METHODS FOR PROVIDING OPTIMIZED NEUROSTIMULATION
Disclosed herein are methods for neurostimulation therapy for spinal cord injury. More particularly, the present invention relates to methods for neurostimulation therapy for spinal cord injury. More particularly, the present invention relates to methods for providing multiple independent, simultaneous waveforms in neurostimulation therapy while minimizing or substantially eliminating undesirable interactions between the waveforms.
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This application is a divisional of prior application Ser. No. 15/752,280, filed Feb. 13, 2018, which was the National Stage of International Application No. PCT/US2016/047535, filed Aug. 18, 2016, which claims the benefit of U.S. Provisional Patent Application No. 62/206,937, filed 19 Aug. 2015, all of which are incorporated herein by reference.
FIELD OF THE INVENTIONEmbodiments of the present invention relate to methods for neurostimulation therapy for spinal cord injury. More particularly, embodiments of the present invention relate to methods for providing multiple independent, simultaneous waveforms in neurostimulation therapy while minimizing or substantially eliminating undesirable interactions between the waveforms.
BACKGROUNDSerious spinal cord injuries (SCI) result in partial (incomplete) or substantially complete loss of sensory motor function below the level of the spinal lesion. For individuals with incomplete loss of motor function, substantial recovery of standing and stepping recovery has been demonstrated with task specific physical rehabilitation training. Recently, task specific physical rehabilitation training has been combined with epidural stimulation (ES) of the spinal cord in patients with incomplete and complete motor paralysis. High density epidural stimulating electrode arrays can provide spatially selective stimulation to regions of the spinal cord to facilitate or cause muscle movement.
SCI and other conditions may benefit from the delivery of stimulus intended to enable or excite multiple neurological responses using an implantable neurostimulator. A targeted neurological function, such as blood pressure, may respond to a particular electrical stimulus or waveform at a specific location, amplitude, frequency, pulse width or a combination thereof. Other functions, such as muscle flexon, may require a different waveform to produce the desired response. For situations where multiple neurological functions need to be stimulated at the same time, the different stimulus signals may interfere and prevent the desired responses or even cause an undesired and potentially dangerous overstimulated condition.
The circuit shown in
The common approach in the industry for managing interaction between waveforms is to not allow overlap of stimulus pulses between electrode pairs or sets. One product, the Precision Spectra™ stimulator offered by Boston Scientific, allows for independent variation of the frequency and pulse width for up to four simultaneous waveforms. The product, as understood by the inventors, manages interactions between waveforms by detecting waveform overlap, defined as pulses within 3 milliseconds (ms) of each other, and if detected, automatically delaying one the pulses by 3 ms. This approach has several shortcomings, including (1) no user understanding of the effect this pulse delay has on the frequency change of the waveform—the more overlapping pulses are delayed, the greater the effect on the frequency change of the waveform—or even which waveform was affected, (2) no user control or feedback, as the waveform management is performed autonomously by hardware, (3) no pre-processing of the phase relationship between waveforms to minimize the number of overlap occurrences, (4) no option to select the length of the delay or select which of the overlapping pulses receives the delay, (5) no option to “blank” or refrain from emitting the overlapping pulse at a particular instant in time, (6) no ability to prioritize which of the overlapping waveforms will be blanked or phase shifted, (7) no ability to change the recharge width of the pulse, (8) no ability to change the shorting width of the pulse, and (9) no ability to accommodate global shorting windows. The assembly and delivery of sophisticated stimulation patterns while minimizing undesirable interactions between waveforms remains a challenge.
SUMMARYDisclosed herein are methods for minimizing undesirable interactions between waveforms, particularly in neurostimulation therapy for spinal cord injury. Methods include modifying characteristics of independent, simultaneous waveforms with overlapping pulses, and hardware-based solutions for minimizing or substantially eliminating interactions between pulses.
It will be appreciated that the various apparatus and methods described in this summary section, as well as elsewhere in this application, can be expressed as a large number of different combinations and subcombinations. All such useful, novel, and inventive combinations and subcombinations are contemplated herein, it being recognized that the explicit expression of each of these combinations is unnecessary.
A better understanding of the present invention will be had upon reference to the following description in conjunction with the accompanying drawings.
For the purposes of promoting an understanding of the principles of the invention, reference will now be made to selected embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended; any alterations and further modifications of the described or illustrated embodiments, and any further applications of the principles of the invention as illustrated herein are contemplated as would normally occur to one skilled in the art to which the invention relates. At least one embodiment of the invention is shown in great detail, although it will be apparent to those skilled in the relevant art that some features or some combinations of features may not be shown for the sake of clarity.
