500 microseconds, such as between approximately 50 microseconds and approximately 200 microseconds.

[0096] Accordingly, in some examples, stimulation generation circuitry 202 generates therapeutic electrical stimulation signals in accordance with the electrical parameters noted above. Other ranges of therapy parameter values may also be useful, and may depend on the target stimulation site within patient 112. While stimulation pulses are described, stimulation signals may be of any form, such as continuous-time signals (e.g., sine waves) or the like.

[0097] In addition to delivering therapeutic electrical stimulation signals, stimulation generation circuitry 202 may be configured to deliver one or more ping stimulation pulses for evoking the evoked signals (e.g., where information indicative of the ERNA signals are stored as evoked signals 216). In one or more examples, the ping stimulation pulses may be subtherapeutic, but may be therapeutic in other examples. Example parameters of the one ormore ping stimulation pulses for evoking the evoked signals include amplitude within range of 0 to 7.5 mA, such as 0 to 5 mA, frequency within range of 5 Hz to 250 Hz, such as 80 to 220 Hz, and pulse width in range of 20 to 450 microseconds, such as 60 to 120 microseconds.

[0098] Processing circuitry 210 may include fixed function processing circuitry and / or programmable processing circuitry, and may comprise, for example, any one or more of a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), discrete logic circuitry, or any other processing circuitry configured to provide the functions attributed to processing circuitry 210 herein may be embodied as firmware, hardware, software or any combination thereof. Processing circuitry 210 may control stimulation generation circuitry 202 according to therapy programs stored in memory 212 to apply particular parameter values specified by one or more of programs, such as voltage amplitude or current amplitude, pulse width, and / or pulse rate.

[0099] In the example shown in FIG. 2, the set of electrodes 116 includes electrodes 116A, 116B, 116C, and 116D, and the set of electrodes 118 includes electrodes 118A, 118B, 118C, and 118D. Processing circuitry 210 also controls stimulation generation circuitry 202 to generate and apply the stimulation signals to selected combinations of electrodes 116, 18. Stimulation generation circuitry 202 includes a plurality of pairs of voltage sources, current sources, voltage sinks, or current sinks connected to each of electrodes 116, 118 such that each pair of electrodes has a unique signal circuit. In other words, in these examples, each of electrodes 116, 118 is independently controlled via its own signal circuit (e.g., via a combination of a regulated voltage source and sink or regulated current source and sink), as opposed to switching signals between electrodes 116, 118.

[0100] Sensing circuitry 204 is configured to monitor signals from any combination of electrodes 116, 118. Although sensing circuitry 204 is incorporated into a common housing with stimulation generation circuitry 202 and processing circuitry 210 in FIG. 2, in other examples, sensing circuitry 204 may be in a separate housing from IMD 106 and may communicate with processing circuitry 210 via wired or wireless communication techniques.

[0101] In some examples, sensing circuitry 204 includes one or more amplifiers, filters, and analog-to-digital converters. Sensing circuitry 204 may be used to sense physiological signals, such as LFP measurements for storage as LFP measurements 214 and evoked signals (e.g., ERNA signals) for storage as evoked signals 216. In some examples, sensing circuitry 204 measures LFP and ERNA signals from a particular combination of electrodes 116, 118.In some cases, the particular combination of electrodes for sensing includes different electrodes than a set of electrodes 116, 118 used to deliver electrical stimulation signals (e.g., therapeutic electrical stimulation signals or electrical stimulation signals for evoking ERNA signals). Alternatively, in other cases, the particular combination of electrodes used for sensing includes at least one of the same electrodes as a set of electrodes used to deliver stimulation signals to patient 120. Sensing circuitry 204 may provide signals to an analog-to- digital converter, for conversion into a digital signal for processing, analysis, storage, or output by processing circuitry 210. An example of sensing circuitry 204 is illustrated in FIG. 4.

[0102] Electrodes 116, 118 on respective leads 114 may be constructed of a variety of different designs. For example, one or both of leads 114 may include two or more electrodes at each longitudinal location along the length of the lead, such as multiple electrodes, e.g., arranged as segments, at different perimeter locations around the perimeter of the lead at each of the locations.

[0103] As an example, one or both of leads 114 may include circumferentially-segmented DBS arrays of electrodes and non-segmented electrodes (e.g., ring electrodes). As one example, there may be a first ring electrode of electrodes 116 around the perimeter of lead 114A at a first longitudinal location on lead 114A (e.g., location A). Below the first ring electrode, there may be three segmented electrodes of electrodes 116 around the perimeter of lead 114A at a second longitudinal location on lead 114A (e.g., location B). Below the three segmented electrodes, there may be another set of three segmented electrodes of electrodes 116 around the perimeter of lead 114A at a third longitudinal location of lead 114A (e.g., location C). Below the three segmented electrodes, there may be a second ring electrode of electrodes 116 around the perimeter of lead 114A (e.g., location D). Electrodes 118 may be similarly positioned along lead 114B.

[0104] The above is one example of the array of electrodes, and the example techniques should not be considered limited to such an example. There may be other configurations of electrodes for DBS. Moreover, the example techniques are not limited to DBS, and other electrode configurations are possible.

[0105] In one example, the electrodes 116, 118 may be electrically coupled to stimulation generation circuitry 202 and sensing circuitry 204 via respective wires that are straight or coiled within the housing of the lead and run to a connector at the proximal end of the lead. In another example, each of the electrodes 116, 118 of the leads 114 may be electrodesdeposited on a thin film. The thin film may include an electrically conductive trace for each electrode that runs the length of the thin film to a proximal end connector. The thin film may then be wrapped (e.g., a helical wrap) around an internal member to form the leads 114. These and other constructions may be used to create a lead with a complex electrode geometry.

[0106] Telemetry circuitry 208 supports wireless communication between IMD 106 and an external programmer 104 or another computing device under the control of processing circuitry 210. Processing circuitry 210 of IMD 106 may receive, as updates to programs, values for various parameters such as magnitude and electrode combination, from programmer 104 via telemetry circuitry 208. The updates to the therapy programs may be stored within therapy programs 214 portion of memory 211. Telemetry circuitry 208 in IMD 106, as well as telemetry modules in other devices and systems described herein, such as programmer 104, may accomplish communication by radiofrequency (RF) communication techniques. In addition, telemetry circuitry 208 may communicate with external medical device programmer 104 via proximal inductive interaction of IMD 106 with programmer 104. Accordingly, telemetry circuitry 208 may send information to external programmer 104 on a continuous basis, at periodic intervals, or upon request from IMD 106 or programmer 104.

