Cluster headache: forehead sweating pattern during heating and pilocarpine tests. Variation as a function of time.

Thirty-one patients with cluster headache were examined with regard to their forehead sweating pattern, by means of the Evaporimeter. Sweating was stimulated in two different ways: by body heating and by parenterally administered pilocarpine. The resulting increase in evaporation was frequently measured at different positions on both sides of the forehead, and the possibility of variations in the pattern related to the passage of time was specifically scrutinized. Some typical patterns emerged. The previously reported, marked asymmetries of response (deficient heat-induced sweating and pilocarpine supersensitivity of the symptomatic side) at the medial positions in the forehead were confirmed. However, the asymmetries invariably faded to some extent with the passage of time. Patients with cluster headache show gross similarities with, but also some minor differences from, the sweat pattern of patients with brain stem lesions causing a Horner's syndrome. A subdivision of the material into groups in accordance with the pupillometric pattern after sympathomimetic stimulation made it clear that the cases of definite evaporimetric asymmetries ("typical reactions") belonged to the group with a typical pupillometric pattern. These results suggest that from an "autonomic" point of view, subpopulations may exist within the clinical entity of cluster headache.