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

2. 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…

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

4. Introduction To Conus Monitoring

5. 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

6. 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

7. 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.

8. Initial Conus Stimulation

9. Signal Dropout at Cage Insertion

10. 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