[0107] Power source 220 delivers operating power to various components of IMD 106. Power source 220 may include a small rechargeable or non-rechargeable battery and a power generation circuit to produce the operating power. Recharging may be accomplished through proximal inductive interaction between an external charger and an inductive charging coil within IMD 104. In some examples, power requirements may be small enough to allow IMD 104 to utilize patient motion and implement a kinetic energy-scavenging device to trickle charge a rechargeable battery. In other examples, traditional batteries may be used for a limited period of time.

[0108] The DBS therapy is defined by one or more therapy programs 214 having one or more parameters stored within memory 211. For example, the one or more parameters include a current amplitude (for a current-controlled system) or a voltage amplitude (for a voltage-controlled system), a pulse rate or frequency, and a pulse width, or a number of pulses per cycle. In examples where the electrical stimulation is delivered according to a “burst” of pulses, or a series of electrical pulses defined by an “on-time” and an “off-time,” the one or more parameters may further define one or more of a number of pulses per burst,an on-time, and an off-time. Processing circuitry 210, via electrodes 116, 118, delivers DBS to patient 120 and may adjust one or more parameters defining the electrical stimulation therapy based on corresponding parameters of the sensed one or more signals of brain 120.

[0109] In some examples, processing circuitry 210 continuously measures the one or more LFP in real time. In other examples, processing circuitry 210 periodically samples the one or more LFP according to a predetermined frequency or after a predetermined amount of time. In some examples, processing circuitry 210 periodically samples the signal at a frequency of approximately 150 Hertz. In some examples, processing circuitry 210 may determine ERNA signals periodically, or according to a predetermined schedule.

[0110] As described above, therapy schedule 218 may define a plurality of therapies (e.g., therapy programs). Therapy schedule 218 may define stimulation cycling between stimulation on (on-time of cycle) and stimulation off (off-time of cycle). In some examples, therapy schedule 218 may define stimulation cycling between two or more of amplitudes of stimulation, stimulation pattems / frequencies, stimulation pulse widths, stimulation electrodes, stimulation leads, or transition rates for adaptive DBS.[oni] In general, therapy schedule 218 may define a first therapy and a second therapy, and when processing circuitry 210 is to transition from the first therapy to the second therapy and back from the second therapy to the first therapy. There may be more than two therapies, but for ease, the examples are described with a first therapy and a second therapy.

[0112] Having therapy schedule 218 may be beneficial for various reasons. For instance, therapy schedule 218 may be beneficial for device longevity of IMD 106 (e.g., reducing drain of power source 220) and to reduce stimulation habituation (also called accommodation).Therapy schedule 218 may initially provide optimized therapy, but it may be possible that changes to patient 112 (e.g., acute or long term changes) results in therapy schedule 218 defining suboptimal therapy. For instance, therapy schedule 218 may not properly reflect changes based on patient activity throughout the day or night, disease state changes, and / or medication changes.

[0113] In accordance with one or more examples, as described above, prior to a scheduled transition from a first therapy of the therapy schedule 218 to a second therapy of the therapy schedule 218, processing circuitry 210 may cause delivery (e.g., via stimulation generation circuitry 202) of one or more ping stimulation pulses configured to evoke an evoked signal 216 in brain 120 of patient 112. The ping stimulation pulses may be subtherapeutic, but are not limited to being subtherapeutic. For instance, the one or moreping stimulation pulses may be configured to deliver subtherapeutic intensity below a therapeutic threshold. The subtherapeutic intensity may refer to one or combination of amplitude, pulse width, or frequency of the ping stimulation pulses, and the therapeutic threshold may refer to a threshold at which the stimulation pulses generate therapeutic impact.

[0114] That is, as described, the parameters for the ping stimulation pulses may be different than the parameters for electrical stimulation that is used for therapeutic results. In some examples, the ping stimulation pulses may provide some therapeutic results, but the efficacy may be less than the efficacy of therapeutic electrical stimulation. As an example, to reduce power consumption, an amplitude or frequency of the ping stimulation pulses may be at or near the minimum amplitude or frequency needed to evoke an evoked signal that can be sensed, and there may be little to no, or at least less than desired, therapeutic benefit of electrical stimulation at such amplitude or frequency.

[0115] Processing circuitry 210 may determine, based on the evoked signal 216, whether to deviate from or change the therapy schedule. In some examples, processing circuity 210 may also receive information indicative of a local field potential (LFP) signal (e.g., LFP measurements 214) sensed from patient 112, where the LFP signal is an intrinsic signal sensed from patient 112 (e.g., generated without delivery of stimulation pulses, but could be affected by stimulation signals). Processing circuitry 210 may determine, based on the evoked signal and the LFP signal (e.g., LFP measurement 214), whether to deviate from or change the therapy schedule.

[0116] To determine whether to deviate from or change the therapy schedule, processing circuitry 210 may be configured to determine, based on the evoked signal 216 and / or LFP signal, whether to remain with the first therapy, even if therapy schedule 218 indicates to transition to the second therapy, transition to the second therapy having a set of one or more parameters, as scheduled, or update the set of one or more parameters for the second therapy and then transition to the second therapy based on the updated set of one or more parameters. For example, processing circuitry 210 may evaluate one or more characteristics of evoked signals 216, such as latency of the evoked signals 216 or a decay interval of the evoked signals 216. Processing circuitry 210 may also evaluate the amplitude and / or frequency of evoked signals 216.

[0117] The characteristics of the evoked signals 216 and / or LFP measurements 214 may assist in determination of changes to patient 112. For instance, the characteristics of evokedsignals 216 and / or LFP measurements 214 may indicate disease progression or medication wash in or wash out. In some examples, processing circuitry 210 may output evoked signals 216 that a clinician can use to determine how the disease is progressing, and possibly determine parameters for different stages (e.g., Stage 1 parameters, Stage 2 parameters, and so forth).

[0118] In some examples, the characteristics of the evoked signals 216 and / or LFP measurements 214 may assist in determination of the effects of medication. For example, processing circuitry 210 (e.g., through programmer 104) may receive information indicative of a medication schedule of patient 112 and / or from patient input. Processing circuitry 210 may generate association information that associates the evoked signal 216 with the medication schedule. For example, processing circuitry 210 may mark which ones of evoked signals 216 are associated with which time, and indicate what the status of a particular medication should be at that time. For instance, the generated association information may indicate how much time passed since patient 112 took the medication with a particular one of evoked signals 216 and / or LFP measurements 214.