Any reference to “invention” within this document herein is a reference to an embodiment of a family of inventions, with no single embodiment including features that are necessarily included in all embodiments, unless otherwise stated. Further, although there may be references to “advantages” provided by some embodiments of the present invention, it is understood that other embodiments may not include those same advantages, or may include different advantages. Any advantages described herein are not to be construed as limiting to any of the claims.
Specific quantities (spatial dimensions, angles, dimensionless parameters, etc.) may be used explicitly or implicitly herein, such specific quantities are presented as examples and are approximate values unless otherwise indicated. Discussions pertaining to specific compositions of matter are presented as examples and do not limit the applicability of other compositions of matter, especially other compositions of matter with similar properties, unless otherwise indicated.
The present invention comprises methods for minimizing undesirable interactions between waveforms, particularly in nerve stimulation therapy for spinal cord injury. In nerve stimulation therapy, an electrode array comprising a plurality of electrodes disposed on a flexible biocompatible material is provided. Preferably, the electrodes comprise one or more biocompatible metals or alloys, as known in the art. Sets of electrodes within the array generate waveforms, the electrode array being configured to generate at least two simultaneous waveforms, each waveform having a frequency, a pulse width, a phase and at least one pulse.
The electrode array and resulting waveforms may be optimized to reduce overlapping pulses between waveforms by software or hardware-based solutions. In some embodiments, waveforms are optimized by at least one of altering the phase of the waveform, altering the frequency of the waveform, altering the pulse width of the waveform, delaying a pulse of the waveform and blanking a pulse of the waveform.
The first method of waveform optimization is phase optimization. This method uses a computed delay to find the optimal position of waveforms relative to each other for the purpose of avoiding as many overlapping pulses as possible. Waveforms are assigned a priority and their phase is adjusted to optimize the higher priority waveform first. Referring to
The steps in this method can be summarized as follows: (1) count the number of collisions between two waveforms, W1 and W2, over a period of time T; (2) delay the lower priority waveform, in this case W2, an increment and recount collisions in period T; (3) repeat steps 1 and 2 until the increment reaches the period of the highest frequency waveform being compared; (4) adopt the delay (also referred to as “phase shift”) that results in the lowest number of collisions; and (5) blank specific pulses from the W2 (the lower priority waveform) to remove the collision in order to produce a corrected W2. In the event that an additional waveform is used, steps 1-5 are repeated such that the additional waveform is compared to W1 and corrected W2, a phase shift is adopted for the additional waveform that minimizes collisions with higher priority waveforms, and overlapping pulses are blanked to produce a corrected additional waveform. The steps may be repeated as needed for further simultaneous waveforms.
A second method of waveform optimization is an alternating frequency approach. In this method, the frequency of a lower priority waveform is varied to avoid overlapping with the higher priority waveform. In some embodiments, the lower priority waveform varies between two predetermined frequencies to avoid collisions with a higher priority waveform. Combining two frequencies on one waveform allows an interval to form so that no blanking or delayed reset is required. This two frequency approach eliminates a missing pulse and hence small gaps with no active stimulus.
Referring now to
The third method for managing waveforms is a charge balance time optimization approach. A typical neurostimulation pulse includes a wait period (X), charge pulse (1), inter-pulse delay (0.05), a recharge pulse (4), and a shorting period (4). The numbers correspond to the relative length of that portion of the pulse, with the length of the wait period being variable. The duration of the pulse and subsequent delay, recharge pulse and shorting period are determined by neurological needs and the need to balance charge on the electrode. In some cases it is possible to shorten pulses or parts of pulses to help eliminate overlap conditions between waveforms. In particular, the charge balance portion of the pulse (i.e., the recharge pulse and shorting period) may be reduced. For example, the recharge pulse (also referred to as the recharge period) could be reduced from (4) to (3) and the shorting period from (4) to (2) resulting in an approximate 33% reduction in duration for the active portion of the pulse. Brief periods of charge balance time optimization may be used to allow spacing between pulses from different waveforms and reduce the need to blank a pulse.
