The preservation of muscle tone during REM phases is the single most important symptom of RBD. It entails involuntary myoclonic jerks throughout the body as well as movements of limbs and head, likely resembling motor dream enactment [6]. Affected individuals execute possibly aggressive or violent motions that may lead to self-injury, harm to third parties and damage to objects [7]. More complex presentations have also been described. Patients may gesture, punch, kick, sit up or leap from bed, grab somebody or something [8]. Their behavior is generally unintentional and not directed against a determined person or item. They may or may not wake up and recall their vivid dreams. Fatigue and excessive daytime sleepiness are a common consequence of RBD [9].

Ventilation is usually not affected.

• Nightmare

  His nocturnal behavior was screaming, thrashing of arms, punching or kicking his spouse, and falling out of bed associated with nightmares of being attacked by what he described as, "terrible animals frightening me." [ncbi.nlm.nih.gov]

  Nightmares Children are more likely to have nightmares than adults. Nightmares occur during REM sleep, more commonly when fever, excessive fatigue, or mental distress is present or after alcohol has been ingested. [merckmanuals.com]

  Suffering from nightmares where you cry, punch kick jump and grab uncontrollably? You might have (RBD) Rapid Eye Movement Sleep Behavior Disorder. [medicaldaily.com]

  Patients suffering REM sleep behaviour disorders dream nightmares in which they are attacked and pursued, with the particularity that they express them by screaming, crying, punching and kicking while sleeping. [sciencedaily.com]

• Asymptomatic

  Reference values for sleep-related respiratory variables in asymptomatic European children and adolescents. Pediatr Pulmonol 2007;42:159-167. [ Links ] 18. Carskadon M, Rechtschaffen A. Monitoring and staging human sleep. [scielo.br]

  Alpha-synuclein pathology in the spinal cords of neurologically asymptomatic aged individuals. Neurology. 2006; 66 :1100–1102. [ PubMed ] [ Google Scholar ] 124. Fujishiro H, Frigerio R, Burnett M, et al. [ncbi.nlm.nih.gov]

  Mailman and Xuemei Huang, Lateralized Basal Ganglia Vulnerability to Pesticide Exposure in Asymptomatic Agricultural Workers, Toxicological Sciences, 10.1093/toxsci/kfx126, 159, 1, (170-178), (2017). [doi.org]

• Nocturnal Awakening

  […] that fall down (6.4); items 7 and 8, nocturnal awakenings; item 9, general disturbances of sleep; and item 10, the presence of any neurological disorder. [bmcneurol.biomedcentral.com]

• Nausea

  […] been reported.[ 38, 39 ] The most common adverse effect associated with melatonin treatment in McCarter et al’s patient-reported outcomes study was sleepiness in 29% of 25 treated RBD patients, followed by trouble thinking (12%), unsteadiness (8%), nausea [ncbi.nlm.nih.gov]

  Adverse effects for rivastigmine (>5%) include nausea, vomiting, tremor, diarrhea, falls, vertigo/dizziness, and hypotension; rarely, hallucinations have been reported (4.7%). [doi.org]

• Vomiting

  Adverse effects for rivastigmine (>5%) include nausea, vomiting, tremor, diarrhea, falls, vertigo/dizziness, and hypotension; rarely, hallucinations have been reported (4.7%). [doi.org]

• Tachycardia

  […] require dream-enactment, 5 since about 30% of reported RBD cases in the world literature do not have dream-enactment (usually in patients with neurodegenerative disorders, including dementia), as reviewed. 6 Autonomic nervous system activation (viz, tachycardia [sleepreviewmag.com]

• Restless Legs Syndrome

  We present the case of a patient with multiple system atrophy who presented with central apnea as the only sleep disordered breathing, associated with REM behavior disorder and restless legs syndrome. [ncbi.nlm.nih.gov]

  It is similar to other sleep disorders that involve motor activity, such as sleepwalking and restless legs syndrome/periodic limb movement disorder (RLS/PLMD). [healthcommunities.com]

  Restless legs syndrome (RLS) was diagnosed using four essential criteria for RLS, as previously described by the International Restless Legs Syndrome Study Group [ 35 ]. [bmcneurol.biomedcentral.com]

  Restless Legs Syndrome Task Force of the Standards of Practice Committee of the American Academy of Sleep Medicine. An update on the dopaminergic treatment of restless legs syndrome and periodic limb movement disorder. Sleep. 2004;27:560–83. [doi.org]

  Restless Leg Syndrome Causes: Experts aren’t sure what causes RLS, but theorize that it’s hereditary. Medications have also been known to cause RLS. Pregnant women sometimes suffer from RLS. [fastcompany.com]

• Behavior Disorder

  REM sleep behavior disorder as the presenting symptom of multiple system atrophy. [ncbi.nlm.nih.gov]

  Treatment outcomes in REM sleep behavior disorder. Sleep Med. 2013;14(3):237–42. [doi.org]

• Abnormal Behavior

  Study Objectives: To describe a group of patients referred because of abnormal sleep behaviors that were suggestive of rapid eye movement (REM) sleep behavior disorder (RBD) in whom video-polysomnography ruled out RBD and showed the reported behaviors [ncbi.nlm.nih.gov]

  REM-sleep Behavior Disorder ( RBD ) is a parasomnia characterized by abnormal behaviors that emerge during REM sleep, potentially leading to injury. [sleepio.com]

• Psychiatric Manifestation

  This study aimed to discover if RBD affects the prevalence and severity of Parkinson’s by looking at UPDRS scores, UMSARS scores, special sensory function, psychiatric manifestations and reported quality of life of people with and without RBD. [davisphinneyfoundation.org]

