NonREM parasomnias

Federica Provini MD (

Dr. Provini of the University of Bologna and IRCCS Institute of Neurological Sciences of Bologna received speakers' fees from Italfarmaco and Pfizer.

Giuseppe Loddo MD (Dr. Loddo of the University of Bologna has no relevant financial relationships to disclose.)
Antonio Culebras MD FAAN FAHA FAASM, editor. (

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

Originally released October 11, 1993; last updated May 12, 2020; expires May 12, 2023

This article includes discussion of parasomnias, NREM parasomnias, arousal disorders, confusional arousals, sleep terror, sleepwalking, sleep-related eating disorder, exploding head syndrome, and nocturnal enuresis. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.


Parasomnias are undesirable but not always pathological events. They consist 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, occurring more frequently in children. 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. Many problems hamper a differential diagnosis between non-REM parasomnias and epileptic seizures occurring during sleep. In this article, the authors describe the characteristics of the most frequent parasomnias, suggesting the key points for a decisive diagnostic workup.

Key points


• Parasomnias are common, especially among children.


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


• NREM parasomnias are usually benign phenomena but sometimes could lead to injuries affecting not only the patient but also the bed partner.


• Parasomnias must be distinguished from epileptic seizures arising from sleep.


• 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. Perhaps the most famous literary examples of parasomnia are the sleepwalking and sleeptalking events by Lady Macbeth in Shakespeare's Macbeth, Moncrieff's Somnambulist, a play regarding a nighttime walking phantom, and Bellini's La Sonnambula, an innocent girl who suffers from a quirk of nature, hence, eliciting sympathy and compassion. In the novel Tess of the d'Urbervilles Thomas Hardy describes 1 of the most fascinating and convincing scenes of sleepwalking ever written (Parrino 2016). 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).

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