Distal sensory latency measurement of the superficial radial nerve in normal adult subjects.

The antidromic distal sensory latency of the superficial radial nerve was studied using 2 methods: (I) Recording from a major branch of a nerve as it crosses the extensor pollicis longus tendon, using segments of 10, 12, and 14cm; (II) Recording from the thumb, using segments of 14, 16, and 18cm. The mean latency, to the peak of the negative response, using method I, was 3.1 +/- 0.4 msec (+/- 2SD) and for method 2 was 3.5 +/- 0.6 msec (+/- 2SD), both for the 14cm segment. The amplitude by method I was significantly larger than by method II, making it easier to record. The hand should be warmed if the latency value is outside the normal range and the skin temperature is less than 31C.