Therapy system stability determination

Abstract

In general, devices, systems, and techniques are described for determining an system stability score indicative of a stability, or instability, of the functioning of a medical device. In one example, a system includes processing circuitry configured to determine, based on one or more system characteristics, a system integrity metric indicative of integrity of a medical device, determine, based on one or more therapy characteristics, a therapy metric indicative of therapy stability of the medical device, and determine, based on one or more sensing characteristics, a sensing metric indicative of sensing stability of the medical device. The processing circuitry can then determine, based on the system metric, the therapy metric, and the sensing metric, a system stability score, and, responsive to determining that the system stability score indicates instability of the medical device, perform an action selected to improve the system stability score.

Description

Docket No.: A0013076W001THERAPY SYSTEM STABILITY DETERMINATIONCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of priority to U.S. Provisional Application No. 63 / 726,097 filed November 27, 2024, which is incorporated herein by reference in its entirety.TECHNICAL FIELD

[0002] This disclosure generally relates to medical devices, and, more particularly, medical devices that deliver 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 may deliver electrical stimulation therapy via one or more leads that include electrodes located proximate to target locations associated with the brain, the spinal cord, pelvic nerves, peripheral nerves, or the gastrointestinal tract of a patient. Hence, electrical stimulation may be used in different therapeutic applications, such as deep brain stimulation (DBS), spinal cord stimulation (SCS), pelvic stimulation, gastric stimulation, or peripheral nerve field stimulation (PNFS).

[0004] 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 amplitude, a pulse width, and a pulse frequency as stimulation parameters. A set of parameters, such as a set including electrode combination, electrode polarity, voltage or current 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] In general, the disclosure describes devices, systems, and techniques for determining a system stability score for a device or system, such as a medical device. The system stability score may be a metric that indicates a level of stability in the functioning ofDocket No.: A0013076W001 the medical device. Instability may indicate that one or more changes may need to be made to the medical device to improve the functioning of the medical device, such as improved physiological sensing, therapy delivery, or a combination of both. A determination of system stability may indicate that the medical device is functioning correctly for efficacious monitoring and / or treatment of the patient. The system stability score may be automatically determined by the system in order to confirm correct function or flag situations where the system may need to be adjusted to regain proper function.

[0006] The system may determine the system stability score from multiple metrics that track different aspects of medical device function. One example metric is a system metric indicative of system integrity for the medical device. The system may determine the system metric based on one or more system characteristics such as battery life, impedance measurements, signal quality measurements, and the like. Another metric is a therapy metric that is calculated based on one or more therapy characteristics. The one or more therapy characteristics may represent quantified user-requested changes to therapy, where increased changes to therapy may be indicative of ineffective and unstable therapy delivery. The user- requested changes may be from a clinician (or other health care professional) or the patient. Another metric is a sensing metric that the system can determine based on one or more sensing characteristics representative of any volatility in the sensing of a physiological signal from the patient. The system may determine the system stability score as a binary or gradient value that could be configured to indicate instability if any metric exceeds a threshold, if a predetermined number of metrics exceeds the respective thresholds, or some other function of the metrics set to reflect an issue with medical device functioning. The medical device may be configured to sense physiological signals such as local field potential (LFP) signals in some examples. In some examples, the medical device may also be configured to deliver electrical stimulation therapy (e.g., DBS therapy or other type of therapy) to the patient based on the system stability score.

[0007] In one example, a system includes processing circuitry configured to: obtain one or more system characteristics related to functionality of a medical device; determine, based on the one or more system characteristics, a system integrity metric indicative of integrity of the medical device; obtain one or more therapy characteristics indicative of user requested changes to therapy delivered by the medical device; determine, based on the one or more therapy characteristics, a therapy metric indicative of therapy stability of the medical device; obtain one or more sensing characteristics representative of physiological signals sensed by the medical device; determine, based on the one or more sensing characteristics, a sensingDocket No.: A0013076W001 metric indicative of sensing stability of the medical device; determine, based on the system metric, the therapy metric, and the sensing metric, a system stability score; and responsive to determining that the system stability score indicates instability of the medical device, perform an action selected to improve the system stability score.

[0008] In another example, a method includes obtaining, by processing circuitry, one or more system characteristics related to functionality of a medical device; determining, by the processing circuity and based on the one or more system characteristics, a system integrity metric indicative of integrity of the medical device; obtaining, by the processing circuitry, one or more therapy characteristics indicative of user requested changes to therapy delivered by the medical device; determining, by the processing circuity and based on the one or more therapy characteristics, a therapy metric indicative of therapy stability of the medical device; obtaining, by the processing circuitry, one or more sensing characteristics representative of physiological signals sensed by the medical device; determining, by the processing circuity and based on the one or more sensing characteristics, a sensing metric indicative of sensing stability of the medical device; determining, by the processing circuity and based on the system metric, the therapy metric, and the sensing metric, a system stability score; and responsive to determining that the system stability score indicates instability of the medical device, performing an action selected to improve the system stability score.

[0009] In another example, a non-transitory computer-readable medium includes instructions that, when executed, control processing circuitry to: obtain one or more system characteristics related to functionality of a medical device; determine, based on the one or more system characteristics, a system integrity metric indicative of integrity of the medical device; obtain one or more therapy characteristics indicative of user requested changes to therapy delivered by the medical device; determine, based on the one or more therapy characteristics, a therapy metric indicative of therapy stability of the medical device; obtain one or more sensing characteristics representative of physiological signals sensed by the medical device; determine, based on the one or more sensing characteristics, a sensing metric indicative of sensing stability of the medical device; determine, based on the system metric, the therapy metric, and the sensing metric, a system stability score; and responsive to determining that the system stability score indicates instability of the medical device, perform an action selected to improve the system stability score.

[0010] 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, andDocket No.: A0013076W001 advantages of the techniques will be apparent from the description and drawings, and from the claims.BRIEF DESCRIPTION OF DRAWINGS

[0011] FIG. l is a conceptual diagram illustrating an example system that includes an implantable medical device (IMD) configured to sense electrical signals and / or deliver DBS to a patient according to an example of the techniques of the disclosure.

[0012] FIG. 2 is a block diagram of the example IMD of FIG. 1 for sensing electrical signals and / or delivering DBS therapy according to an example of the techniques of the disclosure.

[0013] 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.

[0014] FIG. 4 is a block diagram illustrating an example system that includes an external device, such as a server, and one or more computing devices that are coupled to an implantable medical device and external programmer shown in FIG. 1 via a network.

[0015] FIG. 5 is a flow chart of an example technique for determining a system stability score for a medical device.

[0016] FIG. 6 is a conceptual diagram of an example process for determining a system stability score based on several different types of metrics for a medical device.DETAILED DESCRIPTION

[0017] This disclosure describes example devices, systems, and techniques for determining a system stability score for a device or system, such as a medical device. The system stability score may be a metric that indicates a level of stability in the functioning of the medical device. A patient may suffer from one or more symptoms that can be reflected in one or more different types of physiological signals (e.g., electric signals, movement signals, chemical signals, temperature signals, etc.) that can be sensed by one or more sensors. For example, a patient may suffer from brain disorder such as Parkinson’s disease, Alzheimer’s disease, or another type of movement disorder that can be monitored using a sensed electrical signal such as an LFP signal, evoked resonant neural activity (ERNA) signal, or other such signal. In some examples, these signals are monitored to track symptoms. In some examples, these physiological signals can be used as feedback to automatically adjust one or more parameters that define electrical stimulation in a closed-loop manner. A medical deviceDocket No.: A0013076W001 can deliver electrical stimulation to the patient in an attempt to reduce the symptoms of the patient’s condition.

[0018] The management of the medical device, such as for chronic DBS therapy for conditions such as Parkinson's disease, can be important for ensuring long-term therapeutic efficacy and patient well-being. While DBS has demonstrated significant benefits in managing motor symptoms, challenges can persist in maintaining therapy stability over extended periods of time for the patient. For example, various functionality of the medical device may change over time and may go unnoticed until symptoms are no longer treated and / or side effects occur. It can be difficult for a clinician that only sees the patient a few times a year or less to identify any problems with the medical device. In addition, the patient may not be able to detect when various aspects of the medical device are no longer functioning as desired.

[0019] As described herein, a system can leverage a wealth of longitudinal data collected from the medical device or other devices associated with a patient under chronic DBS therapy. The system can use and / or develop algorithms that can assess long-term therapy stability or other system stability that can affect therapy. By systematically analyzing data that may be associated with system integrity, device interaction, and Local Field Potential (LFP) signal variability, the system can utilize a more comprehensive picture (e.g., a system stability score) of the patient's therapeutic stability and device performance. This system stability score can enable clinicians to make informed decisions about therapy adjustments, predict potential issues before they become critical, enable automated corrections to aspects of the medical device, and ultimately improve patient outcomes.

[0020] In one example, the system can employ an algorithmic strategy based on at least three fundamental metrics that can indicate long-term stability of the medical device. First, the system can analyze sequential measurements of metrics that can identify device health and longevity, such as impedance, signal quality, and battery status. These types of metrics may be referred to as system metrics that can be representative of long-term system integrity. For example, patterns in these measurements can indicate whether the device is functioning optimally or if there are emerging issues that need attention.

[0021] Second, the system can evaluate therapy stability through the number and / or frequency of changes in DBS programming settings. Frequent adjustments to one or more parameters that define therapy by clinicians and / or patients may indicate instability in therapy. These adjustments can be referred to as a therapy metric. The system may furtherDocket No.: A0013076W001 analyze the patient's condition and device settings in response to instability indicated by the therapy metric.

[0022] Third, the system can monitor the evolution of LFP signal volatility and the longterm evolution of the LFP dynamic to uncover insights into the patient's neurophysiological stability. These sensing changes, or lack thereof, may be referred to as sensing metrics. Stable LFP signals suggest consistent therapeutic effects, whereas increased variability may suggest changes in the patient's condition or other instability in the patient’s condition. The increased variability of LFP signals (or other physiological signals) may be induced by one or more of medication, physical activity, or other conditions (e.g., comorbidities). However, the system could characterize these other aspects in the signal and remove that variability from future signals. In this manner, the system may be able to isolate the variability in the sensed signal that is caused by the target condition instead of other extraneous factors. In some examples, the system may identify the target condition (or other desired cause of the instability) by identifying characteristics in the signal, such as progressive increases or decreases in signal dispersion or abrupt deviation from a normal trend. The system can integrate these different types of metrics (e.g., the system metric, therapy metric, and sensing metric) to generate a robust analytic framework for long-term DBS therapy management, enhancing both the reliability of the system and the quality of life for patients. For example, the system can determine and monitor a system stability score indicative of any instability in one or more of the metrics that are monitored.

[0023] In this manner, instability may indicate that one or more changes may need to be made to the medical device to improve the functioning of the medical device, such as improved physiological sensing, therapy delivery, or a combination of both. A determination of system stability may indicate that the medical device is functioning correctly for efficacious monitoring and / or treatment of the patient. The system stability score may be automatically determined by the system in order to confirm correct function or flag situations where the system may need to be adjusted to regain proper function.

[0024] The system may determine the system stability score from one or more different metrics that track different aspects of medical device function. One example metric is a system metric indicative of system integrity for the medical device. The system may determine the system metric based on one or more system characteristics such as battery life, impedance measurements, signal quality measurements, and the like. Another metric is a therapy metric that is calculated based on one or more therapy characteristics. The one or more therapy characteristics may represent quantified user-requested changes to therapy,Docket No.: A0013076W001 where increased changes to therapy may be indicative of ineffective and unstable therapy delivery. Another metric is a sensing metric that the system can determine based on one or more sensing characteristics representative of any volatility in the sensing of a physiological signal from the patient. The system may determine the system stability score as a binary or gradient value that could be configured to indicate instability if any metric exceeds a threshold, if a predetermined number of metrics exceeds the respective thresholds, or some other function of the metrics set to reflect an issue with medical device functioning.

