Where is the ideal reference site for recording the thenar compound muscle action potential
Wee, A.S.; Ashley, R.A.
Electromyography and Clinical Neurophysiology 28(5): 249-252
1988
ISSN/ISBN: 0301-150X PMID: 3191874 Document Number: 316266
In recording electrophysiologic signals, placement of recording electrodes are important variables in determining the resultant shape of the potential. The choice of reference site is as important as the selection of active recording location. When recording the thenar compound muscle action potential (CMAP), the thumb is frequently used as the reference site. In order to define this location exactly, we compared thenar CMAPs obtained from different regions along the thumb. No potential difference was noted between electrodes that were situated at and distal to the interphalangeal joint, either on the dorsal or palmar surface. This finding suggests that the distal thumb segment may ideally serve as the reference site for recording the thenar CMAP, since exact placement of the electrode is not crucial along this segment.