Comparison of median and radial sensory studies to the thumb.

There are multiple reports of neurological injury from both the implantation and the removal of devices utilized in orthopedics. Nerve conduction studies can be a valuable tool in evaluating the acuity, severity, and prognosis of these injuries, as well as in tracking their course. This study was undertaken in an effort to create a large normative database for examining median and radial sensory nerve conduction studies to the first digit. An antidromic technique was employed utilizing a 10-cm distance between the stimulating and recording electrodes. Two hundred three asymptomatic volunteers were tested. Onset latency, peak latency, onset-to-peak amplitude, peak-to-peak amplitude, area, rise time, and duration of the waveforms were measured. Males, older subjects, and those with higher body mass index (BMI) were found to have lower amplitude and area on the median nerve studies. Age was the only variable which demonstrated significant correlation with differing results on the radial nerve studies. Mean onset latencies were 2.1 +/- 0.2 ms for the median nerve and 2.0 +/- 0.2 ms for the radial nerve. Mean peak latencies were 2.7 +/- 0.2 ms for the median nerve and 2.6 +/- 0.2 ms for the radial nerve. Mean peak-to-peak amplitude for the median nerve was 45 +/- 24 muV and for the radial nerve was 12 +/- 9 muV. The upper limit of normal difference in median-versus-radial onset latency was 0.5 ms (0.6 ms for peak latency). The upper limit of normal difference in radial-minus-median onset latency was 0.3 ms (0.4 ms for peak latency).