Mixed nerve conduction studies of the median and ulnar nerves.

The median mixed nerve conduction study, using an 8-cm technique across the wrist, has been described as a particularly sensitive test for carpal tunnel syndrome. This test is usually performed along with a similar ulnar study to detect relative slowing of one nerve v the other. Several authors have investigated the normal range in nerve conductions of this test. Most of these studies were performed using relatively small numbers of subjects, and some did not use standardized distance measurement and temperature control. They also did not measure all the waveform variables that are easily obtained with modern equipment. The purpose of this study was to create a large database of normal values for the median and ulnar studies. Two hundred forty-eight subjects were tested bilaterally. Data were collected for onset latency, peak latency, onset-to-peak amplitude, peak-to-peak amplitude, area, rise time, duration, side-to-side variability, and between-nerve variability. Increasing age, body mass index, and male gender correlated with decreasing amplitude and area values. For both nerves, the mean onset latency was 1.6 +/- 0.2 ms, and the mean peak latency was 2.1 +/- 0.2 ms. For the median nerve, the mean onset-to-peak amplitude was 75 +/- 47 microV, and the mean peak-to-peak amplitude was 80 +/- 48 microV. For the ulnar nerve, the mean onset-to-peak amplitude was 27 +/- 17 microV, and the mean peak-to-peak amplitude was 29 +/- 22 microV. Mean side-to-side difference for the median and ulnar onset and peak latencies was 0.0 +/- 0.2 ms. The mean difference between onset and peak latencies between the nerves was 0.0 +/- 0.2 ms. The other results are presented in the article.