Patent Description:
This disclosure generally relates to electrical stimulation and recording.

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). Document <CIT> relates to electrical stimulation devices.

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.

In general, the disclosure describes devices, systems, and techniques for dynamic neural sensing by an implantable medical device (IMD). Sensed electrical signals can serve as control signals for electrical stimulation therapies. Some electrical stimulation patterns (e.g., largely continuous tonic stimulation) may allow for relatively straightforward ways to embed sensing periods. As electrical stimulation concepts and forms become more complex (e.g., in terms of varying parameters and attributes), the ability to sense electrical signals becomes more challenging due to the increased number of interactions between stimulation parameters and sensing parameters, as well as the fact that the interactions may not be static over time.

In accordance with one or more techniques of this disclosure, as opposed to using a static sensing pattern, an IMD may use a dynamic sensing pattern. For instance, the IMD may dynamically determine when to perform sensing and/or dynamically determine which electrodes to utilize for the sensing. As one example, the IMD may determine which electrodes of a plurality of electrodes to utilize for sensing at a particular time based on which of the plurality of electrodes are to be used to deliver stimulation at the particular time (e.g., the IMD may select sensing electrodes that "sandwich" a stimulation electrode). The IMD may determine whether to perform sensing during delivery of stimulation (e.g., sense in parallel with stimulation delivery), to perform sensing when stimulation is not being delivered, or to perform sensing both during delivery of stimulation and when stimulation is not being delivered. The IMD may "tag" or otherwise mark which sense data was measured during stimulation delivery and which was not.

The IMD may perform closed-loop stimulation based on results of the sensing. The IMD may utilize either all of the sensing data or a sub-set of the sensing data. As one example, the IMD may not perform closed-loop stimulation based on sensing data measured while stimulation is being delivered. For instance, the IMD may blank inputs to the closed-loop algorithm during stimulation delivery. As another example, the IMD may perform closed-loop stimulation based on both sensing data measured while stimulation is being delivered.

Although this disclosure is directed to DBS therapy, the systems, devices, and techniques described herein may similarly detect movement of leads and electrodes implanted outside of the brain, such as near other nerves or muscles for different diagnostic or therapeutic applications, such as spinal cord stimulation (SCS), pelvic stimulation, gastric stimulation, or peripheral nerve field stimulation (PNFS). Moreover, a human patient is described for example purposes herein, but similar systems, devices, and techniques may be used for other animals in other examples.

<FIG> is a conceptual diagram illustrating an example system <NUM> that includes an implantable medical device (IMD) <NUM> configured to deliver DBS to patient <NUM> according to an example of the techniques of the disclosure. As shown in the example of <FIG>, example system <NUM> includes medical device programmer <NUM>, implantable medical device (IMD) <NUM>, lead extension <NUM>, and leads 114A and 114B with respective sets of electrodes <NUM>, <NUM>. In the example shown in <FIG>, electrodes <NUM>, <NUM> of leads 114A, 114B are positioned to deliver electrical stimulation to a tissue site within brain <NUM>, such as a deep brain site under the dura mater of brain <NUM> of patient <NUM>. In some examples, delivery of stimulation to one or more regions of brain <NUM>, such as the subthalamic nucleus, globus pallidus or thalamus, may be an effective treatment to manage movement disorders, such as Parkinson's disease. Some or all of electrodes <NUM>, <NUM> also may be positioned to sense neurological brain signals within brain <NUM> of patient <NUM>. In some examples, some of electrodes <NUM>, <NUM> may be configured to sense neurological brain signals and others of electrodes <NUM>, <NUM> may be configured to deliver adaptive electrical stimulation to brain <NUM>. In other examples, all of electrodes <NUM>, <NUM> are configured to both sense neurological brain signals and deliver adaptive electrical stimulation to brain <NUM>.

IMD <NUM> 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 <NUM>) that includes a stimulation generator configured to generate and deliver electrical stimulation therapy to patient <NUM> via a subset of electrodes <NUM>, <NUM> of leads 114A and 114B, respectively. The subset of electrodes <NUM>, <NUM> that are used to deliver electrical stimulation to patient <NUM>, and, in some cases, the polarity of the subset of electrodes <NUM>, <NUM>, 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 <NUM> and target tissue site (e.g., selected based on the patient condition). The group of electrodes <NUM>, <NUM> includes at least one electrode and can include a plurality of electrodes. In some examples, the plurality of electrodes <NUM> and/or <NUM> may have a complex electrode geometry such that two or more electrodes of the lead are located at different positions around the perimeter of the respective lead (e.g., different positions around a longitudinal axis of the lead).

In some examples, the neurological signals (e.g., an example type of electrical signals) sensed within brain <NUM> may reflect changes in electrical current produced by the sum of electrical potential differences across brain tissue. Examples of neurological brain signals include, but are not limited to, electrical signals generated from local field potentials (LFP) sensed within one or more regions of brain <NUM>, 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 <NUM> of patient <NUM>.

In some examples, the neurological brain signals that are used to select a stimulation electrode combination may be sensed within the same region of brain <NUM> as the target tissue site for the electrical stimulation. As previously indicated, these tissue sites may include tissue sites within anatomical structures such as the thalamus, subthalamic nucleus or globus pallidus of brain <NUM>, as well as other target tissue sites. The specific target tissue sites and/or regions within brain <NUM> may be selected based on the patient condition. Thus, due to these differences in target locations, in some examples, the electrodes used for delivering electrical stimulation may be different than the electrodes used for sensing neurological brain signals. In other examples, the same electrodes may be used to deliver electrical stimulation and sense brain signals. However, this configuration would require the system to switch between stimulation generation and sensing circuitry and may reduce the time the system can sense brain signals.

