Delirium: definition, epidemiology, and diagnosis.

This article serves to (1) review the relationship of the terms "delirium" and "encephalopathy," (2) describe delirium as defined in current diagnostic systems, (3) summarize the epidemiology and theories of pathogenesis, (4) review clinical diagnostic approaches, and (5) highlight the history using EEG in the study of delirium in the psychiatric literature. Delirium is an important medical syndrome with significant implications; there is continued need for better physiologic measures of the underlying brain dysfunction.