Cluster headache: on the mechanism behind attack-related sweating.

Eighteen cluster headache patients were studied using body heating or exercise tests; all but two of them were also studied with a pilocarpine test (0.1 mg/kg body wt, s.c.). Evaporimeter measurements were made on both sides of the forehead under standard conditions in a thermo room. Heat- and exercise-induced sweating was clearly less pronounced on the symptomatic side than on the non-symptomatic side of the forehead, and was significantly different compared to controls. Pilocarpine on the other hand induced a clearly more pronounced response on the symptomatic side than on the non-symptomatic side, which was also statistically significantly higher than in the control group. These findings suggest a supersensitivity of the sweat glands to pilocarpine on the symptomatic side of the forehead in most cases of cluster headache.