REM sleep behavior disorder
Rapid eye movement (REM) sleep behavior disorder (RBD) is a newly described disorder, recognized as a distinct clinical entity following a series of reports in 1986 of adults with RBD. RBD is the best-studied REM sleep parasomnia. Clinically, RBD is characterized by loss of normal voluntary muscle atonia during REM sleep associated with complex behavior while dreaming. According to the International Classification of Sleep Disorders, the minimal diagnostic criteria include movements of the body or limbs associated with dreaming and at least one of the following criteria: potentially harmful sleep behavior, dreams that appear to be acted out, and sleep behavior that disrupts sleep continuity (American Sleep Disorders Association, 1997). In 1965, experimental models showed that cats with bilateral pontine lesions adjacent to the locus ceruleus act out their dreams.
Pathophysiology
Normally, generalized atonia of muscles occurs during REM sleep. This atonia results from active inhibition of motor activity by pontine centers (ie, perilocus ceruleus) that exert an excitatory influence on the medulla (ie, magnocellularis neurons) via the lateral tegmentoreticular tract. These neuronal groups, in turn, hyperpolarize the spinal motor neuron postsynaptic membranes via the ventrolateral reticulospinal tract. In RBD, the brainstem mechanisms generating the muscle atonia normally seen in REM sleep may be interfered with.
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. Recent 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. Results were similar to the functional studies such as perfusion and metabolic impairment pattern observed in diffuse Lewy body (DLB) disease and to some extent in Parkinson disease. Similar cortical activity in the frontal and temporal regions was impaired only during wakefulness.
The subcortical structures involved in the pathophysiology of RBD provide dopaminergic (nigrostriatal neurons), noradrenergic (locus coeruleus), and cholinergic innervation (pedunculopontine tegmental nucleus) of the cerebral cortex and play a role in cortical activation during wakefulness and REM sleep.
In essence, RBD may be the prodrome of neurodegenerative disease, such as DLB or Parkinson disease. 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 recent 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. In the reported cases, 32% of patients had injured themselves and 64% had assaulted their spouses. Subdural hematomas occurred in 2 patients.
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. In a recent report by Olson et al, of 93 patients with RBD, only 12 (13%) were females.
Age
Typically, RBD is a disease of elderly persons. The risk increases after the sixth decade, although the disease may occur at all ages, including childhood.
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