The percentage of overlap of two colliding pulses is an indicator as to the effectiveness of using charge balance time optimization as a solution. Referring now to
A fourth method of managing waveform interactions is by blanking a lower priority waveform. In this method, upon detection, calculation or prediction of an overlap of pulses between a higher priority waveform and a lower priority waveform, the pulse of the lower priority waveform is blanked. However, blanking a pulse can result in a small signal void that may be undesirable. Another option to blanking an overlapping pulse is to add a pulse to delay the waveform so it can be reset to restart the waveform in its initial position. This is similar to the two frequency approach described in the second method. However, in this case, the frequency that is produced by the corrected delay occurs for one period and is calculated on a collision by collision basis.
In some embodiments the priority of waveforms may be changeable. In the examples depicted in
Pulse collisions are typically avoided to isolate patient stimuli and maintain a balanced charge on neurostimulator electrodes. However, a purposeful pulse collision may be used to determine details about the equivalent circuit of the array or study the impact of field shapes on neuro responses. For this reason it may be desirable to generate collisions under controlled conditions.
The first four methods of optimization disclosed herein may be implemented in software controlling an implanted neurostimulator. In some embodiments, a technical user interface (TUI), such as a general purpose computer, or a patient user interface (PUI), such as a portable dedicated computing device, a smartphone or other portable computing device, run software communicatively coupled to the implanted neurostimulator and capable of adjusting the characteristics of waveforms generated by the neurostimulator. In some embodiments, the clinicians initially use the TUI in a clinical setting to evaluate the SCI patients to identify the set of waveforms necessary to generate responses from the patient, such as standing, leg flexion, leg extension, blood pressure control, bladder control, etc. Overlapping pulses often occur when generating multiple simultaneous pulses that have different frequencies that are not harmonically related to each other, as shown in
The optimum set of waveforms and their characteristics (e.g., frequency, amplitude, phase, delay, and pulse width) are unique to each patient. The clinician uses the TUI to identify waveforms needed by a patient to elicit a desired response, such as waveforms stimulating leg muscles to elicit a walking motion, in conjunction with waveforms maintaining the patient's blood pressure at a safe level. The clinician determines the priority of the various wave forms based on the patient's physiological needs. For example, waveforms maintaining blood pressure are more critical to the patient's health than waveforms eliciting a walking motion so blood pressure-related waveforms will be designated as higher priority than walking-related waveforms. These waveforms are then optimized using one or more of the methods described above. Once these optimized waveforms are determined, they can be transferred from the TUI to the PUI for the patient to activate at the patient's discretion. In preferred embodiments, the patient uses the PUI to select what motor responses, such as standing or walking, or physiological responses, such as blood pressure control, that he or she wishes to enact, and the PUI instructs the patient's implanted neurostimulator to enact the predetermined waveforms to enact such responses in the patient. In a preferred embodiment, PUI is configured such that the patient can only run waveforms optimized by the TUI, and the patient cannot create or modify waveforms or combinations thereof.
Using the TUI to manage the overlapping pulse waveforms provides clinicians with control over how the overlapping waveforms are modified to reduce or eliminate the problem. In some embodiments, the TUI runs software is designed to display waveforms and show what percentage of overlap exists and where the overlap occurs in time, as shown in
Referring now to
In some embodiments, the process depicted in
Embodiments of the present invention relate to hardware-dependent methods of managing waveform interactions. In a fifth method for optimization, independent and isolated power supplies are used to correct the overlapping pulse issue. Referring now to
Examples of this fifth method for optimization are shown in
A sixth method of managing waveform interactions includes the use of anodes or cathodes at a fixed potential to provide shielding of the electric field between independent and simultaneous waveforms. Using common ground electrodes physically positioned between stimulation electrodes to shield and separate the stimulation electrodes can effectively compare to managing waveform interactions by using isolated power supplies. It can minimize the interference of two overlapping pulses from two different stimulation electrodes. Test results show that the effectiveness of such shield can compare to the results of using electrodes with two isolated power supplies.
Referring now to
Various aspects of different embodiments of the present invention are expressed in paragraphs X1, X2, and X3 as follows:
X1. One aspect of the present invention pertains to a method for providing optimized neurostimulation, including providing an electrode array configured to generate at least two simultaneous waveforms, each waveform including a frequency, a charge balance time, a phase and at least one pulse; optimizing at least one of the at least two simultaneous waveforms to reduce pulse collisions by at least one of altering the phase of the waveform, altering the frequency of the waveform, optimizing the charge balance time of the waveform, delaying a pulse of the waveform, and blanking a pulse of the waveform; and activating the electrode array to generate the at least two simultaneous waveforms.