Electrical stimulation generated by IMD <NUM> may be configured to manage a variety of disorders and conditions. In some examples, the stimulation generator of IMD <NUM> is configured to generate and deliver electrical stimulation pulses to patient <NUM> via electrodes of a selected stimulation electrode combination. However, in other examples, the stimulation generator of IMD <NUM> 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 <NUM> 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 <NUM> 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 combination for delivering stimulation to patient <NUM>, pulse frequency, pulse width, and a current or voltage amplitude of the pulses. As previously indicated, the electrode combination may indicate the specific electrodes <NUM>, <NUM> that are selected to deliver stimulation signals to tissue of patient <NUM> and the respective polarities of the selected electrodes. IMD <NUM> may deliver electrical stimulation intended to contribute to a therapeutic effect. In some examples, IMD <NUM> may also, or alternatively, deliver electrical stimulation intended to be sensed by other electrode and/or elicit a physiological response, such as an evoked compound action potential (ECAP), that can be sensed by electrodes.

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

As shown in <FIG>, implanted lead extension <NUM> is coupled to IMD <NUM> via connector <NUM> (also referred to as a connector block or a header of IMD <NUM>). In the example of <FIG>, lead extension <NUM> traverses from the implant site of IMD <NUM> and along the neck of patient <NUM> to cranium <NUM> of patient <NUM> to access brain <NUM>. In the example shown in <FIG>, leads 114A and 114B (collectively "leads <NUM>") are implanted within the right and left hemispheres, respectively, of patient <NUM> in order deliver electrical stimulation to one or more regions of brain <NUM>, which may be selected based on the patient condition or disorder controlled by therapy system <NUM>. 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 <NUM> and IMD <NUM> implant sites are contemplated. For example, IMD <NUM> may be implanted on or within cranium <NUM>, in some examples. Or leads <NUM> may be implanted within the same hemisphere or IMD <NUM> may be coupled to a single lead implanted in a single hemisphere. Although leads <NUM> may have ring electrodes at different longitudinal positions as shown in <FIG>, leads <NUM> may have electrodes disposed at different positions around the perimeter of the lead (e.g., different circumferential positions for a cylindrical shaped lead) as shown in the examples of <FIG>.

Leads <NUM> illustrate an example lead set that include axial leads carrying ring electrodes disposed at different axial positions (or longitudinal positions). In other examples, leads may be referred to as "paddle" leads carrying planar arrays of electrodes on one side of the lead structure. In addition, as described herein, complex lead array geometries may be used in which electrodes are disposed at different respective longitudinal positions and different positions around the perimeter of the lead.

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

In the example shown in <FIG>, electrodes <NUM>, <NUM> of leads <NUM> are shown as ring electrodes. Ring electrodes may be used in DBS applications because ring electrodes are relatively simple to program and are capable of delivering an electrical field to any tissue adjacent to electrodes <NUM>, <NUM>. In other examples, electrodes <NUM>, <NUM> may have different configurations. For example, in some examples, at least some of the electrodes <NUM>, <NUM> of leads <NUM> 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 <NUM>, rather than one ring electrode, such as shown in <FIG>. In this manner, electrical stimulation may be directed in a specific direction from leads <NUM> to enhance therapy efficacy and reduce possible adverse side effects from stimulating a large volume of tissue. In some examples, a housing of IMD <NUM> may include one or more stimulation and/or sensing electrodes. In alternative examples, leads <NUM> may have shapes other than elongated cylinders as shown in <FIG>. For example, leads <NUM> may be paddle leads, spherical leads, bendable leads, or any other type of shape effective in treating patient <NUM> and/or minimizing invasiveness of leads <NUM>.

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

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

When programmer <NUM> is configured for use by the clinician, programmer <NUM> may be used to transmit initial programming information to IMD <NUM>. This initial information may include hardware information, such as the type of leads <NUM> and the electrode arrangement, the position of leads <NUM> within brain <NUM>, the configuration of electrode array <NUM>, <NUM>, initial programs defining therapy parameter values, and any other information the clinician desires to program into IMD <NUM>. Programmer <NUM> may also be capable of completing functional tests (e.g., measuring the impedance of electrodes <NUM>, <NUM> of leads <NUM>). In some examples, programmer <NUM> may receive sensed signals or representative information and perform the same techniques and functions attributed to IMD <NUM> herein. In other examples, a remote server (e.g., a standalone server or part of a cloud service) may perform the functions attributed to IMD <NUM>, programmer <NUM>, or any other devices described herein.

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

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

Programmer <NUM> may also provide an indication to patient <NUM> when therapy is being delivered, when patient input has triggered a change in therapy or when the power source within programmer <NUM> or IMD <NUM> needs to be replaced or recharged. For example, programmer <NUM> may include an alert LED, may flash a message to patient <NUM> 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.

Therapy system <NUM> may be implemented to provide chronic stimulation therapy to patient <NUM> over the course of several months or years. However, system <NUM> may also be employed on a trial basis to evaluate therapy before committing to full implantation. If implemented temporarily, some components of system <NUM> may not be implanted within patient <NUM>. For example, patient <NUM> may be fitted with an external medical device, such as a trial stimulator, rather than IMD <NUM>. 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 <NUM> provides effective treatment to patient <NUM>, the clinician may implant a chronic stimulator within patient <NUM> for relatively long-term treatment.

Although IMD <NUM> is described as delivering electrical stimulation therapy to brain <NUM>, IMD <NUM> may be configured to direct electrical stimulation to other anatomical regions of patient <NUM> in other examples. In other examples, system <NUM> may include an implantable drug pump in addition to, or in place of, IMD <NUM>. Further, an IMD may provide other electrical stimulation such as spinal cord stimulation to treat a movement disorder.

