Reference Values for Median Nerve Conduction to the Pronator Quadratus

Foley BS, Roslonski ET, Buschbacher RM. Reference values for median nerve conduction to the pronator quadratus.ObjectiveTo derive a normative database for nerve conduction values of the median nerve to the pronator quadratus using a large and varied subject population.DesignDescriptive study.SettingPrivate office or university-based clinic.ParticipantsVolunteers (N=207), recruited, without risk factors for neuropathy.InterventionsNot applicable.Main Outcome MeasuresOnset 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).ResultsBecause 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 23cm or less was 3.8±0.4ms; the comparable values for those subjects with distances of 23.5 to 24.5cm was 4.0±0.4ms; and for those with distances of 25cm and more, 4.5±0.4ms. The amplitude and area varied with age. The mean amplitude for those subjects under 60 years of age was 4.4±1.8mV, while those 60 years and over had an amplitude of 3.7±1.7mV. The upper limit of normative side-to-side variability for latency was 0.6ms, and the upper limit decrease in amplitude from 1 side to the other was 37%.ConclusionsThis study establishes normative values for the median motor nerve conduction to the pronator quadratus.