Changes in the distribution of nerve conduction velocities in diabetics.

To examine which of the faster or slower large myelinated nerve fibers (alpha fiber group) are affected earlier by diabetes mellitus (DM), the distribution of nerve conduction velocities (DCV) and conventional sensory nerve conduction velocities (SCV) in the median nerve were measured in 10 male DM patients aged 35-58 (mean 50) years. The patients had suffered from DM for 0-30 (mean 11) years; their fasting blood sugar (FBS) levels were 105-363 (mean 219) mg/100 ml. The DCV was expressed by the conduction velocities below which 10, 20, ......, 80 and 90% of active fibers lie (V10, V20, ......, V80 and V90 velocities, respectively). In DM patients, the V30 to V90 velocities of the DCV as well as the SCV were significantly smaller than those of age-matched male controls. The results of multiple regression analysis indicated that FBS was inversely related to V50 to V90 velocities; duration of the disease was also significantly related to V80 and V90 velocities. These data suggest that faster nerve fibers are more susceptible to DM than slower fibers are; changes in conduction velocities of the faster fibers are closely associated with FBS and duration of DM.