Patients with REM Sleep Behaviour Disorder (RBD) experience abnormal movements during REM (dream) sleep, such as ‘acting out dreams’. This is a rare condition caused by abnormalities in the brain’s behaviour when shifting between dream and non-dream states.
RBD is predominantly seen in older males, some of whom later develop neurodegenerative disorders (such as Parkinson’s disease, multiple system atrophy or dementia). RBD in the younger population, especially young female patients, is likely to be associated with medication, narcolepsy, or a structural central nervous system lesion.
When dreaming occurs during Rapid Eye Movement (REM) sleep in normal patients, the brain blocks signals from being sent to the muscles, in order to prevent us from acting out dreams. In patients with RBD, signals from the brain to muscles are not blocked during REM sleep, allowing the sufferer to act out dreams (which are often violent, horrific or frightening in nature).
Due to the unusual nature of the condition, RBD is often misdiagnosed as a disorder of arousal, a seizure or a limb movement disorder.