[REM sleep behavior disorder in dementia with Lewy bodies]

REM sleep behavior disorder (RBD) is included in the diagnostic criteria for dementia with Lewy bodies (DLB), and is useful for being distinguished from Alzheimer's disease. However, RBD can precede DLB for a few years and be a warning symptom when associated with visuospatial disorders and hypometabolism in occipital regions by SPECT. When RBD are associated with dangerous behaviors or increased risk of fall out of bed, they must be treated. However, RBD can be difficult to be differentiated from hallucinations related to nocturnal delirium, both symptoms being frequently associated.