Structural neuroimaging of Alzheimer's disease and other dementias.

This paper reviews the use of imaging techniques to aid in the clinical diagnosis of dementia. Two approaches are distinguished. One is the exclusionary approach in which imaging is used to rule out diseases that would mimic or cause dementia; based on the literature, this approach yields very little, if any, information that was not identified clinically. The more positive approach uses imaging as a diagnostic tool to identify changes specific for causes of dementia; any assessment of medial temporal lobe atrophy on Magnetic Resonance Imaging (MRI) will result in a reasonably high positive likelihood ratio distinguishing AD patients from non-demented individuals, but fails to distinguish AD patients from patients with other dementias. For a diagnosis of vascular dementia imaging is necessary, although not all vascular changes fulfill requirements of being relevant to dementia. Potentially of more importance, given the higher prevalence of AD, is the identification of concomitant vascular changes in AD that may be amenable to therapy, and may be used to identify subgroups. Structural and functional MRI techniques have great potential in identifying patients at risk for AD, which will allow for a very early treatment with drugs that slow or even halt progression.