Paired study of the dorsal cutaneous ulnar and superficial radial sensory nerves.

Nerve conduction studies of the dorsal cutaneous ulnar nerve (DCU) have been suggested as a useful technique for identifying distal ulnar nerve lesions. In this study a standardized method was used to establish normal conduction parameters of the DCU that were compared to conduction parameters of the superficial radial sensory nerve (SR) in the same extremity. Fifty-five extremities of 33 neurologically healthy subjects aged 22 to 69 years (mean = 37; SD = 13) were examined. Dorsal hand skin temperature of each subject was 31 to 36 C. The DCU and SR were antidromically stimulated 14cm proximal to plastic-mounted bipolar electrodes placed on the dorsum of the hand over each nerve. Latency to onset, latency to peak, and amplitude (mean +/- 2SD) for the DCU were 2.2 +/- 0.3msec, 2.8 +/- 0.5msec, and 24 +/- 17 microV; and for the SR were 2.2 +/- 0.3msec, 2.8 +/- 0.3msec, and 32 +/- 18 microV, respectively. Significant correlations (p less than 0.005) were found between the DCU and SR latencies to onset, and DCU and SR latencies to peak. These results suggest that distal sensory latencies of the DCU and SR are similar, and that a paired study of these nerves may be useful in distinguishing distal ulnar nerve entrapment syndromes when routine studies are equivocal.