Median 14-cm and 7-cm antidromic sensory studies to digits two and three.

The purpose of this study was to derive a normative database for the median digital sensory conduction study using a large and varied subject population. Two hundred fifty-eight asymptomatic volunteers were tested with antidromic sensory technique at 14- and 7-cm distances to digits 2 and 3. Onset latency, peak latency, onset-to-peak amplitude, peak-to-peak amplitude, area, rise time, and duration were recorded. A repeated analysis of variance was performed, with the nerve conduction study measures as the dependent variables and age, race, gender, body mass index, and height as the independent variables. Factors that were significant at the P < or = 0.01 level were used to create separate normal ranges. Both increasing age and increasing body mass index correlated with decreasing amplitudes and area. No other correlations were noted between the results and the physical characteristics. For digit 3, the mean 14-cm onset latency was 2.7 +/- 0.3 ms and mean peak latency was 3.4 +/- 0.3 ms. The mean onset-to-peak amplitude was 41 +/- 20 microV for all subjects taken together. Mean rise time was 0.7 +/- 0.1 ms and mean duration was 2.1 +/- 0.4 ms. Mean side-to-side difference in onset and peak latencies was 0.0 +/- 0.2 ms. The upper limits of normal side-to-side differences in amplitudes and area were approximately 50%-60%.