REM Sleep Behavior Disorder: a Prodromal Synucleinopathy

Rapid eye movement sleep behavior disorder (RBD) is an abnormal condition that constitutes dream enactment behavior occurring during rapid eye movement (REM) phase sleep with loss of normal muscular atonia. Idiopathic RBD is a recognized risk factor for the development of alpha-synuclein neuropathology, often referred to as Lewy body disorders (LBD) like Parkinson disease, multiple system atrophy and dementia with Lewy bodies, with conversion rates of 80-90 % over a lifetime. In the past decade, studies have described multiple features of idiopathic RBD subjects that resemble patients with alpha-synucleinopathies, with specific abnormalities in olfaction, vision, gait, cognition, autonomic dysfunction, impaired cortical activity, and dopaminergic abnormalities in neuroimaging, leading to the idea that idiopathic RBD is a prodromal synucleinopathy that can precede neurodegenerative disease by decades.