Parasomnias (also known as disorders of arousal) are a group of sleep disorders characterized by abnormal behavioral, experiential, or physiological events occurring in association with sleep, specific sleep stages, or sleep-wake transitions.

The most common parasomnias are the group of non-rapid eye movement (NREM) sleep arousal disorders and rapid eye movement (REM) sleep behavior disorder. These conditions serve as a reminder that sleep and wakefulness are not mutually exclusive and that sleep is not necessarily a global, whole-brain phenomenon.

Some key questions can be asked to screen for parasomnias:

  1. Have you ever hurt yourself or your partner while asleep?
  2. Do you eat or drink without full awareness during the night?
  3. Do you or your bed partner believe that you move your arms, legs, or body too much or have unusual behaviour during sleep?
  4. Do you move while dreaming as though you are attempting to carry out a dream?


You can REMember events (i.e. - no confusion, no amnesia) in REM parasomnias!

Comparison of Parasomnias

Parasomnia Type Stage of Arousal Time of Night EEG during event EMG during event Unresponsive during event Autonomic activity Anmesia Confusion post-episode Family history of parasomnias
Confusional Arousal NREM NREM Stage 2-4 Anytime N/A Low Yes Low Yes Yes Yes
Sleepwalking NREM NREM Stage 3-4 First 2 hours Mixed Low Yes Low Yes Yes Yes
Sleep terrors NREM NREM Stage 3-4 First 2 hours Mixed Low Yes High Yes Yes Yes
REM sleep behaviour disorder REM REM Anytime (but more likely later half) Characteristic of REM High Yes High No No (can remember the dreams!) No
Nightmare disorder REM REM Anytime N/A N/A Yes High No No (can remember the dreams!) No

Brief arousals from SWS is suggestive of parasomnias (think: the brain is fast asleep, but muscles and other movements are occurring and this showing on PSG).