[0025] The system can perform various actions in response to the state of the system's stability score. In some examples, the system can control the display of the system stability score on a user interface for presentation to a user. The system can display this system stability score in any state, such as a stable system stability score to indicate the medical device is functioning correctly or an unstable system stability score to indicate the medical device, patient, or other device can use some attention and adjustment. The system stability score may be a binary score, indicating only a stable or unstable state of the medical device. In other examples, the system stability score may be used to provide multiple different states of stability, identify which elements of the medical device, system, or patient may need attention, or otherwise provide insight into what metrics are no longer stable. In some examples, any metric becoming unstable may trigger an unstable system stability score. In other examples, the system may calculate the system stability score using some type of function that incorporates similar or different contributions of respective metrics to the overall system stability score.

[0026] In response to the system stability score, the system can take automated corrections to one or more aspects of medical device function. For example, if the system is no longer stable, the medical device may automatically adjust one or more stimulation parameters that define therapy, adjust when or how physiological signals are sensed, adjust one or more parameters that define closed-loop stimulation, turn off therapy delivery, perform one or more diagnostic tests on the medical device, and / or any other action.

[0027] These various features of the systems and techniques described herein may provide advantages over other systems and improve system functionality and patient outcomes. For example, the techniques herein enable the system to identify when a medical device, patient, or other element of a system is no longer stable for monitoring and / or delivering therapy to the patient. This automated process can enable the system to monitor long-term stability of the therapy or monitoring solution in order to provide early detection of any problems. In addition, the automated process may enable the system to take automaticDocket No.: A0013076W001 corrective action for the medical device and / or quickly transmit a message to a user for manual review of one or more aspects of the system. The system stability score may thus reduce clinician time, reduce costs, and improve patient outcomes.

[0028] LFP signals are generally described herein as an example electrical signal sensed from the patient, but any other physiological signals may be used in other examples.Example physiological signals include evoked resonant neural activity (ERNA) signals, evoked compound action potential (ECAP) signals, compound action potentials, electroencephalogram (EEG) signals, electromyograph (EMG) signals, cardiac signals, nerve signals, temperature signals, movement signals, and the like. In addition, DBS therapy is described as one example therapy. However, other therapies may be adjusted based on a system stability score, such as spinal cord stimulation (SCS), pelvic stimulation, gastric stimulation, peripheral nerve field stimulation (PNFS), medication schedule, etc. Any of these signals, therapies, or combinations thereof can be applicable to one or more metrics or system stability score as described herein.

[0029] 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. DBS may be open loop or adaptive (aDBS) in the sense that IMD 106 may adjust, increase, or decrease the value of one or more stimulation parameters that define the DBS. ' For example, system 100 may use one or more sensed signals of the patient as a control signal such that the IMD 106 adjusts the magnitude of the one or more parameters of the electrical stimulation in response to the magnitude or change in magnitude of the one or more sensed signals and / or based on the system stability score or one or more related metrics. This process enables system 100 to automatically adjust stimulation therapy in response to changes to the patient's condition, such as changes to brain activity indicative of a level of therapy efficacy.

[0030] 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 the brain 120, such as the subthalamic nucleus, globus pallidus, or thalamus, may be an effective treatment to manage movement disorders, such as Parkinson’s disease. Some or all of the electrodes 116, 118 may also be positioned to sense bioelectrical brain signals within the brain 120 of the patient 112.Docket No.: A0013076W001In some examples, some of the electrodes 116, 118 may be configured to sense bioelectrical brain signals, and others of the electrodes 116, 118 may be configured to deliver adaptive electrical stimulation to the brain 120. In other examples, all of the electrodes 116, 118 are configured to both sense bioelectrical brain signals and deliver adaptive electrical stimulation to the brain 120.

[0031] IMD 106 includes a therapy module (e.g., which may include processing circuitry, signal generation circuitry or other electrical circuitry configured to perform the functions attributed to IMD 106) that includes a stimulation generator configured to generate and deliver electrical stimulation therapy to patient 112 via a subset of electrodes 116, 118 of leads 114A and 114B, respectively. The subset of electrodes 116, 118 that are used to deliver electrical stimulation to patient 112, and, in some cases, the polarity of the subset of electrodes 116, 118, may be referred to as a stimulation electrode combination. As described in further detail below, the stimulation electrode combination can be selected for a particular patient 112 and target tissue site (e.g., selected based on bioelectrical signal information and the patient's 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.

[0032] According to some techniques of the disclosure, system 100, via IMD 106, delivers electrical stimulation therapy defined by one or more parameters, such as voltage or current amplitude, adjusted in response to a signal deviating from a range defined by a homeostatic window (e.g., a window defined by one or more thresholds to which a brain signal is compared, such as a lower threshold and upper threshold). The homeostatic window may be used as part of an adaptive stimulation mode for adjusting stimulation therapy over time. In some examples, system 100 may change other parameters in response to sensed signals such as stimulation pulse frequency, pulse burst duration, pulse burst frequency, duty cycle, or electrode combination. Furthermore, the adjustable stimulation parameters may have parameter limits (lower and / or upper limits) to reduce the possibility of undesired stimulation being delivered during automated closed-loop control. These one or more thresholds and / or limits may be adjusted based on one or more periodicity metrics.

[0033] As described herein, “reducing” or “suppressing” the symptoms of the patient refers to alleviating, in whole or in part, the severity of one or more symptoms of the patient. In one example, the clinician makes a determination of the severity of one or more symptoms of Parkinson’s disease of patient 112 with reference to the Unified Parkinson's DiseaseDocket No.: A0013076W001Rating Scale (UPDRS) or the Movement Disorder Society-Sponsored Revision of the Unified Parkinson’s Disease Rating Scale (MDS-UPDRS). A discussion of the application of the MDS-UPDRS is provided by Movement Disorder Society-Sponsored Revision of the Unified Parkinson’s Disease Rating Scale (MDS-UPDRS): Scale Presentation and Clinimetric Testing Results, C. Goetz et al, Movement Disorders, Vol. 23, No. 15, pp. 2129-2170 (2008), the content of which is incorporated herein in its entirety.

[0034] System 100 can monitor one or more signals of the patient for selecting one or more parameters defining stimulation and / or adjusting stimulation in a closed-loop manner. In one example, the signal is a bioelectrical signal of a patient, such as a brain signal (e.g., LFP) with a frequency within a Beta frequency band and / or a Gamma frequency band of the brain of the patient. For example, the monitored signal may be a power of the respective Beta frequency band and / or Gamma frequency band (determined based on which frequency varies during stimulation delivery and / or under the influence of medication). In yet a further example, the signal can be a signal indicative of a physiological parameter of the patient, such as the severity of a symptom of the patient, a movement of the patient, a posture of the patient, a respiratory function of the patient, a heart rate, or an activity level of the patient. System 100 may use a single signal or a combination of different signals for initially selecting and / or adjusting one or more parameters that define subsequent stimulation therapy. System 100, via IMD 106, can be configured to deliver electrical stimulation to the patient, wherein one or more parameters defining the electrical stimulation are proportional to the magnitude of the monitored signal or adjusted in response to a magnitude of the monitored signal exceeding one or more thresholds.

[0035] System 100 may be configured to treat one or more patient conditions, such as a movement disorder, neurodegenerative impairment, a mood disorder, or a seizure disorder of patient 112. Patient 112 ordinarily is a human patient. In some cases, however, therapy system 100 may be applied to other mammalian or non-mammalian, non-human patients. While movement disorders and neurodegenerative impairment are primarily referred to herein, in other examples, therapy system 100 may provide therapy to manage symptoms of other patient conditions, such as, but not limited to, seizure disorders (e.g., epilepsy) or mood (or psychological) disorders (e.g., major depressive disorder (MDD), bipolar disorder, anxiety disorders, post-traumatic stress disorder, dysthymic disorder, and obsessive- compulsive disorder (OCD)). At least some of these 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 controlDocket No.: A0013076W001 impairment, motion impairment or other movement problems, such as rigidity, spasticity, bradykinesia, rhythmic hyperkinesia, nonrhythmic hyperkinesia, and akinesia. In some cases, the movement disorder may be a symptom of Parkinson’s disease. However, the movement disorder may be attributable to other patient conditions. Any therapy can be adjusted or managed based on the system stability score one or more metrics in order to improve the patient-specific details of the therapy for potentially improved efficacy.

[0036] In some examples, the bioelectrical signals sensed within brain 120 may reflect changes in electrical current produced by the sum of electrical potential differences across brain tissue. Examples of bioelectrical brain signals include, but are not limited to, electrical signals generated from local field potentials (LFP) sensed within one or more regions of brain 120, such as an electroencephalogram (EEG) signal, or an electrocorticogram (ECoG) signal. Local field potentials, however, may include a broader genus of electrical signals within brain 120 of patient 112.

[0037] In some examples, the bioelectrical 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 the brain 120, as well as other target tissue sites. The specific target tissue sites and / or regions within the brain 120 may be selected based on the patient condition. Thus, in some examples, the electrodes used for delivering electrical stimulation may be different than the electrodes used for sensing bioelectrical brain signals. In other examples, the same electrodes may be used to deliver electrical stimulation and sense brain signals. However, this configuration may require system 100 to switch between stimulation generation and sensing circuitry and may reduce the time system 100 can sense brain signals.

[0038] Electrical stimulation generated by IMD 106 may be configured to manage a variety of disorders and conditions. In some examples, the stimulation generator of IMD 106 is configured to generate and deliver electrical stimulation pulses to patient 112 via electrodes of a selected stimulation electrode combination. However, in other examples, the stimulation generator of IMD 106 may be configured to generate and deliver a continuous wave signal, e.g., a sine wave or triangle wave. In either case, a stimulation generator within IMD 106 may generate the electrical stimulation therapy for DBS according to a therapy program that is selected at that given time in therapy. In examples in which IMD 106 delivers electrical stimulation in the form of stimulation pulses, a therapy program may include a set of therapy parameter values (e.g., stimulation parameters), such as a stimulation electrode combinationDocket No.: A0013076W001 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 are selected to deliver stimulation signals to tissue of patient 112 and the respective polarities of the selected electrodes.

[0039] IMD 106 may be implanted within a subcutaneous pocket above the clavicle, or, alternatively, on or within cranium 122 or at any other suitable site within patient 112. Generally, IMD 106 is constructed of a biocompatible material that resists corrosion and degradation from bodily fluids. IMD 106 may comprise a hermetic housing to substantially enclose components, such as a processor, therapy module, and memory.

[0040] As shown in FIG. 1, implanted lead extension 110 is coupled to IMD 106 via connector 108 (also referred to as a connector block or a header of IMD 106). In the example of FIG. 1, lead extension 110 traverses from the implant site of IMD 106 and along the neck of patient 112 to cranium 122 of patient 112 to access brain 120. In the example shown in FIG. 1, leads 114A and 114B (collectively “leads 114”) are implanted within the right and left hemispheres, respectively, of patient 112 in order deliver electrical stimulation to one or more regions of brain 120, which may be selected based on the patient condition or disorder controlled by therapy system 100. The specific target tissue site and the stimulation electrodes used to deliver stimulation to the target tissue site, however, may be selected, e.g., according to the identified patient behaviors and / or other sensed patient parameters. Other lead 114 and IMD 106 implant sites are contemplated. For example, IMD 106 may be implanted on or within cranium 122, in some examples. Or leads 114 may be implanted within the same hemisphere or IMD 106 may be coupled to a single lead implanted in a single hemisphere.

