Rapid Eye Movement (REM) Sleep Behaviour Disorder

• Traumatic brain injuries, farming and pesticides exposure, and lower education are risk factors.^[1]
• REM sleep behaviour disorder overwhelmingly affects males older than 50 years, but increasingly this disorder is being identified in females and in younger individuals.
• Symptoms in young individuals, particularly young females, should raise the possibility of narcolepsy or medication-induced REM sleep behaviour disorder.

• REM sleep behaviour disorder can result in injuries to bed partners, and/or falls and physical injuries to the affected individual
• Almost 90% of patients with REM sleep behaviour disorder will go on to develop a Parkinson's-plus disorder such as Parkinson's disease, Lewy body dementia, or multiple system atrophy (MSA).^[2]

• Untreated sleep apnea may worsen or mimic RBD symptoms.^[3]
  • There are even case reports of pseudo-RBD resolving by treating the underlying sleep apnea.^[4]

• The prevalence of REM sleep behaviour disorder is approximately 0.5% in the general population.
  • It is more common in males than females.
• Prevalence in patients with psychiatric disorders may be greater, possibly related to medications prescribed for the psychiatric disorder.

Repeated episodes of arousal during sleep associated with vocalization and/or complex motor behaviours.

These behaviours arise during rapid eye movement (REM) sleep and therefore usually occur more than 90 minutes after sleep onset, are more frequent during the later portions of the sleep period, and uncommonly occur during daytime naps.

Upon awakening from these episodes, the individual is completely awake, alert, and not confused or disoriented.

Either of the following:

1. REM sleep without atonia on polysomnographic recording
2. A history suggestive of REM sleep behaviour disorder and an established synucleinopathy diagnosis (e.g., Parkinson’s disease, multiple system atrophy).

The behaviours cause clinically significant distress or impairment in social, occupational, or other important areas of functioning (which may include injury to self or the bed partner).

The disturbance is not attributable to the physiological effects of a substance (e.g. - a drug of abuse, a medication) or another medical condition.

Coexisting mental and medical disorders do not explain the episodes.

• The clinical question: “Have you ever been told (or suspected yourself) that you seem to 'act out your dreams' while asleep (e.g. - punching, flailing your arms in the air, making running movements)?” is highly sensitive and specific for REM sleep behaviour disorder (sensitivity 93.8%, specificity 87.2%)^[5]

The onset of REM sleep behaviour disorder may be gradual or rapid, and the course is usually progressive. The disorder is thought to be due to loss of spinal inhibition in REM. It is aggravated by SSRI use, and typically occurs in the last 1/3 of sleep.

• There is a very high association with the later appearance of an underlying neurodegenerative disorder, in particular synucleinopathies.
• REM sleep behaviour disorder is highly prevalent in individuals with Parkinson's disease (30 to 50%), multiple system atrophy (80 to 95%), and Lewy body dementia (50 to 80%). REM sleep behaviour disorder associated with neurodegenerative disorders may actually improve as the underlying neurodegenerative disorder progresses.^[6]
• REM sleep behaviour disorder often predates any other sign of these disorders by many years (often more than a decade).

• Video polysomnography (not a regular polysomnography) is essential for the diagnosis of RBD.^[7]
• Polysomnography shows:
  • Increased tonic and/or phasic electromyographic activity during REM sleep (normally expect muscle atonia)
  • The increased muscle activity variably affects different muscle groups (submentalis, bilateral extensor digitorum, and bilateral anterior tibialis muscle groups)
  • Frequent periodic and aperiodic extremity electromyography activity during non-REM (NREM) sleep, termed REM sleep without atonia
• Clinical dream-enacting behaviours coupled with the polysomnographic finding of REM without atonia is necessary for the diagnosis of REM sleep behaviour disorder.
• REM sleep without atonia without a clinical history of dream-enacting behaviours is simply an asymptomatic polysomnographic observation.
• It is not known whether isolated REM sleep without atonia is a precursor to REM sleep behaviour disorder.

• Placing padding on floors, safety planning with bed partners to avoid injuries are important first steps.

• High dose melatonin is now favoured over the use of benzodiazepines such as clonazepam.^[8][9]
• In the past, low dose benzodiazepines such as clonazepam (generally 0.5mg qHS, up to 4 mg qHS) used to be commonly prescribed.^[10][11]
  • However, the risks of respiratory depression, falls, cognitive impairment, and dependence risks are of considerable concern, and thus melatonin is now favoured.
    • The typical dose range is melatonin 3 mg to 12 mg PO qHS
  • There should also be caution in prescribing this medication in individuals with obstructive sleep apnea, gait disorders, or dementia.

• Narcolepsy:
  • REM sleep behavior disorder is present concurrently in approximately 30% of patients with narcolepsy.
• Non-REM sleep arousal disorders
  • Individuals with Non-REM parasomnias (i.e. - sleep walking and sleep terrors) usually experience this in the first half of the night, have amnesia of the event, and have confusion (see comparison table below).
• Sleep paralysis
• Hypnopompic or hypnogogic hallucinations
• Nightmare disorder
• Nocturnal seizures
• Secondary RBD can also occur secondary to other neurologic disorders, sleep disorders, and medications
  • Obstructive sleep apnea^[12]
  • Medication-induced REM Sleep Behaviour Disorder
    • Tricyclic antidepressants, selective serotonin reuptake inhibitors (especially SSRIs!), serotonin-norepinephrine reuptake inhibitors, and beta-blockers, may result in polysomnographic evidence of REM sleep without atonia and in frank REM sleep behaviour disorder. It is not known whether the medications per se result in REM sleep behaviour disorder or they unmask an underlying predisposition to the disorder.^[13]
  • If there are REM sleep behaviour disorder symptoms in young individuals, particularly young females, the clinician should be aware of the possibility of a narcolepsy or medication-induced REM sleep behaviour disorder
• Other specified dissociative disorder (sleep-related psychogenic dissociative disorder)
• Malingering