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  • Updated 05.08.2020
  • Released 09.09.1993
  • Expires For CME 05.08.2023

Rapid eye movement sleep behavior disorder

Introduction

This article includes discussion of rapid eye movement sleep behavior disorder, REM sleep behavior disorder, and RSBD. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.

Overview

In this article, the author reviews and updates REM sleep behavior disorder (RBD), characterized by REM sleep without atonia (RSWA) with potentially injurious dream enactment. The RSWA of RBD is due to dysfunction of REM-related circuitry in the pons and medulla and often predates the development of Parkinson disease or other disorders of alpha-synuclein pathology. Other pathogenic processes include orexin deficiency, pontomedullary lesions, limbic dysfunction, hypothalamic dysfunction, as well as toxic effects from serotonergic antidepressant medications. Management of RBD is focused on decreasing sleep-related injury through changes in the sleeping environment and, if necessary, bedtime melatonin and/or clonazepam. As RBD is a prodromal syndrome of alpha-synuclein degeneration, it is an ideal target for disease modifying agents.

Key points

• Under nonpathological circumstances, REM sleep is characterized by an activated brain state in combination with skeletal muscle paralysis. This paradox, wake-like brain activity combined with flaccid motor function, prevents the enactment of dream activity. In REM sleep behavior disorder (RBD), REM sleep atonia is lost and patients act out dream mentation.

• The majority of patients with spontaneously occurring RBD (idiopathic RBD, iRBD) will eventually demonstrate signs and symptoms of neurodegenerative disorders, most commonly one of the synucleinopathies (Parkinson disease, dementia with Lewy bodies, and multiple system atrophy), often after a prolonged interval lasting decades. RBD in the setting of other neurodegenerative diseases such as Alzheimer disease suggests co-mingling synucleinopathy.

• iRBD patients have an approximately 6% risk per year after RBD diagnosis of being diagnosed with Parkinson disease, dementia with Lewy bodies, or multiple system atrophy.

• Parkinson disease patients with RBD have more rapid disease progression, more cognitive impairment, and more postural instability and falls, with an overall worse prognosis compared with Parkinson disease patients without RBD.

• Other causes of RBD include pontomedullary lesions, such as those from vascular injuries, mass lesion, or demyelinating disease. Commonly prescribed antidepressant medications, particularly selective serotonin reuptake inhibitors, result in RBD through uncertain mechanisms. Patients with narcolepsy due to dysfunction in the orexin hypothalamic circuit, which stabilizes sleep states, may also demonstrate RBD, but it may be less likely to develop a neurodegenerative disease than iRBD. By failing to stabilize REM sleep from wakefulness, orexin pathology results in cortical activation, but without REM sleep atonia.

• RBD management options include bedtime administrations of low-dose (0.5 to 1.0 mg) clonazepam or high-dose (6 to 12 mg) melatonin. For patients with medication refractory disease, a customized bed alarm may help prevent sleep-related injury.

Historical note and terminology

In 1817, James Parkinson wrote a monograph titled, “An Essay on the Shaking Palsy” (116). This first comprehensive description of the disorder described frequently disrupted sleep. Parkinson hinted at a disorder of agitated dream enactment emerging from sleep.

“His (Case VI) attendants observed, that of late the trembling would sometimes begin in his sleep, and increase until it awakened him: when he always was in a state of agitation and alarm.”

“…when exhausted nature seizes a small portion of sleep, the motion becomes so violent as not only to shake the bed-hangings, but even the floor and sashes of the room.”

After the discovery of REM sleep in the 20th century, investigations explored the brainstem mechanisms of REM skeletal muscle paralysis. In 1965, experimental lesions of pontine regions adjacent to the locus coeruleus in cats caused absence of the expected REM sleep atonia and prominent motor behaviors during REM sleep (74).

Subsequently, in 1982, Dr. Carlos Schenck and Dr. Mark Mahowald evaluated a 68-year-old man with a history of violent dream enactment behavior. A subsequent polysomnogram demonstrated REM sleep without atonia along with vigorous dream enactment behavior. In 1986, Schenck and Mahowald published a series of patients with violent dream enactment behavior with a paucity of REM atonia and named the condition “REM sleep behavior disorder” (139). In 10 years, 38% of these original RBD patients had developed a parkinsonian syndrome, and within 25 years, the prevalence had risen to 81% (Schenck and Mahowald 2013).

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