As discussed above, IMD <NUM> may sense neurological signals (e.g., electrical signals) of patient <NUM>. For instance, circuitry of IMD <NUM> may sense a differential voltage level across two electrodes of leads <NUM>. IMD <NUM> may utilize the sensed electrical signals as control signals for electrical stimulation therapies. Some electrical stimulation patterns (e.g., largely continuous tonic stimulation) may allow for relatively straightforward ways to embed sensing periods. As electrical stimulation concepts and forms become more complex (e.g., in terms of varying parameters and attributes), the ability to sense electrical signals becomes more challenging due to the increased number of interactions between stimulation parameters and sensing parameters, as well as the fact that the interactions may not be static over time.

In accordance with one or more techniques of this disclosure, as opposed to using a static sensing pattern, IMD <NUM> may use a dynamic sensing pattern. For instance, IMD <NUM> may dynamically determine when to perform sensing and/or dynamically determine which electrodes to utilize for the sensing. As one example, IMD <NUM> may determine which electrodes of electrodes <NUM>, <NUM> to utilize for sensing at a particular time based on which of electrodes of electrodes <NUM>, <NUM> are to be used to deliver stimulation at the particular time (e.g., IMD <NUM> may select sensing electrodes that "sandwich" a stimulation electrode). IMD <NUM> may determine whether to perform sensing during delivery of stimulation (e.g., sense in parallel with stimulation delivery), to perform sensing when stimulation is not being delivered, or to perform sensing both during delivery of stimulation and when stimulation is not being delivered.

Utilizing a dynamic sensing pattern may present one or more advantages. As one example, by having IMD <NUM> dynamically determine when to perform sensing and/or dynamically determine which electrodes to utilize for the sensing, IMD <NUM> may be able to maintain sensing capabilities (e.g., regardless of simulation complexity). As another example, by having IMD <NUM> dynamically determine when to perform sensing and/or dynamically determine which electrodes to utilize for the sensing, the programming burden may be reduced (e.g., as sensing windows and/or electrodes may not have to be explicitly programmed).

The architecture of system <NUM> illustrated in <FIG> is shown as an example. The techniques as set forth in this disclosure may be implemented in the example system <NUM> of <FIG>, 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>.

<FIG> is a block diagram of the example IMD <NUM> of <FIG> for delivering DBS therapy. In the example shown in <FIG>, IMD <NUM> includes processor <NUM>, memory <NUM>, stimulation generator <NUM>, sensing module <NUM>, switch module <NUM>, telemetry module <NUM>, sensor <NUM>, and power source <NUM>. Each of these modules may be or include electrical circuitry configured to perform the functions attributed to each respective module. For example, processor <NUM> may include processing circuitry, switch module <NUM> may include switch circuitry, sensing module <NUM> may include sensing circuitry, and telemetry module <NUM> may include telemetry circuitry. Switch module <NUM> may not be necessary for multiple current source and sink configurations. Memory <NUM> 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 <NUM> may store computer-readable instructions that, when executed by processor <NUM>, cause IMD <NUM> to perform various functions. Memory <NUM> may be a storage device or other non-transitory medium.

In the example shown in <FIG>, memory <NUM> stores therapy programs <NUM> that include respective stimulation parameter sets that define therapy. Each stored therapy program <NUM> 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 non-overlapping (e.g., time-interleaved) basis. Memory <NUM> may also include dynamic sensing instructions <NUM> that define the process by which processor <NUM> dynamically determines when to perform sensing and/or dynamically determines which electrodes to utilize for the sensing.

Stimulation generator <NUM>, under the control of processor <NUM>, generates stimulation signals for delivery to patient <NUM> via selected combinations of electrodes <NUM>, <NUM>. An example range of electrical stimulation parameters believed to be effective in DBS to manage a movement disorder of patient include:.

Accordingly, in some examples, stimulation generator <NUM> generates electrical stimulation signals in accordance with the electrical stimulation parameters noted above. Other ranges of therapy parameter values may also be useful, and may depend on the target stimulation site within patient <NUM>. While stimulation pulses are described, stimulation signals may be of any form, such as continuous-time signals (e.g., sine waves) or the like. Stimulation signals configured to elicit ECAPs or other evoked physiological signals may be similar or different from the above parameter value ranges.

Processor <NUM> 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 processor <NUM> herein may be embodied as firmware, hardware, software or any combination thereof. Processor <NUM> may control stimulation generator <NUM> according to therapy programs <NUM> stored in memory <NUM> 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.

In the example shown in <FIG>, the set of electrodes <NUM> includes electrodes 116A, 116B, 116C, and 116D, and the set of electrodes <NUM> includes electrodes 118A, 118B, 118C, and 118D. Processor <NUM> also controls switch module <NUM> to apply the stimulation signals generated by stimulation generator <NUM> to selected combinations of electrodes <NUM>, <NUM>. In particular, switch module <NUM> may couple stimulation signals to selected conductors within leads <NUM>, which, in turn, deliver the stimulation signals across selected electrodes <NUM>, <NUM>. Switch module <NUM> may be a switch array, switch matrix, multiplexer, or any other type of switching module configured to selectively couple stimulation energy to selected electrodes <NUM>, <NUM> and to selectively sense neurological brain signals with selected electrodes <NUM>, <NUM>. Hence, stimulation generator <NUM> is coupled to electrodes <NUM>, <NUM> via switch module <NUM> and conductors within leads <NUM>. In some examples, however, IMD <NUM> does not include switch module <NUM>.

