Carpal tunnel syndrome: neurophysiological results of surgery based on preoperative electrodiagnostic testing.

Fifty-three hands with carpal tunnel syndrome had pre- and postoperative evaluations of median nerve distal motor latency (from wrist to thenar muscles) and orthodromic sensory nerve conduction velocity (from thumb and middle finger to wrist). At 6 months we observed a neurophysiological return to normal in all cases with normal preoperative distal motor latency and in about 50% of the hands with preoperative distal motor latency between 4 and 6 ms. Prolongation of the distal motor latency over 6 ms was not followed by return to neurophysiological normality, although some degree of sensory function was restored in the majority of cases.