Feedback control of neuromodulation device

1 . A method of controlling a neural stimulus, the neural stimulus being defined by at least one stimulus parameter, the method comprising:

applying a neural stimulus to a neural tissue of a patient in accordance with a stimulus parameter, the stimulus parameter being at a first stimulus intensity level;

measuring a response of the neural tissue, the response being evoked by the neural stimulus;

determining a second stimulus intensity level, based on a predetermined activation plot intercept point that indicates an intersection point for a plurality of activation plots associated with the neural tissue, the first stimulus intensity level, the measured response of the neural tissue and a predetermined target recruitment level;

adjusting the stimulus parameter to the second stimulus intensity level; and

applying a further neural stimulus to the neural tissue in accordance with the adjusted stimulus parameter.

2 . The method of claim 1 , further comprising

determining a threshold stimulus intensity level, based on the activation plot intercept point, the first stimulus intensity level and the measured response of the neural tissue,

wherein determining the second stimulus intensity level comprises determining the second stimulus intensity level based on the threshold stimulus intensity level and the target recruitment level.

3 . The method of claim 2 , wherein determining the second stimulus intensity level comprises determining a multiplication of the threshold stimulus intensity level and the target recruitment level plus one.

4 . The method of claim 2 , wherein the activation plot intercept point comprises an intercept stimulus intensity term and an intercept evoked response term.

5 . The method of claim 4 , wherein the intercept stimulus intensity term is a positive non-zero value.

6 . The method of claim 1 , wherein determining the second stimulus intensity level comprises calculating an estimated recruitment level, and determining a difference between the estimated recruitment level and the target recruitment level.

7 . The method of claim 1 , further comprising receiving configuration information indicative of the activation plot intercept point.

8 . The method of claim 1 , further comprising receiving configuration information indicative of the target recruitment level.

9 . The method of claim 1 , wherein each activation plot is indicative of a relationship between evoked responses of the neural tissue and a plurality of stimulus intensity levels, for one of a plurality of different postures of the patient.

10 . The method of claim 1 ,

wherein each activation plot of the plurality of activation plots is indicative of a relationship between the at least one stimulus parameter and an evoked response of the neural tissue,

wherein each relationship comprises a monotonically increasing linear section, and the monotonically increasing linear section can be extrapolated on a Cartesian plane to produce an extrapolated linear section, and

wherein the extrapolated linear section of each activation plot of the plurality of activation plots passes through the activation plot intercept point.

11 . The method of claim 4 , wherein determining the threshold stimulus intensity level comprises:

determining a first term to be equal to the intercept evoked response term multiplied by the first stimulus intensity level;

determining a second term to be equal to the intercept stimulus intensity term multiplied by the measured response of the neural tissue;

determining a third term to be equal to the measured response of the neural tissue added to the intercept evoked response term;

determining a fourth term to be equal to the first term added to the second term; and

determining the threshold stimulus intensity level to be equal to the fourth term divided by the third term.

12 . An implantable device for controllably generating a neural stimulus, the neural stimulus being defined by at least one stimulus parameter, the device comprising:

a stimulator configured to apply a neural stimulus to a neural tissue of a patient, in accordance with the at least one stimulus parameter;

measurement circuitry for measuring an evoked response of the neural tissue;

a communication port for receiving information from a data source; and

a controller configured to:

control the stimulator to apply the neural stimulus, in accordance with a stimulus parameter, the stimulus parameter being at a first stimulus intensity level;

measure a response of the neural tissue, the response being evoked by the neural stimulus;

determine a second stimulus intensity level, based on a predetermined activation plot intercept point that indicates an intersection point for a plurality of activation plots associated with the neural tissue, the first stimulus intensity level, the measured response of the neural tissue and a predetermined target recruitment level;

adjust the at least one stimulus parameter to the second stimulus intensity level; and

control the stimulator to apply a further neural stimulus to the neural tissue in accordance with the adjusted stimulus parameter.

13 . The device of claim 12 , further comprising firmware for configuring the controller.

14 . A system for controlling a neural stimulus for application to a neural tissue of a patient, the neural stimulus being defined by at least one stimulus parameter, the system comprising a configuration module and an implantable device configured to be in electrical communication with the neural tissue,

the configuration module comprising a transmission port for transmitting information indicative of an activation plot intercept point to the implantable device, the activation plot intercept point indicating an intersection point for a plurality of activation plots associated with the neural tissue; and

the implantable device comprising:

a stimulator configured to apply the neural stimulus to a neural tissue of a patient in accordance with the at least one stimulus parameter;

measurement circuitry for measuring an evoked response of the neural tissue;

a reception port for receiving the information from the configuration module; and

a controller configured to:

control the stimulator to apply the neural stimulus to a neural tissue of a patient, in accordance with a stimulus parameter, the stimulus parameter being at a first stimulus intensity level;

measure a response of the neural tissue, the response being evoked by the neural stimulus;

determine a second stimulus intensity level, based on the activation plot intercept point, the first stimulus intensity level, the measured response of the neural tissue and a predetermined target recruitment level;

adjust the stimulus parameter to the second stimulus intensity level; and

control the stimulator to apply a further neural stimulus to the neural tissue in accordance with the adjusted stimulus parameter.

15 . The system of claim 14 , further comprising a fitting module for determining the activation plot intercept point, the fitting module comprising instructions which, when executed by one or more processors, causes performance of the following:

determining a plurality of activation plots, each activation plot based on one of a plurality of activation data sets;

adjusting at least one of the plurality of activation plots, such that all of the plurality of activation plots, when extrapolated, intercept at an activation plot intercept point; and

communicating information indicative of the activation plot intercept point to the implantable device.