Understanding Idiopathic Rem Sleep Behavior Disorder

Idiopathic REM sleep behaviour disorder (iRBD) is a sleep disorder characterised by unpleasant dreams and vigorous behaviours during REM sleep that can result in injuries. Patients with iRBD have no known neurological diseases or motor or cognitive complaints. However, iRBD is not harmless and is often a prelude to synucleinopathies such as Parkinson's disease, dementia with Lewy bodies, or multiple system atrophy.

Idiopathic REM sleep behaviour disorder (iRBD) is a parasomnia in which patients act out their dreams

IRBD is usually diagnosed in patients over the age of 50, although it has been observed in younger patients. It is more common in men than women and its clinical course is generally chronic and progressive. The prevalence of iRBD is estimated to be between 0.5% and 2%, although larger population-based studies suggest it could be as high as 5% to 13% in older adults.

IRBD is strongly associated with synucleinopathies, especially Parkinson's disease, dementia with Lewy bodies, and multiple system atrophy. It is thought that iRBD may be an early sign of a slowly evolving neurodegenerative disorder or a long-term predictor of it. In long-term prospective studies, between 30% and 65% of patients with iRBD developed a neurodegenerative disorder, most frequently Parkinson's disease and dementia with Lewy bodies. The time between the onset of iRBD and the onset of the neurodegenerative disorder was around a decade, with increasing conversion rates across longer follow-up periods.

IRBD can be treated with either melatonin or clonazepam to reduce the potential for injury.

iRBD is characterised by unpleasant dreams and vigorous behaviours during REM sleep that can result in injuries

Idiopathic REM sleep behaviour disorder (iRBD) is characterised by unpleasant dreams and vigorous behaviours during REM sleep that can result in injuries. Patients with iRBD have no known neurological diseases or motor or cognitive complaints. However, this sleep disorder is not harmless. iRBD is often a prelude to synucleinopathies such as Parkinson's disease, dementia with Lewy bodies, or multiple system atrophy.

IRBD is a parasomnia in which the normal paralysis of REM sleep is lost, causing patients to 'act out' their dreams. It is more common in men and usually emerges after the age of 50, although it has also been observed in younger patients. The prevalence of iRBD has been estimated to be between 0.5% and 2%.

IRBD is strongly associated with neurodegenerative diseases, especially synucleinopathies such as Parkinson's disease, dementia with Lewy bodies, and multiple system atrophy. A history of iRBD may begin several years or decades before the onset of any clear daytime symptoms of motor, cognitive, or autonomic impairments, suggesting that iRBD is the presenting manifestation of a neurodegenerative process.

IRBD is considered symptomatic when it occurs in direct association with a previously diagnosed neurodegenerative disease or when there is another known underlying pathology such as a brain lesion.

IRBD is diagnosed when there is a clinical history of sleep-related complex motor behaviours or REM sleep complex vocal or motor behaviours recorded during polysomnography, accompanied by REM sleep atonia loss (REM sleep without atonia). Confirmatory collateral history from a bed partner is necessary, especially when the patient has cognitive impairment.

The two main pharmacological treatments for iRBD are melatonin and clonazepam. Melatonin has fewer adverse effects and better tolerability than clonazepam.

iRBD is a powerful early sign of Parkinson's disease, dementia with Lewy bodies, and multiple system atrophy

Idiopathic REM sleep behaviour disorder (iRBD) is a parasomnia in which the normal paralysis of REM sleep is lost, causing patients to physically act out their dreams. iRBD is a powerful early indicator of Parkinson's disease, dementia with Lewy bodies, and multiple system atrophy. Observational studies have shown that most patients with iRBD will eventually develop a neurodegenerative disease, almost always a synucleinopathy. This makes iRBD patients ideal candidates for neuroprotective therapy trials.

The neurodegenerative synuclein aggregation disorders, including Parkinson's disease, dementia with Lewy bodies, and multiple system atrophy, all have a prodromal interval during which neurodegenerative symptoms are present but full clinical disease has not yet developed. This interval can last over a decade, providing an opportunity to intervene with early treatment.

