Method and apparatus for neurostimulation with prevention of neural accommodation

Abstract

A neurostimulation system delivers neurostimulation to a patient using one or more primary parameters and one or more secondary parameters. The one or more primary parameters are controlled for maintaining efficacy of the neurostimulation. The one or more secondary parameters are adjusted for preventing the patient from developing neural accommodation. In various embodiments, values for the one or more secondary parameters are varied during the delivery of the neurostimulation for prevention of neural accommodation that may result from a constant or periodic pattern of stimulation pulses.

1 . An implantable medical device, comprising:
 a stimulation output circuit configured to deliver neurostimulation during therapy sessions;   a storage device configured to store values of a plurality of stimulation parameters including one or more primary parameters each having a value selected for efficacy of the neurostimulation and one or more secondary parameters each having a value adjustable for preventing neural accommodation while maintaining the efficacy of the neurostimulation, the values including a plurality of value sets for the one or more secondary parameters, the value sets each being a set of one or more values each given to one of the one or more secondary parameters;   a control circuit configured to control the delivery of the neurostimulation using the plurality of stimulation parameters, the control circuit including a parameter adjuster configured to adjust one or more parameters of the plurality of parameters, the parameter adjuster including a secondary parameter adjuster configured to select a subset of one or more value sets from the stored plurality of value sets for the one or more secondary parameters for each session of the therapy sessions such that the one or more secondary parameters are adjusted randomly through the therapy sessions; and   an implantable housing encapsulating the stimulation output circuit, the storage device, and the control circuit.   
     
     
         2 . The device of  claim 1 , wherein the secondary parameter adjuster is configured to randomly select each value set of the subset of one or more value sets from the stored plurality of value sets for each session of the therapy sessions. 
     
     
         3 . The device of  claim 1 , further comprising:
 a sensing circuit configured to sense one or more physiological signals indicative of a degree of modulation of one or more physiological functions by the neurostimulation; and   a neural accommodation detector configured to detect neural accommodation indicated by a substantial decrease in the degree of modulation of the one or more physiological functions by the neurostimulation;   and wherein the secondary parameter adjuster is configured to adjust the one or more secondary parameters in response to a detection of the indication of neural accommodation.   
     
     
         4 . The device of  claim 1 , wherein the secondary parameter adjuster is configured to select value sets from the stored plurality of value sets for the one or more secondary parameters, generate a sequence of value sets for the each therapy session including the selected value sets, and dynamically adjust the one or more secondary parameters according to the sequence of value sets during the each therapy session. 
     
     
         5 . The device of  claim 4 , wherein the secondary parameter adjuster is configured to randomize an order of the selected value sets in the sequence of value sets. 
     
     
         6 . The device of  claim 1 , wherein the control circuit is configured to control the delivery of the neural stimulation using a dosing parameter of the one or more primary parameters, the dosing parameter specifying a measure of total dose of the neurostimulation for a therapy session and representing a number of electrical pulses delivered during the therapy session. 
     
     
         7 . The device of  claim 6 , wherein the control circuit is configured to control the delivery of the neurostimulation using a duty cycle including an on-period during which the neurostimulation is delivered and an off-period during which the neurostimulation is not delivered, the duty cycle being a parameter of the one or more primary parameters. 
     
     
         8 . The device of  claim 7 , wherein the secondary parameter adjuster is configured to adjust a duration of a ramp during which a stimulation intensity gradually increases from zero to its value specified for the on-period when the ramp ends at a beginning of the on-period, or gradually decreases from its value specified for the on-period to zero the ramp starting at an end of the on-period, the duration of the ramp being a parameter of the one or more secondary parameters. 
     
     
         9 . The device of  claim 7 , wherein the secondary parameter adjuster is configured to adjust the on-period and the off-period without varying the duty cycle, the on-period and the off-period each being a parameter of the one or more secondary parameters. 
     
     
         10 . The device of  claim 6 , wherein the control circuit is configured to control the delivery of the neurostimulation using a measure of total dosing for a therapy session of the therapy sessions, the therapy session having a session duration that is divided into a plurality of segments, the measure of total dosing being a parameter of the one or more primary parameters, and wherein the secondary parameter adjuster is configured to adjust an on-off parameter specifying whether each segment of the plurality of segments is an on-segment or an off-segment, the on-segment being a segment of the plurality of segment during which the neurostimulation is delivered, the off-segment being a segment of the plurality of segment during which the neurostimulation is not delivered, the on-off parameter being a parameter of the one or more secondary parameters. 
     
     
         11 . A method for operating an implantable medical device, comprising:
 receiving values of a plurality of stimulation parameters including one or more primary parameters each having a value selected for efficacy of neurostimulation and one or more secondary parameters each having a value adjustable for preventing neural accommodation while maintaining the efficacy of the neurostimulation, the values including a plurality of value sets for the one or more secondary parameters, the value sets each being a set of one or more values each given to one of the one or more secondary parameters;   storing the received values of the plurality of stimulation parameters;   delivering neurostimulation during therapy sessions; and   controlling the delivery of the neurostimulation using the plurality of stimulation parameters, the controlling including selecting a subset of one or more value sets from the stored plurality of value sets for the one or more secondary parameters for each session of the therapy sessions and adjusting the one or more secondary parameters during the therapy sessions, wherein the subset is selected to allow for adjusting the one or more secondary parameters randomly through the therapy sessions.   
     
     
         12 . The method of  claim 11 , wherein the selecting comprises randomly selecting each value set of the subset of one or more value sets from the stored plurality of value sets for each session of the therapy sessions. 
     
     
         13 . The method of  claim 11 , further comprising:
 sensing one or more physiological signals indicative of a degree of modulation of one or more physiological functions by the neurostimulation;   detecting neural accommodation indicated by a substantial decrease in the degree of modulation of the one or more physiological functions by the neurostimulation; and   adjusting the one or more secondary parameters in response to a detection of the neural accommodation.   
     
     
         14 . The method of  claim 11 , comprising:
 selecting value sets from the stored plurality of value sets for the one or more secondary parameters;   generating a sequence of value sets for the each therapy session including the selected value sets; and   dynamically adjusting the one or more secondary parameters according to the sequence of value sets during the each therapy session.   
     
     
         15 . The method of  claim 14 , wherein generating the sequence of value sets comprises randomizing an order of the selected value sets in the sequence of value sets. 
     
     
         16 . The method of  claim 11 , wherein the one or more primary parameters comprises a dosing parameter specifying a measure of total dose of the neurostimulation for a therapy session and representing a number of electrical pulses delivered during the therapy session. 
     
     
         17 . The method of  claim 16 , wherein the one or more primary parameters comprises a duty cycle including an on-period during which the neurostimulation is delivered and an off-period during which the neurostimulation is not delivered. 
     
     
         18 . The method of  claim 17 , wherein the one or more secondary parameters comprise a duration of a ramp during which a stimulation intensity gradually increases from zero to its value specified for the on-period when the ramp ends at a beginning of the on-period, or gradually decreases from its value specified for the on-period to zero the ramp starting at an end of the on-period. 
     
     
         19 . The method of  claim 17 , wherein the one or more secondary parameters comprise the on-period and the off-period. 
     
     
         20 . The method of  claim 13 , wherein the one or more primary parameters comprise a measure of total dosing for a therapy session of the therapy sessions, the therapy session having a session duration that is divided into a plurality of segments, and the one or more secondary parameters comprise an on-off parameter specifying whether each segment of the plurality of segment is an on-segment or an off segment, the on-segment being a segment of the plurality of segment during which the neurostimulation is delivered, the off-segment being a segment of the plurality of segment during which the neurostimulation is not delivered.