Neurophysiological Apparatus and Procedures

Abstract

Neurophysiological instruments and techniques are improved through various enhancements. Stimulation of an instrument is possible while it is advancing into the spine or elsewhere, alerting the surgeon to the first sign the instrument or device (screw) may be too near a nerve. A directional probe helps surgeons determine the location of the hole in the pedicle. Electrically insulating sleeves prevent shunting into the soft tissues. According to a different improvement, the same probe to be used to stimulate different devices, such as screws and wires. Electrical impulses may be recorded from non-muscle regions of the body, including the spine and other portions of the central nervous system as opposed to just the extremities.

What is claimed is: 
     
         1 . A method for determining the direction of a pedicle breach during pilot hole formation, comprising the steps of:
 forming an access corridor to a pedicle in a patient;   forming a pilot hole in the pedicle by advancing an instrument into the pedicle;   rotating the instrument about a longitudinal axis during the pilot hole formation while simultaneously applying a stimulation signal to the instrument; and   determining the direction of the breach by monitoring neuromuscular responses to successive stimulation signals during the rotation of the instrument.   
     
     
         2 . The method of  claim 1 , wherein the instrument is configured to transmit an electric stimulation to the pedicle from a neurophysiology monitoring system communicatively linked to the instrument. 
     
     
         3 . The method of  claim 2 , wherein the neurophysiology monitoring system detects the presence of the breach by determining a stimulation threshold at which muscles innervated by a nerve adjacent to the pedicle respond to the successive stimulation signals. 
     
     
         4 . The method of  claim 3 , wherein the instrument comprises an electrode, wherein the method comprises the additional step of:
 determining a position of the electrode about the longitudinal axis when the stimulation threshold is lowest to indicate the direction of the breach.   
     
     
         5 . The method of  claim 4 , wherein the instrument is insulated to prevent shunting of the stimulation signal along the length of the instrument. 
     
     
         6 . The method of  claim 5 , wherein the instrument includes a first uninsulated portion forming the electrode. 
     
     
         7 . The method of  claim 1 , wherein the pilot hole extends between an outer surface of the pedicle and an interior location within the pedicle. 
     
     
         8 . A method for determining directionality during surgery, comprising the steps of:
 forming an access corridor to a pedicle target site in a patient;   advancing an instrument into the pedicle; and   rotating the instrument about a longitudinal axis and simultaneously transmitting an electrical signal to a nerve adjacent the pedicle from a neurophysiology monitoring system communicatively linked to the instrument to determine the direction of a breach detected in the pedicle during pilot hole formation.   
     
     
         9 . The method of  claim 8 , wherein the neurophysiology monitoring system detects the breach by determining a threshold stimulation level at which muscles innervated by the nerve respond to the stimulation signal. 
     
     
         10 . The method of  claim 9 , wherein the instrument comprises an electrode, wherein the method comprises the additional step of:
 determining a position of the electrode about the longitudinal axis when the stimulation threshold is lowest to indicate the direction of the breach.   
     
     
         11 . The method of  claim 10 , wherein the instrument is insulated to prevent shunting of the stimulation signal along the length of the instrument. 
     
     
         12 . The method of  claim 11 , wherein the instrument includes a first uninsulated portion forming the electrode. 
     
     
         13 . A method for determining the direction of a pedicle breach during hole formation, comprising the steps of:
 rotating an instrument about a longitudinal axis during formation of a pilot hole within a pedicle while simultaneously applying a stimulation signal to the instrument; and   determining the direction of the breach by monitoring neuromuscular responses to successive stimulation signals during the rotation of the instrument.   
     
     
         14 . The method of  claim 13 , wherein the instrument comprises a proximal end and a distal end, the distal end terminating at a distal tip, the distal tip having an electrode arranged along a single side of the distal tip. 
     
     
         15 . The method of  claim 14 , wherein the instrument is configured to transmit an electric stimulation to the pedicle from a neurophysiology monitoring system communicatively linked to the instrument. 
     
     
         16 . The method of  claim 15 , wherein the neurophysiology monitoring system detects the presence of the breach by determining a stimulation threshold at which muscles innervated by a nerve adjacent to the pedicle respond to the successive stimulation signals. 
     
     
         17 . The method of  claim 16 , wherein the method comprises the additional step of:
 determining a position of the electrode about the longitudinal axis when the stimulation threshold is lowest to indicate the direction of the breach.   
     
     
         18 . The method of  claim 17 , wherein the instrument is insulated to prevent shunting of the stimulation signal along the length of the instrument. 
     
     
         19 . The method of  claim 18 , wherein the instrument includes a first uninsulated portion forming the electrode. 
     
     
         20 . The method of  claim 13 , wherein the pilot hole extends between an outer surface of the pedicle and an interior location within the pedicle.