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  • Updated 08.15.2023
  • Released 05.26.2020
  • Expires For CME 08.15.2026

REM sleep-related parasomnias



Parasomnias are common undesirable physical events or experiences during entry into sleep, within sleep, or during arousals from sleep. Parasomnias are due to inappropriate activation of the cognitive process or physiological systems, such as the motor or autonomic nervous system. For this reason, parasomnias are conditions constituting a window into brain function during sleep. When episodes are frequent, they can result in sleep disruption and injuries, with adverse health or psychosocial consequences for the patients, bed partners, or both. It is, thus, necessary for clinicians to recognize, evaluate, and manage these sleep disorders. Parasomnias may occur during non-rapid eye movement sleep, rapid eye movement sleep, or during the sleep-wake transition. REM-related parasomnias include REM sleep behavior disorder, recurrent isolated sleep paralysis, and nightmare disorder. In this article, the authors describe the characteristics of REM-related parasomnias, suggesting the key points for a decisive diagnostic workup.

Key points

• Parasomnias are common in the general population.

• The large number of parasomnias underscores that sleep is not simply a quiescent state but can involve experiences or behaviors that are more or less complex.

• Some parasomnias are usually benign phenomena (eg, isolated sleep paralysis); other parasomnias (eg, REM sleep behavior disorder) are true diseases that could lead to injuries affecting not only the patient but also their bed partner.

• Parasomnias must be distinguished from other sleep-related motor behaviors (eg, epileptic seizures arising from sleep).

• The evaluation of parasomnias depends on an accurate history and clear description of the events.

• Video-polysomnography remains the most useful support for the final diagnosis.

Historical note and terminology

Parasomnias have attracted the interest of writers and scholars for centuries. Their sometimes dramatic manifestations have been described by many. Miguel de Cervantes described a typical REM sleep behavior disorder episode in which Don Quixote shouts and vigorously attacks some wineskins while dreaming that he is fighting a giant (18). The description of the monstrous metamorphosis of Gregor Samsa, the protagonist of The Metamorphosis by Kafka, has been interpreted as a nightmare (35). Sleep paralysis plays a role in the writing of great novelists, including Dostoevsky in The Brothers Karamazov and Maupassant (The Horla) (46). In the fine arts, Johann Heinrich Füssli’s 1775 painting “The Nightmare” may reflect sleep paralysis with a hypnagogic hallucination (46).

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