Placement of recording electrode in median and peroneal nerve conduction studies

Motor nerve conduction examinations were performed on the median and peroneal nerves of thirteen normal women (mean age equals 20.4 years). The purpose in this study was to determine the difference and variation of latencies and amplitudes when measured from various recording sites over the abductor pollicis brevis and extensor digitorum brevis. Optimal areas of four square centimeters over the center of the abductor pollicis brevis and over the proximal portion of the extensor digitorum brevis were found to be the most favorable for recording maximum action potential amplitude and shortest latency. The muscle action potentials were found to be diphasic with a sharp onset in a negative direction from the oscilloscope base line when recorded within the optimal area of each muscle. The results of this study indicate that there is a margin for error in recording electrode placement (3 to 4 cm2) before the action potential amplitude or latency measurements are significantly affected.