Three cases of parasomnias similar to sleep terrors occurring during sleep-wake transitions from REM sleep.

Sleep terrors are a non-rapid eye movement (NREM) sleep related parasomnia characterized by abrupt terror with a frightening scream. However, it remains unknown whether sleep terrors occur only from NREM sleep. We evaluated three cases of a sleep terrors-like parasomnia which occurred exclusively during arousals from rapid eye movement (REM) sleep. These parasomnia events occurred at REM sleep-wake transitions, manifesting with screaming or crying, similar to sleep terrors, without alertness or clear orientation. The patients were all young adult females without notable medical conditions. REM sleep behavior disorder and nocturnal frontal lobe epilepsy were not detected based on their video-polysomnographic findings. These three cases should be provisionally diagnosed as "Parasomnia, Unspecified" according to the International Classification of Sleep Disorders, third edition, however, the phenomenological diagnosis is proposed to be "Disorders of Arousal from REM Sleep." Our reported cases indicate that sleep terrors may also arise from REM sleep.