[0119] Processing circuitry 210 may output the generated association information (e.g., to programmer 104). The generated association information may assist a clinician in determining medication compliance, or help determine if there should be a change in medication type, dosage, schedule, etc. The generated information may also assist a clinician in determining efficacy of medication alone, stimulation alone, and combined efficacy of medication and stimulation. For instance, in addition to sensing evoked signals from the one or more ping stimulation pulses, the processing circuitry 210 may be configured to sense evoked signals from delivery of therapeutic electrical stimulation. The clinician may evaluate the evoked signals evoked from delivery of therapeutic electrical stimulation that are associated with times when medication is present in patient 112 to determine the combined efficacy of stimulation and medication. The clinician may use such information to better understand medication compliance, as well as to inform patients when to take more medication.

[0120] In some examples, the clinician or processing circuitry 210 may also determine changes to therapy schedule 218 based on the generated association information. For example, processing circuitry 210 may evaluate the evoked signals 216 and / or LFP measurements 214 when patient 112 is taking medication, and delay transition from the firsttherapy to the second therapy based on evaluating evoked signals 216 and / or LFP measurements 214.

[0121] Processing circuitry 210 may be configured to control delivery of electrical stimulation therapy based on the determination of whether to deviate from or change the therapy schedule 218. For example, if processing circuitry 210 determined to remain with the first therapy when the therapy schedule 218 indicates to transition to the second therapy, processing circuitry 210 may cause stimulation generation circuitry 202 to deliver electrical stimulation according to the first therapy. If processing circuitry 210 determined to transition to the second therapy having a set of one or more parameters as scheduled, processing circuitry 210 may cause stimulation generation circuitry 202 to deliver electrical stimulation according to the second therapy. If processing circuitry 210 determined to update the set of one or more parameters for the second therapy and then transition to the second therapy based on the updated set of one or more parameters, processing circuitry 210 may determine the updated sets of one or more parameters, and cause stimulation generation circuitry 202 to deliver electrical stimulation according to the second therapy having the updated set of one or more parameters.

[0122] FIG. 3 is a block diagram of the external programmer 104 of FIG. 1. Although programmer 104 may generally be described as a hand-held device, programmer 104 may be a larger portable device or a more stationary device. In addition, in other examples, programmer 104 may be included as part of an external charging device or include the functionality of an external charging device. As illustrated in FIG. 3, programmer 104 may include processing circuitry 310, memory 312, user interface 302, telemetry circuitry 308, and power source 320. Memory 312 may store instructions that, when executed by processing circuitry 310, cause processing circuitry 310 and external programmer 104 to provide the functionality ascribed to external programmer 104 throughout this disclosure. Each of these components, or modules, may include electrical circuitry that is configured to perform some or all of the functionality described herein. For example, processing circuitry 310 may include processing circuitry configured to perform the processes discussed with respect to processing circuitry 310.

[0123] In general, programmer 104 comprises any suitable arrangement of hardware, alone or in combination with software and / or firmware, to perform the techniques attributed to programmer 104, and processing circuitry 310, user interface 302, and telemetry circuitry 308 of programmer 104. In various examples, programmer 104 may include one or moreprocessors, which may include fixed function processing circuitry and / or programmable processing circuitry, as formed by, for example, one or more microprocessors, DSPs, ASICs, FPGAs, or any other equivalent integrated or discrete logic circuitry, as well as any combinations of such components. Programmer 104 also, in various examples, may include a memory 312, 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 310 and telemetry circuitry 308 are described as separate modules, in some examples, processing circuitry 310 and telemetry circuitry 308 may be functionally integrated with one another. In some examples, processing circuitry 310 and telemetry circuitry 308 correspond to individual hardware units, such as ASICs, DSPs, FPGAs, or other hardware units.

[0124] Memory 312 (e.g., a storage device) may store instructions that, when executed by processing circuitry 310, cause processing circuitry 310 and programmer 104 to provide the functionality ascribed to programmer 104 throughout this disclosure. For example, memory 312 may include instructions that cause processing circuitry 310 to obtain a parameter set from memory or receive a user input and send a corresponding command to IMD 106, or instructions for any other functionality. In addition, memory 312 may include a plurality of programs, where each program includes a parameter set that defines stimulation therapy.

[0125] User interface 302 may include a button or keypad, lights, a speaker for voice commands, a display, such as a liquid crystal (LCD), light-emitting diode (LED), or organic light-emitting diode (OLED). In some examples the display may be a touch screen. User interface 302 may be configured to display any information related to the delivery of stimulation therapy, identified patient behaviors, sensed patient parameter values, patient behavior criteria, or any other such information. User interface 302 may also receive user input via user interface 302. The input may be, for example, in the form of pressing a button on a keypad or selecting an icon from a touch screen.

[0126] Telemetry circuitry 308 may support wireless communication between IMD 106 and programmer 104 under the control of processing circuitry 310. Telemetry circuitry 308 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 308 provides wireless communication via an RF or proximal inductive medium. In some examples, telemetry circuitry 308 includes an antenna, which may take on a variety of forms, such as an internal or external antenna.

[0127] Examples of local wireless communication techniques that may be employed to facilitate communication between programmer 104 and IMD 106 include RF communication according to the 802.11 or Bluetooth specification sets or other standard or proprietary telemetry protocols. In this manner, other external devices may be capable of communicating with programmer 104 without needing to establish a secure wireless connection.

[0128] In some examples, processing circuitry 310 of external programmer 104 defines the parameters of electrical stimulation therapy, stored in memory 312, for delivering DBS to patient 120. In one example, processing circuitry 310 of external programmer 104, via telemetry circuitry 308, issues commands to IMD 106 causing IMD 106 to deliver electrical stimulation therapy via electrodes 116, 118 via leads 114.

[0129] In one or more examples, programmer 104 may be configured to perform one or more of the example techniques described in this disclosure. For instance, processing circuitry 310 may be configured to perform one or more of the example operations described above with respect to processing circuitry 210.

