Sympathetic skin response in diabetic neuropathy.

Sympathetic function test was undertaken using the sympathetic skin response (SSR), a technique for assessment of sudomotor activity, in 67 diabetics, and the results were compared with those from 45 age-matched normal subjects. The SSR was readily elicitable in normal subjects, but absent in six patients with diabetes. In 28 patients, the SSR was preserved, but their amplitude was below the normal range. The decrease in the SSR amplitude correlated well with a fall in motor and sensory conduction velocity. The SSR magnitude correlated well to the impaired R-R interval variation during deep breathing and the heart rate increase and the blood pressure change on standing, indicating a close correlation between the disturbance of sudomotor function and that of other sympathetic and parasympathetic functions. Most of the patients with clinical evidence of dysautonomia and with insulin treatment revealed diminished or absent SSR.