Abstract Details

Title Waveform Analysis of Transcranial Motor Evoked Potentials (TcMEPs) To Predict Impending Motor Deficits in Spinal Surgeries

Topic Clinical Neurophysiology

Presentation(s) P02 - (-)

Poster/Presentation
Number 234

Objective

Background BACKGROUND: Although a 50% amplitude decrease in somatosensory evoked potentials (SSEPs) correlates with potentially reversible spinal cord injury, there is no corresponding standard warning criteria for TcMEPs. IONM physicians usually alert surgeons after TcMEPs have been completely lost when it is likely that motor injury has already occurred. Other criteria have been proposed but lack consensus.

Design/Methods DESIGN/METHODS: Eleven true-positive cases in 2011-2012 were retrospectively identified at our center: TcMEPs changes occurred during spinal surgery and the patient had a new postoperative motor deficit. TcMEP latency, amplitude, duration, turns, phases, area-under-the-curve (AUC) and an intraoperative-spinal-cord-index (ISCI) were measured or calculated for each involved muscle group at the time of complete TcMEP loss and for five sets of TcMEPs immediately prior.

Results RESULTS: Among the 11 identified cases there were 18 muscle groups monitored with the following changes: 5 TcMEPs increased in latency, 10 TcMEPs decreased in amplitude, 8 TcMEPs decreased in AUC, and 9 TcMEPs decreased in ISCI. The amplitude, AUC, and ISCI tended to decrease before the complete TcMEP loss; however, latency change did not occur before TcMEP loss.

Conclusions CONCLUSIONS: In this retrospective series of motor compromise, there was a trend towards a smaller and simpler waveform before a complete TcMEP loss was detected by IONM. These results also suggest that TcMEPs should be obtained more frequently during IONM to increase the sensitivity of impending motor compromise. Further research on TcMEP waveform changes and the use of different stimulation parameters is warranted to help identify early warning neurophysiologic criteria that can alert physicians before motor injury becomes irreversible.

Authors/Disclosures
Scheherazade Le, MD (Stanford University) PRESENTER	Dr. Le has nothing to disclose.
	No disclosure on file
Sungho K. Cho, MD	Dr. Cho has nothing to disclose.
Rana K. Zabad, MD, FAAN (University of Nebraska Medical Center)	Dr. Zabad has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Bayer. Dr. Zabad has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Biogen. Dr. Zabad has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Genentech. Dr. Zabad has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Celgene/BMS. Dr. Zabad has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Genzyme. Dr. Zabad has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Merck Serono. Dr. Zabad has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Teva Neurosciences. Dr. Zabad has received personal compensation in the range of $500-$4,999 for serving as a Consultant for TG Therapeutics. Dr. Zabad has received personal compensation in the range of $500-$4,999 for serving on a Speakers Bureau for Teva. Dr. Zabad has received personal compensation in the range of $500-$4,999 for serving on a Speakers Bureau for Novartis. Dr. Zabad has received personal compensation in the range of $500-$4,999 for serving on a Speakers Bureau for Genentech. Dr. Zabad has received personal compensation in the range of $500-$4,999 for serving on a Speakers Bureau for BMS. The institution of Dr. Zabad has received research support from Adamas. The institution of Dr. Zabad has received research support from Biogen. The institution of Dr. Zabad has received research support from Novartis. The institution of Dr. Zabad has received research support from Sun Pharma. The institution of Dr. Zabad has received research support from Parexel & MedDay Pharmaceuticals.
Leslie H. Lee, MD, FAAN	Dr. Lee has nothing to disclose.
Viet Nguyen, MD	Dr. Nguyen has received personal compensation for serving as an employee of Biogen. Dr. Nguyen has stock in Biogen.
Jaime R. Lopez, MD (Stanford University School of Medicine)	An immediate family member of Dr. Lopez has received personal compensation for serving as an employee of AbbVie. Dr. Lopez has received personal compensation in the range of $500-$4,999 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for Journal of Clinical Neurophysiology. Dr. Lopez has received personal compensation in the range of $10,000-$49,999 for serving as an Expert Witness for medical-legal consulting.

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