REM sleep is characterized by a paucity of muscle activity with near complete somatic muscular atonia. REM sleep behaviour disorder is characterized by the intermittent loss of REM atonia due to disinhibition of normally inhibitory mid-brain projections to spinal motor neurons. This, in conjunction with an active dream state, results in behavioural release and the apparent "acting out of dreams". Abnormal behaviours include sleep talking, yelling, limb movement, and complex motor activities. Patients with REM sleep behaviour disorder arouse from sleep to full alertness often with complete recall of fearful dream content, which may involve being chased or attacked. The motor behaviour exhibited tends to correlate with dream content. REM sleep periods typically occur in the latter half of the night. The most common symptom at time of presentation is injury of the patient or bed partner. As a result of the behaviors, bed partners often simply move to another bed or room. Also, patients and families may have a sense of guilt or shame regarding the behaviors, even though the behaviors may not be consistent with patients' personalities. This is particularly true when sexual behaviors are involved. Sleep disruption and daytime sleepiness are often part of the history. REM sleep behaviour disorder tends to be a disease that occurs in older men, although women and people of all ages may be affected. The reason for the strong predominance toward men, with an approximately nine-to-one men-to-women ratio, is not clearly known. The average age of onset is between 52.4 years to 60.9 years. Unlike those who experience sleep terrors, the victim will recall vivid dreams. The frequency of these episodes varies from once every few weeks to several times a night. Episodes tend to occur 90 min or more after sleep onset, when the first REM period typically begins. (Mahowald et al., 2005).
REM sleep behavior disorder has been linked to a number of other neurological conditions; thus, a careful review of systems and a physical examination are crucial. Polysomnography monitoring in patients with REM sleep behavior disorder reveals increased tonic and/or phasic electromyographic activity, often accompanied by muscle twitching, extremity flailing, or vocalization during REM sleep. REM sleep behavior disorder is often associated with a growing number of underlying neurologic disorders, and may be induced by numerous medications, particularly selective serotonin reuptake inhibitors (Boeve et al., 2004).
REM sleep behavior disorder can be controlled with medication. Clonazepam is the mainstay in the treatment of REM sleep behavior disorder and leads to either a complete or partial response in approximately 90% of cases. Before it is prescribed, the potential benefits of treatment should be weighed against the possible side effects. Other medications have been tried when clonazepam is not effective or is poorly tolerated. Discussions related to safety are very important, because precautionary measures may prevent serious injury to the patient or family members (Schenck et al., 2002).
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