[0041] Existing lead sets include axial leads carrying ring electrodes disposed at different axial positions and so-called “paddle” leads carrying planar arrays of electrodes. Selection of electrode combinations within an axial lead, a paddle lead, or among two or more different leads presents a challenge to the clinician. In some examples, more complex lead array geometries may be used.

[0042] 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 electrical stimulation to one or more target tissue sites within brain 120 to manage patient symptoms associated with a movement disorder of patient 112. Leads 114 may be implanted to position electrodes 116, 118 at desired locations of brain 120 through respective holes in cranium 122.Docket No.: A0013076W001Leads 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.

[0043] 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 or aDBS applications because they are relatively simple to program and are capable of delivering an electrical field to any tissue adjacent to electrodes 116, 118. In other examples, electrodes 116, 118 may have different configurations. For example, in some examples, at least some of the electrodes 116, 118 of leads 114 may have a complex electrode array geometry that is capable of producing shaped electrical fields. The complex electrode array geometry may include multiple electrodes (e.g., partial ring or segmented electrodes) around the outer perimeter of each lead 114, rather than one ring electrode. In this manner, electrical stimulation may be directed in a specific direction from leads 114 to enhance therapy efficacy and reduce possible adverse side effects from stimulating a large volume of tissue. In some examples, a housing of IMD 106 may include one or more stimulation and / or sensing electrodes. In alternative examples, leads 114 may have shapes other than elongated cylinders as shown in FIG. 1. For example, leads 114 may be paddle leads, spherical leads, bendable leads, or any other type of shape effective in treating patient 112 and / or minimizing invasiveness of leads 114.

[0044] In the example shown in FIG. 1, IMD 106 includes a memory to store a plurality of therapy programs that each define a set of therapy parameter values. In some examples, IMD 106 may select a therapy program from the memory based on various parameters, such as sensed patient parameters and the identified patient behaviors. IMD 106 may generate electrical stimulation based on the selected therapy program to manage the patient symptoms associated with a movement disorder. In some examples, IMD 106 may include instructions for determining the system stability score and / or related metrics in order to monitor correct functioning of IMD 106 or other elements over time.

[0045] 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 selectDocket No.: A0013076W001 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. Programmer 104 may be any type of device that is configured to communicate with IMD 106, such as a smart watch, hand-held computer, mobile device, recharger, or any other device.

[0046] 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). In addition, or as an alternative, to programmer 104, a different external computing device may perform any of the functionality of programmer 104. The external computing device may be a networked device and in communication with IMD 106 directly or via programmer 104.

[0047] The clinician may also store therapy programs within IMD 106 with the aid of programmer 104. During a programming session, system 100 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, system 100 may select one or more stimulation electrode combinations with which stimulation is delivered to brain 120. During the programming session, system 100 may evaluate the efficacy of the specific program being evaluated based on feedback provided by the clinician, patient 112, or based on one or more physiological parameters of patient 112 (e.g., muscle activity, muscle tone, rigidity, tremor, etc.). The periodicity metrics may also be stored and / or used to identify the different states or changes in the patient over time.

[0048] 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. When programmer 104 is configured forDocket No.: A0013076W001 use by patient 112 (e.g., a patient programmer), programmer 104 may have a limited set of adjustments and / or data available to the user compared with a clinician programmer. In this manner, the patient programmer version may prevent the patient from causing detrimental changes to therapy, but allow the patient to make some adjustments to therapy as desired.

[0049] 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 112 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.

[0050] 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.

[0051] Although IMD 104 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 in other examples. In other examples, system 100 may include an implantable drug pump in addition to, or in place of, IMD 106. Further, an IMD may provide other electrical stimulation such as spinal cord stimulation to treat a movement disorder.

[0052] In some examples, system 100 can define a homeostatic window (e.g., one or more thresholds of an adaptive stimulation mode) and / or a therapeutic window for delivering aDBS to patient 112. System 100 may adaptively deliver electrical stimulation and adjust one or more parameters defining the electrical stimulation within a parameter range defined by upper and lower parameter limits of the therapeutic window based on the activity of the sensed bioelectrical signal, e.g., LFP signal, evoked resonant neural activity (ERNA), and EEG, within the homeostatic window. As described herein, system 100 may automatically suggest one or more parameter limits based on sensed bioelectrical signals. System 100 may adjust the one or more parameters defining the electrical stimulation in response to the sensed signal falling below the lower threshold or exceeding the upper threshold of the homeostaticDocket No.: A0013076W001 window (e.g., from the sensed bioelectric signals) but may not adjust the one or more parameters defining the electrical stimulation such that they fall below the lower limit or exceed the upper limit of the therapeutic window.

[0053] In one example, external programmer 104 issues commands to IMD 106, via instructions transmitted from external programmer 104 to IMD 106, causing IMD 106 to deliver electrical stimulation therapy via electrodes 116, 118 via leads 114. As described above, in one example, the therapeutic window can define an upper bound and / or a lower bound for one or more parameters (e.g., amplitude or pulse width) defining the delivery of electrical stimulation therapy to patient 112. In other words, the one or more bounds for the therapeutic window may refer to the limits of values that the parameter defining stimulation can be adjusted. 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. 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. In one example, the therapeutic window defines an upper bound and a lower bound for one or more parameters, such as upper and lower threshold for a current amplitude of the electrical stimulation therapy (in current-controlled systems) or upper and lower threshold of a voltage amplitude of the electrical stimulation therapy (in voltage-controlled systems). While the examples herein are typically given with respect to adjusting a voltage amplitude or a current amplitude, the techniques herein may equally be applied to a homeostatic window and a therapeutic window using other parameters, such as, e.g., pulse rate or pulse width. Example implementations of the therapeutic window are provided in further detail below. In addition, stimulation may be withheld, or delivered, during periods of time based on the one or more periodicity metrics.

[0054] Typically, a patient programmer 104 may not have access to adjustments to any thresholds or limits for sensing or stimulation related to aDBS. For example, patient programmer 104 may only enable a patient to adjust a stimulation parameter value between limits set by the clinician programmer. However, in other examples, system 100 may provide aDBS by permitting a patient 112, e.g., via a patient programmer 104, to indirectly adjust the activation, deactivation, and magnitude of the electrical stimulation by adjusting the lower and upper threshold of the homeostatic window. In one example, the patient programmer 104 may only be enabled to adjust an upper or lower threshold of the homeostatic window a small magnitude or percentage of the clinician-set value. In another example, by adjusting one orDocket No.: A0013076W001 both thresholds of the homeostatic window, patient 112 may adjust the point at which the sensed signal deviates from the homeostatic window, triggering system 100 to adjust one or more parameters of the electrical stimulation within a parameter range defined by the lower and upper threshold of the therapeutic window.

[0055] Hence, in some examples, system 100, via programmer 104 or IMD 106, may adjust one or more parameters of the electrical stimulation, such as voltage or current amplitude, within the therapeutic window based on patient input that adjusts the homeostatic window, or based on one or more signals, such as sensed physiological parameters or sensed bioelectrical signals, or a combination of two or more of the above. In particular, system 100 may adjust a parameter of the electrical stimulation, automatically in response to the sensed signal satisfying the one or more thresholds of the homeostatic window and / or in response to patient input that adjusts the homeostatic window, provided the value of the electrical stimulation parameter is constrained to remain within a range specified by the upper and lower bound of the therapeutic window. This range may be considered to include the upper and lower bound themselves.

[0056] In some examples where system 100 adjusts multiple parameters of the electrical stimulation, system 100 may adjust at least one of a voltage amplitude or current amplitude, a stimulation frequency, a pulse width, or a selection of electrodes, and the like. In such an example, system 100 may set an order or sequence for adjustment of the parameters (e.g., adjust voltage amplitude or current amplitude, then adjust stimulation frequency, and then adjust the selection of electrodes). In other examples, system 100 may randomly select a sequence of adjustments to the multiple parameters. In either example, system 100 may adjust a value of a first parameter of the parameters of the electrical stimulation. If the signal does not exhibit a response to the adjustment of the first parameter, system 100 may adjust a value of a second parameter of the parameters of the electrical stimulation, and so on until the signal returns to within the homeostatic window.

[0057] To adaptively adjust a parameter that defines DBS based on a bioelectrical signal, for example, two or more electrodes 116, 118 of IMD 106 may be configured to monitor a bioelectrical signal (e.g., an LFP signal) of patient 112. In some examples, at least one of electrodes 116, 118 may be provided on a housing of IMD 106, providing a unipolar stimulation and / or sensing configuration. In one example, the bioelectrical signal may be selected to be a signal within a Beta frequency band of brain 120 of patient 112. For example, bioelectrical signals within the Beta frequency band of patient 112 may correlate to one or more symptoms of Parkinson’s disease in patient 112. Generally, bioelectrical signals withinDocket No.: A0013076W001 the Beta frequency of patient 112 may be approximately proportional to the severity of the symptoms of patient 112. For example, as tremor induced by Parkinson’s disease increases, bioelectrical signals within the Beta frequency of patient 112 increase (e.g., magnitude of the signal and / or spectral power). Moreover, bioelectrical signals within the Beta frequency are considered proportional because system 100 may be configured such that an increase in signal magnitude may trigger system 100 to increase delivered stimulation therapy magnitude according to disclosed techniques. Similarly, as tremor induced by Parkinson’s disease decreases, bioelectrical signals within the Beta frequency of patient 112 decrease (e.g., magnitude of the signal and / or spectral power), and the decrease may trigger system 100 to decrease the magnitude of delivered stimulation. However, in some examples, these relationships between signal changes and symptom changes may be inversed for some patients which require the system to react in an inverse manner. In some examples, one or more frequencies in the Gamma band may be responsive to stimulation for some patients. This Gamma band responsiveness may come with or without Beta suppression from stimulation therapy.

[0058] In some examples, each of a sensor within IMD 106 is an accelerometer, a bonded piezoelectric crystal, a mercury switch, or a gyro. In some examples, these sensors may provide a signal that indicates a physiological parameter of the patient, which in turn varies as a function of patient activity. For example, the device may monitor a signal that indicates the heart rate, electrocardiogram (ECG) morphology, electroencephalogram (EEG) morphology, respiration rate, respiratory volume, core temperature, subcutaneous temperature, or muscular activity of the patient. Any of these sensed signals may be used to identify a patient event that may be a symptom and / or side effect of the patient.

[0059] In some examples, the sensors generate a signal both as a function of patient activity and patient posture. For example, accelerometers, gyros, or magnetometers may generate signals that indicate both the activity and the posture of a patient 112. External programmer 104 may use such information regarding posture to determine whether external programmer 104 should perform adjustments to the therapeutic window.

[0060] For example, in order to identify posture, the sensors such as accelerometers may be oriented substantially orthogonally with respect to each other. In addition to being oriented orthogonally with respect to each other, each of the sensors used to detect the posture of a patient 112 may be substantially aligned with an axis of the body of a patient 112. When accelerometers, for example, are aligned in this manner, the magnitude and polarity of DC components of the signals generate by the accelerometers indicate the orientation of theDocket No.: A0013076W001 patient relative to the Earth’s gravity, e.g., the posture of a patient 112. Further information regarding use of orthogonally aligned accelerometers to determine patient posture may be found in a commonly assigned U.S. Patent No. 5,593,431, which issued to Todd J. Sheldon, the entire content of which is incorporated by reference herein.

