Motor and sensory nerve action potentials of the median and ulnar nerves were studied in 50 normal subjects. The distal latency, amplitude and area were compared between the two nerves of the same healthy subject. Regarding motor conduction study, the distal latency and amplitude ratio of the median to ulnar nerve were 1.26 and 1.03, respectively.

The amplitude and area of the median sensory nerve action potentials were significantly larger than those of the ulnar nerve, and the distal latency and amplitude ratio of the median to ulnar sensory action potential were 0.98 and 1.23, respectively. The difference of the sensory distal latency was -0.06msec.

A comparison of the parameters between median and ulnar nerve conduction study can be used in the diagnosis of the carpal tunnel syndrome and is particulary useful in those patients who show normal median motor and sensory latency.