Tibial nerve conduction to the flexor digiti minimi brevis.

Abstract

This study was performed to create an improved database of normative data for tibial motor conduction to the flexor digiti minimi brevis. A total of 205 volunteers were tested to measure lateral tibial motor latency, amplitude, area, and duration. Side-to-side variability was analyzed. A repeated measures analysis of variance was performed with the waveform measures as the dependent variables and age, gender, height, and bimalleolar width as independent variables. An association was noted between increasing age and decreasing amplitude and area. The normal range was derived as mean +/- 2 SD and at the 97th (third) percentile of observed values. Mean onset latency was 6.4 ms (SD, 1.0). Mean amplitude varied by age and ranged from 4.7 mV to 7.8 mV (SD, 3.1-3.2). The upper limit of side-to-side latency variation was 1.8 ms (at mean + 2 SD) or 1.5 ms (at the 97th percentile). The upper limit of normal variation in amplitude from one side to the other was 4.6 mV (by mean + 2 SD) or 6.3 mV (at the 97th percentile). This corresponded to a 58% drop in amplitude. The upper limit of normal difference between the medial and lateral branches was an increase of 3.5 ms of the lateral over the medial latency or a medial latency that was within 0.3 ms of the lateral latency (or longer). The other measures are presented in the article.