[0061] Other sensors that may generate a signal that indicates the posture of a patient 112 include electrodes that generate a signal as a function of electrical activity within muscles of a patient 112, e.g., an electromyogram (EMG) signal, or a bonded piezoelectric crystal that generates a signal as a function of contraction of muscles. Electrodes or bonded piezoelectric crystals may be implanted in the legs, buttocks, chest, abdomen, or back of a patient 112, and coupled to one or more of external programmer 104 and IMD 106 wirelessly or via one or more leads. Alternatively, electrodes may be integrated in a housing of the IMD 106, or piezoelectric crystals may be bonded to the housing when IMD 106 is implanted in the buttocks, chest, abdomen, or back of a patient 112. The signals generated by such sensors when implanted in these locations may vary based on the posture of a patient 112, e.g., may vary based on whether the patient is standing, sitting, or lying down. These signals may be monitored as part of the sensing metric that can contribute to the overall system stability score for long term system monitoring.

[0062] Further, the posture of a patient 112 may affect the thoracic impedance of the patient. Consequently, sensors may include an electrode pair, including one electrode integrated with the housing of IMDs 106 and one of electrodes 116, 118, that generate a signal as a function of the thoracic impedance of a patient 112, and IMD 106 may detect the posture or posture changes of a patient 112 based on the signal. In one example (not depicted), the electrodes of the pair may be located on opposite sides of the patient’s thorax. For example, the electrode pair may include electrodes located proximate to the spine of a patient for delivery of SCS therapy, and IMD 106 with an electrode integrated in its housing may be implanted in the abdomen or chest of patient 112. As another example, IMD 106 may include electrodes implanted to detect thoracic impedance in addition to leads 114 implanted within the brain of patient 112. The posture or posture changes may affect the delivery of DBS or SCS therapy to patient 112 for the treatment of any type of bioelectrical disorder, and may also be used to detect or confirm patient sleep, as described herein.

[0063] Additionally, changes of the posture of a patient 112 may cause pressure changes with the cerebrospinal fluid (CSF) of the patient. Consequently, sensors may include pressure sensors coupled to one or more intrathecal or intracerebroventricular catheters, or pressure sensors coupled to HMDs 106 wirelessly or via one of leads 114. CSF pressure changesDocket No.: A0013076W001 associated with posture changes may be particularly evident within the brain of the patient, e.g., may be particularly apparent in an intracranial pressure (ICP) waveform.

[0064] Accordingly, in some examples, instead of, or in addition to, monitoring a bioelectrical signal of the patient, system 100 monitors one or more signals from sensors indicative of a magnitude of a physiological parameter of patient 112. Upon detecting that one or more signals from sensors exceed the upper bound of a homeostatic window, system 100 increases stimulation at a maximum ramp rate determined by system 100 until one or more signals from sensors return to within the homeostatic window, or until the magnitude of the electrical stimulation reaches an upper limit of a therapeutic window determined by system 100. Similarly, upon detecting that one or more signals from sensors falls below the lower bound of the homeostatic window, system 100 decreases stimulation at a maximum ramp rate determined by system 100 until one or more signals from sensors return to within the homeostatic window, or until the magnitude of the electrical stimulation reaches a lower limit of a therapeutic window determined by system 100. Upon detecting that one or more signals from sensors are within the threshold of the homeostatic window, system 100 holds the magnitude of the electrical stimulation constant.

[0065] Such a system 100 for delivering aDBS to the patient by monitoring a physiological parameter may provide advantages over other techniques that use a bioelectrical signal as a threshold in that the techniques of the disclosure allow an IMD to control delivery of therapy using hysteresis. In other words, such a system 100 can be configured to use the physiological parameter (alone or in addition to a sensed bioelectric signal) of the patient to create a closed loop feedback algorithm for not only controlling the delivery of therapy, but also controlling the magnitude of the delivered therapy. Such a system may be less intrusive on the activity of a patient because system 100 adapts the stimulation to the current needs of the patient, and thus may reduce the side effects that the patient experiences.

[0066] In some circumstances, system 100, as described herein, may deliver, based on the upper and lower threshold of the homeostatic window, a lower magnitude of electrical stimulation than patient 112 requires to prevent breakthrough of his or her symptoms. For example, a patient receiving therapy from an IMD 106 that controls delivery of electrical stimulation therapy using the homeostatic window may, in certain circumstances, experience results that are less optimal than if the patient received continuous electrical stimulation therapy at a maximum therapy magnitude. To prevent these occurrences, system 100 may determine a value for the at least one electrical stimulation parameter as defined by theDocket No.: A0013076W001 homeostatic window, as described above. Further, the IMD 106 of system 100 may increase the value for the at least one electrical stimulation parameter by a bias amount greater than the determined magnitude defined by the homeostatic window so as to further prevent breakthrough of the symptoms of patient 112. Thus, system 100 may avoid delivering electrical stimulation therapy that is of a magnitude that may be insufficient for prevention of symptom breakthrough.

[0067] As described herein, IMD 106 may monitor one or more metrics that can be used as part of the system stability score. For example, IMD 106 may monitor battery status, impedance measurements for one or more electrodes, and / or signal quality measurements as different characteristic values. IMD 106 may calculate a system metric using one or more of these different characteristic values. IMD 106 may also, or alternatively, monitor characteristics of therapy representative of user and / or automated changes to one or more parameters that define stimulation delivery. These characteristics of therapy may be used to calculate a therapy metric indicative of the stability of the therapy provided by IMD 106. IMD 106 may also, or alternatively, monitor characteristics of sensed data indicative of changes to the patient and / or physiological detection. These characteristics may be characteristics of one or more physiological signals sensed by IMD 106. IMD 106 may determine a sensing metric based on these characteristics of the physiological signals. Together, IMD 106 may determine an overall system stability score based on the system metric, the therapy metric, and the sensing metric. In some examples, IMD 106 may weight these metrics and / or use any or all of the metrics as independent triggers for changing the system stability score. IMD 106 may perform various actions in response to the system stability score indicating an instability, such as changes to one or more parameters defining therapy, stopping or starting therapy, changing one or more aspects of sensing signals, and / or transmitting the system stability score and / or other information to programmer 104 for display via a user interface for user assistance.

[0068] The architecture of system 100 illustrated in FIG. 1 is shown as an example. The techniques as set forth in this disclosure may be implemented in the example system 100 of FIG. 1, as well as other types of systems not described specifically herein. Nothing in this disclosure should be construed so as to limit the techniques of this disclosure to the example architecture illustrated by FIG. 1.

[0069] FIG. 2 is a block diagram of the example IMD 106 of FIG. 1 configured for delivering deep brain stimulation therapy. In the example shown in FIG. 2, IMD 106 includes processing circuitry 210, memory 211, stimulation generator 202, sensing module 204,Docket No.: A0013076W001 switch module 206, telemetry module 208, sensor 212, and power source 220. Each of these modules may be or include electrical circuitry configured to perform the functions attributed to each respective module. For example, processing circuitry 210 may include one or more processors part of the processing circuitry, switch module 206 may include switch circuitry, sensing module 204 may include sensing circuitry, stimulation generator 202 may include stimulation generation circuitry, and telemetry module 208 may include telemetry circuitry. Switch module 204 may not be necessary for multiple current source and sink configurations in which each current source and sink are directly connected to each electrode, but may be connected or disconnected via a respective switch. Memory 211 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 211 may store computer-readable instructions that, when executed by processing circuitry 210, cause IMD 106 to perform various functions. Memory 211 may be a storage device or other non-transitory medium.

[0070] In the example shown in FIG. 2, memory 211 stores therapy programs 214 and sense electrode combinations and associated stimulation electrode combinations 218 in separate memories within memory 211 or separate areas within memory 211. Each stored therapy program 214 defines a particular set of electrical stimulation parameters (e.g., a therapy parameter set), such as a stimulation electrode combination, electrode polarity, current or voltage amplitude, pulse width, and pulse rate. In some examples, individual therapy programs may be stored as a therapy group, which defines a set of therapy programs with which stimulation may be generated. The stimulation signals defined by the therapy programs of the therapy group may be delivered together on an overlapping or nonoverlapping (e.g., time-interleaved) basis. Therapy programs 214 may also store adaptive stimulation parameters that define adaptive stimulation, such as one or more thresholds for a homeostatic window and / or one or more limits for a therapeutic window (e.g., parameter limits). Processing circuitry 210 may directly change and / or update any of these parameter values based on commands from programmer 104, for example. In some examples, memory 211 may also include instructions for determining one or more metrics and / or the overall system stability score for monitoring the stability of IMD 106 and / or other sensors, devices, etc.

[0071] Sense and stimulation electrode combinations 218 stores sense electrode combinations and associated stimulation electrode combinations. As described above, in some examples, the sense and stimulation electrode combinations may include the sameDocket No.: A0013076W001 subset of electrodes 116, 118, a housing of IMD 106 functioning as an electrode, or may include different subsets or combinations of such electrodes. Thus, memory 211 can store a plurality of sense electrode combinations and, for each sense electrode combination, store information identifying the stimulation electrode combination that is associated with the respective sense electrode combination. The associations between sense and stimulation electrode combinations can be determined, e.g., automatically by processing circuitry 210. In some examples, corresponding sense and stimulation electrode combinations may comprise some or all of the same electrodes. In other examples, however, some or all of the electrodes in corresponding sense and stimulation electrode combinations may be different. For example, a stimulation electrode combination may include more electrodes than the corresponding sense electrode combination in order to increase the efficacy of the stimulation therapy. In some examples, as discussed above, stimulation may be delivered via a stimulation electrode combination to a tissue site that is different than the tissue site closest to the corresponding sense electrode combination but is within the same region, e.g., the thalamus, of brain 120 in order to mitigate any irregular oscillations or other irregular brain activity within the tissue site associated with the sense electrode combination.

[0072] Stimulation generator 202, under the control of processing circuitry 210, generates stimulation signals for delivery to patient 112 via selected combinations of electrodes 116, 118. An example range of electrical stimulation parameters believed to be effective in DBS to manage a movement disorder of patient include:

[0073] 1. Pulse Rate, i.e., Frequency: between approximately 1 Hertz and approximately500 Hertz, such as between approximately 40 to 185 Hertz or such as approximately 140 Hertz.

[0074] 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.

[0075] 3. In the alternative case of a current controlled system, Current Amplitude: between approximately 0.2 milliamps to approximately 100 milliamps, such as between approximately 1.3 milliamps and approximately 2.0 milliamps.

[0076] 4. Pulse Width: between approximately 10 microseconds and approximately 5000 microseconds, such as between approximately 100 microseconds and approximately 1000 microseconds, or between approximately 180 microseconds and approximately 450 microseconds.Docket No.: A0013076W001

[0077] Accordingly, in some examples, stimulation generator 202 generates electrical stimulation signals in accordance with the electrical stimulation parameters noted above, subject to application of the upper and lower threshold of a therapeutic window to one or more of the parameters, such that an applicable parameter resides within the range prescribed by the window. 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.

[0078] 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 generator 202 according to therapy programs 214 stored in memory 211 to apply particular stimulation parameter values specified by one or more of programs, such as voltage amplitude or current amplitude, pulse width, or pulse rate.

[0079] 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 switch module 206 to apply the stimulation signals generated by stimulation generator 202 to selected combinations of electrodes 116, 118. In particular, switch module 204 may couple stimulation signals to selected conductors within leads 114, which, in turn, deliver the stimulation signals across selected electrodes 116, 118. Switch module 206 may be a switch array, switch matrix, multiplexer, or any other type of switching module configured to selectively couple stimulation energy to selected electrodes 116, 118 and to selectively sense bioelectrical brain signals with selected electrodes 116, 118. Hence, stimulation generator 202 is coupled to electrodes 116, 118 via switch module 206 and conductors within leads 114. In some examples, however, IMD 106 does not include switch module 206.

