Functional imaging techniques in the diagnosis of non-Alzheimer dementias.

Functional imaging (positron emission tomography -- PET, single photon emission tomography -- SPECT, magnetic resonance spectroscopy -- MRS) enables regional cerebral function to be assessed in vivo in dementias. There are three basic approaches to examining the patterns of cerebral function associated with specific disorders: First, abnormalities in resting levels of regional cerebral metabolism and blood flow can be examined. Second, patients can be asked to perform cognitive tasks with a view to demonstrating aberrations in their pattern of cerebral activation. Third, resting dysfunction of brain pharmacology can be revealed. The bulk of the research on non-Alzheimer dementias has been performed with PET and SPECT and this review will concentrate on these two modalities.