Evaluation of Transcutaneous Stimulation of the Thoraco-Lumbo Conus Interim Results of a Feasibility Study Guy Fogel MD, William Taylor MD May 2013

Introduction To Conus Monitoring The Navigational Utility of NVM5® stimulated EMG has been well established It is proposed that more information during retraction may be gathered by monitoring a greater section of the motor neural pathway…

Introduction To Conus Monitoring This may be accomplished by transcutaneous electrical stimulation above the surgical site, and recording from muscle groups below

Introduction To Conus Monitoring

Methods Set up using NVM5® using MEP modality with surface electrodes Stimulation cathode posterior at conus; anode anterior below umbilicus TIVA is not required, due to direct motor. No complications such as tongue laceration (a limitation of trans-cranial MEPs) Same requirement as EMG for absence of paralytic

Methods Recording from major muscles of the lower extremities Establish a pre-op MEP baseline for comparison of subsequent stim results Repeat motor stims at key surgical steps in the XLIF procedure, integrated with surgical workflow Perform final motor stims after retractor removal and at closing

Results 12 XLIF cases under IRB using the method Reproducible responses were obtained in all subjects Relatively insensitive to body mass and electrode placement Stim levels ranged from 150 to 900 mA All but one had normal Conus study and normal neurologic after surgery. One of the 12 had post-op groin and thigh pain without weakness. This correlated to signal drop during surgery.

Initial Conus Stimulation

Signal Dropout at Cage Insertion

Conclusions Reproducible responses were obtained in 100% of subjects, regardless of BMI for the range observed There were no observed complications related to the monitoring method A continuation and expansion of the study is in process to add pre and post op neural exams to correlate with the monitoring results Without surgeon user interface-- Not ready for prime time This is preliminary data that will require regulatory hurdles including updated FDA 510K