Method and System For Physiological Target Localization From Macroelectrode Recordings and Monitoring Spinal Cord Function

Abstract

Provided herein are a method and system are provided for the localization of clinically relevant electrophysiological signals necessary for the proper placement of the electrodes for nervous system stimulation. The system provides electrical and mechanical means to stimulate or excite neural structures in order to elicit specific neural responses. The method can include mechanical vibratory stimulation, cutaneous electrical stimulation, electrical stimulation of the peripheral nerves, or photic stimulation, and recording of local field potentials and extracting evoked potentials in response to stimulation. The method also includes extracting components of the evoked potentials that relate the signal in the evoked potentials to specific anatomical structures and localization of the source of the evoked potentials recorded so as to identify the location of the source relative to the recording electrode with high resolution by sampling the evoked potentials with a relative large (macro) electrode that is moved in small incremental steps.

1 . A method of targeting a medical device in a patient, comprising:
 stimulating, with a stimulating device, the patient's peripheral nervous system;   recording, using a macroelectrode recording electrode inserted within a region of interest in the patient, a field potential evoked from the stimulation;   calculating, using at least one processor, the evoked potential from the stimulation;   advancing, with a drive, the recording electrode along a trajectory;   stimulating for a second time, with the stimulating device, the patient's peripheral nervous system;   recording, using the macroelectrode recording electrode, a field potential evoked from the second stimulation;   calculating, using at least one processor, the evoked potential from the second stimulation;   determining, using at least one processor and based at least on the evoked potential from the first stimulation and the evoked potential from the second stimulation, a position along a path travelled by the recording electrode at which the evoked potential is largest;   determining, using at least one processor, a distance r from the position point on the recording electrode path where the evoked potential is largest to a source of the evoked potential in a plane orthogonal to a long axis of the macroelectrode; and   determining, using at least one processor, whether r is less than a predetermined threshold, wherein the predetermined threshold Y is a radius of an effective volume of tissue activation with an intended therapeutic brain stimulation for an intended target of the brain stimulation.   
     
     
         2 . The method according to  claim 1 , wherein the stimulation is mechanical. 
     
     
         3 . The method according to  claim 1 , wherein the stimulation is electrical. 
     
     
         4 . The method according to  claim 1 , wherein the stimulation is mechanical and visual. 
     
     
         5 . The method according to any of the preceding  claim 1 , wherein the step of determining the distance r is accomplished using a Radon transform or variation thereof. 
     
     
         6 . The method according to  claim 1 , wherein the recording electrode is a segmented lead electrode. 
     
     
         7 . The method according to  claim 6 , wherein the distance r is calculated using the equation r=((V02/Vx2−1)1/2)/dx, wherein V0 is the potential at an electrode recording the highest evoked potential, Vx is the potential at any other electrode, and dx is the distance from the electrode having potential V0 and the electrode having potential Vx. 
     
     
         8 . A system for implanting a medical device within a patient, comprising:
 a macroelectrode recording electrode and drive;   at least one stimulator;   at least one processor in communication with the recording electrode and the at least one stimulator; and   a non-transitory computer readable medium in communication with the at least one processor and having one or more computer programs stored thereon that when executed by the one or more processors cause the system to perform the operations of:
 stimulating, with the at least one stimulator, the patient's peripheral nervous system; 
   recording, with the recording electrode, a field potential evoked from the stimulation;   calculating, using at least one processor, the evoked potential from the stimulation;   advancing, by controlling a drive, the recording electrode;   stimulating for a second time, with the at least one stimulator, the patient's peripheral nervous system;   recording, with the recording electrode, a field potential evoked from the second stimulation;   calculating, using at least one processor, the evoked potential from the second stimulation;   determining, using at least one processor and based at least in part on the field potential evoked from the first stimulation and the field potential evoked from the second stimulation, a distance r from the recording electrode to a source of the evoked potential in a plane orthogonal to a long axis of the macroelectrode; and   determining, using at least one processor, whether r is less than a predetermined threshold Y;   wherein the predetermined threshold Y is a radius of an effective volume of tissue activation with an intended therapeutic brain stimulation for an intended target of the brain stimulation.   
     
