Ulnar nerve motor conduction to the abductor digiti minimi.

Abstract

Ulnar motor study to the abductor digiti minimi is commonly performed, but a more extensive database of normative values using modern electrodiagnostic and statistical techniques and temperature control is needed for this test. Demographic subgroups of age, gender, and height should be evaluated using a large subject population to determine whether separate normal ranges should be created for subsets of the general population. In this study, 248 volunteers were tested to measure ulnar motor latency, amplitude, area, duration, and nerve conduction velocity. Side-to-side and distal-to-proximal variability was analyzed. A repeated measures analysis of variance was performed with the waveform measures as the dependent variables and age, gender, and height as independent variables. None of the results were found to vary significantly (at the P < or = 0.01 level) with the subjects' physical characteristics, and thus, the data for all subjects were pooled to create a normative database. The normal range was derived as mean +/- 2 standard deviations and at the 97th (third) percentile of observed values. Mean latency was 3.0 +/- 0.3 ms, and amplitude was 11.6 +/- 2.1 mV. Mean nerve conduction velocity was 61 m/s across all segments tested. The upper limit of normal side-to-side variability (mean + 2 standard deviations) for latency was 0.6 ms; for amplitude, it was 3.6 mV. The upper limit of normal drop in conduction velocity across the elbow was 15 m/s (at the 97th percentile). Additional data are presented for all variables measured, as well as for side-to-side variability and distal-to-proximal change.