REM Sleep Disorder

Background: 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. Recent studies by Eisensehr et al using iodine 123 123I-immunoperoxidase technique (IPT) single photon-emission computed tomography (SPECT) demonstrated that striatal presynaptic dopamine transporters are reduced in idiopathic RBD. 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:

  • In the US: 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.
  • Internationally: 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 the elderly. The risk increases after the sixth decade, although the disease may occur at all ages, including childhood.

 

CLINICAL

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History:

  • The presenting complaint is violent dream-enacting behaviors during REM sleep, often causing self-injury or injury to the bed partner. The dream-enacting behaviors are usually nondirected and may include punching, kicking, leaping, or running from bed while still in REM sleep.
  • 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:

  • RBD may be idiopathic or it may occur in association with various neurological conditions, such as brainstem neoplasm, multiple sclerosis affecting brain stem, olivopontocerebellar atrophy (OPCA), progressive supranuclear palsy (PSP), or Shy-Drager syndrome.
  • The incidence of RBD is increased in Parkinson disease, and RBD may precede the development of parkinsonism by several years. The relationship between RBD and Parkinson disease is complex, however, as not all patients with RBD develop parkinsonism.
  • Additional degeneration of brainstem neurons is postulated to play a significant role in the control of this condition.

Article from:     http://www.emedicine.com/neuro/topic524.htm

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