Method and apparatus for estimating neural recruitment

• US 9,974,455 B2
• Filed: 05/11/2012
• Issued: 05/22/2018
• Est. Priority Date: 05/13/2011
• Status: Active Grant

• Current Assignee: Saluda Medical Pty Ltd.
• Original Assignee: Saluda Medical Pty Ltd.
• Inventors: Parker, John Louis, Laird, James Hamilton, Karantonis, Dean Michael
• Primary Examiner(s): Dougherty, Sean
• Assistant Examiner(s): FERNANDES, PATRICK M
• Application Number:
  US14/117,152
• Publication Number:
  US 20140194771A1
• Time in Patent Office: 2,202 Days
• CPC Class Codes: A61B 5/24 Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
• CPC Class Codes: A61N 1/0551 Spinal or peripheral nerve electrodes
• CPC Class Codes: A61N 1/36071 Pain
• CPC Class Codes: A61N 1/36135 using physiological parameters

Abstract

An implantable device for estimating neural recruitment arising from a stimulus, has a plurality of electrodes. A stimulus source provides stimuli to be delivered from the electrodes to neural tissue. Measurement circuitry obtains a measurement of a neural signal sensed at the electrodes. A control unit is configured to control application of a selected stimulus to neural tissue using the stimulus electrodes; and after the selected neural stimulus, apply a probe stimulus having a short pulse Width. A remnant neural response evoked by the probe stimulus is measured; and the control unit estimates from the remnant neural response a neural recruitment caused by the selected neural stimulus.

Claims

1. A method of determining neural recruitment arising from a selected neural stimulus, the method comprising:

applying the selected neural stimulus from at least one stimulus electrode;

at a time t after conclusion of the selected neural stimulus, applying a probe stimulus having a short pulse width;

measuring, with measurement circuitry, a remnant neural response evoked by the probe stimulus;

changing t;

repeating the applying the selected neural stimulus, the applying the probe stimulus, the measuring and the changing, to determine variations in the remnant neural response measure with varying t, and

from at least one measured remnant neural response, determining neural recruitment caused by the selected neural stimulus using a control unit.

2. The method of claim 1, wherein the selected neural stimulus has a pulse width in the range of 100-500 μ

s.

3. The method of claim 1, further comprising applying a second probe stimulus after the refractory period of fibres recruited by either the selected stimulus or the probe stimulus, and obtaining a second measure of evoked neural response as caused by the second probe stimulus.

4. The method of claim 3 further comprising determining the neural recruitment arising from the selected neural stimulus by comparing the remnant neural response to the second measure.

5. The method of claim 1 further comprising identifying a value t_r at which an increase in the remnant neural response with increasing t arises, and taking t_r as an estimate for the refractory period of the fibre population recruited by the selected stimulus.

6. The method of claim 1 further comprising monitoring the refractory period over time in order to diagnose onset or progression of a disease.

13. The method of claim 1, wherein the at least one measured remnant neural response define a curve.

7. An implantable device for determining neural recruitment arising from a selected neural stimulus, the device comprising:

a plurality of electrodes including one or more nominal stimulus electrodes and one or more nominal sense electrodes;

a stimulus source for providing stimuli to be delivered from the one or more stimulus electrodes to neural tissue;

measurement circuitry for obtaining a measurement of a neural signal sensed at the one or more sense electrodes; and

a control unit configured to control application of a selected stimulus to neural tissue using the stimulus electrodes;

the control unit further configured to, at a time t after conclusion of the selected neural stimulus, apply a probe stimulus having a short pulse width;

the control unit further configured to measure a remnant neural response evoked by the probe stimulus;

the control unit further configured to change t;

the control unit further configured to repeat the applying the selected neural stimulus, the applying the probe stimulus, the measuring and the changing, to determine variations in the remnant neural response measure with varying t; and

the control unit further configured to determine from at least one measured remnant neural response a neural recruitment caused by the selected neural stimulus.

8. The implantable device of claim 7, wherein the selected neural stimulus has a pulse width in the range of 100-500 μ

s.

9. The implantable device of claim 7 wherein the control unit is further configured to apply a second probe stimulus after the refractory period of fibres recruited by either the selected stimulus or the probe stimulus, and to obtain a second measure of evoked neural response as caused by the second probe stimulus.

10. The implantable device of claim 9 wherein the control unit is further configured to estimate the neural recruitment arising from the selected neural stimulus by comparing the remnant neural response to the second measure.

11. The implantable device of claim 7 wherein the control unit is further configured to identify a value t_r at which an increase in the remnant neural response with increasing t arises, and take t_r as an estimate for the refractory period of the fibre population recruited by the selected stimulus.

12. The implantable device of claim 7 wherein the control unit is further configured to monitor the refractory period over time in order to diagnose onset or progression of a disease.

14. The implantable device of claim 7, wherein the control unit is further configured to generate a curve based on the at least one measured remnant neural response.