Parasomnias

Parasomnias are unusual episodes or behaviours occurring during sleep which disturb the patient or others

• violent or unusual night-time attacks may arise from deep non-Rapid eye movement (REM) sleep (night terrors and sleepwalking) or from REM sleep [sleep paralysis, severe recurrent nightmares, REM behaviour disorder(RBD)]
• treatments depend on which disorder is present

Diagnosis of parasomnias

• assessment of parasomnia may be possible with a detailed history from patient or witness, but in general for adequate diagnosis, referral to a specialist sleep centre for polysomnography and video recording may be necessary especially for RBD where loss of REM atonia is seen

Notes:

• sleep consists of two strikingly different states:
  • Rapid eye movement sleep (REM) and non-rapid eye movement sleep (NREM), which alternate in a cyclical fashion
    • sleep begins with a “shallow” Stage 1 of NREM and “deepens” to NREM Stages 2, 3, and 4
      • which are followed by the first brief episode of REM in approximately 90 minutes
    • after the first sleep cycle, NREM and REM sleep continue alternating in a cyclical fashion
      • duration of each cycle is approximately 90 minutes
    • stages 3 and 4 of NREM sleep (also known as deep sleep, delta sleep, or slow wave sleep) predominate during the first third of the night
    • REM sleep episodes become longer as the night progresses, and the longest REM periods are found in the last third of the night

Reference:

• Wilson S et al. British Association for Psychopharmacology consensus statement on evidence-based treatment of insomnia, parasomnias and circadian rhythm disorders: An update. J Psychopharmacol. 2019 Aug;33(8):923-947
• Zanigi S et al. REM behaviour disorder and neurodegenerative diseases. Sleep Medicine 12 (2011) S54–S58
• Carskadon MA, Dement WC. Normal human sleep: An overview. In: Kryger MH, Roth T, Dement WC, editors. Principles and Practice of Sleep Medicine. Philadelphia, PA: WB Saunders; 2005. pp. 13–23.