Clinical correlates of PET- and SPECT-identified defects in dementia.

Functional imaging studies in patients with dementia have focused primarily on the reliability of scan patterns to correctly diagnose specific diseases, particularly Alzheimer's disease. Results from these studies have important implications as disease-specific treatments become available. A complementary approach is to examine the relationships between patterns of altered brain function and specific behaviors. This tactic has potential impact on understanding normal brain organization as well as targeting symptom-specific treatments. Regional abnormalities have been identified in dementia patients that correlate with specific behavioral deficits: disturbances of language and visuospatial function, impaired verbal fluency and selective attention, and the presence of delusions and depression. These patterns are seen in patients with Alzheimer's disease as well as with dementias of other etiologies. The specificity of these patterns for disease-specific and disease-independent symptoms is unknown.