Functional imaging in dementia: an overview.

Functional brain imaging using both positron emission tomography and single photon emission computed tomography has been widely applied to the study of dementing diseases. This article reviews the basic approach of the clinician to the problem of dementia, which primarily entails the exclusion of treatable or reversible causes. Structural brain imaging using magnetic resonance imaging or computed tomography to search for reversible structural brain lesions is a key component of this evaluation. Functional imaging may provide clinicians with additional information helpful in establishing the cause of dementia after a reversible illness has been ruled out. Limitations in the data supporting the use of functional images still exist, however, and these images must be interpreted in the context of the overall clinical presentation.