[0130] FIG. 4 is a block diagram illustrating an example of a sensing circuitry of FIG. 2 in further detail. As illustrated in FIG. 4, sensing circuitry 204 includes LFP sensing circuitry 400 and evoked sensing circuitry 402. LFP sensing circuitry 400 may be configured to specifically determine LFP measurements, and evoked sensing circuitry 402 may be configured to specifically sense evoked signals (e.g., ERNA signals).

[0131] For instance, an LFP can generally be measured at any time, including instances when IMD 106 is delivering electrical stimulation (e.g., therapeutic electrical stimulation signals or one or more ping stimulation pulses configured to evoke the evoked signals). This is because the LFP is intrinsically generated by a signal source (e.g., one or more neurons) within brain 120 of patient 122. Accordingly, LFP sensing circuitry 400 may be configured to continuously determine LFP measurements, periodically determine LFP measurements, or determine LFP measurements in accordance with a schedule irrespective of when stimulation generation circuitry 202 is configured to deliver the stimulation (e.g., therapeutic electrical stimulation signals or the one or more ping stimulation pulses).

[0132] Evoked sensing circuitry 402 may, however, sense evoked signals in response to delivery of the one or more ping stimulation pulses. Accordingly, during the time the electrical stimulation signal is being delivered, and prior to the delivery of the electrical stimulation signal, evoked sensing circuitry 402 may be configured to not sense evoked signals.

[0133] Furthermore, in response to delivery of the one or more ping stimulation pulses, the signal that sensing circuitry 204 senses may be a composite signal includes at least two components. The first component is the evoked signal that is evoked due to the delivery of the electrical stimulation signal. The second component may be the LFP, which may still be present even with delivery of the one or more ping stimulation pulses.

[0134] Accordingly, processing circuitry 210 may be configured to differentiate between the LFP measurement and the evoked signal in such a composite signal. In some examples, LFP sensing circuitry 400 may be configured to filter out signals that are out of the frequency band of the LFP band of interest (e.g., outside of the beta band). Evoked sensing circuitry 402 may be similarly configured to filter out signals that are out of the frequency band of evoked signals (e.g., filter out signals outside the 270 to 340 Hz range). Accordingly, processing circuitry 210 may receive the LFP measurements from LFP sensing circuitry 400 and the evoked signals from evoked sensing circuitry 402.

[0135] The example of sensing circuitry 204 of FIG. 4 is one example, and should not be considered limiting. In some examples, sensing circuitry 204 may not necessarily include LFP sensing circuitry 400 and evoked sensing circuitry 402. In such examples, processing circuitry 210 may receive the composite signal that includes both the LFP and the evoked signals, when one or more ping stimulation pulses configured to evoke evoked signals is delivered by stimulation generation circuitry 202. To differentiate between the evoked signals and the LFP, processing circuitry 210 may be configured to determine the LFP measurement immediately before stimulation generation circuitry 202 delivers the one or more ping stimulation pulses configured to evoke an evoked signal. Then, when processing circuitry 210 receive the composite signal that includes the LFP and the evoked signal, processing circuitry 210 may subtract the LFP measurement taken immediately before stimulation circuitry 202 delivered the one or more ping stimulation pulses from the composite signal to determine the evoked signal.

[0136] FIG. 5 is a graph illustrating an example of an evoked signal. For instance, FIG. 5 illustrates evoked signal 500 that is sensed by sensing circuitry 204 in response to stimulation generation circuitry 202 delivering one or more ping stimulation pulses. In FIG. 5, time TO refers to the end of the delivery of the one or more ping stimulation pulses. In one or more examples, the ping stimulation pulses may be subtherapeutic (e.g., have an intensity that is less than a therapeutic threshold), but may still be perceived by patient 112. That is, while the ping stimulation pulses do not necessary provide therapy, patient 112 may feel them.Patient 112 may, via programmer 104, adjust the amplitude, pulse width, frequency, etc. of ping stimulation pulses in the event that perception of the ping stimulation pulses is unwanted. The stimulation intensity may refer to the stimulation amplitude, pulse width, frequency, or any combination thereof.

[0137] As described above, processing circuitry 210 may evaluate various characteristics of evoked signal 500 to determine whether to deviate from or change therapy schedule 218. As one example, processing circuitry 210 may determine latency, which is the time from the delivery of one or more ping stimulation pulses to the first peak (Pl) of the evoked signal 500, represented as time Tl. There may be other examples of latency, such time from the delivery of one or more ping stimulation pulses to beginning of the evoked signal 500. Latency may be time from the delivery of one or more ping stimulation pulses (e.g., from the start of the ping stimulation pulses or from the end of the ping stimulation pulses) to any one or more of peaks Pl, P2, P3, or P4 of evoked signal 500, to any one of valleys VI, V2, or V3 of evoked signal 500, or time between peak Pl to VI, time between VI to P2, time between P2 to V2, and so forth. Peaks Pl, P2, P3, and P4 are local peaks, and valleys VI, V2, and V3 are local valleys. Accordingly, there may be various examples of latency, and the example techniques are not limited to a particular technique to determine latency.

[0138] As another example, processing circuitry 210 may determine a decay interval, which the time evoked signal 500 takes to dampen out and completely decay, represented as time T2. That is, the decay interval may be the difference between time T2 and time Tl . The decay interval may be the amount of time it takes an absolute value of the amplitude of evoked signal 500 to drop below a threshold, and stay below that threshold The decay interval may be time from delivery of one or more ping stimulation pulses to time when there is complete decay (e.g., time from TO to T2) or amplitude is less than threshold. Accordingly, there may be various examples of decay interval, and the example techniques are not limited to a particular technique to determine decay interval.

[0139] Other example characteristics may include the amplitude or frequency of evoked signal 500. For instance, processing circuitry 210 may determine the value of any one or more of peaks Pl, P2, P3, and P4 or valleys VI, V2, or V3 of evoked signal 500. Processing circuitry 210 may determine a peak-to-valley value indicative of a difference between peak Pl and valley VI, peak P2 and valley V2, or peak P3 and valley V3, or valley-to-peak value indicative of a difference between valley VI and peak P2, valley V2 and peak P3, or valley V3 and peak P4.

[0140] In one or more examples, processing circuitry 210 may utilize the characteristics of evoked signal 500 to determine whether to deviate from or change the therapy schedule. As one example, there may be baseline characteristics of an evoked signal. One example of the baseline characteristics may be characteristics of an evoked signal measured at implant. Another example of the baseline characteristics may be characteristics that tend to indicate therapy efficacy. The baseline characteristics may be different for each patient, and may be based on patient anatomy. As an example of baseline characteristics, which may be patient dependent, include peak to valley amplitude of 50 to 800 micro-volts, a resonant frequency of 250 to 350 Hz, and a peak latency of 3 to 5 milliseconds.

