Archive | 2019
REM Sleep Behavior Disorder in Narcolepsy
Abstract
Narcolepsy is a central nervous system hypersomnia characterized by a loss of boundaries between wake and sleep and altered manifestations of rapid eye movement (REM) sleep. Type 1 narcolepsy (NT1), formerly called narcolepsy with cataplexy, is the primary form of narcolepsy due to the loss of hypothalamic hypocretin (orexin)-producing neurons and characterized by excessive daytime sleepiness and by cataplexy, sleep paralysis, and hypnagogic/hypnopompic hallucinations. All the above listed symptoms are considered REM sleep-wakefulness dissociated states, and they frequently overlap. REM sleep behavior disorder (RBD), characterized by intermittent loss of REM sleep muscle atonia and intense motor and/or verbal dream-enacting activity, and REM sleep without atonia (RWA), characterized by wakeful EMG muscle tone surfacing during REM sleep muscle atonia, are also seen as dissociated REM sleep-wakefulness states common in NT1. In NT1 patients, RBD may occur in every REM sleep period, equally represented in the first and in the second part of the night, and at the sleep-onset REM period. RBD in NT1 patients is usually not an every-night phenomenon. Nevertheless, RBD can be the first, often overlooked, heralding symptom of NT1. RBD and RWA in NT1 have a different pathophysiology from that reported in idiopathic RBD, and they do not seem to indicate a prelude to parkinsonism, dysautonomia, or dementia. RBD is rarely a primary and important complaint (i.e., leading to injuries) for NT1 patients, who usually display non-violent enacted behaviors (i.e., task-oriented, reminiscent of lively interactions with objects or other persons).