Method and apparatus for application of a neural stimulus

Patent metadata

Field	Value
Publication number	US-11426587-B2
Application number	US-202217576060-A
Country	US
Kind code	B2
Filing date	Jan 14, 2022
Priority date	May 13, 2011
Publication date	Aug 30, 2022
Grant date	Aug 30, 2022

Abstract

A method of applying a neural stimulus with an implanted electrode array involves applying a sequence of stimuli configured to yield a therapeutic effect while suppressing psychophysical side effects. The stimuli sequence is configured such that a first stimulus recruits a portion of the fibre population, and a second stimulus is delivered within the refractory period following the first stimulus and the second stimulus being configured to recruit a further portion of the fibre population. Using an electrode array and suitable relative timing of the stimuli, ascending or descending volleys of evoked responses can be selectively synchronised or desynchronised to give directional control over responses evoked.

First claim

The invention claimed is:

1. A method of controlling a neural stimulus, the method comprising:
applying a neural stimulus from an electrode array comprising at least one stimulus electrode to a neural pathway of a patient, the stimulus being defined by at least one stimulus parameter, the electrode array being subject to movement relative to the neural pathway;
measuring a neural response evoked by the stimulus, the neural response comprising an evoked compound action potential, wherein a distance between the electrode array and the neural pathway is subject to change induced by movement of the electrode array relative to the neural pathway;
deriving from the measured neural response a feedback variable;
comparing a target value with the feedback variable;
adjusting, based on the comparison, a value of the at least one stimulus parameter; and
repeating the applying, measuring, deriving, comparing, and adjusting,

wherein the adjusting or the comparing reduces variations in recruitment induced by the change in distance.

2. The method of claim 1 , wherein the reducing the variations comprises applying a compensating function to the feedback variable that compensates for altered measurement sensitivity resulting from the change in distance.

3. The method of claim 2 , wherein the compensated feedback variable is representative of neural recruitment.

4. The method of claim 2 , wherein applying the compensating function comprises:
estimating the distance between the electrode array and the neural pathway, and
scaling the feedback variable based on the estimated distance.

5. The method of claim 4 , wherein estimating the distance comprises:
applying a probe stimulus to the neural pathway;
measuring a neural response evoked by the probe stimulus; and
estimating the distance relative to a calibration point using the measured response.

6. The method of claim 4 , wherein estimating the distance comprises using spectral characteristics of the measured neural response.

7. The method of claim 2 , wherein applying the compensating function comprises:
estimating a distance-dependent scaling factor, and
scaling the feedback variable using the distance-dependent scaling factor.

8. The method of claim 7 , wherein estimating the distance-dependent scaling factor comprises:
measuring a neural response evoked by the stimulus at a distant sense electrode;
computing a first ratio, being a ratio of an intensity of the evoked neural response at the distant sense electrode to an intensity of an evoked neural response measured at the distant electrode at a reference distance;
computing a second ratio, being a ratio of the intensity of the measured neural response to an intensity of an evoked neural response measured at the reference distance; and
estimating the distance-dependent scaling factor by subtracting the first ratio from the second ratio.

9. The method of claim 1 , wherein the reducing the variations comprises adjusting the target value.

10. The method of claim 9 , wherein adjusting the target value comprises:
estimating a threshold, being a minimum stimulus at which a neural response arises, and
scaling a base target by the estimated threshold.

11. The method of claim 1 , wherein the feedback variable comprises a peak-to-peak amplitude of the measured neural response.

12. An implantable device for controllably applying a neural stimulus, the device comprising:
an electrode array comprising one or more stimulus electrodes and one or more sense electrodes;
a stimulus source configured to deliver a stimulus via the one or more stimulus electrodes to a neural pathway, the electrode array being subject to movement relative to the neural pathway;
measurement circuitry for measuring a neural response sensed at the one or more sense electrodes; and
a control unit configured to:
control application of a neural stimulus as defined by at least one stimulus parameter;
measure via the measurement circuitry a neural response evoked by the stimulus, the neural response comprising an evoked compound action potential, wherein a distance between the electrode array and the neural pathway is subject to change induced by movement of the electrode array relative to the neural pathway;
derive from the measured neural response a feedback variable;
compare a target value with the feedback variable; and
adjust, based on the comparison, a value of the at least one stimulus parameter,

wherein the adjusting or the comparing reduces variations in recruitment induced by the change in distance.

13. The implantable device of claim 12 , wherein the reducing the variations comprises applying a compensating function to the feedback variable that compensates for altered measurement sensitivity resulting from the change in distance.

14. The implantable device of claim 13 , wherein the compensated feedback variable is representative of neural recruitment.

15. The implantable device of claim 13 , wherein applying the compensating function comprises:
estimating the distance between the electrode array and the neural pathway, and
scaling the feedback variable based on the estimated distance.

16. The implantable device of claim 15 , wherein estimating the distance comprises:
applying a probe stimulus to the neural pathway;
measuring a neural response evoked by the probe stimulus; and
estimating the distance relative to a calibration point using the measured response.

17. The implantable device of claim 15 , wherein estimating the distance comprises using spectral characteristics of the measured neural response.

18. The implantable device of claim 13 , wherein applying the compensating function comprises:
estimating a distance-dependent scaling factor, and
scaling the feedback variable using the distance-dependent scaling factor.

19. The implantable device of claim 18 , wherein estimating the distance-dependent scaling factor comprises:
measuring a neural response evoked by the stimulus at a distant sense electrode;
computing a first ratio, being a ratio of an intensity of the evoked neural response at the distant sense electrode to an intensity of an evoked neural response measured at the distant electrode at a reference distance;
computing a second ratio, being a ratio of the intensity of the measured neural response to an intensity of an evoked neural response measured at the reference distance; and
estimating the distance-dependent scaling factor by subtracting the first ratio from the second ratio.

20. The implantable device of claim 12 , wherein the wherein the reducing the variations comprises adjusting the target value.

21. The implantable device of claim 20 , wherein adjusting the target value comprises:
estimating a threshold, being a minimum stimulus at which a neural response arises, and
scaling a base target by the estimated threshold.

22. The implantable device of claim 12 , wherein the feedback variable comprises a peak-to-peak amplitude of the measured neural response.

Assignees

• Saluda Medical Pty Ltd

Inventors

• Parker John Louis
• Wah James Hamilton
• Karantonis Dean Michael
• Obradovic Milan
• Gorman Robert Bruce

Classifications

• A61N1/36071

  Pain · CPC title

• A61N1/0551

  Spinal or peripheral nerve electrodes · CPC title

• A61N1/36139 Primary

  with automatic adjustment · CPC title

• A61N1/36167

  Timing, e.g. stimulation onset · CPC title