[0141] In some examples, the clinician or patient 112 may control the parameters of the ping stimulation pulses. For instance, since the ping stimulation pulses are used to generate the evoked signal, the parameters of the ping stimulation pulses may impact the quality of the evoked signal (e.g., whether the evoked signal is usable or not for therapy control). Accordingly, the clinician or patient 112 may adjust the parameters of the ping stimulation pulses to ensure that the evoked signals are usable for therapy control. For instance, the clinician may adjust the ping stimulation pulses to generate an evoked signal that is used for baseline characteristics.

[0142] Processing circuitry 210 may determine the characteristics of evoked signal 500, and compare the determined characteristics to the baseline characteristics. If the determined characteristics and the baseline characteristics are similar (e.g., with a tolerance), processing circuitry 210 may determine that no change or deviation of the therapy schedule is needed. However, if the determined characteristics and the baseline characteristics are not similar (e.g., outside of a tolerance), processing circuitry 210 may determine that change or deviation of the therapy schedule is needed.

[0143] For example, assume that the next therapy schedule is no therapy delivery. If the determined characteristics of evoked signal 500 are not similar to the baseline characteristics, processing circuitry 210 may delay moving to the next therapy schedule. As another example, processing circuitry 210 may update the therapy parameters to try and achieve the baseline characteristics.

[0144] As an example, if latency (or resonant frequency) changes (e.g., increases), such increase in latency or frequency could be indicative that neural network of brain 120 is changing, and processing circuitry 210 may determine that there should be a stimulation amplitude, rate, pulse width, etc. As another example, if peak-to-valley increases too high,processing circuitry 210 may determine to decrease stimulation amplitude or change stimulation frequency. If peak-to-valley decreases, processing circuitry 210 may determine to increase stimulation amplitude or change stimulation frequency.

[0145] By changing stimulation parameters, there is a possibility that evoked signal 500 would so that future evoked signals, like evoked signal 500, are closer to the baseline characteristics. As an example, in clinic, the physician would identify target features of ERNA signal (e.g., determine baseline characteristics), and processing circuitry 210 may determine stimulation parameters of a first therapy keep the characteristics of the ERNA in range when patient 112 is on medication, but a second therapy keeps the characteristics of the ERNA in range when patient 112 is not on medication. Processing circuitry 210 may use the ERNA signal to indicate when to switch between the first therapy and the second therapy.For instance, if the washout of the medication has not occurred, processing circuitry 210 may keep delivering therapy according to the first therapy, but if washout of the medication has occurred, processing circuitry 210 may transition to the second therapy.

[0146] FIG. 6 is a flowchart illustrating an example operation in accordance with techniques of the disclosure. For ease of illustration, the example is described with respect to processing circuitry 210 and IMD 106 of FIG. 2, but the techniques should not be considered limited as such and may be performed by other devices and / or combination of devices in a distributed system.

[0147] Prior to a scheduled transition from a first therapy of the therapy schedule 218 to a second therapy of the therapy schedule 218, processing circuitry 210 may be configured to cause delivery of one or more ping stimulation pulses configured to evoke an evoked signal 216 in a brain 120 of a patient 112 (600). The one or more ping stimulation pulses may be subtherapeutic, but not limited to being subtherapeutic. For example, the one or more ping stimulation pulses may be configured to deliver subtherapeutic intensity below a therapeutic threshold. The subtherapeutic intensity may refer to one or combination of amplitude, pulse width, or frequency of the ping stimulation pulses, and the therapeutic threshold may refer to a threshold at which the stimulation pulses generate therapeutic impact.

[0148] The second therapy, in which therapeutic stimulation is delivered, may immediately follow the first therapy in the therapy schedule 218. In some examples, the first therapy defines a first set of one or more parameters, and processing circuitry 210 is configured to cause delivery of a first electrical stimulation in accordance with the first set of one or more parameters for the first therapy.

[0149] In some examples, the first therapy includes no delivery of stimulation pulses, or the second therapy includes no delivery of stimulation pulses. For instance, the first therapy may be part of the off-cycle, or the second therapy may be part of the off-cycle.

[0150] Processing circuitry 210 may be configured to determine, based on the evoked signal, whether to deviate from or change the therapy schedule (602). For instance, if the first therapy includes no delivery of stimulation pulses and the second therapy includes delivery of stimulation pulses for therapeutic effect, the processing circuity 210 may determine that therapy does not need to be turned back on, allowing for power saving. If the second therapy includes no delivery of stimulation pulses and the first therapy includes delivery of stimulation pulses for therapeutic effect, the processing circuity 210 may determine that therapy should be prolonged to address patient condition. Accordingly, the first therapy or the second therapy may include no delivery of stimulation pulses.

[0151] In some examples, processing circuitry 210 may be configured to receive information indicative of a local field potential (LFP) signal sensed from patient 112, where the LFP signal is an intrinsic signal (e.g., generated without delivery of stimulation pulses, but could be affected by stimulation signals). Processing circuitry 210 may be configured to determine, based on the evoked signal and the LFP signal, whether to deviate from or change the therapy schedule. In one or more examples, to determine whether to deviate from or change the therapy schedule, the processing circuitry 210 may be configured to determine, based on the evoked signal, whether to remain with the first therapy when the therapy schedule indicates to transition to the second therapy, transition to the second therapy having a set of one or more parameters as scheduled, or update the set of one or more parameters for the second therapy and then transition to the second therapy based on the updated set of one or more parameters.

[0152] In some examples, processing circuitry 210 may determine a latency of the evoked signal or determine a decay interval of the evoked signal. Processing circuitry 210 may be configured to determine, based on the latency of the evoked signal or the decay interval of the evoked signal, whether to deviate from or change the therapy schedule. In some examples, processing circuitry 210 may be configured to determine an amplitude or frequency of the evoked signal. Processing circuitry 210 may be configured to determine, based on the amplitude or frequency of the evoked signal, whether to deviate from or change the therapy schedule.

