Optimal recording electrode placement for radial motor nerve conduction study using extensor indicis muscle: Cadaver and electrophysiological studies

INTRODUCTION/AIMS The aim of this study was to determine the optimal combination of active (E1) and reference (E2) recording electrode placements for the radial motor nerve conduction study recording over the extensor indicis muscle using surface electrodes. METHODS Thirty-six upper limbs from 18 fresh frozen cadavers were dissected to determine the midpoint of the extensor indicis muscle. Radial nerve conduction study was performed in 112 arms of 56 healthy subjects. Six combinations of three E1 and two E2 sites were studied. The stimulation site was 8 cm proximal to the E1 electrode. RESULTS The optimal combination of placement sites for the E1 and E2 electrodes to provide the largest amplitude is E1 electrode at the distal 1/4 point of the forearm length and E2 electrode at the extensor indicis tendon point in the wrist. DISCUSSION Optimal recording electrode placement may increase the accuracy and reproducibility of radial motor nerve conduction studies.