X2. Another aspect of the present invention pertains to a method for providing optimized neurostimulation, including providing an electrode array comprising a plurality of electrodes, wherein the plurality of electrodes are divided into at least two groups of electrodes, and wherein the electrode array is configured to generate at least two simultaneous waveforms; providing a power source for each group of electrodes, each power source being electrically isolated and physically separate from each other power source; and activating the electrode array to generate the at least two simultaneous waveforms.
X3. A further aspect of the present invention pertains to a method for providing optimized neurostimulation, including providing an electrode array comprising a plurality of electrodes; grouping the plurality of electrodes into a first group including at least one electrode configured to generate a first waveform, a second group including at least one electrode configured to generate a second waveform, and a third group including at least one electrode with a fixed potential, wherein the third group is located between the first group and the second group; and activating the electrode array to generate at least one of the first waveform and the second waveform.
Yet other embodiments pertain to any of the previous statements X1, X2, or X3 which are combined with one or more of the following other aspects.
The method further comprising identifying one of the at least two simultaneous waveforms as a high priority waveform, and wherein the optimizing is applied to a waveform other than the high priority waveform.
Wherein said optimizing includes at least two of altering the phase of the waveform, altering the frequency of the waveform, optimizing the charge balance time of the waveform, delaying a pulse of the waveform, and blanking a pulse of the waveform.
Wherein optimizing the charge balance time of the waveform includes at least one of increasing a recharge period, decreasing a recharge period, increasing a shorting period, and decreasing a shorting period.
Wherein optimizing the charge balance time of the waveform includes at least one of decreasing a recharge period and decreasing a shorting period.
The method further comprising transmitting the at least two simultaneous waveforms to a receiver in communication with a processor, the processor being in communication with the electrode array.
Wherein the electrode array is implanted in a patient.
Wherein the transmitting occurs before the activating and after the optimizing.
Wherein the transmitting occurs before the activating.
Wherein the optimizing occurs before the activating.
Wherein the optimizing occurs before the activating and after the transmitting.
Wherein each of the at least two simultaneous waveforms includes non-identical frequencies.
Wherein altering the phase of the waveform includes delaying the phase of the waveform.
Wherein altering the frequency of the waveform includes increasing or decreasing the frequency of the waveform.
Wherein, for each group of electrodes, each electrode within the group shares a common frequency and pulse width.
Wherein the electrode array is implanted in a patent.
Wherein the first group, the second group, and the third group each include at least two electrodes.
The foregoing detailed description is given primarily for clearness of understanding and no unnecessary limitations are to be understood therefrom for modifications can be made by those skilled in the art upon reading this disclosure and may be made without departing from the spirit of the invention.
Claims
1. A method for providing optimized neurostimulation, comprising:
- providing an electrode array comprising a plurality of electrodes, wherein the plurality of electrodes are divided into at least two groups of electrodes, and wherein the electrode array is configured to generate at least two simultaneous waveforms;
- providing a power source for each group of electrodes, each power source being electrically isolated and physically separate from each other power source; and
- activating the electrode array to generate the at least two simultaneous waveforms.
2. The method of claim 1, wherein, for each group of electrodes, each electrode within the group shares a common frequency and pulse width.
3. The method of claim 1, wherein the electrode array is implanted in a patent.
4. A method for providing optimized neurostimulation, comprising:
- providing an electrode array comprising a plurality of electrodes;
- grouping the plurality of electrodes into a first group including at least one electrode configured to generate a first waveform, a second group including at least one electrode configured to generate a second waveform, and a third group including at least one electrode with a fixed potential, wherein the third group is located between the first group and the second group; and
- activating the electrode array to generate at least one of the first waveform and the second waveform.
5. The method of claim 4, wherein the electrode array is implanted in a patient.
6. The method of claim 4, wherein the first group, the second group, and the third group each include at least two electrodes.
Type: Application
Filed: Apr 14, 2021
Publication Date: Jul 29, 2021
Applicant: UNIVERSITY OF LOUISVILLE RESEARCH FOUNDATION, INC. (Louisville, KY)
Inventors: Susan J. Harkema (Louisville, KY), Yangshen Chen (Louisville, KY), Robert S. Keynton (Louisville, KY), Douglas J. Jackson (New Albany, IN), John Naber (Goshen, KY), Thomas Roussel (Louisville, KY), Manikandan Ravi (Louisville, KY)
Application Number: 17/230,280