RBD - An Emerging Clue to Neurodegenerative Disorders

19 years ago. 1 While rapid eye movement (REM) sleep disorder (RBD) was only first identified in the scientific literature in 1986, Schenck and Mahowald noted in their 2002 review of the disorder how Don Quixote was moving about and slaying evil giants on the high plateaus of Spain’s Castile-La Mancha even in his sleep; a sure sign he was in REM sleep, but had lost the normal muscle atonia associated with REM sleep. 2 The violent behavior of the errant knight is a hallmark of RBD, a behavior that can be acutely dangerous for the individual or his (almost 90% of people with RBD are male) bed partner. However, reports that RBD may be an early indicator for the later development of neurodegenerative disorders, 2 raises the possibility that RBD may be of much greater medical importance than just the danger associated with acting out one’s dreams. A paper in this issue of SLEEP by Consens et al 3 provides further evidence for a link between RBD and neurodegenerative disorder. This paper describes a quantitative method for assessing the severity of RBD polysomnographic (PSG) features in patients at risk for RBD secondary to neurodegenerative disorders. Conversely, there is now compelling evidence that RBD may be an initial manifestation of Parkinson disease (PD), as well as with a number of other neurological disorders, including narcolepsy, multiple symptom atrophy (MSA) and dementia. 2,4 The finding that RBD represents an early warning for the later development of devastating neurological disorders makes it imperative that valid and reliable methods be obtained for assessing patients at risk for RBD. The quantitative method for detecting RBD used by Consens et al involves 2 different PSG scores that measure tonic and phasic events associated with electromyography activity. If such a quantitative method, as originally described by Lapierre and Montplaisir, 5 can be used to detect possible RBD in otherwise healthy individuals, it could be an important tool to be used to guide early intervention therapies to delay and/or attenuate the future devel