[0080] Stimulation generator 202 may be a single channel or multi-channel stimulation generator. In particular, stimulation generator 202 may be capable of delivering a single stimulation pulse, multiple stimulation pulses, or a continuous signal at a given time via a single electrode combination or multiple stimulation pulses at a given time via multipleDocket No.: A0013076W001 electrode combinations. In some examples, however, stimulation generator 202 and switch module 206 may be configured to deliver multiple channels on a time-interleaved basis (e.g., pulses from one channel are at least partially alternating with at least some pulses from another channel). For example, switch module 206 may serve to time divide the output of stimulation generator 202 across different electrode combinations at different times to deliver multiple programs or channels of stimulation energy to patient 112. Alternatively, stimulation generator 202 may comprise multiple voltage or current sources and sinks that are coupled to respective electrodes to drive the electrodes as cathodes or anodes. In this example, IMD 106 may not require the functionality of switch module 206 for time-interleaved multiplexing of stimulation via different electrodes.

[0081] 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 at different perimeter locations around the perimeter of the lead at each of the locations A, B, C, and D. On one example, the electrodes may be electrically coupled to switch module 206 via respective wires that are straight or coiled within the housing the lead and run to a connector at the proximal end of the lead. In another example, each of the electrodes of the lead may be electrodes deposited 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 lead 114. These and other constructions may be used to create a lead with a complex electrode geometry.

[0082] Although sensing module 204 is incorporated into a common housing with stimulation generator 202 and processing circuitry 210 in FIG. 2, in other examples, sensing module 204 may be in a separate housing from IMD 106 and may communicate with processing circuitry 210 via wired or wireless communication techniques. Example bioelectrical brain signals include, but are not limited to, a signal generated from local field potentials (LFPs) within one or more regions of brain 28. EEG and ECoG signals are other examples of electrical signals that may be measured within brain 120 or by electrodes placed in other locations with respect to brain 120.

[0083] Sensor 212 may include one or more sensing elements that sense values of a respective patient parameter. For example, sensor 212 may include one or more accelerometers, optical sensors, chemical sensors, temperature sensors, pressure sensors, or any other types of sensors. Sensor 212 may output patient parameter values that may be usedDocket No.: A0013076W001 as feedback to control delivery of therapy. IMD 106 may include additional sensors within the housing of IMD 106 and / or coupled via one of leads 114 or other leads. In addition, IMD 106 may receive sensor signals wirelessly from remote sensors via telemetry module 208, for example. In some examples, one or more of these remote sensors may be external to patient (e.g., carried on the external surface of the skin, attached to clothing, or otherwise positioned external to the patient). Processing circuitry 210 may identify and / or store patient events according to signals from sensor 212.

[0084] Telemetry module 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 stimulation parameters such as magnitude and electrode combination, from programmer 104 via telemetry module 208. The updates to the therapy programs may be stored within therapy programs 214 portion of memory 211. Telemetry module 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 module 208 may communicate with external medical device programmer 104 via proximal inductive interaction of IMD 106 with programmer 104. Accordingly, telemetry module 208 may send information to external programmer 104 on a continuous basis, at periodic intervals, or upon request from IMD 106 or programmer 104.

[0085] 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 220. In some examples, power requirements may be small enough to allow IMD 220 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.

[0086] Processing circuitry 210 of IMD 106 delivers, electrodes 116, 118 interposed along leads 114 (and optionally switch module 206), electrical stimulation therapy to patient 112. The DBS therapy is defined by one or more therapy programs 214 having one or more parameters stored within memory 211 (and may specify the adaptive mode and corresponding one or more thresholds and / or parameter limits). For example, the one or more parameters may include a current amplitude (for a current-controlled system) or a voltage amplitude (forDocket No.: A0013076W001 a voltage-controlled system), a pulse rate or frequency, and a pulse width, or quantity of pulses per cycle. The collection of one or more of these parameter values may define a parameter set that defines each therapy program. 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. In one example, the therapeutic window defines an upper limit and / or a lower limit for a voltage amplitude of the electrical stimulation therapy. In another example, the therapeutic window defines an upper limit and / or a lower limit for a current amplitude of the electrical stimulation therapy. In particular, a parameter of the electrical stimulation therapy, such as voltage or current amplitude, is constrained to a therapeutic window having an upper limit and a lower limit, such that the voltage or current amplitude may be adjusted provided the amplitude remains greater than or equal to the lower limit and less than or equal to the upper limit. It is noted that a single limit may be used in some examples. In some examples, processing circuitry 210 can adjust any parameters of stimulation or parameters defining closed-loop stimulation based on the system stability score.

[0087] In one example, processing circuitry 210, via electrodes 116, 118 of IMD 106, monitors the behavior of a signal of patient 112 that correlates to one or more symptoms of a disease of patient 112 within a homeostatic window. Processing circuitry 210, via electrodes 116, 118, delivers aDBS to patient 112 and may adjust one or more parameters defining the electrical stimulation within a parameter range defined by lower and upper thresholds of a therapeutic window based on the activity of the sensed signal within the homeostatic window.

[0088] In one example, the signal is a bioelectrical signal (e.g., a LFP signal) within the Beta frequency band of brain 120 of patient 112. The signal within the Beta frequency band of patient 112 may correlate to one or more symptoms of Parkinson’s disease in patient 112. Generally speaking, bioelectrical signals within the Beta frequency band of patient 112 may be approximately proportional to the severity of the symptoms of patient 112. For example, as tremor induced by Parkinson’s disease increases, one or more of electrodes 116, 118 detect an increase in the magnitude of bioelectrical signals within the Beta frequency band of patient 112.

[0089] Similarly, as tremor induced by Parkinson’s disease decreases, processing circuitry 210, via the one or more of electrodes 116, 118, detects a decrease in the magnitude of the bioelectrical signals within the Beta frequency band of patient 112. In another example, the signal is a bioelectrical signal within the Gamma frequency band of brain 120 of patientDocket No.: A0013076W001112. The signal within the Gamma frequency band of patient 112 may also correlate to one or more side effects of the electrical stimulation therapy. However, in contrast to bioelectrical signals within the Beta frequency band, generally speaking, bioelectrical signals within the Gamma frequency band of patient 112 may be approximately inversely proportional to the severity of the side effects of the electrical stimulation therapy. For example, as side effects due to electrical stimulation therapy increase, processing circuitry 210, via the one or more of electrodes 116, 118, detects a decrease in the magnitude of the signal within the Gamma frequency band of patient 112. Similarly, as side effects due to electrical stimulation therapy decrease, processing circuitry 210, via the one or more of electrodes 116, 118, detects an increase in the magnitude of the signal within the Gamma frequency band of patient 112.

[0090] In response to detecting that the signal of the patient, e.g., a sensed bioelectrical signal, has deviated from the homeostatic window, processing circuitry 210 dynamically adjusts the magnitude of the one or more parameters of the electrical stimulation therapy such as, e.g., pulse current amplitude or pulse voltage amplitude, to drive the signal of the patient back into the homeostatic window. For example, wherein the signal is a bioelectrical signal within the Beta frequency band of brain 120 of patient 112, processing circuitry 210, via the one or more of electrodes 116, 118, monitors the Beta magnitude of patient 112. Upon detecting that the Beta magnitude of patient 112 exceeds the upper bound of the homeostatic window, processing circuitry 210 increases a magnitude of the electrical stimulation delivered via electrodes 116, 118 at a maximum ramp rate, e.g., determined automatically or by the clinician until the magnitude of the bioelectrical signal within the Beta band falls back to within the homeostatic window, or until the magnitude of the electrical stimulation reaches an upper limit of a therapeutic window determined by system 100 (FIG. 1). Similarly, upon detecting that the Beta magnitude of patient 112 falls below the lower bound of the homeostatic window, processing circuitry 210 decreases stimulation magnitude at a maximum ramp rate determined by system 100 until the Beta magnitude rises back to within the homeostatic window, or until the magnitude of the electrical stimulation reaches a lower limit of a therapeutic window determined by system 100. Upon detecting that the Beta magnitude is presently within the threshold of the homeostatic window or has returned to within the threshold of the homeostatic window, processing circuitry 210 holds the magnitude of the electrical stimulation constant.

[0091] In some examples, processing circuitry 210 continuously measures the signal in real time. In other examples, processing circuitry 210 periodically samples the signal according to a predetermined frequency or after a predetermined amount of time. In someDocket No.: A0013076W001 examples, processing circuitry 210 periodically samples the signal at a frequency of approximately 150 Hertz.

[0092] Furthermore, processing circuitry 210 delivers electrical stimulation therapy that is constrained by an upper limit and a lower limit of a therapeutic window. In some examples, values defining the therapeutic window are stored within memory 211 of IMD 106. For example, in response to detecting that the brain signal has deviated from the homeostatic window, processing circuitry 210 of IMD 106 may adjust one or more parameters of the electrical stimulation therapy to provide responsive treatment to patient 112. For example, in response to detecting that the signal has exceeded an upper threshold of the homeostatic window and prior to delivering the electrical stimulation therapy, processing circuitry 210 increases an amplitude of stimulation (e.g., but not above the upper limit) in order to bring the signal back down below the upper threshold. For example, in a voltage-controlled system wherein the clinician has set the upper limit of the therapeutic window to be 3 Volts, processing circuitry 210 can increase the voltage amplitude to values no greater than 3 Volts in an attempt to decrease the brain signal below the upper threshold.

[0093] In another example, in response to detecting that the signal has fallen below a lower threshold of the homeostatic window and prior to delivering the electrical stimulation therapy, processing circuitry 210 decreases the voltage amplitude, for example, but not lower than the magnitude of the lower limit. For example, in the above voltage-controlled system wherein the clinician has set the lower bound of the therapeutic window to be 1.2 Volts, processing circuitry 210 can decrease the voltage amplitude down to no lower than 1.2 Volts in an attempt to raise the brain signal back above the lower threshold and into the homeostatic window. Thus, processing circuitry 210 of IMD 106 may deliver aDBS to patient 112 wherein the one or more parameters defining the aDBS is within the therapeutic window defined by a lower and upper limit for the parameter.

[0094] In the foregoing example, the limit of the therapeutic window is inclusive (i.e., the upper and lower limit are valid values for the one or more parameters). However, in other examples, the limit of the therapeutic window is exclusive (i.e., the upper and lower limits are not valid values for the one or more parameters). In such an example of an exclusive therapeutic window, processing circuitry 210 instead sets the adjustment to the one or more parameters to be the next highest valid value (in the case of an adjustment potentially exceeding the upper limit) or the next lowest valid value (in the case of an adjustment potentially exceeding the lower limit).Docket No.: A0013076W001

[0095] In another example, values defining the therapeutic window are stored within a memory 311 of external programmer 104. In this example, in response to detecting that the signal has deviated from the homeostatic window, processing circuitry 210 of IMD 106 transmits, via telemetry module 208, data representing the measurement of the signal to external programmer 104. In one example, in response to detecting that the signal has exceeded an upper threshold of the homeostatic window, processing circuitry 210 of IMD 106 transmits, via telemetry module 208, data representing the measurement of the signal to external programmer 104. External programmer 104 may determine to adjust a parameter value to reduce the signal below the upper threshold as long as the parameter value remains within the one or more limits to the parameter.

[0096] In another example, processing circuitry 210, via telemetry module 208 and from external programmer 104, receives instructions to adjust one or more limits of the therapeutic window. For example, such instructions may be in response to patient feedback on the efficacy of the electrical stimulation therapy, or in response to one or more sensors that have detected a signal of the patient. Such signals from sensors may include bioelectrical signals, such as a signal within the Beta frequency band or signal within the Gamma frequency band of brain 120 of patient 112, or physiological parameters and measurements, such as a signal indicating one or more of a patient activity level, posture, and respiratory function. Further, such signals from sensors may indicate a lack of reduction of one or more symptoms of the patient 112, such as tremor or rigidity or the presence of side effects due to electrical stimulation therapy, such as paresthesia. In response to these instructions, processing circuitry 210 may adjust one or more thresholds of the homeostatic window. For example, processing circuitry 210 may adjust the magnitude of the upper threshold, the lower threshold, or shift the overall position of the homeostatic window such that the threshold, defined by the homeostatic window, for adjustment of the one or more parameters of electrical stimulation, is itself adjusted. Thereafter, processing circuitry 210, via electrodes 116 and 118, delivers the adjusted electrical stimulation to patient 112.

