Diagnostic issues in dementia: neuroimaging as a surrogate marker of disease.

Structural neuroimaging is a routine component of the diagnostic evaluation of dementia that is used to rule out potential causes of mental impairment, whereas functional imaging can differentiate different forms of dementia. Neuroimaging also offers promise as a surrogate marker for clinical trials, and new technologies have been developed to provide measures of amyloid plaques and neurofibrillary tangles, the neuropathological hallmarks of Alzheimer's disease. Combining imaging with genetic risk data will likely improve diagnostic accuracy. These new findings warrant reconsideration of current guidelines on the use of neuroimaging in diagnosis and research in dementia.