Brain disease and psychiatric illness: when should a psychiatrist order a CAT scan?

Because psychiatric symptoms are frequently the earliest signs of CNS pathology, the author outlines the structural brain diseases that may underlie several psychiatric syndromes and describes the computerized axial tomographic (CAT) scan findings associated with those diseases. On the basis of an awareness of these conditions and a cost-benefit analysis, the following indications for CAT scanning of psychiatric patients are proposed: 1) confusion and/or dementia of unknown cause, 2) first episode of a psychosis of unknown etiology, 3) movement disorder of unknown etiology, 4) anorexia nervosa, 5) prolonged catatonia, and 6) first episode of major affective disorder or personality change after age 50.