RBD, Rapid Eye Movement Sleep Behavior Disoder

Clinic

• Rapid eye movement sleep behavior disorder or REM behavior disorder
• It is a sleep disorder in which people act out their dreams. It involves abnormal behavior during REM sleep.
• The major feature of RBD is loss of muscle atonia (i.e. 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 Parkinson's disease or dementia with Lewy bodies).
• Melatonin is useful in the treatment of RBD

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

Main symptoms

• 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 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.
• Because violence in dreams is more likely to be recalled, this could be an artifact of recall bias or selection bias. The individual with RBD may not be aware of having it. When awakened, people may be able to recall the dream they were having, which will match the actions they were performing.
• As the first indication of an underlying neurodegenerative disorder or synucleinopathy, symptoms of RBD may begin years or decades before the onset of another condition. Abnormal sleep behaviors may begin decades before any other symptoms, often as the first clinical indication if another condition.

Other symptoms

• Reduced motor abilities
• Posture and gait changes
• Mild cognitive impairment
• Alterations in the sense of smell
• Impairments in color vision
• Autonomic dysfunction (Orthostatic hypotension, Constipation, Urinary problems and Sexual dysfunction)
• Depression

Smptomatic RBD

It can also be associated with

• Narcolepsy
• Guillain–Barré syndrome
• Limbic encephalitis
• Morvan's syndrome

Causes

• RBD occurs when there is a loss of normal voluntary muscle atonia during REM sleep resulting in motor behavior in response to dream content.
• It is most often associated with the elderly and in those with neurodegenerative disorders such as
  • Parkinson's disease
  • Multiple system atrophy
  • Lewy body dementias

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.

Differential Diagnosis

• Non-REM parasomnias (sleepwalking, sleep terrors)
• Periodic limb movement disorder
• Severe obstructive sleep apnea
• Dissociative disorders

Polysomnography plays an important role in confirming RBD diagnosis.