V. Parasomnias
Parasomnias consist of sleep disorders that are not abnormalities of the sleep process but are, instead, undesirable physical phenomena that occur during sleep. Disorders of arousal, partial arousal, and sleep-wake transition are all parasomnias. These disorders refer to episodic nocturnal events such as sleepwalking, sleep terrors, and confusional arousals. Sleep enuresis, nightmare disorder, REM sleep behavior disorder, and sleep-related eating disorder are also parasomnias.
Disorders of arousal from NREM sleep include confusional arousals, sleepwalking, and sleep terrors. Usually they occur during a partial arousal from delta sleep, or slow-wave sleep, in the first part of the night. Episodes often are more frequent in children and lessen in adults, but some adults still have frequent, bothersome, and potentially dangerous events. Patients often have family members with a history of similar disorders.
Parasomnias usually associated with REM sleep usually occur later in the night and include REM sleep behavior disorder, recurrent isolated sleep paralysis, and nightmare disorder. Patients with REM sleep behavior disorder appear to be acting out their dreams; for example, they may punch their bed partner and, when awakened, will report that they were dreaming of fighting. This disorder is more common in males, over the age of fifty, particularly with an underlying neurologic disorder such as Parkinson disease. Nightmare disorder is more common among children than adults but may occur at any age. When awakened from a nightmare patients are fully alert and report that they have been dreaming; in contrast, patients are difficult to awaken from an episode of night terrors and usually do not report having a dream.
Other parasomnias include sleep enuresis (bedwetting), sleep-related eating disorder, sleep-related groaning (catathrenia) and exploding head syndrome. Parasomnias may be observed in the sleep laboratory on any night, but patients are rarely referred for polysomnography primarily because of a parasomnia.