Objectives: The purpose of this study was to report the differences in the wrist – elbow median mixed nerve forearm evoked potential (WEmix) in subjects with carpal tunnel syndrome (CTS) and a control sample; identifiy correlations and predictive relationships between traditional nerve conduction (NCS) measures of CTS and WEmix; highlight methodological considerations for varying reports in the existing literature pertaining to WEmix; and discuss implications for the clinical use of WEmix and opportunities for further research. Background: The literature is clear that induced axon loss in animals and not demyelination result in RAA which is also time depenedent. There is controversy regarding WEmix as a measure of retrograde axonal atrophy (RAA) in CTS and there are several methodological considerations that may explain this debate. Subjects and Methods: A convenience sample of 38 subjects with electrophysiological evidence of CTS and 31 control volunteers who met the inclusion criteria comprised the sample. Standard NCS used to determine CTS as well as direct and indirect mixed NCS in the forearm were obtained in all subjects. Two-way analysis of variance, Pearson’s correlation coefficients and multiple regressions were used to evaluate the data. Results: There were significantly different findings between groups in all traditional NCS, WEmix and Altmix parameters. There were mild to moderate correlations between WEmix parameters and some traditional NCS measures of CTS. There were significant regressions in WEmix amplitude and velocity with median sensory and motor amplitude. Conclusions: There is a difference in WEmix amplitude and velocity between control and CTS subjects. Measures of axon integrity are predictive of RAA as measured by WEmix, which is consistent with the animal literature. Future research should consider severity and duration of CTS as well as multivariate statistics in the evaluation of WEmix as a measure of RAA. WEmix has potential clinical utility. Normative studies and use of WEmix in the differential assessment of a variety of clinical conditions is suggested.
