Abstract

Hypnic headache syndrome is a rare headache disorder characterized by recurrent nocturnal attack at a consistent time that awaken the patients from sleep frequently. The pathophysiology is not well known, but a “perturbation of chronologic rhythm” and 'REM related phenomenon' have been suggested. We herein describe two patients with nocturnal headache compatible with a hypnic headache syndrome and the polysomnographic findings and discuss about the clinical features and the pathophysiology. Korean Journal of Headache 1(1):86-91, 2000