Sympathetic Skin Response in Amyotrophic Lateral Sclerosis.

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder characterized by progressive loss of motor neurons, but it is increasingly recognized to be a more disseminated disease. The literature on the involvement of the sympathetic skin response (SSR) in ALS is few.We reviewed the literature with specific emphasis on SSR in ALS and investigated SSR in 120 patients with sporadic ALS and in 130 age-matched healthy subjects to determine the effects of SSR in ALS patients. The SSR was conducted in all ALS patients and healthy subjects.We found prolonged mean SSR latency in ALS patients, and the mean SSR amplitude is reduced compared with that of control subjects, especially in their low extremities (P 0.05). Yet, whichever arm or leg involved, the overall difference in lower extremity SSR measurements between the two groups is significant (P 0.05).The SSR impairment occurs mainly in lower extremities, which is earlier than clinical manifestation of autonomic nervous impairment in ALS. This may be a subclinical manifestation of ALS. We hypothesize that these results are caused by damage to the unmyelinated postganglionic fibers in ALS patients.