System and Methods for Performing Neurophysiologic Assessments During Spine Surgery

Abstract

The present invention relates generally to an algorithm aimed at neurophysiology monitoring, and more particularly to an algorithm capable of quickly finding stimulation thresholds over multiple channels of a neurophysiology monitoring system.

1 . A system for performing neurophysiologic assessments during surgery, comprising:
 a stimulator configured to deliver an electrical stimulation signal to the motor cortex of a patient;   at least one sensor configured to detect neuromuscular responses evoked by the stimulation signal; and   a control unit in communication with the stimulator and the sensor, the control unit being configured to (a) direct transmission of the stimulation signal, (b) receive evoked neuromuscular response data from the sensor, (c) assess spinal cord health by identifying a relationship between the stimulation signal and the neuromuscular response, and (d) communicate the relationship between the stimulation signal and the neuromuscular response to a user via at least one of alpha-numeric indicia and audio.   
   
   
       2 . The system of  claim 1 , wherein the stimulation signal comprises a predetermined number of pulses separated by an interpulse gap, each pulse having a pulse width and a current level. 
   
   
       3 . The system of  claim 2 , wherein the number of pulses ranges from 1 to 8 constant current monophasic pulses, the interpulse gap ranges from 1 ms to 10 ms, and the pulse width ranges from 50 μs to 400 μs. 
   
   
       4 . The surgical system of  claim 3 , wherein the monophasic pulses are at least one of positive phase pulses and negative phase pulses. 
   
   
       5 . The system of  claim 1 , wherein the current level ranges from 0 milliamps to 1000 milliamps. 
   
   
       6 . The system of  claim 2 , wherein the control unit is configured to optimize the stimulation signal at least one of before conducting a neurophysiologic assessment of the spinal cord and after a response to the stimulation signal stops being detected during the neurophysiologic assessment. 
   
   
       7 . The system of  claim 6 , wherein the control unit optimizes the stimulation signal by modifying at least one of the number of pulses, the interpulse gap, the pulse width, and the current level before the neurophysiologic assessment of the spinal cord. 
   
   
       8 . The system of  claim 1 , wherein the relationship identified is the lowest stimulation current necessary to evoke a neuromuscular response. 
   
   
       9 . The system of  claim 1 , wherein the control unit is configured to perform a threshold hunting algorithm to identify the lowest stimulation current necessary to evoke a neuromuscular response. 
   
   
       10 . The system of  claim 9 , wherein the threshold hunting algorithm is based on successive approximation. 
   
   
       11 . The system of  claim 10 , wherein the successive approximation involves: (a) establishing a bracket within which the lowest stimulation current is contained; and (b) successively bisecting the bracket until the lowest stimulation current is determined within a specified accuracy. 
   
   
       12 . The system of  claim 9 , wherein the control unit is configured to perform the threshold hunting algorithm for neuromuscular responses from multiple muscle myotomes. 
   
   
       13 . The system of  claim 1 , further comprising a display in communication with the control unit for displaying the alpha-numeric indicia. 
   
   
       14 . The system of  claim 13 , wherein the display includes touch-screen control capabilities to allow a user to interface with the control unit. 
   
   
       15 . The system of  claim 14 , wherein the touch-screen control allows a user to at least one of select the parameters of the stimulation signal and set a reminder to apply the stimulation signal at a specified time. 
   
   
       16 . The system of  claim 14 , wherein the display is configured to communicate at least one of a baseline neuromuscular response threshold, a secondary neuromuscular response threshold, and the difference between the baseline neuromuscular response threshold and the secondary neuromuscular response threshold. 
   
   
       17 . The system of  claim 1 , wherein the stimulation signal is generated under the direction of the control unit in one of an automatic mode and a manual mode. 
   
   
       18 . The system of  claim 17 , wherein the automatic mode involves having the control unit automatically determine the lowest stimulation current necessary to evoke a neuromuscular response and communicating the lowest stimulation current to a user. 
   
   
       19 . The system of  claim 17 , wherein the manual mode involves having a user set the stimulation current and communicating to the user whether or not a neuromuscular response has been detected for the selected stimulation current. 
   
   
       20 . The system of  claim 1 , comprising a bite-block for placement in the patient's mouth. 
   
   
       21 . The system of  claim 20 , wherein the bite-block is in communication with the control unit and the control unit cannot generate a stimulation signal unless the bite-block is positioned within the patient's mouth. 
   
   
       22 . The system of  claim 21 , wherein the bite-block contains at least one electrode in communication with the control unit. 
   
   
       23 . The system of  claim 1 , comprising a second stimulator configured to deliver a second electrical stimulation signal to one or more peripheral nerves within the patient, the control unit being further configured to direct transmission of the second stimulation signal, (b) receive evoked neuromuscular response data from the sensor in response to the second stimulation signal, (c) assess at least one of bone integrity, nerve direction, nerve pathology, and neuromuscular pathway integrity by identifying a relationship between the second stimulation signal and the neuromuscular response, and (d) communicate the relationship between the stimulation signal and the neuromuscular response to a user via at least one of alpha-numeric indicia and audio. 
   
