Neuromonitoring Systems and Methods

Abstract

Systems, devices, and methods are described for neuromonitoring. A minimum stimulus signal required to elicit a threshold neuromuscular response is determined by delivery of stimulus signals to tissue and detection of neuromuscular responses in muscle tissue. The strength of the delivered stimulus signals is varied, for example by adjusting the current amplitude or pulse width of the signals, and muscle responses are measure, for example by detecting EMG signals. The delivered stimuli and corresponding responses are then used to determine a stimulation threshold. The stimulation threshold may be used to indicate at least one of nerve proximity and pedicle integrity.

What is claimed is: 
     
         1 . A system for neuromonitoring, comprising:
 a surgical instrument for delivering stimulus signals to tissue including or adjacent to a nerve; and   a processing system comprising:
 a detection module configured to detect, in muscle tissue, a first neuromuscular response in response to a first stimulus signal having a first pulse width and to detect a second neuromuscular response in response to a second stimulus signal having a second pulse width; 
 a processing module in communication with the detection module and configured to determine a stimulation threshold for the nerve from the first and second stimulus signal pulse widths and the first and second neuromuscular responses, the stimulation threshold being an estimate of a minimum pulse width required to elicit a neuromuscular response greater than or equal to a predetermined threshold, wherein the stimulation threshold is different from the first and second pulse widths; and 
 a communications module in communication with the processing module and configured to communicate an indicator of the stimulation threshold to indicate at least one of nerve proximity and pedicle integrity. 
   
     
     
         2 . The system of  claim 1 , wherein the surgical instrument comprises a probe coupled to an electrical source. 
     
     
         3 . The system of  claim 2 , further comprising a stimulating electrode disposed on a distal end of the probe. 
     
     
         4 . The system of  claim 1 , wherein the detection module comprises a sensing electrode configured to detect EMG signals. 
     
     
         5 . The system of  4 , wherein the sensing electrode comprises a surface EMG electrode. 
     
     
         6 . The system of  claim 4 , wherein the sensing electrode comprises a needle EMG electrode. 
     
     
         7 . The system of  claim 1 , wherein the detection module is configured to detect neuromuscular responses in the muscle tissue during predetermined time windows. 
     
     
         8 . The system of  claim 7 , wherein the predetermined time windows are offset from delivery times of the first and second stimulus signals. 
     
     
         9 . The system of  claim 7 , wherein the predetermined time windows are offset based on a signal transit time associated with the nerve and the muscle tissue. 
     
     
         10 . The system of  claim 1 , wherein the processing system further comprises a control module configured to deliver a plurality of stimulus signals, each stimulus signal having a larger pulse width than a preceding stimulus signal. 
     
     
         11 . The system of  claim 10 , wherein the control module is further configured to increase the pulse width of the stimulus signals in the plurality of stimulus signals at a constant increment. 
     
     
         12 . The system of  claim 10 , wherein the control module is further configured to increase the pulse width of the stimulus signals in the plurality of stimulus signals at varying increments. 
     
     
         13 . The system of  claim 1 , wherein the detection module is further configured to apply a voltage level threshold to detected EMG signals. 
     
     
         14 . The system of  claim 13 , wherein the detection module is further configured to cross-correlate detected EMG signals with an EMG response template. 
     
     
         15 . The system of  claim 13 , wherein the detection module is further configured to apply a correlation level threshold to the cross-correlation. 
     
     
         16 . The system of  claim 1 , wherein the communications module comprises a display configured to display an indication of electric charge. 
     
     
         17 . The system of  claim 16 , wherein the indication of electric charge is displayed in coulombs. 
     
     
         18 . The system of  claim 1 , wherein the communications module comprises a display configured to display a distance between the nerve and the surgical instrument. 
     
     
         19 . The system of  claim 18 , wherein the processing module is configured to calculate the displayed distance from the stimulation threshold. 
     
     
         20 . The system of  claim 1 , wherein the communications module comprises a display configured to display a pulse width corresponding to the stimulation threshold.