Hypnic Headache Syndrome: Association of the Attacks with Rem Sleep

We describe the polysomnographic data of two patients with nocturnal headache attacks fulfilling the clinical criteria for hypnic headache syndrome. Two overnight polysomnographic studies were performed in each patient. Four nocturnal headache attacks were captured, all emerging from the REM phase of sleep. Our findings suggest a close relationship between the REM phase of sleep and the appearance of hypnic headache attacks.