Hypnic headache: PSG evidence of both REM- and NREM-related attacks.

Hypnic headache (HH) occurs exclusively during sleep. Six attacks were recorded during nocturnal polysomnographic (PSG) monitoring of 10 HH patients. The PSG data obtained indicate that the attacks arose directly from sleep: four from non-REM and two from REM sleep. In no patient were the HH attacks found to show any close temporal relationship with sleep-related breathing abnormalities.