[0097] 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 some examples, programmer 104 may be referred to as a tablet computing 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 a processing circuitry 310, memory 311, user interface 302, telemetry module 308, and power source 320.Docket No.: A0013076W001Memory 311 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.

[0098] 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 module 308 of programmer 104. In various examples, programmer 104 may include one or more processors, 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 311, 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 module 308 are described as separate modules, in some examples, processing circuitry 310 and telemetry module 308 may be functionally integrated with one another. In some examples, processing circuitry 310 and telemetry module 308 correspond to individual hardware units, such as ASICs, DSPs, FPGAs, or other hardware units.

[0099] Memory 311 (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 311 may include instructions that cause processing circuitry 310 to obtain a parameter set from memory, select one or more parameters for electrical stimulation or adaptive stimulation according to sensed signals, or receive user input and send a corresponding command to IMD 104, or instructions for any other functionality. In addition, memory 311 may include a plurality of programs, where each program includes a parameter set that defines stimulation therapy. In some examples, memory 311 may store sensed physiological signals (or representative information) one or more metrics and / or instructions for determining the one or more metrics, determining the system stability score, and / or instructions for performing one or more actions based on the system stability score.Docket No.: A0013076W001

[0100] 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, automatically selected parameters, prompts for user input regarding stimulation parameters or adaptive stimulation parameters, patient behavior criteria, or any other such information. User interface 302 may also receive user input via user interface 302. The user input may be, for example, in the form of pressing a button on a keypad or selecting an icon from a touch screen. The user input may indicate that a patient event has occurred, and may, in some examples, indicate the type of patient event (e.g., a symptom occurred, a side effect occurred, or any other type of patient event). In some examples, processing circuitry 310 may time stamp this patient event to correlate with sensed signals later retrieved from IMD 106. In some examples, processing circuitry 310 may transmit the indication of the patient event to IMD 106 to associate the patient event and store sensed signals and / or immediately request the sensed signals from IMD 106 for association with the patient event and storage in memory 311 for further processing. User interface 302 may refer to hardware configured to present information to the user and / or receive input from the user. In some examples, processing circuitry 310 directly controls this hardware. In other examples, processing circuitry 310 may communicate with drive hardware that controls hardware of user interface 302. In some examples, user interface 302 may include display and / or interactive display configurations as described herein.

[0101] Telemetry module 308 may support wireless communication between IMD 106 and programmer 104 under the control of processing circuitry 310. Telemetry module 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 module 308 provides wireless communication via an RF or proximal inductive medium. In some examples, telemetry module 308 includes an antenna, which may take on a variety of forms, such as an internal or external antenna. In some examples, telemetry modules 308 may support communications with intermediate devices between programmer 104 and IMD 106 or other external devices.

[0102] 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, inductive telemetry,Docket No.: A0013076W001 or any 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. As described herein, telemetry module 308 may be configured to transmit a spatial electrode movement pattern or other stimulation parameter values to IMD 106 for delivery of stimulation therapy.

[0103] In some examples, processing circuitry 310 of external programmer 104 defines the parameters of a homeostatic therapeutic window, stored in memory 311, for delivering aDBS to patient 112. In one example, processor 311 of external programmer 104, via telemetry module 308, issues commands to IMD 106 causing IMD 106 to deliver electrical stimulation therapy via electrodes 116, 118 via leads 114. Programmer 104 may also determine the system stability score and / or one or more metrics used to calculate the system stability score.

[0104] The following examples illustrate various user interfaces and techniques for managing the sensing of physiological signals, such as brain signals, determining the metrics and / or system stability score, programming adaptive stimulation therapy, and managing electrical stimulation as described herein. Programmer 104, or another external computing device, may output the user interfaces and screens described herein. The example user interface screens may be separately presented or selectable in any order, or programmer 106 (for example) may present each screen in order as part of one or more automated programming processes to assist the user through the programming process for setting up or adjusting adaptive stimulation therapy. User input may be prompted at various times, either to select parameter values or to confirm automatically selected parameter values. In some examples, programmer 106 may perform each step automatically and present the user with fully automated and selected parameters at the end of the process. The user may confirm the parameter values or review one or more of the parameter values using each respective screen of the user interface as needed to customize the stimulation therapy, which may include adaptive stimulation therapy such as aDBS. In other examples, IMD 106 may perform some or all of the techniques described for determining the system stability score and / or metrics upon which the system stability score is based.

[0105] FIG. 4 is a block diagram illustrating an example system 1400 that includes an external device, such as a server 482, and one or more computing devices 484A-484N, that are coupled to IMD 106 and external programmer 104 shown in FIG. 1 via a network 486. In this example, IMD 106 may use its telemetry circuit 88 to communicate with external programmer 104 via a first wireless connection, and to communicate with an access point 488Docket No.: A0013076W001 via a second wireless connection. In some examples, system 400 may include additional devices. For example, system 400 may also include communication device 402 which may be an intermediary device that is configured to communicate with IMD 106 via one communication protocol and communicate with programmer 104 and / or network 486 with a different communication protocol. Communication device 402 may provide other functionality, such as recharging functionality for a rechargeable battery of IMD 106. Communication device 402 may be referred to as an “intermediate device” that can act to transfer data between IMD 106 and network 486 and other servers or computing devices.

[0106] System 400 may be a part of a digital health platform that can share information between devices and enable certain functionality, such as sharing information sensed or otherwise obtained by IMD 106 and / or programmer 104 to other remote computing devices in addition to transferring updated sensing and / or programming instructions from remote computing devices such as server 482 and / or computing devices 484A-484N back to programmer 104 and / or IMD 106. In some examples, the techniques described herein may be commanded to be performed remotely via system 400. For example, any of the devices of system 400, such as programmer 104, server 482, or computing device 484N, may be configured to perform at least some or all of the techniques described herein for determining the system stability score and / or related metrics.

[0107] In the example of FIG. 4, access point 488, external programmer 104, server 482, and computing devices 484A-484N are interconnected, and able to communicate with each other, through network 486. In some cases, one or more of access point 488, external programmer 104, server 482, and computing devices 484A-484N may be coupled to network 486 through one or more wireless connections. IMD 106, external programmer 104, server 482, and computing devices 484A-484N may each comprise one or more processors, such as one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), programmable logic circuitry, or the like, that may perform various functions and operations, such as those described in this disclosure.

[0108] Access point 488 may comprise a device, such as a home monitoring device, that connects to network 486 via any of a variety of connections, such as telephone dial-up, digital subscriber line (DSL), cable modem connections, fiber optic communications, etc. In other examples, access point 488 may be coupled to network 486 through different forms of connections, including wired or wireless connections.Docket No.: A0013076W001

[0109] During operation, IMD 106 may collect and store various forms of data. For example, IMD 106 may collect sensed electrical signals and / or event data during therapy delivery that indicate therapy efficacy and / or disease state of patient 12. In some cases, IMD 106 may directly analyze the collected data to evaluate the patient 12, such as identifying events and / or sensed data. In other cases, however, IMD 106 may send stored data relating to events and / or other sensed data to external programmer 104 and / or server 482, either wirelessly or via access point 488 and network 1486, for remote processing and analysis. For example, IMD 106 may transmit sensed information, such as event data, to computing device 484A, and computing device 484A can evaluate the sensed information and generated updated stimulation parameters, event data, or other information pertaining to the patient.

[0110] In some cases, server 482 may be configured to provide a secure storage site for archival of information that has been collected from IMD 106, external programmer 104, or any other devices of system 400. Network 486 may comprise a local area network, wide area network, or global network, such as the Internet. In some cases, external programmer 104 or server 482 may assemble sensed data, event data, or other therapy information in web pages or other documents for viewing by trained professionals, such as clinicians, via viewing terminals associated with computing devices 484A-484N. In this manner, system 400 functioning as a digital health platform may enable cloud-based functionality for any of the processes and / or user interactions described herein.[oni] For example, a user may be able to log into the digital health platform of system 400 via one or more devices such as any of computing devices 484A-484N. In one example, a user may log into the digital health platform using computing device 484A. The user may interact with a user interface that is displayed via an internet browser or specific application. In some examples, the user interface may present information of suggested parameter limits, suggested thresholds, system stability score or related metrics, or other recommended information for view and / or confirmation by a clinician. The user interface can receive the confirmation input, and then system 400 may then transmit the updated limits, thresholds, system stability score or related metrics, etc. back to programmer 104 and / or IMD 106 via network 486.

[0112] FIG. 5 is a flow chart of an example technique for determining a system stability score for a medical device. The example of FIG. 5 will be described with respect to programmer 104 and processing circuitry 310. However, some or all of these techniques may alternatively be performed by other devices or systems, such as IMD 106, server 482, orDocket No.: A0013076W001 another external device. In some examples, multiple devices may perform these techniques in a distributed manner toward completion.

[0113] As shown in the example of FIG. 5, processing circuitry 310 obtains one or more system characteristics related to functionality of a medical device (500). Example system characteristics may include one or more of a battery life estimate for a battery of the medical device, an impedance value of one or more electrodes coupled to the medical device, or a sensed signal quality value of one or more signals sensed by the medical device.

[0114] For the battery life estimate, for example, embedded software in the clinician programmer can be executed by processing circuitry 310 to estimate the battery longevity based on the programming setting in the “active group,” which may be the current group identifying values for different stimulation parameters defining stimulation delivery. Processing circuitry 310 can monitor the rate of change in battery life estimate and determine whether the battery level is sufficient for delivering sustainable therapy given the system’s active settings.

[0115] For measuring the impedance values, processing circuitry 310 may measure the impedance of each electrode coupled to IMD 106. This impedance may be representative of mechanical integrity of the electrode, connectors, and conductors, and also the electrodetissue interface which can change over time. This impedance measurement is typically done during clinic visits, but could be performed by IMD 106 outside of the clinic. While the clinician’s programmer can raise a flag when the measured impedance is out-of-range, processing circuitry 310 can track the longitudinal trend in sequential impedance measurements for the different electrodes or electrode combinations. Taking into account the parameters that can impact impedance measurement, such as whether the electrode was used for delivering the therapy, the elapsed time from the lead implant date, and / or the trend in the LFP signals, processing circuitry 310 can use a growth curve and a standard table stored in memory to determine the system integrity.

[0116] For signal quality measurements, processing circuitry 310 can perform a signal quality check can help detect for troublesome artifacts such as ECG in sensed electrical signals (in one example). If a sense channel has a known ECG artifact, this artifact can be informative to the clinician. The clinician and / or device can adjust the sense frequency to lessen the impact of ECG on the sensed signal. In some examples, intermittent artifacts often appear in sensed signals (real-time streaming of data and / or stored data) data prior to the impedance measurement indicating an issue. In this manner, the signal quality measurement is a characteristic that can indicate when these artifacts appear sooner than other issuesDocket No.: A0013076W001 become apparent and when a potential device problem may be occurring. In some examples, a significant difference in impedance values between sensing electrodes can also impact the sensing quality. Processing circuitry 310 may use this impedance mismatch between electrodes or electrode combinations as a characteristic that can also provide valuable insight on signal quality as part of the system metric.

