REM sleep behavior disorder

REM sleep behavior disorder (RBD), a condition of dream enactment, often predates Parkinson’s disease (PD) and is the result of early neurodegenerative processes in the brainstem. Normally, REM sleep is characterized by vivid mentation combined with skeletal muscle paralysis. This REM atonia is diminished or absent in RBD, which enables patients to act out their dreams with violent, injurious nocturnal behaviors. Consistent with an impending neurodegenerative disorder, patients with RBD demonstrate subtle motor, autonomic, and cognitive changes frequently seen in synucleinopathies. These disorders include PD as well as multiple system atrophy (MSA) and dementia with Lewy bodies (DLB). In PD, RBD is linked with the akinetic–rigid predominant subtype, gait freezing, and predicts aggressive cognitive impairment. Clinical management is focused upon decreasing the potential for sleep-related injuries (SRIs), treating comorbid sleep disorders, and eliminating exacerbating agents. High-dose melatonin, low-dose clonazepam, and combined melatonin–clonazepam appear to be effective therapies.