REM parasomnias

Federica Provini MD (

Dr. Provini of the University of Bologna and IRCCS Institute of Neurological Sciences of Bologna received speakers' fees from Eisai Japan and Italfarmaco and consulting fees from Zambon.

Luca Baldelli MD (

Dr. Baldelli of the University of Bologna has no relevant financial relationships to disclose.

Antonio Culebras MD, editor. (

Dr. Culebras of SUNY Upstate Medical University at Syracuse received an honorariums from Jazz Pharmaceuticals for a speaking engagements.

Originally released May 26, 2020; expires May 26, 2023

This article includes discussion of REM parasomnias, REM sleep behavior disorder (RBD), nightmares disorder, and recurrent isolated sleep paralysis. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.


Parasomnias are undesirable events, consisting in abnormal behaviors during sleep due to the inappropriate activation of the cognitive process or physiological systems such as the motor and/or autonomic nervous system. For this reason, parasomnias are conditions constituting a window into brain function during sleep. Parasomnias are common in the general population. 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. In this article, the authors describe the characteristics of REM parasomnias, suggesting the key points for a decisive diagnostic workup.

Key points


• Parasomnias are common.


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


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


• Parasomnias must be distinguished from other 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. The description of the monstrous metamorphosis of Gregor Samsa, the protagonist of The Metamorphosis by Kafka, has been interpreted as a nightmare (Perciaccante and Coralli 2016). Sleep paralysis plays a role in the writing of great novelists, including Dostoevsky in The Brothers Karamazov and Maupassant (The Horla) (Stefani et al 2019). In the fine arts, Johann Heinrich Füssli's 1775 painting “The Nightmare” may reflect sleep paralysis with a hypnagogic hallucination (Stefani et al 2019).

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