Programming of neuromodulation therapy
A neuromodulation system and method. An implantable electrode array comprises a plurality of electrodes. A stimulus source provides neural stimuli delivered via stimulus electrodes to neural tissue to evoke neural responses. Measurement circuitry captures signal windows sensed from the neural tissue subsequent to each stimulus. A control unit controls the neural stimuli according to a stimulus intensity parameter. A processor introduces a perturbation to the parameter from a baseline stimulus intensity. A time series of intensities of the evoked neural responses is obtained, from which a time series of estimates of at least one physiological characteristic of the neural tissue is obtained. Each physiological characteristic being variable as a result of a posture wave. A baseline value of each physiological characteristic is estimated from the time series of estimates of each physiological characteristic.
1 . A neuromodulation system comprising:
an implantable electrode array comprising a plurality of electrodes;
a stimulus source configured to provide neural stimuli to be delivered via one or more stimulus electrodes to neural tissue proximal to the implantable electrode array in order to evoke neural responses from the neural tissue, the one or more stimulus electrodes being selected from the plurality of electrodes;
measurement circuitry configured to capture signal windows sensed from the neural tissue via one or more sense electrodes subsequent to respective neural stimuli, the one or more sense electrodes being selected from the plurality of electrodes;
a control unit configured to control the stimulus source to provide the neural stimuli according to respective values of a stimulus intensity parameter; and
a processor configured to:
instruct the control unit to control the stimulus source to provide the neural stimuli according to perturbed values of the stimulus intensity parameter, the perturbed values comprising a perturbation from a baseline stimulus intensity;
process the captured signal windows from the measurement circuitry in order to measure a time series of intensities of the evoked neural responses;
extract, using the measured neural response intensity time series, time series of estimates of at least one physiological characteristic of the neural tissue, wherein each physiological characteristic varies around a baseline value as a result of a posture wave; and
estimate the baseline value of each physiological characteristic from the time series of estimates of each physiological characteristic.
2 . The neuromodulation system of claim 1 , wherein the stimulus intensity parameter perturbation comprises an oscillatory waveform with a period that is short compared to a period of the posture wave.
3 . The neuromodulation system of claim 2 , wherein the processor is configured to extract the time series of estimates of each physiological characteristic by separating a component of variation of the measured neural response intensity time series that is stimulus-induced from a component of variation of the measured neural response intensity time series that is induced by the posture wave.
4 . The neuromodulation system of claim 1 , wherein the stimulus intensity parameter perturbation comprises pairs of different intensity separated by an interval that is short compared to a period of the posture wave.
5 . The neuromodulation system of claim 1 , wherein the processor is configured to estimate the baseline value of one of the one or more physiological characteristics by forming a histogram of the time series of estimates of the physiological characteristic.
6 . The neuromodulation system of claim 1 , wherein there are a plurality of physiological characteristics, and the processor is configured to estimate the baseline value of each physiological characteristic by forming a joint histogram from the time series of estimates of each physiological characteristic.
7 . The neuromodulation system of claim 1 , wherein the processor is further configured to estimate a range of variation of one of the one or more physiological characteristics from the time series of estimates of the physiological characteristic.
8 . The neuromodulation system of claim 1 , wherein the processor is further configured to set a feedback parameter according to the baseline estimate of one of the one or more physiological characteristics.
9 . The neuromodulation system of claim 8 , wherein the control unit is further configured to:
process each captured signal window from the measurement circuitry in order to measure an intensity of each evoked neural response; and
adjust, using the feedback parameter, the stimulus intensity parameter so as to bring the measured neural response intensity towards a target neural response intensity.
10 . The neuromodulation system of claim 9 , wherein the processor is further configured to:
extract a representative value of stimulus intensity parameter corresponding to the target neural response intensity;
adjust the target neural response intensity; and
repeat the extracting and adjusting, yielding a plurality of (representative stimulus intensity, target response intensity) value pairs.
11 . The neuromodulation system of claim 10 , wherein the processor is further configured to:
estimate the baseline value of each physiological characteristic from the plurality of (representative stimulus intensity, target response intensity) value pairs.
12 . The neuromodulation system of claim 11 , wherein the processor is configured to estimate the baseline value of each physiological characteristic by fitting an activation plot to the plurality of (representative stimulus intensity, target response intensity) value pairs.
13 . The neuromodulation system of claim 12 , wherein the one or more physiological characteristics are a slope and a threshold of the fitted activation plot.
14 . The neuromodulation system of claim 12 , wherein the processor is further configured to calculate a confidence interval around the baseline value of each physiological characteristic.
15 . The neuromodulation system of claim 1 , further comprising an external computing device configured to communicate with the control unit that is co-located with, and in communication with, the measurement circuitry and the stimulus source within an implantable electronics module.
16 . The neuromodulation system of claim 15 , wherein the processor is part of the external computing device and is configured by program instructions stored in an instruction memory of the external computing device.
17 . The neuromodulation system of claim 1 , wherein the processor is part of the control unit.
18 . A method of estimating a baseline value of one or more physiological characteristics of a patient, the method comprising:
delivering neural stimuli to neural tissue according to respective values of a stimulus intensity parameter in order to evoke neural responses from the neural tissue;
perturbing the stimulus intensity parameter by a small amount from a baseline stimulus intensity;
sensing on the neural tissue subsequent to respective neural stimuli and capturing signal windows from the neural tissue;
processing the captured signal windows in order to measure a time series of intensities of the evoked neural responses;
extracting, using the measured neural response intensity time series, a time series of estimates of at least one physiological characteristic of the neural tissue, wherein each physiological characteristic varies around a baseline value as a result of a posture wave; and
estimating the baseline value of each physiological characteristic from the time series of estimates of each physiological characteristic.
19 . A non-transitory computer readable medium for estimating a baseline value of one or more physiological characteristics of a patient, the medium comprising instructions which, when executed by one or more processors, causes performance of the following:
delivering neural stimuli to neural tissue according to respective values of a stimulus intensity parameter in order to evoke neural response from the neural tissue;
perturbing the stimulus intensity parameter by a small amount from a baseline stimulus intensity;
sensing on the neural tissue subsequent to respective neural stimuli and capturing signal windows from the neural tissue;
processing the captured signal windows in order to measure a time series of intensities of the evoked neural responses;
extracting, using the measured neural response intensity time series, time series of estimates of at least one physiological characteristic of the neural tissue, wherein each physiological characteristic varies around a baseline value as a result of a posture wave; and
estimating the baseline value of each physiological characteristic from the time series of estimates of each physiological characteristic.