Pupillary functional asymmetry in patients with muscle contraction headache.

Twenty-five patients with 'muscle contraction headache' (MCH) underwent tyramine pupillary tests, and 15 of them also underwent physiologic pupillary tests and cold pressor tests. Twenty healthy controls underwent tyramine pupillary tests, physiologic pupillary tests, and cold pressor tests. In the tyramine pupillary tests and the physiologic pupillary tests, the controls showed a symmetric mydriasis. In contrast, MCH patients showed asymmetric mydriasis after tyramine instillation and in the physiologic pupillary tests. In the cold pressor tests MCH patients reacted in the same manner as the controls. It is suggested that MCH patients have pupillary sympathetic imbalance. The role of this imbalance in the pathogenesis of MCH remains uncertain.