Nerve conduction velocity to different muscles in peroneal pressure neuropathy.

The variability inherent in nerve conduction velocity (NCV) studies suggests that multiple measurements may yield more information than a single measurement. To test this hypothesis, three motor nerve conduction velocities (NCVs) of the peroneal nerve were measured: to the extensor digitorum brevis muscle over the fibular head and in the lower leg, and to the tibialis anterior muscle over the fibular head. Three groups were studied: controls, polyneuropathy cases and peroneal pressure neuropathy cases. Over the fibular head, NCVs recorded from the tibialis anterior were consistently higher than those from the extensor digitorum brevis, and showed a higher number of abnormalities. Differences between NCVs, their Z-scores and Mahalanobis distances were compared to study the influence of variance differences and covariances. The best compromise between true and false positives was found to be a comparison between NCVs over the fibular head recorded from the tibialis anterior and the leg segment recorded from the extensor digitorum muscle. Z-scores are more useful than Mahalanobis distances in this respect.