[0153] Processing circuitry 210 may be configured to control delivery of electrical stimulation therapy based on the determination (604). As an example, to control of delivery of electrical stimulation therapy based on the determination, the processing circuitry 210 may be configured to cause delivery of electrical stimulation therapy based on the second set of one or more parameters or updated second set of one or more parameters. The second set of one or more parameters or the updated second set of one or more parameters being different than the first set of one or more parameters (e.g., of the first therapy).

[0154] For example, as described above, if processing circuitry 210 determined to remain with the first therapy when the therapy schedule 218 indicates to transition to the second therapy, processing circuitry 210 may cause stimulation generation circuitry 202 to deliver electrical stimulation according to the first therapy. If processing circuitry 210 determined to transition to the second therapy having a set of one or more parameters as scheduled, processing circuitry 210 may cause stimulation generation circuitry 202 to deliver electrical stimulation according to the second therapy. If processing circuitry 210 determined to update the set of one or more parameters for the second therapy and then transition to the second therapy based on the updated set of one or more parameters, processing circuitry 210 may determine the updated sets of one or more parameters, and cause stimulation generation circuitry 202 to deliver electrical stimulation according to the second therapy having the updated set of one or more parameters.

[0155] In one or more examples, the scheduled transition may be considered as a first scheduled transition. Therapy schedule 218 may define a second scheduled transition for transitioning from the second therapy back to the first therapy. For example, if the first therapy is off-cycle, therapy schedule 218 may define when to transition to the off-cycle. Processing circuitry 210 may then transition from second therapy back to the first therapy based on the second scheduled transition (606).

[0156] However, in some examples, processing circuitry 210 may automatically transition from the second therapy back to the first therapy. For example, the evoked signal described above to transition from the first therapy to the second therapy may be considered as a first evoked signal. Processing circuitry 210 may be configured to determine a second evoked signal prior to the second scheduled transition from the second therapy back to the first therapy. Processing circuitry 210 may be configured to transition from the second therapy back to the first therapy based on the second evoked signal. For instance, if the second evoked signal indicates that there should be delay in transitioning back because thepatient is still likely to experience unwanted symptoms, processing circuitry 210 may keep delivering the second therapy.

[0157] In one or more examples, processing circuitry 210 via programmer 104 or some other manner may output information for presenting to a clinician whether there was deviation or change in the therapy schedule. For instance, programmer 104 may display to the clinician instances where there was a change or deviation in the therapy schedule. Processing circuitry 210 may also output for display on programmer 104 information indicative of the evoked signal after change in therapy schedule. The clinician may use such information for therapy adjustment during future patient visits, and / or use such information to group patients together for determining therapy schedules for patients in a similar cohort.

[0158] FIG. 7 is another flowchart illustrating an example operation in accordance with techniques of the disclosure. Similar to FIG. 6, for ease of illustration, the example is described with respect to processing circuitry 210 and IMD 106 of FIG. 2, but the techniques should not be considered limited as such and may be performed by other devices and / or combination of devices in a distributed system.

[0159] As described above for FIG. 6 and elsewhere, prior to a scheduled transition from a first therapy of the therapy schedule 218 to a second therapy of the therapy schedule 218, processing circuitry 210 may be configured to cause delivery of one or more ping stimulation pulses configured to evoke an evoked signal 216 in a brain 120 of a patient 112 (700).

[0160] The second therapy, in which therapeutic stimulation is delivered, may immediately follow the first therapy in the therapy schedule 218. In some examples, the first therapy includes no delivery of stimulation pulses. In some examples, the first therapy defines a first set of one or more parameters, and processing circuitry 210 is configured to cause delivery of a first electrical stimulation in accordance with the first set of one or more parameters for the first therapy.

[0161] Processing circuitry 210 may be configured to determine, based on the evoked signal, whether to deviate from or change the therapy schedule (702). In some examples, processing circuitry 210 may be configured to receive information indicative of a local field potential (LFP) signal sensed from patient 112, where the LFP signal is an intrinsic signal (e.g., generated without delivery of stimulation pulses, but could be affected by stimulation signals). Processing circuitry 210 may be configured to determine, based on the evoked signal and the LFP signal, whether to deviate from or change the therapy schedule.Processing circuitry 210 may utilize latency, decay interval, amplitude, frequency, etc. of theevoked signal and / or LFP to determine whether to device from or change the therapy schedule. Processing circuitry 210 may be configured to control delivery of electrical stimulation therapy based on the determination.

[0162] For example, if processing circuitry 210 determined to not deviate or change the therapy schedule (NO of 702), processing circuitry 210 may transition from the first therapy schedule to the second therapy schedule (704). That is, processing circuitry 210 may determine to transition to the second therapy having a set of one or more parameters as scheduled. Processing circuitry 210 may control delivery of electrical stimulation therapy according to the second therapy (706).

[0163] If processing circuitry 210 determined to deviate or change the therapy schedule (YES of 702), processing circuitry 210 may determine whether to remain with the first therapy (708). Processing circuitry 210 may utilize any one or more of the latency, decay interval, amplitude, frequency, etc. of the evoked signal or LFP to determine whether to remain with the first therapy.

[0164] If processing circuitry 210 determined to remain with the first therapy (YES of 708), processing circuitry 210 may control delivery of electrical stimulation according to the first therapy (710). If processing circuitry 210 determined to not remain with the first therapy (NO of 708), processing circuitry 210 may update one or more parameters for the second therapy (712). Processing circuitry 210 may utilize any one or more of the latency, decay interval, amplitude, frequency, etc. of the evoked signal or LFP to update one or more parameters for the second therapy. Processing circuitry 210 may control delivery of electrical stimulation therapy according to the updated one or more parameters (714).

[0165] The following describes one or more examples that may be performed separately or in various combinations in accordance with techniques described in this disclosure.

[0166] Example 1. A system for therapy scheduling, the system comprising: one or more memories configured to store a therapy schedule; and processing circuitry coupled to the one or more memories and configured to: prior to a scheduled transition from a first therapy of the therapy schedule to a second therapy of the therapy schedule, cause delivery of one or more ping stimulation pulses configured to evoke an evoked signal in a brain of a patient; determine, based on the evoked signal, whether to deviate from or change the therapy schedule; and control delivery of electrical stimulation therapy based on the determination.

[0167] Example 2. The system of example 1, wherein to determine whether to deviate from or change the therapy schedule, the processing circuitry is configured todetermine, based on the evoked signal, whether to remain with the first therapy when the therapy schedule indicates to transition to the second therapy, transition to the second therapy having a set of one or more parameters as scheduled, or update the set of one or more parameters for the second therapy and then transition to the second therapy based on the updated set of one or more parameters.

