The parasomnias refer to clinical disorders consisting of undesirable physical phenomena that occur predominantly during sleep (DCSC, 1990). They have been classified based on the stage of sleep from which they originate. They include both normal and abnormal phenomena. Included in the category of NREM parasomnias are hypnic jerks and hypnic imagery, considered to be normal, in addition to confusional arousals, sleep terrors (pavor nocturnus), and sleepwalking (somnambulism), referred to as disorders of arousal. These all originate from deep NREM sleep, stages 3 and 4. They are all common in childhood and decrease in frequency as age increases. These individuals tend to have a family history of similar disorders. REM parasomnias include nightmares and REM behavior disorder (RBD). A third group consists of disorders that may occur during any or all sleep stages and includes bruxism, enuresis, rhythmic movement disorder (including head-banging), sleep talking (somniloquy), and posttraumatic stress disorder. The following parasomnias may at times need to be considered in the differential diagnosis of seizures associated with sleep.
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