[0117] Processing circuitry 310 can then determine, based on the one or more system characteristics (such as the characteristics identified above), a system metric indicative of integrity of the medical device (502). The system metric may be indicative of a longitudinal trend in one or more of the system characteristics, a magnitude of one or more of the system characteristics, a threshold exceeded by one or more of the system characteristics, a rate of change in one or more of the system characteristics, or any other indication of change. The system metric may be a single value, or may be represented as a multi-value function that can represent one or more of the system characteristics upon which it is determined.

[0118] Processing circuitry 310 can also obtain one or more therapy characteristics indicative of user requested changes to therapy delivered by the medical device (504). The user requested changes may be from a clinician (or other health care professional) or the patient. The therapy characteristics can include at least one of a total number of the user requested changes to the therapy over a period of time or a frequency of the user requested changes to the therapy. The number or frequency of changes may be compared to a threshold or some other indication of when the changes are no longer normal for efficacious therapy. For example, the threshold for the number of changes could be more than one change per day. Processing circuitry 310 could flag the change once the number exceeds this threshold. In some examples, the threshold may correspond to an absolute value, an average value for the patient, a weighted or rolling average for the patient (e.g., changes made further in time from the last clinic visit may be weighted greater than changes made right after a clinic visit), or other type of threshold. The threshold can be patient-specific or determined based on a population of patients, clinician selected, or some other information. In some examples, processing circuitry 310 may filter out, or otherwise remove, user requested changes from this metric determination if the user comes back to the previous value. This return to value could indicate that the user requested change was an accident or otherwise inadvisable as the previous therapy was actually stable. Processing circuitry 310 may establish a time window or other tracking characteristics to determine when the return to the previous value is due to a single instance of the user trying to identify the preferred value as opposed to whether the user requested change back to the previous value is a different instance in time indicative ofDocket No.: A0013076W001 therapy instability. In some examples, processing circuitry 310 may use a time window to cluster a number of related requested changes into a single user requested change for the purposes of counting the user requested change. For example, the user may press an increase amplitude button seven times to reach the desired amplitude, but this set of changes may only be counted as a single user requested change for the therapy metric.

[0119] These types of changes can be indicative of the user attempting to correct for ineffective therapy and / or perceived side effects. In some examples, the user requested changes can include at least one of a change to an amplitude at least partially defining electrical stimulation therapy, a change to a pulse width at least partially defining the electrical stimulation therapy, a change to one or more electrode combinations used to deliver the electrical stimulation therapy, a switch to a different program at least partially defining the electrical stimulation therapy, turning adaptive stimulation off (e.g., disabling closed-loop stimulation that automatically adjusts a stimulation parameter value based on a sensed signal), a change to a group of stimulation programs that define respective sets of stimulation parameter values, or a change to a sense parameter that defines sensing a physiological signal by the medical device. In this manner, the user requested change may be a change to a parameter that directly defines the stimulation therapy that is delivered, a parameter that defines how the system can automatically adjust a stimulation parameter value in response to a sensed signal (e.g., closed-loop stimulation), or otherwise defines some aspect of the instructions that define delivery of therapy. Although the changes may be user requested (e.g., by a clinician or patient) the characteristics may include automated changes to stimulation parameters. Processing circuitry 310 can then determine, based on the one or more therapy characteristics, a therapy metric indicative of therapy stability of the medical device (506). The therapy metric may be indicative of whether or not any of the changes to therapy have exceeded their respective thresholds, for example.

[0120] Processing circuitry 310 can also obtain one or more sensing characteristics representative of physiological signals sensed by the medical device (508). Example sensing characteristics include one or more of a baseline shift in the physiological signals, a longterm trend of the physiological signals, a variability of the physiological signals, or a pattern of the physiological signals. As discussed herein, the physiological signal may be any type of signal, but LFP signals are used in one example for illustrative purposes. The baseline shift could be the low level magnitude changing for the sensed signal over time. A long-term trend could be a change in the average, frequency, etc. of the signal over time. The variability of the signal could be different types of variabilities. In one example, theDocket No.: A0013076W001 variability could include an LFP coefficient of variation, which can refer to the ratio of the standard deviation to the mean. Processing circuitry 310 may compare the coefficient of variation to a threshold that separates stable from unstable signals, where greater coefficient of variation indicates less stability. One example, threshold may be 0.7, where any values above that threshold indicates unstable signals (i.e., the standard deviation of the sensed signals is too large in comparison to the average of the signals). In other examples, the variability could be an LFP spectral power variance from average, or any other variance in other components of the sensed signal. The pattern can be a type of quantification of fluctuation or repeating changes. Thes changes can refer to cyclic changes, which may be caused by a circadian rhythm, day and night cycle changes, or medication cycle changes. Other physiological signals that can be sensed and used for one or more sensing characteristics include one or more of an evoked resonance neural activity (ERNA) signal, ECAP, EEG, movement signal (e.g., from one or more accelerometers), heart rate, heart rate variability, voiding cycles, etc.

[0121] Processing circuitry 310 can determine, based on the one or more sensing characteristics, a sensing metric indicative of sensing stability of the medical device (510). The sensing metric may be a binary indicator of stability or instability, or may be a multistage or continuum of stability based one the one or more sensing characteristics monitored. Processing circuitry 310 can then determine, based on the system metric, the therapy metric, and the sensing metric, a system stability score (512). This system stability score may be based on all of the metrics that are monitored. In other examples, the system stability score may be determined based on a single metric, two metrics, or more than three metrics. In some examples, the system stability score may be based on any metrics that are available at that time and disregard metrics that are not available due to unavailable data or actions not taken (e.g., therapy not currently delivered). Processing circuitry 310 may control user interface 302 to display the system stability score (514). This may be an optional step. In some examples, the system stability score may be displayed even when stable to indicate to the user that IMD 106 is functioning properly. In some examples, the system stability score may only be shown when an action is needed by the user and / or the system is attempting to automatically correct the instability.

[0122] If no metric is unstable, or the system stability score is otherwise stable (“NO” branch of block 516), processing circuitry 310 can continue to obtain characteristics and determine respective metrics. If any metric is unstable, or the system stability score is otherwise unstable (“YES” branch of block 516), processing circuitry 310 can perform anDocket No.: A0013076W001 action selected to improve the system stability score (518). In some examples, processing circuitry 310 can perform an action that includes determining an adjustment to at least one of a value of a stimulation parameter defining the electrical stimulation therapy or a value of a parameter defining closed-loop adjustment of the value of the stimulation parameter. The stimulation parameter may be an amplitude, pulse width, frequency, electrode combination, ramp rate, cycling time, or any other parameter that defines the delivery of electrical stimulation. A parameter defining closed-loop stimulation may be a threshold or other function that sensed signals are compared against for automatic adjustment of a stimulation parameter. Processing circuitry 310 can then control stimulation circuitry to deliver the electrical stimulation therapy according to the adjustment to the one or more parameters. In other examples, processing circuitry 310 may adjust another type of therapy, such as adjust delivery of a medication (or transmit a request to a clinician to review medication dosage), delivery of magnetic field therapy, or the like. In some examples, the action may include transmitting the system stability metric to a clinician via a remote dashboard, control IMD 106 to perform an updated impedance check or other system checks such as checking battery health, recharging capability, lead connections, etc.

[0123] In some examples, an unstable system stability score may not actually be reflective of improper functioning of IMD 106 or other device. Instead, the instability may be reflective of a temporary action or condition of the patient that does not require corrective action. In other words, there may be situations in which processing circuitry 310 should not adjust or request adjustment of any aspects of sensing or therapy. For example, in response to the system stability score being unstable, processing circuitry 310 may perform an action that includes controlling a display device of programmer 104 or other device to prompt a user to confirm abnormal patient activity occurred. This abnormal patient activity could be different sleep activity, unrelated patient trauma, unusual device usage, or infrequency activity by the patent (e.g., the patient ran a marathon or otherwise stressed the body). Processing circuitry 310 can receive confirmation input confirming that the abnormal patient activity occurred and, responsive to receiving the confirmation input, set a flag to ignore the system stability score for a proceeding period of time. In this manner, processing circuitry 310 may ignore the system stability score for the period of time to allow the patient to return to normal activity. After the period of time, processing circuitry 310 may again return to processing the processing circuitry 310 as normal function. In some examples, processing circuitry 310 (or any device that determines the system stability metric) may triage actions based on the severity of the system stability score and / or what types of actions may be taken.Docket No.: A0013076W001For example, lower severity instability may cause processing circuitry 310 to flag and store the system stability metric for later transmission or review by a user. Alternatively, processing circuitry 310 may determine a higher severity system stability metric and responsively take more aggressive action such as requesting immediate clinician intervention and / or terminating closed-loop stimulation or stimulation therapy completely.

[0124] In some examples, some or all of the various metrics (or data collected upon which a metric is determined) may be transmitted by IMD 106 and / or programmer 104 according to a schedule or whenever data can be sent. Programmer 104 or another device can then send this information to a networked service (e.g., server 482) or a networked computer device 404N for continual monitoring and generation of the system stability metric. In this manner, external devices can offload some of the computational load from IMD 106 to extend battery life.

[0125] In the example of FIG. 5, the different characteristics and metrics are shown as being obtained and determined in a serial manner, such as one after the other. In other examples, the order of obtaining different characteristics and / or determining metrics may be different. In some examples, processing circuitry 310 may simultaneously be operating to collect different characteristics and update respective metrics as they are available. In this manner, processing circuitry 310 may be independently updating respective metrics, and then the system stability score, as information becomes available or at some determined schedule instead of in the linear manner shown in this one example.

[0126] FIG. 6 is a conceptual diagram of an example process for determining a system stability score based on several different types of metrics for a medical device. As shown in the example of FIG. 6, the function of system 600 may include different metrics that are used to inform the stability score, similar to the technique described in FIG. 5. System 600 may include system metric 602, therapy metric 606, and sensing metric 610. System metric 602 may refer to the system integrity, which may track longitudinal trend in device health and longevity measures. Example measures may be included in the system characteristics 604, and may include electrode impedance and battery status.

[0127] Therapy metric 606 may refer to the therapy stability and may include the characterization of long-term device interactions. These interactions may be included in the therapy characteristics 608, such as total number and frequency of changes in programming settings per time unit. Sensing metric 610 may refer to LFP volatility (and / or other types of signals) that can be derived based on sensing characteristics 612. Sensing metric 610 mayDocket No.: A0013076W001 represent the longitudinal evolution of LFP dispersion & dynamic under invariant settings, across different settings, and over different spans (e.g., days-nights, weeks, etc.).

[0128] System metric 602, therapy metric 606, and sensing metric 610 may together inform the overall system stability score 620 that indicates the overall stability. System stability score 620 may be binary for stable or unstable. Alternatively, system stability score 620 may represent different magnitudes associated with respective actions that can be taken.

[0129] The following examples are described herein.

[0130] Example 1. A system comprising: processing circuitry configured to: obtain one or more system characteristics related to functionality of a medical device; determine, based on the one or more system characteristics, a system metric indicative of integrity of the medical device; obtain one or more therapy characteristics indicative of user requested changes to therapy delivered by the medical device; determine, based on the one or more therapy characteristics, a therapy metric indicative of therapy stability of the medical device; obtain one or more sensing characteristics representative of physiological signals sensed by the medical device; determine, based on the one or more sensing characteristics, a sensing metric indicative of sensing stability of the medical device; determine, based on the system metric, the therapy metric, and the sensing metric, a system stability score; and responsive to determining that the system stability score indicates instability of the medical device, perform an action selected to improve the system stability score.

[0131] Example 2. The system of example 1, wherein the one or more system characteristics comprises at least one of: a battery life estimate for a battery of the medical device; an impedance value of one or more electrodes coupled to the medical device; or a sensed signal quality value of one or more signals sensed by the medical device.