     
         9 . The system according to  claim 8 , wherein the stimulator is a mechanical stimulator. 
     
     
         10 . The system according to  claim 8 , wherein the stimulator is electrical. 
     
     
         11 . The system according to  claim 8 , wherein the stimulator comprises a mechanical stimulator and a visual stimulator. 
     
     
         12 . The system according to  claim 8 , wherein the step of determining the distance r is accomplished using a Radon transform or variation thereof. 
     
     
         13 . The system according to  claim 8 , wherein the recording electrode is a segmented lead electrode. 
     
     
         14 . The system according to  claim 13 , wherein the distance r is calculated using the equation r=((V02/Vx2−1)1/2)/dx, wherein V0 is the potential at an electrode recording the highest evoked potential, Vx is the potential at any other electrode, and dx is the distance from the electrode having potential V0 and the electrode having potential Vx. 
     
     
         15 . (canceled) 
     
     
         16 . A system for implanting a medical device within a patient, comprising:
 at least one processor adapted to be in communication with a macroelectrode recording electrode, a drive, and at least one stimulator; and   a non-transitory computer readable medium in communication with the at least one processor and having one or more computer programs stored thereon that when executed by the one or more processors cause the system to perform the operations of:
 recording, with the macroelectrode recording electrode, a first field potential evoked from stimulation of the patient's peripheral nervous system; 
   calculating, using at least one processor, a first evoked potential from the first stimulation;   advancing, with the drive, the recording electrode;   recording, with the macroelectrode recording electrode, a second field potential evoked from a second stimulation of the patient's peripheral nervous system;   calculating, using at least one processor, a second evoked potential from the second stimulation;   determining, using at least one processor and based on at least the first evoked potential and the second evoked potential, a distance r from the recording electrode to a source of the evoked potential in a plane orthogonal to a long axis of the macroelectrode; and   determining, using at least one processor, whether r is less than a predetermined threshold Y,   wherein the predetermined threshold Y is a radius of an effective volume of tissue activation with an intended therapeutic brain stimulation for an intended target of the brain stimulation.   
     
     
         17 . The method of  claim 1 , wherein the macroelectrode recording electrode is a single lead macroelectrode. 
     
     
         18 . The method of  claim 1 , wherein the steps of determining a position along the recording electrode at which the evoked potential is largest and determining a distance r from the position on the recording electrode where the evoked potential is largest to a source of the evoked potential comprises:
 calculating a detected voltage at a plurality of virtual positons on the macroelectrode recording electrode by:   stimulating, with a stimulating device, the patient's peripheral nervous system;   recording, using the macroelectrode recording electrode inserted within a region of interest in the patient, a first field potential evoked from the stimulation;   calculating, using at least one processor, a first voltage from the stimulation;   advancing, with a drive, the macroelectrode recording electrode along a trajectory;   stimulating for a second time, with the stimulating device, the patient's peripheral nervous system;   calculating, using at least one processor, a second voltage from the second stimulation;   determining, using at least one processor and based on a distance that the macroelectrode is advanced, a subset of the plurality of virtual positions that overlap based on an identity of virtual positions that detected the first and second evoked potentials;   calculating, using at least one processor, a sum of voltages for the subset based on the first evoked potential and determining a sum of voltages for the subset based on the second evoked potential;   calculating, using at least one processor a difference between the summed voltages for the subset and a sum of the voltages for all virtual positions on the macroelectrode; and   determining, based on the difference, a virtual position along the recording electrode at which the evoked potential is largest and determining a distance r from the virtual position on the recording electrode where the evoked potential is largest to a source of the evoked potential in a plane orthogonal to a long axis of the macroelectrode.