Median and radial sensory latencies to digit I: normal values and usefulness in carpal tunnel syndrome.

Median and radial sensory latencies were recorded from digit I at a distance of 10cm in 78 neurologically healthy people aged 20 to 79 years. The mean median latency was 2.5 +/- 0.3ms, and mean radial latency was 2.4 +/- 0.2ms. Both were measured to the negative peak. Twenty individuals with carpal tunnel syndrome determined by traditional electrodiagnostic techniques had at least 1ms longer latency in median nerve than the median latency for the healthy control group. This technique is useful in diagnosis of carpal tunnel syndrome.