Stimulation generator <NUM> may be a single channel or multi-channel stimulation generator. In particular, stimulation generator <NUM> 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 multiple electrode combinations. In some examples, however, stimulation generator <NUM> and switch module <NUM> may be configured to deliver multiple channels on a time-interleaved basis. For example, switch module <NUM> may serve to time divide the output of stimulation generator <NUM> across different electrode combinations at different times to deliver multiple programs or channels of stimulation energy to patient <NUM>. Alternatively, stimulation generator <NUM> 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 <NUM> may not require the functionality of switch module <NUM> for time-interleaved multiplexing of stimulation via different electrodes.

Electrodes <NUM>, <NUM> on respective leads <NUM> may be constructed of a variety of different designs. For example, one or both of leads <NUM> 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 <NUM> 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 <NUM>. These and other constructions may be used to create a lead with a complex electrode geometry.

Although sensing module <NUM> is incorporated into a common housing with stimulation generator <NUM> and processor <NUM> in <FIG>, in other examples, sensing module <NUM> may be in a separate housing from IMD <NUM> and may communicate with processor <NUM> via wired or wireless communication techniques. Example neurological brain signals include, but are not limited to, a signal generated from local field potentials (LFPs) within one or more regions of brain <NUM>. EEG and ECoG signals are examples of local field potentials that may be measured within brain <NUM>. However, local field potentials may include a broader genus of electrical signals within brain <NUM> of patient <NUM>. Instead of, or in addition to, LFPs, IMD <NUM> may be configured to detect patterns of single-unit activity and/or multi-unit activity. IMD <NUM> may sample this activity at rates above <NUM>,<NUM>, and in some examples within a frequency range of <NUM>,<NUM> to <NUM>,<NUM>. IMD <NUM> may identify the wave-shape of single units and/or an envelope of unit modulation that may be features used to differentiate or rank electrodes. In some examples, this technique may include phase-amplitude coupling to the envelope or to specific frequency bands in the LFPs sensed from the same or different electrodes.

Sensor <NUM> may include one or more sensing elements that sense values of a respective patient parameter. For example, sensor <NUM> may include one or more accelerometers, optical sensors, chemical sensors, temperature sensors, pressure sensors, or any other types of sensors. Sensor <NUM> may output patient parameter values that may be used as feedback to control delivery of therapy. IMD <NUM> may include additional sensors within the housing of IMD <NUM> and/or coupled via one of leads <NUM> or other leads. In addition, IMD <NUM> may receive sensor signals wirelessly from remote sensors via telemetry module <NUM>, 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).

Telemetry module <NUM> supports wireless communication between IMD <NUM> and an external programmer <NUM> or another computing device under the control of processor <NUM>. Processor <NUM> of IMD <NUM> may receive, as updates to programs, values for various stimulation parameters such as magnitude and electrode combination, from programmer <NUM> via telemetry module <NUM>. The updates to the therapy programs may be stored within therapy programs <NUM> portion of memory <NUM>. In addition, processor <NUM> may control telemetry module <NUM> to transmit alerts or other information to programmer <NUM> that indicate a lead moved with respect to tissue. Telemetry module <NUM> in IMD <NUM>, as well as telemetry modules in other devices and systems described herein, such as programmer <NUM>, may accomplish communication by radiofrequency (RF) communication techniques. In addition, telemetry module <NUM> may communicate with external medical device programmer <NUM> via proximal inductive interaction of IMD <NUM> with programmer <NUM>. Accordingly, telemetry module <NUM> may send information to external programmer <NUM> on a continuous basis, at periodic intervals, or upon request from IMD <NUM> or programmer <NUM>.

Power source <NUM> delivers operating power to various components of IMD <NUM>. Power source <NUM> 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 <NUM>. In some examples, power requirements may be small enough to allow IMD <NUM> 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.

According to the techniques of the disclosure, processor <NUM> of IMD <NUM> delivers, via electrodes <NUM>, <NUM> interposed along leads <NUM> (and optionally switch module <NUM>), electrical stimulation therapy to patient <NUM>. The DBS therapy is defined by one or more therapy programs <NUM> having one or more parameters stored within memory <NUM>. For example, the one or more parameters include a current amplitude (for a current-controlled system) or a voltage amplitude (for a voltage-controlled system), a pulse rate or frequency, and a pulse width, or quantity of pulses per cycle. In examples where the electrical stimulation is delivered according to a "burst" of pulses, or a series of electrical pulses defined by an "on-time" and an "off-time," the one or more parameters may further define one or more of a number of pulses per burst, an on-time, and an off-time.

As noted above, sensing module <NUM> may sense electrical signals via switch module <NUM> and electrodes of leads <NUM>. However, in some circumstances, delivery of electrical stimulation (e.g., by stimulation generator <NUM> via switch module and electrodes of leads <NUM>) may introduce artifacts, referred to as stimulation artifacts, in the sensed electrical signals. In particular, stimulation artifacts may be instructed by new simulation patterns and/or complex parameter swaps. In general, it may be desirable for IMD <NUM> to mitigate the impact of stimulation artifacts.

In addition to the desire to mitigate stimulation artifacts, other aspects may complicate the sensing of electrical signals. As one example, timing constraints (e.g., continuous firmware management of stimulation, and/or data acquisition and transmission) may complicate the sensing of electrical signals. As another example, hardware constraints (e.g., amplifier timing, signal processing latency, and/or telemetry latency) may complicate the sensing of electrical signals.

Memory <NUM> may also include dynamic sensing instructions <NUM> that define the process by which processor <NUM> dynamically determines when to perform sensing and/or dynamically determines which electrodes to utilize for the sensing. Processor <NUM> may cause sensing module <NUM> to perform sensing at the determined times and/or using the determined electrodes. By dynamically sensing in this way, IMD <NUM> may enable neurophysiological data to be collected more reliably and with more optimal fidelity even during delivery of complex stimulation patterns.

