Influence of age and the severity of median nerve compression on forearm median motor conduction velocity in carpal tunnel syndrome.

Forearm median motor conduction velocity (FMCV) is reduced in carpal tunnel syndrome (CTS). The aim of this study was to investigate the association of FMCV with age and severity of median nerve compression. Forearm median motor conduction velocity and median nerve motor distal latencies were measured in 312 CTS hands. Forearm median motor conduction velocity correlated negatively with age. This correlation persisted in the subgroups of hands with severe and less severe CTS. Forearm median motor conduction velocity correlated negatively with the degree of compression (as measured by median nerve motor distal latencies). This correlation persisted in subgroup of hands with severe CTS but not in less severe ones. Multiple regression analysis comparing the influence of age and median nerve motor distal latencies on FMCV showed higher standardized coefficients (beta) value for age than for median nerve motor distal latencies, suggesting a greater influence for age. The beta value for age is higher in severe group than in less severe group, suggesting that age has higher influence on FMCV in severe group. The degree of compression influences FMCV in hands with severe CTS but not in hands with less severe CTS. This difference in severe and less severe CTS may be because of the differences in the underlying pathophysiological processes in the 2 entities.