Periodic limb movements and other movement disorders in sleep: neuropsychiatric dimensions.

Movement disorders such as Parkinson's disease and Tourette's syndrome, primarily manifest during wakefulness, intrude into sleep. There are some disorders, however, such as periodic limb movements in sleep, restless legs syndrome, paroxysmal nocturnal dystonia, bruxism, and somnambulism, which occur primarily during sleep. The diagnosis and management of these disorders pose a challenge to neuropsychiatric practice, not only because they may be difficult to distinguish from other neuropsychiatric disorders, but also because psychiatric disorders are often co-morbid with them. Study of these disorders is necessary for an understanding of the interaction of sleep and movement, and how disturbance in one may affect the other.