Rapid eye movement ( REM ) sleep behaviour disorder

Rapid eye movement (REM) sleep behaviour disorder:

Rapid eye movement sleep behaviour disorder (RBD) is characterised by dream-enacting behaviour and a loss of normal muscle atonia during REM sleep - may result in injury to the patient or the patient's bed partner

• RBD patients show electromyographic abnormalities during REM sleep
  • exhibit a phenomenon called REM sleep without atonia - elevated muscle tone during REM sleep

The majority of RBD cases occurring in older adults remain idiopathic, at least initially, although a presumptive underlying cause of neurodegeneration and eventual emergence of overt parkinsonism, autonomic, or cognitive dysfunction has been recognized, and RBD may also be seen in younger adults associated with narcolepsy and antidepressant use (2).

• the incidence is estimated at 0.5–1% of those over 55 years, occurs in older people with a steady rise after 55 years and has a male preponderance in older patients (3)
• RBD usually recurs almost every night (4)
• well recognised as the most robust prodromal, non-motor symptom of a subsequent neurodegeneration, typically an alpha synucleinopathy (3)
• several cohorts under long term follow-up have shown that 50% at five years and 91% at 15 years will have developed another neurodegenerative problem
• often associated with Parkinson’s disease (PD) (it is seen in up to 50% of PD patients), Lewy body dementia (~70%), multiple system atrophy (>90%) (3)
• RBD often precedes other symptoms of neurodegeneration by several years (3)

The International Classification of Sleep Disorders (1) states that for patients who had typical episodes of dream-enacting behaviour and showed complex motor behaviours during polysomnography (PSG) but did not show sufficient REM sleep without atonia, RBD may be provisionally diagnosed based on clinical judgment

• patients with RBD typically awaken quickly, become rapidly alert, and can recall the contents of their dreams upon awakening, whereas patients showing abnormal nocturnal behaviours related to other disorders, such as night delirium, epilepsy, and hypoglycaemia due to insulinoma, cannot awaken quickly or report the contents of dreams

DSM-5 criteria for rapid eye movement sleep behaviour disorder are as follows:

• recurrent episodes of arousal during sleep associated with vocalization and/or complex motor behaviours that arise during rapid eye movement (REM) sleep
• on waking from these episodes, the individual is not confused or disoriented and is completely alert
• either of the following is present:
  • REM sleep without atonia on polysomnographic recordings; or
  • a history suggestive of REM sleep behaviour disorder and an established synucleinopathy diagnosis (e.g., Parkinson’s disease, multiple system atrophy)
• the episodes cause significant distress or impairment in social, occupational or other areas of functioning which may include serious injury to self or the bed partner
• the disturbance cannot be explained by the effects of a drug of abuse or medication
• the episodes cannot be attributed to another mental disorder or medical condition

Diagnosis of parasomnias

• assessment of parasomnia may be possible with a detailed history from patient or witness, but in general for adequate diagnosis, referral to a specialist sleep centre for polysomnography and video recording may be necessary especially for RBD where loss of REM atonia is seen (3)

Clonazepam, a benzodiazepine, is the pharmacologic agent which has been the most commonly used treatment for RBD (2). Prolonged-release melatonin has also been used in the management of this condition (2).

References:

1. American Academy of Sleep Medicine. International Classification of Sleep Disorders. 3rd ed. Darien, IL: American Academy of Sleep Medicine; 2014.
2. McGrane IR et al. Melatonin therapy for REM sleep behavior disorder: a critical review of evidence. Sleep Med. 2015 Jan;16(1):19-26.
3. Wilson S et al. British Association for Psychopharmacology consensus statement on evidence-based treatment of insomnia, parasomnias and circadian rhythm disorders: An update. J Psychopharmacol. 2019 Aug;33(8):923-947
4. Zanigi S et al. REM behaviour disorder and neurodegenerative diseases. Sleep Medicine 12 (2011) S54–S58