   
       24 . The system of  claim 23 , further comprising a display in communication with the control unit for displaying the alpha-numeric indicia, wherein the display includes touch-screen control capabilities to allow a user to interface with the control unit. 
   
   
       25 . The system of  claim 24 , wherein the touch-screen control allows a user to selectively switch between any of a variety of screens associated with each of the functions of motor-evoked potential monitoring, bone integrity assessment, nerve direction assessment, nerve pathology assessment, and neuromuscular pathway assessment. 
   
   
       26 . The system of  claim 1 , wherein the control unit and the stimulator communicate via at least one of wire communication and wireless communication. 
   
   
       27 . A system for performing neurophysiologic assessments during surgery, comprising:
 a first stimulator configured to deliver a first electrical stimulation signal to the motor cortex of a patient to perform motor-evoked potential monitoring;   a second stimulator configured to deliver a second electrical stimulation signal to one or more peripheral nerves within the patient to perform at least one of somatosensory evoked potential monitoring, bone integrity assessment, nerve direction assessment, nerve pathology assessment, and neuromuscular pathway assessment;   a processor in communication with the stimulators and a plurality of sensors for detecting the response to the first and second stimulation signals, the processor being configured to (a) direct transmission of the first and second stimulation signals, (b) receive data from the sensors, (c) assess at least one of spinal cord health, bone integrity, nerve direction, nerve pathology, and neuromuscular pathway integrity by identifying a relationship between the stimulation signals and the respective responses, and (d) communicate the relationship between the stimulation signals and the responses to a user via at least one of alpha-numeric indicia and audio.   
   
   
       28 . The system of  claim 27 , wherein the first stimulation signal comprises a predetermined number of pulses separated by an interpulse gap, each pulse having a pulse width and a current level. 
   
   
       29 . The system of  claim 28 , wherein the number of pulses ranges from 1 to 8 constant current monophasic pulses, the interpulse gap ranges from 1 ms to 10 ms, the pulse width ranges from 50 μs to 400 μs, and the current level ranges from 0 milliamps to 1000 milliamps. 
   
   
       30 . The surgical system of  claim 29 , wherein the monophasic pulses are at least one of positive phase pulses and negative phase pulses. 
   
   
       31 . The system of  claim 27 , wherein the processor is configured to optimize the parameters of the first stimulation signal at least one of prior to performing motor-evoked potential monitoring and after a response to the stimulation signal stops being detected during the motor-evoked potential monitoring. 
   
   
       32 . The system of  claim 31 , wherein the processor optimizes the stimulation signal by modifying at least one of the number of pulses, the interpulse gap, the pulse width, and the current level before performing motor-evoked potential monitoring. 
   
   
       33 . The system of  claim 27 , wherein the relationship identified is the lowest stimulation current necessary to evoke a response. 
   
   
       34 . The system of  claim 27 , wherein the processor is configured to perform a threshold hunting algorithm to identify the lowest stimulation current necessary to evoke a response. 
   
   
       35 . The system of  claim 34 , wherein the threshold hunting algorithm is based on successive approximation. 
   
   
       36 . The system of  claim 35 , wherein the successive approximation involves: (a) establishing a bracket within which the lowest stimulation current is contained; and (b) successively bisecting the bracket until the lowest stimulation current is determined within a specified accuracy. 
   
   
       37 . The system of  claim 35 , wherein the processor is configured to perform the threshold hunting algorithm for responses from multiple sites. 
   
   
       38 . The system of  claim 27 , further comprising a display in communication with the processor for displaying the alpha-numeric indicia. 
   
   
       39 . The system of  claim 38 , wherein the display includes touch-screen control capabilities to allow a user to interface with the processor. 
   
   
       40 . The system of  claim 38 , wherein the touch-screen control allows a user to at least one of select the parameters of the first stimulation signal and set a reminder to apply the first stimulation signal at a specified time. 
   
   
       41 . The system of  claim 38 , wherein the display is configured to communicate at least one of a baseline response threshold, a secondary response threshold, and the difference between the baseline response threshold and the secondary response threshold. 
   
   
       42 . The system of  claim 27 , wherein the first stimulation signal is generated under the direction of the processor in one of an automatic mode and a manual mode. 
   
   
       43 . The system of  claim 42 , wherein the automatic mode involves having the processor automatically determine the lowest stimulation current necessary to evoke a response to the first stimulation signal and communicating the lowest stimulation current to a user. 
   
   
       44 . The system of  claim 42 , wherein the manual mode involves having a user set the first stimulation current and communicating to the user whether or not a response has been detected based on the current level of the first stimulation signal. 
   
   
       45 . The system of  claim 27 , comprising a bite-block for placement in the patient's mouth. 
   
   
       46 . The system of  claim 45 , wherein the bite-block is in communication with the processor and the processor cannot generate a stimulation signal unless the bite-block is positioned within the patient's mouth. 
   
   
       47 . The system of  claim 46 , wherein the bite-block contains at least one electrode in communication with the processor.