Systems and methods of providing modulation therapy without patient-perception of stimulation

Abstract

A neuromodulation system and method of providing sub-threshold modulation therapy. Electrical modulation energy is delivered to a target tissue site of the patient at a programmed intensity value, thereby providing therapy to a patient without perception of stimulation. In response to an event, electrical modulation energy is delivered at incrementally increasing intensity values. At least one evoked compound action potential (eCAP) is sensed in a population of neurons at the target tissue site of the patient in response to the delivery of the electrical modulation energy at the incrementally increasing intensity values. One of the incrementally increased intensity values is selected based on the sensed eCAP(s). A decreased intensity value is automatically computed as a function of the selected intensity value. Electrical modulation energy is delivered to the target tissue site of the patient at the computed intensity value, thereby providing sub-threshold therapy to the patient.

What is claimed is: 
     
         1 . A method of providing therapy to a patient, comprising:
 delivering electrical modulation energy to a target tissue site of the patient at a programmed intensity value, thereby providing therapy to the patient without perception of stimulation;   delivering, in response to an event, electrical modulation energy at a series of incrementally increasing intensity values relative to the programmed intensity value;   sensing at least one evoked compound action potential (eCAP) in a population of neurons at the target tissue site of the patient in response to the delivery of the electrical modulation energy at the series of incrementally increasing intensity values;   selecting one of the series of incrementally increased intensity values based on the at least one sensed eCAP;   automatically computing a decreased intensity value as a function of the selected intensity value; and   delivering electrical modulation energy to the target tissue site of the patient at the computed intensity value.   
     
     
         2 . The method of  claim 1 , wherein the perception of stimulation is a perception of paresthesia. 
     
     
         3 . The method of  claim 1 , wherein the programmed intensity value is a programmed amplitude value, and the incrementally increasing intensity values are incrementally increasing amplitude values. 
     
     
         4 . The method of  claim 1 , wherein the programmed intensity value is a programmed pulse width value, and the incrementally increasing intensity values are incrementally increasing pulse width values. 
     
     
         5 . The method of  claim 1 , wherein the selected intensity value corresponds to the intensity value of the delivered electrical modulation energy in response to which a first one of the at least one eCAP is sensed. 
     
     
         6 . The method of  claim 1 , further comprising:
 comparing a characteristic of each of the at least one sensed eCAP to a corresponding characteristic of a reference eCAP indicative of a perception threshold; and   selecting one of the series of incrementally increased intensity values based on the comparison.   
     
     
         7 . The method of  claim 6 , wherein the characteristic of the each sensed eCAP is at least one of peak delay, width, amplitude, and waveform morphology. 
     
     
         8 . The method of  claim 6 , wherein the reference eCAP is stored, the at least one sensed eCAP comprises two or more eCAPs respectively sensed in response to the delivery of the electrical modulation energy at two or more of the intensity values, the method further comprising:
 obtaining the characteristic from the stored reference eCAP; and   determining one of the two or more sensed eCAPs having the characteristic that best matches the characteristic of the reference eCAP, wherein the intensity value of the delivered electrical modulation energy in response to which the determined eCAP is sensed is selected.   
     
     
         9 . The method of  claim 6 , wherein the characteristic of the reference eCAP is a stored threshold value, the at least one sensed eCAP comprises one or more eCAPs respectively sensed in response to the delivery of the electrical modulation energy at each of two or more of the intensity values, the method further comprising determining a function of the one or more sensed eCAPs having the characteristic that equals or exceeds the stored threshold value, wherein the intensity value of the delivered electrical modulation energy in response to which the determined one or more eCAPs is sensed is selected. 
     
     
         10 . The method of  claim 6 , further comprising:
 storing a list of reference eCAPs characteristics, each of which is indicative of a perception threshold when the patient is engaged in a particular physical activity and/or posture;   identifying a physical activity and/or posture in which the patient is currently engaged; and   selecting, from the list of reference eCAP characteristics, the reference eCAP characteristic corresponding to the identified physical activity and/or posture, wherein the selected reference eCAP characteristic is the reference eCAP characteristic to which the characteristic of each of the at least one sensed eCAP is compared.   
     
     
         11 . The method of  claim 1 , wherein the event is one of an identified physical activity and/or posture, a user-initiated signal, a signal indicating migration of an electrode from which the electrical modulation energy is delivered, and a predetermined periodically recurring signal. 
     
     
         12 . The method of  claim 1 , wherein the computed intensity value is a percentage of the selected intensity value. 
     
     
         13 . The method of  claim 12 , wherein the percentage is in the range of 30%-70%. 
     
     
         14 . The method of  claim 12 , wherein the percentage is in the range of 40%-60%. 
     
     
         15 . The method of  claim 12 , wherein the percentage is in the range of 10%-90%. 
     
     
         16 . The method of  claim 1 , wherein the computed function is a difference between the selected intensity value and a constant. 
     
     
         17 . The method of  claim 1 , wherein both the electrical modulation energy delivered at the programmed intensity and the electrical energy delivered at the series of incrementally increasing intensity values comprise electrical pulse trains, and each of the programmed intensity value, incrementally increased intensity value, and computed intensity value is a pulse intensity value. 
     
     
         18 . The method of  claim 1 , wherein the patient suffers from chronic pain in a body region, and the perception of threshold comprises paresthesia perceived by the patient in the body region. 
     
     
         19 . A neuromodulation system, comprising:
 a plurality of electrical terminals respectively configured for being electrically coupled to a plurality of electrodes implanted within a target tissue site;   modulation output circuitry coupled to the plurality of electrical terminals for delivering electrical modulation energy to the target tissue site of the patient at a programmed intensity value, thereby providing therapy to the patient without perception of stimulation;   monitoring circuitry coupled to the plurality of electrical terminals; and   control/processing circuitry configured for:
 directing, in response to an event, the modulation output circuitry to deliver electrical modulation energy at a series of incrementally increasing intensity values relative to the programmed intensity value; 
 prompting the modulation output circuitry to evoke at least one compound action potential (CAP) in a populations of neurons in the target tissue site of the patient in response to the delivery of the electrical modulation energy at the series of incrementally increasing intensity values; 
 prompting the monitoring circuitry to sense the at least one evoked CAP (eCAP); 
 selecting one of the series of incrementally increased intensity values based on the at least one sensed eCAP; 
 automatically computing a decreased value as a function of the selected intensity value; and 
 directing the modulation output circuitry to deliver electrical modulation energy to the target tissue site of the patient at the computed intensity value. 
   
     
     
         20 . The neuromodulation system of  claim 19 , wherein the perception of stimulation is a perception of paresthesia.