Getting a good night's sleep

Introduction Background

Rapid eye movement (REM) sleep behavior disorder (RBD) is a sleep disorder characterized by loss of normal voluntary muscle atonia during REM sleep associated with complex motor behavior while dreaming.1,2,3,4

The International Classification of Sleep Disorders requires the following criteria for the clinical diagnosis of RBD:5

• Presence of REM sleep without atonia (RSWA) on polysomnography (PSG)
• At least one of the following conditions:
  • Sleep-related, injurious, potentially injurious, or disruptive behaviors by history (eg, dream enactment behavior)
  • Abnormal REM sleep behavior documented during PSG monitoring
• Absence of EEG epileptiform activity during REM sleep (unless RBD can be clearly distinguished from any concurrent REM sleep-related seizure disorder)
• Sleep disorder not better explained by another sleep disorder, medical or neurological disorder, mental disorder, medication use, or substance use disorder

Therefore, RSWA is an electrophysiological finding, sought on PSG in evaluation for suspected RBD. Pathophysiology

The precise pathophysiology and neural structures involved in RBD are unknown. Based on recent animal (cats, rats), lesional, and neuropathological studies, sleep-regulating nuclei, particularly the pontine tegmentum, are thought to be involved in the pathogenesis of RBD. Also, a complex interplay of various neurochemical systems, such as noradrenergic, cholinergic, and serotonergic systems, seems to exist in the pathogenesis of RBD.1,6

Normally, generalized atonia of skeletal muscles occurs during REM sleep. This atonia results from active inhibition of the final common pathway of spinal motor neurons via the medullary magnocellular reticular formation (MCRF); this suppresses anterior horn cell activity via projections of the ventral lateral reticulospinal tract. Various pontine nuclei are known to influence the REM and non-REM sleep circuits, including locus coeruleus(LC), pedunculopontine nucleus (PPN), and laterodorsal tegmental nucleus (LDTN).7 In addition, forebrain cortical and subcortical structures, substancia nigra, thalamus, hypothalamus, basal forebrain, and frontal cortex are also involved. However, their precise roles are unknown.

Several studies over the past few years suggested that RBD is frequently associated with neurodegenerative disorders characterized by alpha synuclein deposition, including Parkinson disease (PD), multiple system atrophy (MSA), and Lewy body dementia (LBD); RBD is less frequently associated with nonsynucleinopathies.8,9,1,2,10 Studies have suggested that RBD may be associated with alpha-synuclein – mediated degeneration of sleep-regulating nuclei in the brain stem, particularly the pontine tegmentum.

Studies by Eisensehr et al using iodine 123 (123 I) immunoperoxidase technique (IPT) single photon-emission computed tomography (SPECT) demonstrated that striatal presynaptic dopamine transporters are reduced in idiopathic RBD.11 Studies by Fantini et al demonstrated impairment of cortical activity in idiopathic RBD, particularly in the occipital region during both wakefulness and REM sleep compared with controls.12 Results were similar to the functional studies such as perfusion and metabolic impairment pattern observed in diffuse Lewy body (DLB) disease and in Parkinson disease. Similar cortical activity in the frontal and temporal regions was impaired only during wakefulness.

In essence, RBD may be the prodrome of neurodegenerative disease, such as DLB or Parkinson disease.1 In experimental studies in cats, bilateral pontine lesions resulted in a persistent absence of REM atonia associated with prominent motor activity during REM sleep similar to that observed in RBD in humans.

Frequency United States

The exact incidence and prevalence of RBD are unknown because of inadequate reporting and misdiagnosis. However, a telephone survey indicated a 2% overall prevalence of violent behaviors during sleep, 25% of which were likely to be due to RBD. This gives a prevalence of 0.5% of RBD in the general population.

International

No difference in the frequency of RBD exists internationally.

Mortality/Morbidity

The morbidity and mortality rates of RBD depend on the etiology.

• No death has been reported in idiopathic cases; however, patients and bed partners may experience serious injury.13 In the reported cases, 32% of patients had injured themselves and 64% had assaulted their spouses.4 Subdural hematomas occurred in 2 patients.4
• In secondary cases, the morbidity and mortality rates depend on the specific underlying disease itself.

Race

Racial differences in incidence and prevalence of RBD have not been reported.

Sex

RBD occurs predominantly in males.14 In a recent report by Olson et al, of 93 patients with RBD, only 12 (13%) were females.4

Age

Typically, RBD is a disease of elderly persons.8 The risk increases after the sixth decade, although the disease may occur at all ages, including childhood.14

Clinical History

• The presenting complaint is violent dream-enacting behaviors during REM sleep, often causing self-injury or injury to the bed partner.15 The dream-enacting behaviors are usually nondirected and may include punching, kicking, leaping, crying out, or running from bed while still in REM sleep.16
• Directed behavior, such as homicide, has not been reported.
• The patient may be wakened or may wake spontaneously during the attack and recall vividly the dream that corresponds to the physical action.
• In some cases, an extended prodrome of prominent limb and body movements occurs before the development of RBD.

Physical

The neurologic examination findings are unremarkable in idiopathic cases; in secondary cases, the physical findings depend on the underlying disorder.

Causes

In a recent study, Nightingale et al suggested that 36% of persons with narcolepsy experience symptoms of RBD.17 This link has lead to the identification of a strong association of RBD with HLA class II genes.18

• RBD may be idiopathic. However, several studies have suggested that idiopathic RBD is a potential marker for the later development of neurodegenerative disorders, particularly Parkinson disease (PD) and Lewy body dementia (LBD).8,19,9,1,2,20,10,21,22 The risk varies among different studies. Therefore, evidence suggest that many cases of idiopathic RBD may not be truly idiopathic, leading some to suggest the term cryptogenic rather than idiopathic.23
• RBD may occur in association with various neurological conditions (ie, secondary RBD), including vascular lesions, brainstem neoplasm, demyelinating disease, autoimmune/inflammatory disorders, and neurodegenerative disorders. Recent studies suggested that RBD is more frequently associated with synucleinopathies, including PD, LBD, multiple system atrophy (MSA), and pure autonomic failure (PAF), than with nonsynucleinopathies.

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