• Nocturia

  Sedating medications should be ceased and obstructive sleep apnea, primary sleep disorders, and nocturia should be ruled out. Caffeine is a useful treatment in those without periodic leg movement disorder of sleep or restless leg syndrome [ 95 ]. [doi.org]

• Confusion

  In the two patients with severe motor symptoms, RBD was accompanied by hallucinations and confusion. [ncbi.nlm.nih.gov]

  RBD can be confused with sleepwalking and sleep terrors. In these other disorders, the sleeper is usually confused upon waking up. He or she does not become rapidly alert. [yoursleep.aasmnet.org]

  On the other hand, people who sleepwalk or have night terrors are usually confused and groggy upon waking and don’t become rapidly alert. [everydayhealth.com]

• Somnambulism

  Somnambulism Sitting, walking, or other complex behaviors occur during sleep, usually with the eyes open but without evidence of recognition. [merckmanuals.com]

  Differential diagnosis Several sleep disorders causing behaviors in sleep can be considered in the differential diagnosis, such as sleep walking (somnambulism), sleep terrors, nocturnal seizures, nightmares, psychogenic dissociative states, post-traumatic [bjmp.org]

  NREM parasomnias including night terrors, somnambulism, and confusional arousals are most prevalent in pediatric populations. [ncbi.nlm.nih.gov]

  Anna Szűcs, Anita Kamondi, Rezső Zoller, Gábor Barcs, Pál Szabó and György Purebl, Violent somnambulism: A parasomnia of young men with stereotyped dream-like experiences, Medical Hypotheses, 83, 1, (47), (2014). [doi.org]

Diagnostic criteria for RBD have been defined as follows by the American Academy of Sleep Medicine [10]:

• Involuntary movements are associated with dreams

As well as either one of the following:

• Harmful or potentially harmful behavior during sleep
• Motor dream enactment
• Disruption of sleep continuity

The diagnosis of RBD may be based on these minimal criteria, but is ideally supported by the following polysomnographic findings as obtained during REM sleep:

• Increased chin electromyography tone
• Enhanced chin or limb phasic electromyography twitching associated with excessive myoclonic jerks or complex, vigorous, or violent behavior or the absence of epileptiform activity

These criteria apply if mental disorders have been ruled out. In contrast, concomitant neurodegenerative disease or other neurological disorder are not to be considered at this point. In fact, a considerable subset of RBD patients suffers from additional pathologies like Parkinson's disease.

A sound evidence basis for symptomatic treatment of RBD remains lacking, and randomized controlled treatment trials are needed. [ncbi.nlm.nih.gov]

Prospective outcome and treatment studies of RBD are necessary to enable accurate prognosis and better evidence for symptomatic therapy and future neuroprotective strategies. [ncbi.nlm.nih.gov]

Rapid onset and progression of multifocal deficits may be a clue to paraneoplastic etiology. Early treatment of a limited stage cancer (with or without immunotherapy) may possibly slow progression of neurological symptoms. [ncbi.nlm.nih.gov]

The precise etiology and neural structures involved in RBD are unknown. [emedicine.medscape.com]

This review article considers the epidemiology of RBD, clinical and polysomnographic diagnostic standards for both RBD and RSWA, previously reported associations of RSWA and RBD with neurodegenerative disorders and other potential causes, the pathophysiology [ncbi.nlm.nih.gov]

Pathophysiologically, brainstem and supratentorial mechanisms involving glutamatergic, glycinergic, and GABA-ergic neurotransmission have been implicated. Recently, an animal model of RBD has been described. [ncbi.nlm.nih.gov]

The focus of this review is symptomatic treatment for injury prevention. [ncbi.nlm.nih.gov]

Specialized Alarm System To prevent injury during episodes of RBD an alarm system that gently awakens the patient has been devised. [multiplesystematrophy.org]

This paradox, wake-like brain activity combined with flaccid motor function, prevents the enactment of dream activity. [medlink.com]

In healthy brains, muscles are temporarily paralyzed during sleep to prevent this from happening. [universityherald.com]

Physiologically, longer periods of non-REM sleep are interrupted by short REM phases. A complete sleep cycle comprising all four stages of non-REM sleep as well as a REM phase usually lasts about 100 minutes [1]. Both disturbances of non-REM or REM sleep and irregular cycling are related to sleep disorders.

Dreaming typically occurs during REM sleep. Accordingly, REM phases are characterized by bursts of rapid eye movement, increase of the brain and sympathetic nerve activity, heart rate, and blood pressure, as well as irregular respiration and the absence of muscle tone [2]. Enhanced brain activity is reflected in wake-like electroencephalograms, loss of muscle tone may be depicted by means of electromyography [1]. The preservation of muscle tone during REM phases is pathologic, and affected individuals are diagnosed with REM sleep behavior disorder (RBD), a type of parasomnia [3].

Although the majority of cases is deemed idiopathic, incidence rates are markedly increased among patients suffering from neurodegenerative disorders like Parkinson's disease, dementia with Lewy bodies and multiple system atrophy. In this context, RBD has been proposed as a risk factor for neurodegenerative diseases, and have been shown to precede the latter by decades [4]. This may have major implications for the diagnosis and early treatment of the respective entities. RBD may also be seen in individuals taking antidepressants and in those abusing or withdrawing from alcohol or drugs [5].

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8. Arnulf I. REM sleep behavior disorder: motor manifestations and pathophysiology. Mov Disord. 2012; 27(6):677-689.
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10. American Academy of Sleep Medicine. International Classification of Sleep Disorders, revised: Diagnostic and Coding Manual. Chicago, Illinois: American Academy of Sleep Medicine; 2001.