The sympathetic skin response in diabetic neuropathy and its relationship to autonomic symptoms

OBJECTIVE: To examine the utility of the sympathetic skin response SSR as a measure of impaired autonomic function among diabetic patients in Saudi Arabia. METHODS: In this case-control study, baseline SSR was obtained from 18 healthy subjects, followed by nerve conduction studies, and SSR testing on a consecutive cohort of 50 diabetic patients with peripheral neuropathy. The SSR in diabetic patients was compared between those with autonomic neuropathy and those without autonomic neuropathy. This study was conducted at the King Khaled University Hospital, Riyadh, Saudi Arabia, from June 2006 to June 2007. RESULTS: The SSR was present in all healthy subjects, and in 32 diabetic patients. Among 16 patients with autonomic neuropathy, the SSR was absent in 14 and present in 2, while 4 of 34 patients lacking evidence of autonomic neuropathy had absent SSR. Using Fisher's exact test, we found a strong association between absent SSR and autonomic neuropathy p<0.001, however, not with age or duration of diabetes mellitus. As a diagnostic test of autonomic neuropathy, the SSR had a sensitivity of 87.5%, a specificity of 88.2%, a positive predictive value of 77.8%, and a negative predictive value of 93.7%. CONCLUSION: Absence of the SSR is a reliable indicator of autonomic neuropathy among patients with diabetes mellitus in Saudi Arabia.