In this article, the author reviews parasomnia overlap disorder and status dissociatus. Clinicians are occasionally faced with patients who have clinical features of both nonrapid eye movement (NREM) parasomnias and REM sleep behavior disorder (RBD), making management difficult. The epidemiology, etiology, investigation, and management of this condition are summarized. In addition there is a detailed review of status dissociatus, a severe motor parasomnia in which features of wake and sleep states coexist. Importantly, status dissociatus is occasionally caused by voltage-gated potassium channel antibody syndromes and treatable with immunomodulating therapy.
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• Parasomnia overlap disorder occurs when patients demonstrate features of both nonrapid eye movement (NREM) parasomnias (sleepwalking, confusional arousals) and REM sleep behavior disorder (RBD); it is relatively common in the parasomnia population.
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• Patients with parasomnia overlap disorder are predominantly male and younger than most idiopathic cases of REM sleep behavior disorder.
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• Clinical history alone is insufficient to properly diagnose parasomnia overlap disorder as cryptic confusional arousals and sleepwalking can occur together with RBD. Conversely, subtle dream-enactment behavior is common among adult patients with NREM parasomnias as well as in the general population.
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• Polysomnography in parasomnia overlap disorder typically demonstrates NREM sleep instability in combination with a lack of REM sleep atonia (at times with dream-enactment behaviors).
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• Treatment of parasomnia overlap disorder should be focused on resolving comorbid conditions that fragment sleep, such as sleep-disordered breathing, and the elimination of suspected precipitating pharmacology. Clonazepam is often effective, particularly for patients with violent dream-enactment behavior. For medication-resistant patients, a customized bed alarm may help prevent sleep-related injury.
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• Status dissociatus is an extreme form of parasomnia overlap wherein features of NREM sleep, REM sleep, and wakefulness coexist. This breakdown in wake-sleep state boundaries appears to be caused by pathologies involving GABAergic circuits in the thalamus, including fatal familial insomnia, delirium tremens, Morvan syndrome (and other related antipotassium channel antibody disorders), and anti-NMDA receptor encephalitis. Status dissociatus may also represent the final, fulminant manifestation of multiple system atrophy and dementia with Lewy Bodies (03).
Historical note and terminology
Early reports of sleepwalking date to the writings of Hippocrates and Galen. In 1968, sleepwalking was identified as a disorder of arousal emanating from deep nonrapid eye movement (NREM) sleep (07). In 1986, a series of patients with violent dream-enactment behavior with a paucity of REM sleep atonia was reported, and the condition was named “REM sleep behavior disorder” (RBD) (49). Subsequently, in 1997 a series of 33 cases with combined NREM parasomnias and RBD was reported, with the condition named “parasomnia overlap disorder” (50).
In 1991, status dissociatus was reported in 6 patients with neurodegeneration, anoxic injury, or severe ethanol withdrawal (34). Later, etiologies included prion, neurodegeneration, autoimmune disease, and various toxic etiologies (03).