Reference values for median nerve conduction to the pronator quadratus.

Objective: To derive a normative database for nerve conduction values of the median nerve to the pronator quadratus using a large and varied subject population.

Design: Descriptive study.

Setting: Private office or university-based clinic.

Participants: Volunteers (N=207), recruited, without risk factors for neuropathy.

Interventions: Not applicable.

Main Outcome Measures: Onset latency, duration, amplitude, and area were recorded for all subjects. Side-to-side variability was calculated and the normative ranges were derived (97th percentile of observed values).

Results: Because the latencies increased with longer distances (longer forearms), the data were divided into 3 categories. The mean latency for those subjects whose distance from stimulator to recording electrode was 23 cm or less was 3.8+/-0.4 ms; the comparable values for those subjects with distances of 23.5 to 24.5 cm was 4.0+/-0.4 ms; and for those with distances of 25 cm and more, 4.5+/-0.4 ms. The amplitude and area varied with age. The mean amplitude for those subjects under 60 years of age was 4.4+/-1.8 mV, while those 60 years and over had an amplitude of 3.7+/-1.7 mV. The upper limit of normative side-to-side variability for latency was 0.6 ms, and the upper limit decrease in amplitude from 1 side to the other was 37%.

Conclusions: This study establishes normative values for the median motor nerve conduction to the pronator quadratus.