Median nerve electrophysiologic parameters and psychomotor performance in carpal tunnel syndrome

Psychomotor performance (PMP) involving a repeated, rapid pinch and release task was correlated with median nerve electrophysiologic parameters for control subjects (16 hands) and subjects with carpal tunnel syndrome (CTS) (14 hands). The psychomotor task was used because of its functional resemblance to many work related activities. A strain gauge dynamometer was repeatedly pinched to a predetermined force level using the index finger and thumb and then released as rapidly as possible, while measuring the actual isometric force exerted. Discrete visual and auditory feedback was provided. Median and ulnar nerve motor latencies and amplitudes, as well as median antidromic sensory latencies and amplitudes, and transcarpal latencies and amplitudes were obtained. CTS subjects had longer median motor and sensory latencies and were weaker than controls, however median motor and sensory amplitudes were not statistically different. A strong relationship was observed between electrophysiologic variables and PMP, which could not be accounted for by age differences alone. It is unclear whether the measured differences in PMP are related to sensory or motor deficits.