REM sleep behaviour disorder: not just a bad dream

Rapid eye movement (REM) sleep behaviour disorder (RBD) is a parasomnia characterised by the loss of the normal atonia during the REM stage of sleep, resulting in overt motor behaviours that usually represent the enactment of dreams. Patients will seek medical attention due to sleep-related injuries or unpleasant dream content. Idiopathic RBD which occurs independently of any other disease occurs in up to 2% of the older population. Meanwhile, secondary RBD is very common in association with certain neurodegenerative conditions. RBD can also occur in the context of antidepressant use, obstructive sleep apnoea and narcolepsy. RBD can be diagnosed with a simple screening question followed by confirmation with polysomnography to exclude potential mimics. Treatment for RBD is effective and involves treatment of underlying causes, modification of the sleep environment, and pharmacotherapy with either clonazepam or melatonin. An important finding in the past decade is the recognition that almost all patients with idiopathic RBD will ultimately go on to develop Parkinson disease or dementia with Lewy bodies. This suggests that idiopathic RBD represents a prodromal phase of these conditions. Physicians should be aware of the risk of phenoconversion. They should educate idiopathic RBD patients to recognise the symptoms of these conditions and refer as appropriate for further testing and enrolment into research trials focused on neuroprotective measures.