Dynamic sensing instructions <NUM> may perform the dynamic sensing in accordance with various parameters. Some example parameters follow.

As a first example parameter, if IMD <NUM> is delivering stimulation via a particular electrode (e.g., an electrode at position B of lead 114A), dynamic sensing instructions <NUM> may cause processor <NUM> to determine to sense electrical signals via electrodes that are symmetrically distributed across the particular electrode (e.g., an electrode at position A of lead 114A and an electrode at position C of lead 114A). In some examples, dynamic sensing instructions <NUM> may include instructions that cause processor <NUM> to wait a specified period of time after commencement of stimulation delivery until commencing to sense electrical signals (and/or mark electrical signals measured prior to an end of the specified period as non-viable and mark electrical signals measured after the end of the specified period as viable).

As a second example parameter, if IMD <NUM> is cycling delivery of stimulation, dynamic sensing instructions <NUM> may cause processor <NUM> to perform sensing during off-cycling periods (e.g., sense windows during which IMD <NUM> does not deliver electrical stimulation). In some examples, dynamic sensing instructions <NUM> may include instructions that cause processor <NUM> to wait a specified period of time after commencement of the sense window (e.g., a specified period after cessation of delivery of electrical stimulation) until commencing to sense electrical signals (and/or mark electrical signals measured prior to an end of the specified period as non-viable and mark electrical signals measured after the end of the specified period as viable). The period of time is dynamic. Dynamic sensing instructions <NUM> dynamically adjust the period of time based on a stimulation amplitude they adjust a delay of a sense window based on a determined amplitude. Longer periods of time may follow higher amplitudes and vice versa. In this way, dynamic sensing instructions <NUM> may reduce an amount of unreliable (e.g., invalid) sensing data acquired.

As a third example parameter, dynamic sensing instructions <NUM> may cause processor <NUM> to mark electrical signals sensed via a particular electrode as non-viable if stimulation was actively being delivered via the particular electrode while the electrical signals were sensed. In other words, sensed data (e.g., representing electrical signals) may be marked as non-valid if IMD <NUM> is actively delivering stimulation on sensing contacts.

As a fourth example parameter, dynamic sensing instructions <NUM> may cause processor <NUM> to embed markers/tags/labels/etc. into sensed data to indicate various events and/or to indicate when each stimulation pulse occurred. Example events include on/off, parameter switching, etc..

Dynamic sensing instructions <NUM> may implement any combination of the aforementioned parameters, as well as various other parameters.

<FIG> is a block diagram of the external programmer <NUM> of <FIG> for controlling delivery of DBS therapy according to an example of the techniques of the disclosure. Although programmer <NUM> may generally be described as a hand-held device, programmer <NUM> may be a larger portable device or a more stationary device. In some examples, programmer <NUM> may be referred to as a tablet computing device. In addition, in other examples, programmer <NUM> may be included as part of a bed-side monitor, an external charging device or include the functionality of an external charging device. As illustrated in <FIG>, programmer <NUM> may include a processor <NUM>, memory <NUM>, user interface <NUM>, telemetry module <NUM>, and power source <NUM>. Memory <NUM> may store instructions that, when executed by processor <NUM>, cause processor <NUM> and external programmer <NUM> to provide the functionality ascribed to external programmer <NUM> 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, processor <NUM> may include processing circuitry configured to perform the processes discussed with respect to processor <NUM>.

In general, programmer <NUM> comprises any suitable arrangement of hardware, alone or in combination with software and/or firmware, to perform the techniques attributed to programmer <NUM>, and processor <NUM>, user interface <NUM>, and telemetry module <NUM> of programmer <NUM>. In various examples, programmer <NUM> 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 <NUM> also, in various examples, may include a memory <NUM>, 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 processor <NUM> and telemetry module <NUM> are described as separate modules, in some examples, processor <NUM> and telemetry module <NUM> may be functionally integrated with one another. In some examples, processor <NUM> and telemetry module <NUM> correspond to individual hardware units, such as ASICs, DSPs, FPGAs, or other hardware units.

Memory <NUM> (e.g., a storage device) may store instructions that, when executed by processor <NUM>, cause processor <NUM> and programmer <NUM> to provide the functionality ascribed to programmer <NUM> throughout this disclosure. For example, memory <NUM> may include instructions that cause processor <NUM> to obtain a parameter set from memory, select a spatial electrode movement pattern, provide an interface that recommends or otherwise facilitates parameter value selection, or receive a user input and send a corresponding command to IMD <NUM>, or instructions for any other functionality. In addition, memory <NUM> may include a plurality of programs, where each program includes a parameter set that defines stimulation therapy.

User interface <NUM> 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 <NUM> may be configured to display any information related to the delivery of stimulation therapy, identified patient behaviors, sensed patient parameter values, patient behavior criteria, or any other such information. User interface <NUM> may also receive user input via user interface <NUM>. The input may be, for example, in the form of pressing a button on a keypad or selecting an icon from a touch screen.

Telemetry module <NUM> may support wireless communication between IMD <NUM> and programmer <NUM> under the control of processor <NUM>. Telemetry module <NUM> 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 <NUM> provides wireless communication via an RF or proximal inductive medium. In some examples, telemetry module <NUM> includes an antenna, which may take on a variety of forms, such as an internal or external antenna. In some examples, IMD <NUM> and/or programmer <NUM> may communicate with remote servers via one or more cloud-services in order to deliver and/or receive information between a clinic and/or programmer.

