REM Sleep Behavior Disorder and Narcolepsy

REM (rapid eye movement) sleep behavior disorder (RBD) is a well known parasomnia [1]. Its first description in humans dates back to 1985, and its first description in narcoleptic patients to 1992. Although the precise pathophysiology of RBD remains unclear, it is likely, in the case of RBD associated with narcolepsy, that the altered function of hypocretin pathways projecting from the lateral hypothalamus to the ventrolateral part of the periaqueductal grey matter and the lateral pontine tegmentum has a consistent role. The percentage of narcoleptic patients complaining of clinical RBD lies somewhere between 10 and 15% of the narcoleptic population. The age of onset is younger than in the other forms of chronic RBD. Clinical features are the same as in the other forms of chronic RBD, but the frequency of the episodes is less marked. Associated features include other parasomnias, periodic limb movements in sleep (PLMs) and olfactory dysfunction. Polysomnographic tracings are remarkable for elevated submental electromyographic (EMG) tone and/or excessive phasic submental EMG twitching. Data on human leukocyte antigen (HLA) association and on cerebrospinal fluid (CSF) hypocretin/orexin levels are limited. Clinical variants include RBD induced or worsened by pharmacological agents, most of them being used to treat cataplexy, RBD in narcoleptic children and RBD in the context of symptomatic narcolepsy. Several treatments of RBD are available including clonazepam, melatonin and more recently pramipexole. However, in the absence of any pharmacological trials of these drugs on RBD in narcoleptic patients, it is difficult to provide guidance other than to recommend conventional treatments of RBD.