Does computed tomographic brain imaging have a place in the diagnosis of dementia?

Computed tomographic (CT) scanning of the head is an accepted routine in the evaluation of dementia. This study attempted to identify a patient group in which brain imaging adds meaningful data to the clinical picture.

One hundred patients who met criteria for dementia as defined in the Diagnostic and Statistical Manual of Mental Disorders, Revised Third Edition, underwent computed tomographic imaging. From clinical data alone, 56 of these patients also met the following strict criteria for the diagnosis of probable Alzheimer's disease (PAD): the McKhann criteria for PAD, Diagnostic and Statistical Manual of Mental Disorders, Revised Third Edition, criteria for primary degenerative dementia, a score of less than 4 on the modified Hachinski Ischemia Scale, a normal neurologic examination and symptoms for at least 1 year.

In the PAD group, eight scans (14%) had abnormalities other than atrophy; only three (two showing lacunae and one showing infarct) were of possible clinical significance. In the 44 patients not meeting PAD criteria, 23 scans (52%) were abnormal, including 15 with infarcts, two with periventricular lucencies, three showing tumors, and one showing hydrocephalus.

These results support the diagnostic value of computed tomographic scanning in atypical dementia and its limited utility in PAD. The data indicate that clinical guidelines can be developed for the application of CT in the diagnosis of dementia.