A parasomnia characterized by a partial arousal that occurs during stage IV of non-REM sleep. Affected individuals exhibit semipurposeful behaviors such as ambulation and are difficult to fully awaken. Children are primarily affected, with a peak age range of 4-6 years.

Movements or behaviors associated with sleep, sleep stages, or partial arousals from sleep that may impair sleep maintenance. Parasomnias are generally divided into four groups: arousal disorders, sleep-wake transition disorders, parasomnias of REM sleep, and nonspecific parasomnias. (From Thorpy, Sleep Disorders Medicine, 1994, p191)