Abstract Details

Title Which Nerve Conduction Parameters Can Predict Axonal Degeneration in Carpal Tunnel Syndrome?

Topic Clinical Neurophysiology

Presentation(s) P02 - (-)

Poster/Presentation
Number 229

Objective

Background BACKGROUND: Electromyography (EMG) of the abductor pollicis brevis (APB) muscle is considered optional because it provides the information about axonal loss or ongoing degeneration; however, if this information could be predicted from the nerve conduction studies parameters, the patient could avoid the unpleasant needle EMG examination.

Design/Methods DESIGN/METHODS: CTS patients and normal controls were evaluated using electrodiagnostic techniques, including median distal sensory and motor latencies, sensory nerve action potential, compound muscle action potential (CMAP), forearm median nerve conduction velocity, wrist-palm motor conduction velocity. All CTS patients underwent EMG on abductor pollicis brevis (APB) muscles. and the presence or absence of spontaneous activities on EMG. The association between nerve conduction studies results and EMG findings were investigated.

Results RESULTS: 229 CTS patients and 100 normal controls were enrolled. Abnormal median CMAP amplitude was the best predictor of spontaneous activities on EMG (p < 0.001; OR36.58; 95%CI 15.85-84.43). If median CMAP amplitude was equal to or lower than 2.1 mV, the rate of spontaneous activities was > 95% (positive predictive rate > 95%) and the patients did not need further needle EMG study. Surgical intervention was suggested. If median CMAP was larger than normal limits (>4.9 mV), the rate of no spontaneous activity was >94% (negative predictive rate > 94%) and the patients also did not need EMG study. Abnormal SNAP amplitude was the second best predictor of spontaneous activities on EMG (p < 0.001; OR4.13; 95%CI 2.16-7.90).

Conclusions CONCLUSIONS: In clinical practice, abnormal median CMAP amplitude can predict axonal degeneration in CTS patients. We suggest that the performance of needle EMG should be considered only in those CTS patients whose nerve conduction studies reveal CMAP amplitude between 2.1 mV and the lower normal limit in the current study (4.9 mV).

Authors/Disclosures
Ming-hong Chang, MD (Taichung Veterans General Hospital) PRESENTER	Dr. Chang has nothing to disclose.
Michael S. Okun, MD, FAAN (University of Florida)	Dr. Okun has received personal compensation in the range of $0-$499 for serving on a Scientific Advisory or Data Safety Monitoring board for NIH. Dr. Okun has received personal compensation in the range of $10,000-$49,999 for serving as an officer or member of the Board of Directors for Parkinson's Foundation. Dr. Okun has received personal compensation in the range of $5,000-$9,999 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for JAMA Neurology. Dr. Okun has received personal compensation in the range of $500-$4,999 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for NEJM Journal Watch. The institution of Dr. Okun has received research support from NIH. The institution of Dr. Okun has received research support from Parkinson's Foundation. The institution of Dr. Okun has received research support from Tourette Association of America. The institution of Dr. Okun has received research support from Michael J Fox. Dr. Okun has received publishing royalties from a publication relating to health care.

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