Examples of local wireless communication techniques that may be employed to facilitate communication between programmer <NUM> and IMD <NUM> include RF communication according to the <NUM> or Bluetooth specification sets or other standard or proprietary telemetry protocols. In this manner, other external devices may be capable of communicating with programmer <NUM> without needing to establish a secure wireless connection. As described herein, telemetry module <NUM> may be configured to transmit a spatial electrode movement pattern or other stimulation parameter values to IMD <NUM> for delivery of stimulation therapy.

According to the techniques of the disclosure, in some examples, processor <NUM> of external programmer <NUM> defines the parameters of a homeostatic therapeutic window, stored in memory <NUM>, for delivering DBS to patient <NUM>. In one example, processor <NUM> of external programmer <NUM>, via telemetry module <NUM>, issues commands to IMD <NUM> causing IMD <NUM> to deliver electrical stimulation therapy via electrodes <NUM>, <NUM> via leads <NUM>. As noted above and in accordance with one or more techniques of this disclosure, external programmer <NUM> may issue commands to IMD <NUM> that cause IMD <NUM> to dynamically determine when to perform sensing and/or dynamically determine which electrodes to utilize for the sensing.

<FIG> are conceptual diagrams of example leads <NUM> and <NUM>, respectively, with respective electrodes carried by the lead. As shown in <FIG>, leads <NUM> and <NUM> are examples of leads <NUM> shown in <FIG>. As shown in <FIG>, lead <NUM> includes four electrode levels <NUM> (includes levels 404A-404D) mounted at various lengths of lead housing <NUM>. Lead <NUM> is inserted into through cranium <NUM> to a target position within brain <NUM>.

Lead <NUM> is implanted within brain <NUM> at a location determined by the clinician to be near an anatomical region to be stimulated. Electrode levels 404A, 404B, 404C, and 404D are equally spaced along the axial length of lead housing <NUM> at different axial positions. Each electrode level <NUM> may have one, two, three, or more electrodes located at different angular positions around the circumference (e.g., around the perimeter) of lead housing <NUM>. As shown in <FIG>, electrode level 404A and 404D include a single respective ring electrode, and electrode levels 404B and 404C each include three electrodes at different circumferential positions. This electrode pattern may be referred to as a <NUM>-<NUM>-<NUM>-<NUM> lead in reference to the number of electrodes from the proximal end to the distal end of lead <NUM>. Electrodes of one circumferential location may be lined up on an axis parallel to the longitudinal axis of lead <NUM>. Alternatively, electrodes of different electrode levels may be staggered around the circumference of lead housing <NUM>. In addition, lead <NUM> or <NUM> may include asymmetrical electrode locations around the circumference, or perimeter, of each lead or electrodes of the same level that have different sizes. These electrodes may include semi-circular electrodes that may or may not be circumferentially aligned between electrode levels.

Lead housing <NUM> may include a radiopaque stripe (not shown) along the outside of the lead housing. The radiopaque stripe corresponds to a certain circumferential location that allows lead <NUM> to the imaged when implanted in patient <NUM>. Using the images of patient <NUM>, the clinician can use the radiopaque stripe as a marker for the exact orientation of lead <NUM> within the brain of patient <NUM>. Orientation of lead <NUM> may be needed to easily program the stimulation parameters by generating the correct electrode configuration to match the stimulation field defined by the clinician. In other examples, a marking mechanism other than a radiopaque stripe may be used to identify the orientation of lead <NUM>. These marking mechanisms may include something similar to a tab, detent, or other structure on the outside of lead housing <NUM>. In some examples, the clinician may note the position of markings along a lead wire during implantation to determine the orientation of lead <NUM> within patient <NUM>. In some examples, programmer <NUM> may update the orientation of lead <NUM> in visualizations based on the movement of lead <NUM> from sensed signals.

<FIG> illustrates lead <NUM> that includes multiple electrodes at different respective circumferential positions at each of levels 414A-414D. Similar to lead <NUM>, lead <NUM> is inserted through a burr hole in cranium <NUM> to a target location within brain <NUM>. Lead <NUM> includes lead housing <NUM>. Four electrode levels <NUM> (414A-414D) are located at the distal end of lead <NUM>. Each electrode level <NUM> is evenly spaced from the adjacent electrode level and includes two or more electrodes. In one example, each electrode level <NUM> includes three, four, or more electrodes distributed around the circumference of lead housing <NUM>. Each electrode may be substantially rectangular in shape. Alternatively, the individual electrodes may have alternative shapes, e.g., circular, oval, triangular, rounded rectangles, or the like.

In some examples, electrode levels <NUM> or <NUM> are not evenly spaced along the longitudinal axis of the respective leads <NUM> and <NUM>. For example, electrode levels 404C and 404D may be spaced approximately <NUM> millimeters (mm) apart while electrodes 404A and 404B are <NUM> apart. Variable spaced electrode levels may be useful in reaching target anatomical regions deep within brain <NUM> while avoiding potentially undesirable anatomical regions. Further, the electrodes in adjacent levels need not be aligned in the direction as the longitudinal axis of the lead, and instead may be oriented diagonally with respect to the longitudinal axis.

Leads <NUM> and <NUM> are substantially rigid to prevent the implanted lead from varying from the expected lead shape. Leads <NUM> or <NUM> may be substantially cylindrical in shape. In other examples, leads <NUM> or <NUM> may be shaped differently than a cylinder. For example, the leads may include one or more curves to reach target anatomical regions of brain <NUM>. In some examples, leads <NUM> or <NUM> may be similar to a flat paddle lead or a conformable lead shaped for patient <NUM>. Also, in other examples, leads <NUM> and <NUM> may any of a variety of different polygonal cross sections (e.g., triangle, square, rectangle, octagonal, etc.) taken transverse to the longitudinal axis of the lead.

