Conduction velocity distributions of the human median nerve: comparison of methods.

We have estimated the distribution of conduction velocities (DCV) of large myelinated fibers in the median nerves of 10 normal subjects and a patient with amyotrophic lateral sclerosis (ALS) who had a de-efferented hand, using three different computer-based methods: a 2CAP method, which tests both motor and sensory nerve fibers; and 2MAP and CMAP methods, which test only the alpha motor fibers. The magnitudes of the parameters DCVmax, DCVmean, DCVpeak, and DCVrange all were very similar in the two motor estimations, but all were significantly higher (P less than 0.001 in each case) in the mixed nerve estimates; the differences presumably represent the properties of the faster-conducting sensory fiber population. The 2CAP DCV from the de-efferented nerve resembled those from normal mixed nerve. Compared with DCV analysis, conventional measures of maximal motor and sensory CV were found to be relatively poor indices of the conduction properties of their respective large, myelinated, nerve fiber populations.