Motor nerve conduction velocity measurement as a diagnostic tool

Abstract

A detailed description of a technic for determining peripheral motor nerve conduction velocities is given. Velocities of the fastest conducting alpha motor nerve fibers, terminal nerve conduction times, and residual latencies in normal median and ulnar nerves are presented. These are compared with results obtained in other laboratories. Close agreement indicates the reliability of the determinations. Measurements of motor nerve conduction velocity in normal median nerves with the arm in full extension showed a proximo-distal gradient. Velocity in proximal segments averaged some 10 meters per second greater than that in distal segments. Explanations for this finding are discussed. Three cases of hypertrophic interstitial neuropathy and 2 cases of mild peroneal muscular atrophy showed a marked decrease in conduction velocity of motor nerves. In four of these, terminal conduction times and conduction velocities in ulnar and median nerve segments proximal to the wrist were determined. There was a greater change in terminal conduction times, suggesting a greater distal effect of the neuropathy. The technic has proved useful in the diagnosis of carpal and cubital tunnel syndromes.