[0132] Example 3. The system of any of examples 1 or 2, wherein the one or more therapy characteristics comprises at least one of: a total number of the user requested changes to the therapy over a period of time, or a frequency of the user requested changes to the therapy.

[0133] Example 4. The system of any of examples 1 through 3, wherein the user requested changes comprises at least one of: a change to an amplitude at least partially defining electrical stimulation therapy; a change to a pulse width at least partially defining the electrical stimulation therapy; a change to one or more electrode combinations used to deliver the electrical stimulation therapy; a switch to a different program at least partially defining the electrical stimulation therapy; turning adaptive stimulation off; a change to a group ofDocket No.: A0013076W001 stimulation programs that define respective sets of stimulation parameter values; or a change to a sense parameter that defines sensing a physiological signal by the medical device.

[0134] Example 5. The system of any of examples 1 through 4, wherein the one or more sensing characteristics comprise at least one of a baseline shift in the physiological signals; a long-term trend of the physiological signals; a variability of the physiological signals; or a pattern of the physiological signals.

[0135] Example 6. The system of any of examples 1 through 5, wherein the physiological signals comprise local field potential (LFP) signals.

[0136] Example 7. The system of any of examples 1 through 6, wherein the therapy comprises electrical stimulation therapy, and wherein the processing circuitry is configured to perform the action by at least: determine an adjustment to at least one of a value of a stimulation parameter defining the electrical stimulation therapy or a value of a parameter defining closed-loop adjustment of the value of the stimulation parameter; and control stimulation circuitry to deliver the electrical stimulation therapy according to the adjustment.

[0137] Example 8. The system of any of examples 1 through 7, wherein the processing circuitry is configured to: perform the action by at least controlling a display device of a programmer to prompt a user to confirm abnormal patient activity occurred; receive confirmation input confirming that the abnormal patient activity occurred; and responsive to receiving the confirmation input, set a flag to ignore the system stability score for a proceeding period of time.

[0138] Example 9. The system of any of examples 1 through 8, further comprising an external programmer comprising the processing circuitry.

[0139] Example 10. The system of any of examples 1 through 9, wherein the therapy comprises electrical stimulation therapy, and wherein the system further comprises the medical device comprising: the processing circuitry; and stimulation circuitry configured to deliver the electrical stimulation therapy.

[0140] Example 11. A method comprising: obtaining, by processing circuitry, one or more system characteristics related to functionality of a medical device; determining, by the processing circuity and based on the one or more system characteristics, a system metric indicative of integrity of the medical device; obtaining, by the processing circuitry, one or more therapy characteristics indicative of user requested changes to therapy delivered by the medical device; determining, by the processing circuity and based on the one or more therapy characteristics, a therapy metric indicative of therapy stability of the medical device; obtaining, by the processing circuitry, one or more sensing characteristics representative ofDocket No.: A0013076W001 physiological signals sensed by the medical device; determining, by the processing circuity and based on the one or more sensing characteristics, a sensing metric indicative of sensing stability of the medical device; determining, by the processing circuity and based on the system metric, the therapy metric, and the sensing metric, a system stability score; and responsive to determining that the system stability score indicates instability of the medical device, performing an action selected to improve the system stability score.

[0141] Example 12. The method of example 11, wherein the one or more system characteristics comprises at least one of: a battery life estimate for a battery of the medical device; an impedance value of one or more electrodes coupled to the medical device; or a sensed signal quality value of one or more signals sensed by the medical device.

[0142] Example 13. The method of any of examples 11 or 2, wherein the one or more therapy characteristics comprises at least one of: a total number of the user requested changes to the therapy over a period of time, or a frequency of the user requested changes to the therapy.

[0143] Example 14. The method of example 13, wherein the user requested changes comprises at least one of: a change to an amplitude at least partially defining electrical stimulation therapy; a change to a pulse width at least partially defining the electrical stimulation therapy; a change to one or more electrode combinations used to deliver the electrical stimulation therapy; a switch to a different program at least partially defining the electrical stimulation therapy; turning adaptive stimulation off; a change to a group of stimulation programs that define respective sets of stimulation parameter values; or a change to a sense parameter that defines sensing a physiological signal by the medical device.

[0144] Example 15. The method of any of examples 11 through 14, wherein the one or more sensing characteristics comprise at least one of: a baseline shift in the physiological signals; a long-term trend of the physiological signals; a variability of the physiological signals; or a pattern of the physiological signals.

[0145] Example 16. The method of any of examples 11 through 15, wherein the physiological signals comprise local field potential (LFP) signals.

[0146] Example 17. The method of any of examples 11 through 16, wherein the therapy comprises electrical stimulation therapy, and wherein performing the action comprises: determining an adjustment to at least one of a value of a stimulation parameter defining the electrical stimulation therapy or a value of a parameter defining closed-loop adjustment of the value of the stimulation parameter; and controlling stimulation circuitry to deliver the electrical stimulation therapy according to the adjustment.Docket No.: A0013076W001

[0147] Example 18. The method of any of examples 11 through 17, wherein performing the action comprises controlling a display device of a programmer to prompt a user to confirm abnormal patient activity occurred, and wherein the method further comprises: receiving confirmation input confirming that the abnormal patient activity occurred; and responsive to receiving the confirmation input, setting a flag to ignore the system stability score for a proceeding period of time.

[0148] Example 19. The method of any of examples 11 through 18, wherein performing the action comprises at least one of: displaying the system stability score on a user interface of an external device or delivering, by stimulation circuitry of the medical device and based on the system stability score, the therapy as electrical stimulation therapy to a patient.

[0149] Example 20. A non-transitory computer-readable medium comprising instructions that, when executed, control processing circuitry to: obtain one or more system characteristics related to functionality of a medical device; determine, based on the one or more system characteristics, a system metric indicative of integrity of the medical device; obtain one or more therapy characteristics indicative of user requested changes to therapy delivered by the medical device; determine, based on the one or more therapy characteristics, a therapy metric indicative of therapy stability of the medical device; obtain one or more sensing characteristics representative of physiological signals sensed by the medical device; determine, based on the one or more sensing characteristics, a sensing metric indicative of sensing stability of the medical device; determine, based on the system metric, the therapy metric, and the sensing metric, a system stability score; and responsive to determining that the system stability score indicates instability of the medical device, perform an action selected to improve the system stability score.

[0150] Furthermore, although the disclosure is described with respect to DBS therapy, such techniques may be applicable to IMDs that convey other therapies in which sensed data and event data information is important, such as, e.g., spinal cord stimulation (SCS), pelvic floor stimulation, gastric stimulation, occipital stimulation, functional electrical stimulation, and the like. Also, in some aspects, techniques for evaluating posture state information, as described in this disclosure, may be applied to IMDs that provide other therapy (e.g., drug pumps) or IMDs that are generally dedicated to sensing or monitoring and do not include stimulation or other therapy components.

[0151] The techniques described in this disclosure, including those attributed to IMD 106, programmer 104, or various constituent components, may be implemented, at least in part, in hardware, software, firmware or any combination thereof. For example, variousDocket No.: A0013076W001 aspects of the techniques may be implemented within one or more processors, including one or more microprocessors, DSPs, ASICs, FPGAs, or any other equivalent integrated or discrete logic circuitry, as well as any combinations of such components, embodied in programmers, such as clinician or patient programmers, medical devices, or other devices.

[0152] In one or more examples, the functions described in this disclosure may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored, as one or more instructions or code, on a computer- readable medium and executed by a hardware-based processing unit. Computer-readable media may include computer-readable storage media forming a tangible, non-transitory medium. Instructions may be executed by one or more processors, such as one or more DSPs, ASICs, FPGAs, general purpose microprocessors, or other equivalent integrated or discrete logic circuitry. Accordingly, the term “processor,” as used herein may refer to one or more of any of the foregoing structures or any other structure suitable for implementation of the techniques described herein.

[0153] In addition, in some respects, the functionality described herein may be provided within dedicated hardware and / or software modules. 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. Also, the techniques may be fully implemented in one or more circuits or logic elements. The techniques of this disclosure may be implemented in a wide variety of devices or apparatuses, including an IMD, an external programmer, a combination of an IMD and external programmer, an integrated circuit (IC) or a set of ICs, and / or discrete electrical circuitry, residing in an IMD and / or external programmer.

[0154] Various examples have been described. These and other examples are within the scope of the following claims.

Claims

Docket No.: A0013076W001WHAT IS CLAIMED IS:

1. A system comprising: processing circuitry configured to: obtain one or more system characteristics related to functionality of a medical device; determine, based on the one or more system characteristics, a system metric indicative of integrity of the medical device; obtain one or more therapy characteristics indicative of user requested changes to therapy delivered by the medical device; determine, based on the one or more therapy characteristics, a therapy metric indicative of therapy stability of the medical device; obtain one or more sensing characteristics representative of physiological signals sensed by the medical device; determine, based on the one or more sensing characteristics, a sensing metric indicative of sensing stability of the medical device; determine, based on the system metric, the therapy metric, and the sensing metric, a system stability score; and responsive to determining that the system stability score indicates instability of the medical device, perform an action selected to improve the system stability score.

2. The system of claim 1, wherein the one or more system characteristics comprises at least one of: a battery life estimate for a battery of the medical device; an impedance value of one or more electrodes coupled to the medical device; or a sensed signal quality value of one or more signals sensed by the medical device.

3. The system of any of claims 1 or 2, wherein the one or more therapy characteristics comprises at least one of: a total number of the user requested changes to the therapy over a period of time, or a frequency of the user requested changes to the therapy.

4. The system of any of claims 1 through 3, wherein the user requested changes comprises at least one of:Docket No.: A0013076W001 a change to an amplitude at least partially defining electrical stimulation therapy; a change to a pulse width at least partially defining the electrical stimulation therapy; a change to one or more electrode combinations used to deliver the electrical stimulation therapy; a switch to a different program at least partially defining the electrical stimulation therapy; turning adaptive stimulation off; a change to a group of stimulation programs that define respective sets of stimulation parameter values; or a change to a sense parameter that defines sensing a physiological signal by the medical device.

5. The system of any of claims 1 through 4, wherein the one or more sensing characteristics comprise at least one of a baseline shift in the physiological signals; a long-term trend of the physiological signals; a variability of the physiological signals; or a pattern of the physiological signals.

6. The system of any of claims 1 through 5, wherein the physiological signals comprise local field potential (LFP) signals.

7. The system of any of claims 1 through 6, wherein the therapy comprises electrical stimulation therapy, and wherein the processing circuitry is configured to perform the action by at least: determine an adjustment to at least one of a value of a stimulation parameter defining the electrical stimulation therapy or a value of a parameter defining closed-loop adjustment of the value of the stimulation parameter; and control stimulation circuitry to deliver the electrical stimulation therapy according to the adjustment.

8. The system of any of claims 1 through 7, wherein the processing circuitry is configured to:Docket No.: A0013076W001 perform the action by at least controlling a display device of a programmer to prompt a user to confirm abnormal patient activity occurred; receive confirmation input confirming that the abnormal patient activity occurred; and responsive to receiving the confirmation input, set a flag to ignore the system stability score for a proceeding period of time.

9. The system of any of claims 1 through 8, further comprising an external programmer comprising the processing circuitry.

10. The system of any of claims 1 through 9, wherein the therapy comprises electrical stimulation therapy.

11. The system of claim 10, further comprising the medical device.

12. The system of claim 11, wherein the medical device is an implantable medical device.

13. The system of any of claims 11 or 12, wherein the medical device comprises: the processing circuitry; and stimulation circuitry configured to deliver the electrical stimulation therapy.

14. A non-transitory computer-readable medium comprising instructions that, when executed, control the processing circuitry to perform the function of any of claims 1 through

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