nographic finding of REM without atonia is necessary for the diagnosis of REM sleep behav-
ior disorder. REM sleep without atonia with out a clinical history of dream-enacting
behaviors is simply an asymptomatic polyso mnographic observation. It is not known
whether isolated REM sleep without atonia is a precursor to REM sleep behavior disorder.
Functional Consequences of 
Rapid Eye Movement Sl eep Behavior Disorder
REM sleep behavior disorder may occur in isol ated occasions in otherwise unaffected in-
dividuals. Embarrassment concer ning the episodes can impair social relationships. Indi-
viduals may avoid situations in which others might become aware of the disturbance,
visiting friends overnight, or sleeping with be d partners. Social isolation or occupational
difficulties can result. Uncommonly, REM sleep  behavior disorder may result in serious
injury to the victim or to the bed partner.
Differential Diagnosis
Other parasomnias. Confusional arousals, sleepwalking, and sleep terrors can easily be
confused with REM sleep behavior disorder. In  general, these disorders occur in younger
individuals. Unlike REM sleep behavior disorder, they arise from deep NREM sleep and
therefore tend to occur in the early portion of the sleep period. Awakening from a confu-
sional arousal is associated with confusion, disorientation, and incomplete recall of dream
mentation accompanying the behavior. Polysomnographic monitoring in the disorders of
arousal reveals normal REM atonia.
Nocturnal seizures. Nocturnal seizures may perfectly mimic REM sleep behavior disor-
der, but the behaviors are generally more st ereotyped. Polysomnographic monitoring em-
ploying a full electroencephalographic seiz ure montage may differentiate the two. REM
sleep without atonia is not present on polysomnographic monitoring.