Carpal tunnel syndrome(CTS) is one of the most common peripheral nerve entrapment syndrome. Recently, the effect of wrist flexion and extension posture on median sensory nerve conduction has been considered valuable as an assessment of early CTS. Therefore, we perfomed this study to determine whether flexion or extension of the wrist would produce a change in distal sensory latency of the median nerve and to determine delay pattern on median sensory nerve latency according to a time sequence.

Control group is consist of 15 healthy adults without evidence of peripheral neuropathy and CTS group is consist of 15 patients with evidence of median neuropathy at wrist in conventional nerve conduction study. We measured distal latency and amplitude of median sensory nerve at neutral position of wrist at first, and then with a wrist extension splint, we measured distal latency and amplitude at every 30 second up to 5 minutes. Thereafter, with a wrist flexion splint, we measured the same as above.

The result were as follows: The change in peak latency of the median sensory evoked response after wrist flexion for 5 minutes is 0.05 msec in control group and 0.10 msec in CTS group. There were no significant differences between two groups. The change in peak latency of the median sensory evoked response after wrist extension for 5 minutes is 0.09 msec in control group and 0.19 msec in CTS group. There were significant differences between two groups. The differences between peak latencies of the median sensory evoked response after wrist flexion and extension for 5 minutes were significant. The maximal latency delay occurs within first 30 seconds in both wrist flexion and extension groups of CTS. In wrist flexion group of CTS, most of latency delay occur within 2.5 minutes, in wrist extension group of CTS, latency delay occur up to 5 minutes.

We think that the test of wrist flexion and extension posture by means of wrist splint on median sensory nerve conduction should considered as an assessment of early CTS without evidence of median neuropathy on the conventional nerve conduction study.