快速眼動期睡眠行為障礙

Rapid eye movement sleep behavior disorder (RBD) is a sleep disorder (more specifically a parasomnia) that involves abnormal behaviour during the sleep phase with rapid eye movement (REM sleep). It was first described in 1986.

The major and arguably only abnormal feature of RBD is loss of muscle atonia (paralysis) during otherwise intact REM sleep. This is the stage of sleep in which most vivid dreaming occurs. The loss of motor inhibition leads to a wide spectrum of behavioural release during sleep. This extends from simple limb twitches to more complex integrated movement, in which sufferers appear to be unconsciously acting out their dreams. These behaviours can be violent in nature and in some cases will result in injury to either the patient or their bed partner.

Symptoms

RBD is characterized by the dreamer acting out his or her dreams. These dreams often involve kicking, screaming, punching, grabbing, and even jumping out of bed. When awoken, one can usually recall the dream they were having which will match the actions they were performing, but they will not be aware that they were moving. In a normal sleep cycle, you may experience REM sleep every 1 1/2 to 2 hours every night, which means RBD episodes may occur up to four times a night. In a rare case, they may only happen once a week or once a month.^[1] Episodes occur more towards the morning hours because that is when REM sleep is more frequent. The actions in an episode can result in injuries to oneself or one's bed partner. People can also respond to other people while sleeping and not even know it. This causes them to be aware of things while they're sleeping, which can result in sleep deprivation. ^[2]

Causes

Rapid eye movement behaviour disorder occurs when there is a loss of normal voluntary muscle atonia during REM sleep resulting in motor behaviour in response to dream content. It can be caused by adverse reactions to certain drugs or else during drug withdrawal; however it is most often associated with the elderly and in those with neurodegenerative disorders such as Parkinson disease, and other neurodegenerative diseases^[3] for example multiple system atrophy and Lewy body dementia.

Rapid eye movement behaviour disorder (RBD) is a neurodegenerative disorder that primarily affects older males in their 60’s-70’s, who account for about 85% of all know RBD cases. It is a type of disorder that falls into a category called α–synucleinopathies because it uses a α–synuclein protein in degenerating neurons.^[4] Falling into two categories idiopathic and symptomatic, rapid eye movement behaviour disorder is very uncommon, affecting only about 0.5% of the population. ^[5]

Idiopathic RBD causes

Idiopathic RBD is when the individuals sleep structure seems to be normal but there is a significant increase in the density of REM sleep as well as the percentage of slow wave sleep. This category of RBD is more strongly linked to having a genetic component, as seen throughout familial gene patterns.

Symptomatic RBD causes

Symptomatic RBD is your more characteristically seen disorder. This category of RBD is strongly associated with neurodegenerative diseases. About 15% of parkinsons patients also have RBD, 70% of multiple system atrophy patients also have RBD, and about 85% of lewy body dementia patients also have RBD.^[6] Other reported neurodegenerative associations include shy-drager syndrome, olivo-ponto-cerebellar atrophy, multiple sclerosis, vascular encephalopathies, tourettes, and Guillain-Barre syndrome. It is unsure if RBD precedes these neurodegenerative disorders, if they coincide, or if it follows these disorders.

Physiological causes

Research studies have alluded to physiological behavior of the body that accounts for what causes the symptoms of RBD. Findings have found associations with central nervous system dysfunction and abnormal cortical activity during REM sleep including low beta waves in the occipital lobe as well as increased theta waves in the frontal and occipital lobes. Magnetic resonance imaging (MRI) studies have suggested frontal lobe and pons dysfunctions in RBD patients because of the significantly lower blood flow in these portions of the brain as compared to non-RBD individuals.^[7] Other electrophysiological findings include electromyogram (EMG) intensification in chin muscle tone most predominantly, as well as limb phasic twitching and prolonged excess activity of the extremities.

RBD may also be caused by brainstem damage of neural circuits, which manage the phenomenon of REM sleep.^[8]

Treatment

RBD is treatable. Various medications are prescribed for RBD based on varying symptoms. Low doses of clonazepam is most effective with a 90% success rate, how this drug works to restore REM atonia is unclear, however it is thought to suppress muscle activity, rather than directly restoring atonia. Melatonin is also effective and can also be prescribed as a more natural alternative. For those with Parkinson's and RBD, Levodopa is a popular choice. Pramipexole is another drug which can be an effective treatment option.^[9] Recent evidence has shown melatonin and clonazepam to be comparably effective in treatment of RBD with patients who received melatonin treatment reporting fewer side effects.^[10] In addition, patients with neurodegenerative diseases such as Parkinson's disease reported more favorable outcomes with melatonin treatment.

In addition to medication, it is wise to secure the sleeper's environment in preparation for episodes by removing potentially dangerous objects from the bedroom and either place a cushion round the bed or moving the mattress to the floor for added protection against injuries.^[2][11][12] Patients are advised to maintain a normal sleep schedule, avoid sleep deprivation, and keep track of any sleepiness they may have. Treatment includes regulating neurologic symptoms and treating any other sleep disorders that might interfere with sleep . Sleep deprivation, alcohol, certain medications, and other sleep disorders can all increase RBD, and should be avoided if possible.^[13]

Epidemiology

The most comprehensive assessment so far has estimated RBD prevalence to be about 0.5% in individuals aged 15 to 100.^[14] It is far more common in males: most studies report that only about a tenth of sufferers are female. This may partially be due to a referral bias, as violent activity carried out by men is more likely to result in harm and injury and is more likely to be reported than injury to male bed partners by women, or it may reflect a true difference in prevalence as a result of genetic or androgenic factors. The mean age of onset is estimated to be about 60 years.^[15]

Various conditions are very similar to RBD in that sufferers exhibit excessive sleep movement and potentially violent behaviour. Such disorders include sleepwalking and sleep terrors, which are associated with other stages of sleep, nocturnal seizures and obstructive sleep apnea which can induce arousals from REM sleep associated with complex behaviors. Because of the similarities between the conditions, polysomnography plays an important role in confirming RBD diagnosis.

It is now apparent that RBD appears in association with a variety of different conditions. Narcolepsy has been reported as a related disorder. Both RBD and narcolepsy involve dissociation of sleep states probably arising from a disruption of sleep control mechanisms. RBD has also been reported following cerebrovascular accident and neurinoma (tumour), indicating that damage to the brain stem area may precipitate RBD. RBD is usually chronic, however may be acute and sudden in onset if associated with drug treatment or withdrawal (particularly with alcohol withdrawal) 60% of RBD is idiopathic. This includes RBD that is found in association with conditions such as Parkinson’s disease and dementia with Lewy bodies, where it is often seen to precede the onset of neurodegenerative disease. Monoamine oxidase inhibitors, tricyclic antidepressants, serotonergic synaptic reuptake inhibitors, and noradrenergic antagonists can induce or aggravate RBD symptoms and should be avoided in patients with RBD.

In non-humans

RBD has been diagnosed in non-humans, specifically, dogs.^[16]