[0168] Example 3. The system of any of examples 1 and 2, wherein the processing circuitry is configured to: receive information indicative of a local field potential (LFP) signal sensed from the patient, wherein the LFP signal is an intrinsic signal, wherein the processing circuitry is configured to determine, based on the evoked signal and the LFP signal, whether to deviate from or change the therapy schedule.

[0169] Example 4. The system of any of examples 2 and 3, wherein the second therapy, in which therapeutic stimulation is delivered, immediately follows the first therapy in the therapy schedule.

[0170] Example 5. The system of any of examples 2-4, wherein the first therapy or the second therapy comprises no delivery of stimulation pulses.

[0171] Example 6. The system of any of examples 2-4, wherein the second therapy defines a second set of one or more parameters, wherein the processing circuitry is configured to cause delivery of a first electrical stimulation in accordance with a first set of one or more parameters for the first therapy, and wherein to control of delivery of electrical stimulation therapy based on the determination, the processing circuitry is configured to cause delivery of electrical stimulation therapy based on the second set of one or more parameters or updated second set of one or more parameters, the second set of one or more parameters or the updated second set of one or more parameters being different than the first set of one or more parameters.

[0172] Example 7. The system of any of examples 1-6, wherein the processing circuitry is configured to determine a latency of the evoked signal or determine a decay interval of the evoked signal, and wherein the processing circuitry is configured to determine, based on the latency of the evoked signal or the decay interval of the evoked signal, whether to deviate from or change the therapy schedule.

[0173] Example 8. The system of any of examples 1-7, wherein the processing circuitry is configured to determine an amplitude or frequency of the evoked signal, and wherein the processing circuitry is configured to determine, based on the amplitude or frequency of the evoked signal, whether to deviate from or change the therapy schedule.

[0174] Example 9. The system of any of examples 1-8, wherein the processing circuitry is configured to: receive information indicative of a medication schedule; generate association information that associates the evoked signal with the medication schedule; and output the generated association information.

[0175] Example 10. The system of any of examples 1-9, wherein the scheduled transition comprises a first scheduled transition, and wherein the therapy schedule defines a second scheduled transition for transitioning from the second therapy back to the first therapy.

[0176] Example 11. The system of examples 10, wherein evoked signal is a first evoked signal, and wherein the processing circuitry is configured to determine a second evoked signal prior to the second scheduled transition from the second therapy back to the first therapy, and wherein the processing circuitry is configured to transition from the second therapy back to the first therapy based on the second evoked signal.

[0177] Example 12. The system of any of examples 1-11, wherein the one or more ping stimulation pulses are configured to deliver subtherapeutic intensity below a therapeutic threshold.

[0178] Example 13. The system of any of examples 1-12, wherein the evoked signal is an evoked resonant neural activity (ERNA) signal.

[0179] Example 14. A method for therapy scheduling, the method comprising: prior to a scheduled transition from a first therapy of a therapy schedule to a second therapy of the therapy schedule, causing delivery of one or more ping stimulation pulses configured to evoke an evoked signal in a brain of a patient; determining, based on the evoked signal, whether to deviate from or change the therapy schedule; and controlling delivery of electrical stimulation therapy based on the determination.

[0180] Example 15. The method of example 14, wherein determining whether to deviate from or change the therapy schedule comprises determining, based on the evoked signal, whether to remain with the first therapy when the therapy schedule indicates to transition to the second therapy, transition to the second therapy having a set of one or more parameters as scheduled, or update the set of one or more parameters for the second therapy and then transition to the second therapy based on the updated set of one or more parameters.

[0181] Example 16. The method of any of examples 14 and 15, further comprising: receiving information indicative of a local field potential (LFP) signal sensed from the patient, wherein the LFP signal is an intrinsic signal, wherein determining whether to deviatefrom or change the therapy schedule comprises determining, based on the evoked signal and the LFP signal, whether to deviate from or change the therapy schedule.

[0182] Example 17. The method of any of examples 15 and 16, wherein the second therapy, in which therapeutic stimulation is delivered, immediately follows the first therapy in the therapy schedule.

[0183] Example 18. The method of any of examples 15-17, wherein the first therapy or the second therapy comprises no delivery of stimulation pulses.

[0184] Example 19. The method of any of examples 15-17, wherein the second therapy defines a second set of one or more parameters, the method further comprising causing delivery of a first electrical stimulation in accordance with a first set of one or more parameters for the first therapy, and wherein controlling of delivery of electrical stimulation therapy based on the determination comprises causing delivery of electrical stimulation therapy based on the second set of one or more parameters or updated second set of one or more parameters, the second set of one or more parameters or the updated second set of one or more parameters being different than the first set of one or more parameters.

[0185] Example 20. The method of any of examples 14-19, further comprising: determining a latency of the evoked signal or a decay interval of the evoked signal, and wherein determining whether to deviate from or change the therapy schedule comprises determining, based on the latency of the evoked signal or the decay interval of the evoked signal, whether to deviate from or change the therapy schedule.

[0186] Example 21. The method of any of examples 14-20, further comprising: determining an amplitude or frequency of the evoked signal, and wherein determining, based on the evoked signal, whether to deviate from or change the therapy schedule comprises determining, based on the amplitude or frequency of the evoked signal, whether to deviate from or change the therapy schedule.

[0187] Example 22. The method of any of examples 14-21, further comprising: receiving information indicative of a medication schedule; generating association information that associates the evoked signal with the medication schedule; and outputting the generated association information.

[0188] Example 23. The method of any of examples 14-22, wherein the scheduled transition comprises a first scheduled transition, and wherein the therapy schedule defines a second scheduled transition for transitioning from the second therapy back to the first therapy.

[0189] Example 24. The method of example 23, wherein evoked signal is a first evoked signal, the method further comprising: determining a second evoked signal prior to the second scheduled transition from the second therapy back to the first therapy; and transitioning from the second therapy back to the first therapy based on the second evoked signal.

[0190] Example 25. The method of any of examples 14-24, wherein the one or more ping stimulation pulses are configured to deliver subtherapeutic intensity below a therapeutic threshold.

[0191] Example 26. The method of any of examples 14-25, wherein the evoked signal is an evoked resonant neural activity (ERNA) signal.

