[Analysis of proximal conduction time of the median nerve in patients with diabetes mellitus].

Proximal conduction time (PCT) of the median nerve was calculated from the data obtained by conventional motor conduction studies in 272 diabetics and in 35 age-matched healthy controls. M-latency and F-latency obtained by stimulation at the wrist (Mw and Fw, respectively) and M-latency at the Erb's point (Me) were used to calculate PCT (Fw + Mw - 2Me), which represents turnaround time between Erb's point and anterior horn cell. Each indices were corrected using the standard patient's height of 160cm. Severity of diabetic neuropathy was shown by the polyneuropathy index (PNI), which was calculated from 12 indices derived from the motor nerve conduction studies on 4 nerves of the right arm and leg. Significant differences were found in Mw, Fw and Me between diabetics and controls (p < 0.01), although the results of PCT were similar between them. In diabetics Mw (r = -0.55), Fw (r = -0.56) and Me (r = -0.60) had a significant negative correlation with PNI, but the correlation between PCT and PNI was relatively low (r = -0.22). Using the proximal conduction time calculated readily from conventional motor nerve conduction studies, delay in the proximal conduction was shown to be smaller than that in the distal conduction in diabetic polyneuropathy.