Rapid eye movement sleep behavior disorder or REM 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 Parkinsons 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 characterized by the dreamer acting out their dreams, with complex behaviors. 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 ones bedmate. The sleeping person may be unaware of these movements. Dreams often involve violent or aggressive actions, and an attack theme like being chased by people or animals.
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. Diagnosis
There are two ways to diagnose RBD:  by documenting a history of complex, dream-enactment sleep behaviors, or by polysomnography recording of these behaviors along with REM sleep atonia loss.RBD may be established from clinical interview as well as several validated questionnaires, when sleep studies cannot be performed. Questionnaires such as the Rapid Eye Movement (REM) sleep Behavior Disorder Screening Questionnaire (RBDSQ), the REM Sleep Behavior Questionnaires – Hong-Kong (RBD-HK), the Mayo Sleep Questionnaire (MSQ) and the Innsbruck REM Sleep Behavior Disorder Inventory are well-validated. Individuals with RBD may not be able to provide a history of dream enactment behavior, so bed partners are also consulted.