Rapid eye movement sleep behavior disorder, or REM sleep behavior disorder (RBD), is a sleep disorder in which people act out their dreams. It involves abnormal behavior during the sleep phase with rapid eye movement (REM) sleep. The major feature of RBD is loss of muscle atonia (i.e., the loss of paralysis) during otherwise intact REM sleep (during which paralysis is not only normal but necessary). The loss of motor inhibition leads to sleep behaviors ranging from simple limb twitches to more complex integrated movements that can be violent or result in injury to either the individual or their bedmates. RBD is a very strong predictor of progression to a synucleinopathy (usually Parkinson's disease or dementia with Lewy bodies). Melatonin is useful in the treatment of RBD. RBD was first described in 1986.
Classification RBD is a parasomnia. It is categorized as either idiopathic or symptomatic. Idiopathic RBD is the term used when RBD is not associated with another ongoing neurological condition. When it results from an identifiable cause, RBD is referred to as symptomatic RBD, and considered a symptom of the underlying disorder.
Characteristics RBD is a sleep disorder characterized by the loss of normal skeletal muscle atonia during REM sleep and is associated with prominent motor activity and vivid dreaming. These dreams often involve screaming, shouting, laughing, crying, arm flailing, kicking, punching, choking, and jumping out of bed. The actions in an episode can result in injuries to oneself or one's bedmate. The sleeping person may be unaware of these movements. Dreams often involve violent or aggressive actions, and an attack theme such as being chased by people or animals. Because violence in dreams is more likely to be recalled, this could be an artifact of recall bias or selection bias. The individual with RBD may not be aware of having it. When awakened, people may be able to recall the dream they were having, which will match the actions they were performing. Dream enactment behaviour is a core feature of RBD but is not an exclusive marker of the disorder; therefore, a history of recurrent dream enacting behaviour is only enough to receive a diagnosis of clinically probable RBD and the diagnosis of definite RBD is only given when there is polysomnography confirmation of complex motor behaviour during REM sleep. When RBD occurs in the absence of any known aetiology of the disorder it is referred to as idiopathic, however when RBD arises in relation to another neurological disorder or neurodegenerative disease, it is referred to as secondary or symptomatic RBD. As the first indication of an underlying neurodegenerative disorder or synucleinopathy, symptoms of RBD may begin years or decades before the onset of another condition. Abnormal sleep behaviors may begin decades before any other symptoms, often as the first clinical indication of another condition. RBD is a sleep disorder characterized by the loss of normal skeletal muscle atonia during REM sleep and is associated with prominent motor activity and vivid dreaming. Symptomatic RBD can also be associated with narcolepsy, Guillain–Barré syndrome, limbic encephalitis, and Morvan's syndrome. Other symptoms found in patients with RBD are reduced motor abilities, posture and gait changes, mild cognitive impairment, alterations in the sense of smell, impairments in color vision, autonomic dysfunction (orthostatic hypotension, constipation, urinary problems and sexual dysfunction), and depression.
Causes Rapid eye movement behavior disorder occurs when there is a loss of normal voluntary muscle atonia during REM sleep resulting in motor behavior in response to dream content. It can be caused by adverse reactions to certain drugs or during drug withdrawal; however, it is most often associated with the elderly and in those with neurodegenerative disorders such as Parkinson's disease and other neurodegenerative diseases, for example multiple system atrophy and the Lewy body dementias. The underlying cause of RBD is not well understood, but it is likely that RBD is an early symptom of synucleinopathy rather than a separate disorder. Brainstem circuits that control atonia during REM sleep may be damaged, including those in the pontomedullary brainstem. REM sleep circuits are located in caudal brainstem structures—the same structures that are known to lead to be implicated in the synucleinopathies. Motor deficits like those seen in RBD are known to result from lesions in those circuits. Risk factors for developing RBD are a family history of acting out dreams, prior head injury, farming, exposure to pesticides, low education level, depression, and use of antidepressants. RBD may be acute and sudden in onset if associated with drug treatment or withdrawal (particularly with alcohol withdrawal). Antidepressant medications can induce or aggravate RBD symptoms.
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