Neurochemical imaging of Alzheimer's disease and other degenerative dementias.

A wide variety of neurochemical and functional imaging approaches have been applied to the study of progressive dementias, particularly Alzheimer's disease (AD) and related disorders. Despite considerable progress in the past decade, the cause(s) of most cases of AD remain undetermined and preventive or protective therapies are lacking. Specifically-designed imaging procedures have permitted the testing of pathophysiological hypotheses of the etiology and progression of AD, and have yielded important insights in several areas including the potential roles of cerebral cortical cholinergic lesions, cellular inflammation, and losses of cortical synapses. From the perspective of clinical diagnosis, PET glucose metabolism imaging with use of [18F]2-fluorodeoxyglucose (FDG) is the most sensitive and specific imaging modality yet identified. The overall performance of PET FDG is favorable for routine clinical evaluation of suspected AD, and will likely gain increasing utilization in the near future. Assessments of glucose metabolism and other, specific aspects of neurochemistry in AD will provide direct measures of therapeutic drug actions and may permit distinction of symptomatic versus disease-modifying therapies as they are developed and introduced in clinical trials.