Parasomnias

During sleep, the brain cycles regularly between wakefulness, nonrapid eye movement (NREM) sleep and rapid eye movement (REM) sleep. Nonrapid eye movement sleep is subdivided into four stages: stage I, a transitional stage between wake and sleep; stage II, which makes up most of the sleep period; and stages III and IV, which typically occur in the first half of the night and during which more profound stimulus is required to wake the sleeper. Parasomnias occur when transitions between these stages are blurred (commonly between stages III/IV and the awake state), causing behaviours that lack the complete awareness and mentation associated with wakefulness.1 It is not cost-effective to obtain a polysomnogram for patients with NREM parasomnia, except to exclude other causes of additional sleep instability (e.g., obstructive sleep apnea, periodic limb movement disorder, narcolepsy). Because one of the ICSD diagnostic criteria for REM sleep behaviour disorder requires the demonstration of REM sleep without atonia,1 polysomnography is needed to confirm this diagnosis and to rule out comorbid sleep disorders, such as obstructive sleep apnea or periodic limb movement disorder, which are more prevalent in adults and may need to be a focus of management. Rapid eye movement sleep behaviour disorder is characterized by activity in REM sleep causing injury or sleep disruption. Polysomnography is required to confirm the associated electromyographic abnormalities. In REM sleep behaviour disorder, there is a loss of REM atonia with excessive muscle tone, twitches on electromyography, and movements that often appear to be dream enactment, potentially causing injury to the sleeper or bed partner. Episodes usually occur about once a week, but may be as often as four times nightly over consecutive nights. In contrast to all NREM parasomnias, the sleeper awakens rapidly without confusion and often with good recall of a dream that corresponds with the enacted behaviours that can include talking, laughing, swearing, shouting, reaching, grabbing, flailing, punching, hitting or running.5