REM sleep behavior disorder (RBD) is a sleep disorder in which people physically and vocally act out their dreams during REM sleep. Normally during REM sleep, the body experiences temporary paralysis of most of the bodys muscles while the brain is active and dreaming. However, in RBD, there is a loss of muscle atonia during REM sleep, which means that the paralysis is lost and the person can move and speak. This can lead to abnormal behavior during sleep, such as kicking, punching, arm flailing, or jumping from bed, in response to action-filled or violent dreams. RBD may be associated with other neurological conditions, such as Lewy body dementia, Parkinsons disease, or multiple system atrophy. The onset of RBD can be gradual or sudden, and episodes may occur occasionally or several times a night. Symptoms often worsen with time. RBD can cause injury to the person or their bed partner, especially if they are acting out a violent nightmare. Treatment is usually required to manage the condition and reduce the risk of injury.