As shown in the example of lead <NUM>, the plurality of electrodes of lead <NUM> includes a first set of three electrodes disposed at different respective positions around the longitudinal axis of the lead and at a first longitudinal position along the lead (e.g., electrode level 404B), a second set of three electrodes disposed at a second longitudinal position along the lead different than the first longitudinal position (e.g., electrode level 404C), and at least one ring electrode disposed at a third longitudinal position along the lead different than the first longitudinal position and the second longitudinal position (e.g., electrode level 404A and/or electrode level 404D). In some examples, electrode level 404D may be a bullet tip or cone shaped electrode that covers the distal end of lead <NUM>.

<FIG> is a graph illustrating an example of an electrical signal sensed contemporaneously with delivery of electrical stimulation, in accordance with one or more techniques of this disclosure. As discussed above, IMD <NUM> may dynamically select electrodes to use for sensing of electrical signals. For instance, responsive to determining to deliver electrical stimulation via an electrode EB (e.g., corresponding to an electrode at position B of an electrode of electrodes <NUM>), IMD <NUM> may determine to perform sensing via a pair of electrodes of the plurality of electrodes that are symmetrically distributed across the determined electrode (e.g., electrodes EA and EC). Plot <NUM> may include data representing electrical signals sensed across electrodes EA and EC, and plot <NUM> may include data representing pulses delivered via electrode EB and a case electrode (e.g., monopolar stimulation). In this way, IMD <NUM> may stream sensed electrical signals via one channel of LFP while stimulation is active.

As also discussed above, in some examples, IMD <NUM> may mark some data as viable and may mark some data as non-viable. For instance, IMD <NUM> may wait a specified period of time after adjustment of stimulation delivery until commencing to sense electrical signals (and/or mark electrical signals measured prior to an end of the specified period as non-viable and mark electrical signals measured after the end of the specified period as viable). In the example of <FIG>, IMD <NUM> may adjust stimulation delivery at time T<NUM> (e.g., reduce a pulse frequency), mark data representing electrical signals sensed between T<NUM> and T<NUM> as non-viable, and mark data representing electrical signals sensed between T<NUM> and T<NUM> as viable. The time between T<NUM> and T<NUM> may be the specified period. As shown in <FIG>, IMD <NUM> may again adjust stimulation delivery at time T<NUM> (e.g., increase a pulse frequency), mark data representing electrical signals sensed between T<NUM> and T<NUM> as non-viable, and mark data representing electrical signals sensed between T<NUM> and T<NUM> as viable. The time between T<NUM> and T<NUM> may be the specified period.

<FIG> is a timing diagram illustrating an example combination of stimulation and sensing, in accordance with one or more techniques of this disclosure. In the example of <FIG>, IMD <NUM> may operate under a paradigm of cycles (e.g., frames). Cycles may be sensing cycles, stimulation cycles, or hybrid sensing/simulation cycles. As shown in <FIG>, IMD <NUM> may perform three stimulation cycles followed by two sensing cycles.

In each of the example stimulation cycles, IMD <NUM> may stimulate via one or more electrodes. For instance, as shown in <FIG>, in each of the stimulation cycles, IMD <NUM> may stimulate, successively, via a first electrode (i), a second electrode (ii), and a third electrode (iii).

IMD <NUM> may accomplish stimulation via the first electrode (i) by delivering monopolar stimulation between an electrode EB and a case electrode of IMD <NUM>. IMD <NUM> may accomplish stimulation via the second electrode (ii) by delivering monopolar stimulation between an electrode EC and a case electrode of IMD <NUM>. IMD <NUM> may accomplish stimulation via the third electrode (iii) by delivering monopolar stimulation between an electrode ED and a case electrode of IMD <NUM>.

In each of the example sensing cycles, IMD <NUM> may sense electrical signals via one or more electrodes. For instance, as shown in <FIG>, in each of the sensing cycles, IMD <NUM> may stimulate, concurrently, via a first pair of electrodes (A), a second pair of electrodes (B), and a third pair of electrodes (C).

IMD <NUM> may accomplish sensing via the first pair of electrodes (A) by sensing electrical signals (e.g., voltage across) between electrode EA and EC. IMD <NUM> may accomplish sensing via the second pair of electrodes (B) by sensing electrical signals (e.g., voltage across) between electrode EB and ED. IMD <NUM> may accomplish sensing via the third pair of electrodes (B) by sensing electrical signals (e.g., voltage across) between electrode EC and EE.

Hybrid sensing/stimulation cycles may have various attributes. As one example, hybrid cycles may be particularly compatible with static electrode patterns. As another example, when sensing during a hybrid cycle, IMD <NUM> may stream data from one bipolar pair per lead with stimulation on. As another example, data sensed during hybrid cycles may be confounded by frequency shifts in stimulation patterns (e.g., artifacts).

Sensing cycles may have various attributes. As one example, sensing cycles may be particularly compatible with electrode switching patterns. As another example, when sensing during a sensing cycle, IMD <NUM> may stream data from multiple (e.g., <NUM>) bipolar pairs per lead with stimulation off. As another example, sensing cycles can be scheduled/interleaved with stimulation cycles or hybrid cycles within a pattern. As another example, sensing cycles can be performed after stimulation has been manually paused (e.g., as discussed with reference to <FIG>).

