REM Sleep Behavior Disorder Associated with Parkinson’s Disease and Multiple System Atrophy

Abstract

Violent and other clinical manifestations of REM sleep behaviour disorder (RBD), presenting in sleep laboratories for diagnostic work-up, have been shown to precede the clinical syndrome of neurodegenerative diseases associated with the misprocessing of α-synuclein. At the time of RBD diagnosis, it is still impossible to foresee whether idiopathic RBD will eventually evolve to Parkinson’s disease (PD), multiple system atrophy (MSA) or dementia with Lewy bodies (DLB). Conversely, in newly diagnosed PD, a meta-analysis of published studies has shown that RBD has been identified in a mean 23.6% (range, 4.3–69.4%) of patients and appears to indicate a specific phenotypically defined subtype of the disease. Although not all PD patients with RBD show violent dream-enacting behaviours and RBD severity may vary from night to night, RBD is an important differential diagnosis for abnormal nocturnal behaviours in PD patients as the disease progresses, encompassing also night-time confusional states, hallucinations and periodic limb movements (PLM). Moreover, the appearance of RBD during the course of PD has been shown to indicate the entrance to a more advanced stage of the disease. In MSA the prevalence of RBD has been determined at 88%. While RBD manifestations prodromal to MSA onset are described by many patients, dream-enacting behaviours seem to disappear over time, and physiologic sleep structure becomes severely disturbed. So far, attempts to differentiate the different types of MSA by sleep analysis have failed, and longitudinal sleep laboratory data are insufficient. Recently a small series of patients with pure autonomic failure (PAF) was published, and these patients had developed RBD during the course of the disease, indicating that PAF may be a mild form of CNS α-synucleinopathy.