Correlates of delayed motor nerve conduction and retinopathy in juvenile-onset diabetes mellitus.

Using a protocol designed to eliminate observer bias, we studied the relationship of duration of diabetes, age, blood glucose control, and the presence of retinopathy to motor nerve conduction velocity in patients with juvenile-onset diabetes of short duration. Conduction velocities for both the ulnar and peroneal nerves were significantly slower in the diabetic subjects than in the controls. Duration of diabetes, age, and diabetes control each had significant and independent effects on the prevalence of delayed conduction. Delayed conduction was present in more than 20% of those with diabetes of less than five years' duration, whereas retinopathy was present in none of our subjects with diabetes of the same duration. Moreover, although the presence of retinopathy was closely correlated with the presence of delayed conduction velocity, a number of diabetic subjects had one abnormality but not the other. We believe that delayed nerve conduction and retinopathy in diabetic patients are caused by multifactorial mechanisms that share a common relationship to duration, age, and degree of hyperglycemia, but which differ in at least some fundamental aspects.