[0192] Example 27. A computer-readable storage medium storing instructions thereon that when executed cause one or more processors to: prior to a scheduled transition from a first therapy of a therapy schedule to a second therapy of the therapy schedule, cause delivery of one or more ping stimulation pulses configured to evoke an evoked signal in a brain of a patient; determine, based on the evoked signal, whether to deviate from or change the therapy schedule; and control delivery of electrical stimulation therapy based on the determination.

[0193] Example 28. The computer-readable storage medium of example 27, further comprising instructions that cause the one or more processors to perform the method of any of examples 15-26.

[0194] Example 29. A system for therapy scheduling, the system comprising: means for causing delivery of one or more ping stimulation pulses configured to evoke an evoked signal in a brain of a patient prior to a scheduled transition from a first therapy of a therapy schedule to a second therapy of the therapy schedule; means for determining, based on the evoked signal, whether to deviate from or change the therapy schedule; and means for controlling delivery of electrical stimulation therapy based on the determination.

[0195] Example 30. The system of example 29, further comprising instructions that cause the one or more processors to perform the method of any of examples 15-26.

[0196] The techniques described in this disclosure may be implemented, at least in part, in hardware, software, firmware or any combination thereof. For example, various aspects of the described techniques may be implemented within one or more processors, including one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or any other equivalent integratedor discrete logic circuitry, as well as any combinations of such components. The term “processor” or “processing circuitry” may generally refer to any of the foregoing logic circuitry, alone or in combination with other logic circuitry, or any other equivalent circuitry. A control unit comprising hardware may also perform one or more of the techniques of this disclosure.

[0197] Such hardware, software, and firmware may be implemented within the same device or within separate devices to support the various operations and functions described in this disclosure. In addition, any of the described units, modules or components may be implemented together or separately as discrete but interoperable logic devices. Depiction of different features as modules or units is intended to highlight different functional aspects and does not necessarily imply that such modules or units must be realized by separate hardware or software components. Rather, functionality associated with one or more modules or units may be performed by separate hardware or software components, or integrated within common or separate hardware or software components.

[0198] The techniques described in this disclosure may also be embodied or encoded in a computer-readable medium, such as a computer-readable storage medium, containing instructions. Instructions embedded or encoded in a computer-readable storage medium may cause a programmable processor, or other processor, to perform the method, e.g., when the instructions are executed. 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 CD-ROM, a floppy disk, a cassette, magnetic media, optical media, or other computer readable media.

[0199] Various examples have been described. These and other examples are within the scope of the following claims.

Claims

WHAT IS CLAIMED IS:

1. A system comprising: one or more memories configured to store a therapy schedule; and processing circuitry coupled to the one or more memories and configured to: prior to a scheduled transition from a first therapy of the therapy schedule to a second therapy of the therapy schedule, cause delivery of one or more ping stimulation pulses configured to evoke an evoked signal in a brain of a patient; determine, based on the evoked signal, whether to deviate from or change the therapy schedule; and control delivery of electrical stimulation therapy based on the determination.

2. The system of claim 1, wherein to determine whether to deviate from or change the therapy schedule, the processing circuitry is configured to determine, based on the evoked signal, whether to remain with the first therapy when the therapy schedule indicates to transition to the second therapy, transition to the second therapy having a set of one or more parameters as scheduled, or update the set of one or more parameters for the second therapy and then transition to the second therapy based on the updated set of one or more parameters.

3. The system of any of claims 1 and 2, wherein the processing circuitry is configured to: receive information indicative of a local field potential (LFP) signal sensed from the patient, wherein the LFP signal is an intrinsic signal, wherein the processing circuitry is configured to determine, based on the evoked signal and the LFP signal, whether to deviate from or change the therapy schedule.

4. The system of any of claims 2 and 3, wherein the second therapy, in which therapeutic stimulation is delivered, immediately follows the first therapy in the therapy schedule.

5. The system of any of claims 2-4, wherein the first therapy or the second therapy comprises no delivery of stimulation pulses.

6. The system of any of claims 2-4, wherein the second therapy defines a second set of one or more parameters, wherein the processing circuitry is configured to cause delivery of a first electrical stimulation in accordance with a first set of one or more parameters for the first therapy, and wherein to control of delivery of electrical stimulation therapy based on the determination, the processing circuitry is configured to cause delivery of electrical stimulation therapy based on the second set of one or more parameters or updated second set of one or more parameters, the second set of one or more parameters or the updated second set of one or more parameters being different than the first set of one or more parameters.

7. The system of any of claims 1-6, wherein the processing circuitry is configured to determine a latency of the evoked signal or determine a decay interval of the evoked signal, and wherein the processing circuitry is configured to determine, based on the latency of the evoked signal or the decay interval of the evoked signal, whether to deviate from or change the therapy schedule.

8. The system of any of claims 1-7, wherein the processing circuitry is configured to determine an amplitude or frequency of the evoked signal, and wherein the processing circuitry is configured to determine, based on the amplitude or frequency of the evoked signal, whether to deviate from or change the therapy schedule.

9. The system of any of claims 1-8, wherein the processing circuitry is configured to: receive information indicative of a medication schedule; generate association information that associates the evoked signal with the medication schedule; and output the generated association information.

10. The system of any of claims 1-9, wherein the scheduled transition comprises a first scheduled transition, and wherein the therapy schedule defines a second scheduled transition for transitioning from the second therapy back to the first therapy.

11. The system of claim 10, wherein evoked signal is a first evoked signal, and wherein the processing circuitry is configured to determine a second evoked signal prior to the second scheduled transition from the second therapy back to the first therapy, and wherein the processing circuitry is configured to transition from the second therapy back to the first therapy based on the second evoked signal.

12. The system of any of claims 1-11, wherein the one or more ping stimulation pulses are configured to deliver subtherapeutic intensity below a therapeutic threshold.

13. The system of any of claims 1-12, wherein the evoked signal is an evoked resonant neural activity (ERNA) signal.

14. A computer-readable storage medium storing instructions thereon that when executed cause one or more processors to: prior to a scheduled transition from a first therapy of a therapy schedule to a second therapy of the therapy schedule, cause delivery of one or more ping stimulation pulses configured to evoke an evoked signal in a brain of a patient; determine, based on the evoked signal, whether to deviate from or change the therapy schedule; and control delivery of electrical stimulation therapy based on the determination.

15. The computer-readable storage medium of claim 14, further comprising instructions that when executed cause the one or more processors to perform the features of any of claims

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