In the case of iRBD, the latency from symptom onset to disease phenoconversion averages over 10 years. This means that around 1% of the elderly population has an easily diagnosable but often undetected early-stage neurodegenerative syndrome. Observational studies, mostly from single centres, have suggested that most patients with iRBD will eventually develop a defined neurodegenerative disease.

A large multicentre study assessed the neurodegenerative disease risk and predictors of neurodegeneration in a cohort of iRBD patients. The study found that the overall conversion rate from iRBD to an overt neurodegenerative syndrome was 6.3% per year, with 73.5% converting after a 12-year follow-up. The rate of phenoconversion was significantly increased with:

• Abnormal quantitative motor testing
• Objective motor examination
• Olfactory deficit
• Mild cognitive impairment
• Erectile dysfunction
• Motor symptoms
• An abnormal DAT scan
• Colour vision abnormalities
• Constipation
• REM atonia loss
• Age

Sample size estimates for definitive neuroprotective trials ranged from 142 to 366 patients per arm. This large multicentre study confirms the high phenoconversion rate from iRBD to an overt neurodegenerative syndrome. The findings provide estimates of the relative predictive value of prodromal markers, which can be used to stratify patients for neuroprotective trials.

iRBD is associated with abnormalities such as hyposmia, constipation, and orthostatic hypotension

Idiopathic REM sleep behaviour disorder (iRBD) is a parasomnia characterised by unpleasant dreams and vigorous behaviours during REM sleep, which can result in injuries. iRBD is often a prelude to synucleinopathies such as Parkinson's disease, dementia with Lewy bodies, or multiple system atrophy.

IRBD is associated with several abnormalities, including hyposmia, constipation, and orthostatic hypotension.

Hyposmia, or impaired olfactory function, is a common feature of iRBD. Olfactory dysfunction often precedes the onset of motor or cognitive symptoms in Parkinson's disease and dementia with Lewy bodies, and it is a potential marker of neurodegeneration in iRBD. Studies have found impaired olfactory functioning in patients with iRBD, indicating that hyposmia may be an important indicator of an underlying neurodegenerative disorder.

Constipation is another abnormality associated with iRBD. It is a common symptom in synucleinopathies such as Parkinson's disease and multiple system atrophy. Constipation is included in standardised scales for assessing these diseases, and it has been identified as a potential marker of neurodegeneration in iRBD.

Orthostatic hypotension, or a sudden drop in blood pressure when standing up, is also associated with iRBD. This abnormality is frequently seen in synucleinopathies, particularly Parkinson's disease, where it is considered a marker of neurovegetative impairment. Orthostatic hypotension can precede the onset of motor symptoms and is, therefore, a potential indicator of an underlying neurodegenerative disorder in iRBD patients.

These abnormalities associated with iRBD provide valuable insights into the pathophysiology of the disorder and can serve as potential markers of neurodegeneration, helping to identify individuals at risk of developing neurodegenerative diseases.

iRBD is treated with melatonin or clonazepam to reduce the potential for injury

Idiopathic REM sleep behaviour disorder (iRBD) is a sleep disorder characterised by unpleasant dreams and vigorous behaviours during REM sleep that can result in injuries. iRBD is often a precursor to the synucleinopathies Parkinson's disease, dementia with Lewy bodies, or, less frequently, multiple system atrophy.

Clonazepam and melatonin are the most common treatments for iRBD. Clonazepam is a benzodiazepine that enhances the neurotransmitter gamma-aminobutyric acid (GABA) via the modulation of the GABAA receptor and has antiepileptic properties. Melatonin is a hormone that is essential for regulating your sleep cycle. Both treatments are used to reduce the potential for injury caused by iRBD.

Clonazepam has been used to treat iRBD since its discovery in 1986. It is typically taken 30 minutes before bedtime at a dose of 0.25-2.0 mg. It is considered a first-line therapy for iRBD, but its efficacy has not been proven in randomised clinical trials. It is also associated with side effects such as daytime sedation, confusion, and cognitive impairment.

Melatonin is another first-line therapy for iRBD. It is often used when clonazepam is not suitable due to its side effects. It is typically taken at a dose of 3-12 mg at bedtime. Melatonin has been shown to be effective in reducing RBD symptoms in several studies, but its efficacy has also been disputed.

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