Electrodiagnostic study of sympathetic skin response (SSR) was performed on 40 normal subjects who had no history of sympathetic dysfunction.

The major results were as follows:

1) Stimulating the left median nerve at the wrist, the latencies of the SSR recorded at both palms and soles were: 1.37±0.18 sec (Rt. palm), 1.26±0.15 sec (Lt. palm), 1.66±0.20 sec (Rt. sole), and 1.69±0.18 sec (Lt. sole), respectively.

2) Stimulating the right tibial nerve at the ankle, the latencies of the SSR recorded at both palms and soles were: 1.66±0.22 sec (Rt. palm), 1.62±0.30 sec (Lt. palm), 1.48±0.26 sec (Rt. sole), and 1.62±0.26 sec (Lt. sole), respectively.

3) The Amplitudes of the SSR recorded at the palm were greater than those recorded at the sole regardless of the site of stimulation.

4) The conduction velocity of the postganglionic sympathetic nerve in upper extremity (1.42±0.25 m/sec) was faster than in lower extremity (1.06±0.25 m/sec).