Sympathetic skin response in diabetic neuropathy: a prospective clinical and neurophysiological trial on 100 patients.

Sympathetic skin response (SSR) can be employed to assess axonal damage of sympathetic sudomotor neurons in neuropathy. We examined a population of 100 patients with diabetic neuropathy, and 100 age- and sex-matched healthy volunteers. SSR was recorded from the skin of the hand and foot by means of surface electrodes. Stimulation was applied with 30 mA over the median nerve at the wrist contralateral to the derivation site. Irregular interstimulus intervals of more than one minute were applied. Peak-to-peak amplitude measurement showed values of 2.91 +/- 1.10 mV on the hand and 1.37 +/- 0.54 mV on the foot. Latencies lasted 1.44 +/- 0.10 s on the hand and 2.12 +/- 0.15 s on the foot. A total of 37% of the diabetics showed loss of SSR, a further 39% showed amplitude reductions or latency prolongations: Altogether, 76% of all diabetics did not show normal test results. The clinical stage of diabetic neuropathy exerted a significant influence: the further developed the clinical picture of the disease was, the more pathologic were the results of SSR testing. However, even at early stages of neuropathy abnormal values of amplitude reduction or latency prolongation could be observed in over 50% of the patients. SSR examinations performed in diabetics with no or only slight clinical signs of neuropathy may be able to detect those subjects with autonomic disturbances at an initial stage.