<FIG> is a timing diagram illustrating an example combination of stimulation and sensing, in accordance with one or more techniques of this disclosure. In the example of <FIG>, IMD <NUM> may operate under a paradigm of cycles (e.g., frames). Cycles may be sensing cycles, stimulation cycles, or hybrid sensing/simulation cycles. As shown in <FIG>, IMD <NUM> may perform three hybrid sensing/stimulation cycles followed by two sensing cycles. The electrode definitions of <FIG> may be the same as those discussed above for <FIG>.

As can be seen in <FIG>, during the hybrid sensing/stimulation cycles, IMD <NUM> may dynamically adjust which electrodes as being used for sensing based on the electrode being used to deliver stimulation. For instance, when IMD <NUM> is delivering stimulation via first electrode (i), IMD <NUM> may perform sensing via first pair of electrodes (A) (e.g., sense electrical signals via electrodes symmetrically displaced about the current stimulation electrode). Then, when IMD <NUM> switches from delivering stimulation via the first electrode (i) to delivering stimulation via second electrode (ii), IMD <NUM> may switch to sense electrical signals via second pair of electrodes (B).

<FIG> are timing diagrams illustrating example of user-controlled toggling between cycles, in accordance with one or more techniques of this disclosure. As shown in <FIG>, IMD <NUM> may receive user input that causes IMD <NUM> to switch from a hybrid sensing/stimulation cycle to a sensing cycle. As shown in <FIG>, IMD <NUM> may receive user input that causes IMD <NUM> to switch from alternating stimulation and sensing cycles to a sensing cycle. IMD <NUM> may receive the user input using any suitable means. As one example, IMD <NUM> may receive the user input via a button, such as a button on external programmer <NUM>.

<FIG> is a flowchart illustrating an example technique for dynamic sensing of electrical signals, in accordance with one or more techniques of this disclosure. For purposes of explanation, the technique of <FIG> is described as being performed by IMD <NUM>. However, the technique of <FIG> may be performed other devices.

IMD <NUM> may determine an electrode of a plurality of electrodes of a lead to be used to deliver electrical stimulation to a patient at a particular time (<NUM>). For instance, IMD <NUM> may determine to deliver electrical stimulation via electrode EB and a case electrode of IMD <NUM>.

IMD <NUM> may select, based on the determined electrode, a set of electrodes of the plurality of electrodes (<NUM>). For instance, IMD <NUM> may select, as the set of electrodes, a pair of electrodes of the plurality of electrodes that are symmetrically distributed across the determined electrode. In particular, where the determined electrode is electrode EB, IMD <NUM> may select electrodes EA and EC as the set of electrodes.

IMD <NUM> may sense, via the selected set of electrodes, electrical signals of the patient at the particular time (<NUM>). For instance, at the particular time, IMD <NUM> may deliver monopolar electrical stimulation via the electrode and a case electrode of the IMD while also sensing electrical signals of the patient via the selected set of electrodes. As discussed above with reference to <FIG>, IMD <NUM> may deliver electrical stimulation via electrode EB and a case electrode of IMD <NUM> and sense via electrodes EA and EC.

As discussed above, in some examples, IMD <NUM> may also sense via the set of electrodes during a sense window that does not include the particular time. The sense window may be formed of one or more sense cycles/frames.

IMD <NUM> may tag the sense electrical signals. As one example, IMD <NUM> may tag data representing electrical signals sensed during stimulation cycles (e.g., data sensed during hybrid cycles) as being sensed during delivery of stimulation. As another example, IMD <NUM> may tag data representing electrical signals sensed during sensing cycles as being sensed during the sense window.

IMD <NUM> may perform one or more actions based on the sensed electrical signals. For instance, IMD <NUM> may adjust, based on the sensed electrical signals, delivery of electrical stimulation to the patient. In this way, IMD <NUM> may perform closed-loop stimulation.

The following examples may illustrate one or more examples of our disclosure:.

There may be certain changes in patient or disease state that result in a change of sensing modality being employed by the system. These patient state changes could be driven by biochemical, electrophysical, activity, and postural, or other changes. In these cases, the optimization of neural sensing parameters for a given current sensing modality may not yield the ideal device behavior or patient treatment (i.e., a different biomarker that is acquired via a different sensing modality may provide better insight into the patient state, how to adapt therapy, etc.). Therefore, in addition to or in place of the optimization of any given specific sensing modality, a higher-level sensing modality optimization / priority scheme could be employed to further enhance the device's ability to acquire the most relevant biomarker at any given time.

For example, various aspects of the described techniques may be implemented within one or more processors, such as fixed function processing circuitry and/or programmable processing circuitry, including one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or any other equivalent integrated or discrete logic circuitry, as well as any combinations of such components.

The techniques described in this disclosure may also be embodied or encoded in a computer-readable medium, such as a computer-readable storage medium, containing instructions. Instructions embedded or encoded in a computer-readable storage medium may cause a programmable processor, or other processor, to perform the method, e.g., when the instructions are executed. Computer readable storage media may include random access memory (RAM), read only memory (ROM), programmable read only memory (PROM), erasable programmable read only memory (EPROM), electronically erasable programmable read only memory (EEPROM), flash memory, a hard disk, a CD-ROM, a floppy disk, a cassette, magnetic media, optical media, or other computer readable media.

Claim 1:
A system comprising:
a memory (<NUM>); and
processing circuitry configured to:
determine, an electrode of a plurality of electrodes of a lead to be used to deliver electrical stimulation to a patient at a particular time;
determine an amplitude of the electrical stimulation;
select, based on the determined electrode, a set of electrodes of the plurality of electrodes; and
sense, via the selected set of electrodes, first electrical signals of the patient at the particular time,
wherein the processing circuity is further configured to:
sense, via the selected set of electrodes, second electrical signals during a sense window that does not include the particular time: and
adjust a delay of the sense window based on the determined amplitude of the electrical stimulation.