REM-behaviour disorder

There are two distinct state during normal sleep - non-rapid eye movement (NREM) and rapid eye movement (REM). See the Sleep Cycle page. NREM sleep is divided into four stages (I, II, III and IV).

During REM sleep, rapid eye movements occur, breathing becomes irregular, blood pressure rises, and there is loss of muscle tone (paralysis), it is in this stage of sleep where the individual has dreams. 

During REM the brain is highly active, and the electrical activity recorded in the brain by EEG during REM sleep is similar to that recorded during wakefulness. REM sleep accounts for 20-25% of the sleep period.

In a person with REM sleep behaviour disorder (RBD), the paralysis that normally occurs during REM sleep is incomplete or absent, allowing the person to "act out" his or her dreams. RBD is characterized by the acting out of dreams that are vivid, intense, and violent. Dream-enacting behaviors include talking, yelling, punching, kicking, sitting, jumping from bed, arm flailing, and grabbing. An acute form may occur during withdrawal from alcohol or sedative-hypnotic drugs.

RBD is usually seen in middle-aged to elderly people (more often in men).

REM Sleep Disorder Causes

The exact cause of REM sleep behavior disorder (RBD) is unknown, although the disorder may occur in association with various degenerative neurological conditions such as Parkinson disease, multisystem atrophy, diffuse Lewy body dementia (a slowly progressive brain disorder characterized by the loss of ability to think, reason and remember), and Shy-Drager syndrome (degenerative neurological disorder that affects the brain and other parts of the central nervous system.).

In 55% of persons the cause is unknown, and in 45%, the cause is associated with alcohol or sedative-hypnotic withdrawal, tricyclic antidepressant (such as imipramine), or serotonin reuptake inhibitor use (such as fluoxetine, sertraline, or paroxetine) or other types of antidepressants (mirtazapine).

RBD often precedes the development of these neurodegenerative diseases by several years. In one study, 38% of patients diagnosed with RBD subsequently developed Parkinson disease within an average time of 12-13 years from the onset of RBD symptoms. The prevalence of RBD is increased in persons with Parkinson disease and in multisystem atrophy where it is observed in 69% of these patients. The relationship between RBD and Parkinson disease is complex; however, not all persons with RBD develop Parkinson disease.