REM sleep behaviour disorder: an overview.

REM sleep behaviour disorder (RSBD) is a recently described parasomnia characterised by a history of excessive nocturnal motor activity and absence of muscle atonia during REM sleep. Only limited literature is available on this condition. The exact prevalence is unclear, but recent studies suggest it might not be an uncommon condition. The elderly are more often affected and there is a male preponderance. While transient RSBD can be seen after taking certain drugs or during drug withdrawal, the chronic type is usually idiopathic or associated with an underlying degenerative neurological condition. It can result in considerable distress and/or serious injury to the patients or their bed partners. Differential diagnoses include sleep-walking, night terrors, nightmares, nocturnal seizures, obstructive sleep apnoea, post-traumatic stress disorder, dissociative states and nocturnal confusional states. The dramatic response to clonazepam highlights the importance of recognition and appropriate treatment of this sleep disorder.