Symptomatic REM sleep behaviour disorder

Rapid eye movement (REM) sleep behaviour disorder (RBD) precedes or accompanies many neurodegenerative disorders. In synucleinopathies, including dementia with Lewy bodies, Parkinson's disease and multiple system atrophy, the prevalence of RBD varies from 19% to almost 77% in different reports. In tauopathies, including Alzheimer's disease, corticobasal degeneration, progressive supranuclear palsy and frontotemporal dementia, the prevalence is rare, ranging from 0% to 27%. RBD has however also been described in amyotrophic lateral sclerosis, limbic encephalitis, Guillain-Barre syndrome, Tourette's syndrome, autism, epilepsy and post-traumatic stress disorder. The present paper reviews the current literature on symptomatic RBD and on RBD induced by drug administration, antidepressants, tricyclics and newer drugs, which are often described as precipitating factors for RBD. Controversial findings, flaws in categorisation and hypothetical aetiological mechanisms are also discussed.