Beyond the hippocampus - MRI volumetry confirms widespread limbic atrophy in AD

Objective: To examine volumetric changes in limbic structures in patients w ith probable AD using planimetric measures on MRI. Methods: Limbic structur es (i.e., hippocampus, amygdala, anterior thalamus, hypothalamus, mamillary bodies, basal forebrain, septal area, fornix, and cingulate, orbitofrontal , and parahippocampal cortices) were traced on 3D T1-weighted MR images of 40 patients with mild to moderate AD and 40 age-, sex-, and education-match ed normal control subjects. Limbic volumes were compared between groups and the predictive ability was assessed. Results: Overall, limbic structures s howed significant atrophy in AD patients compared with normal control subje cts. Differences (p < 0.05) were found in all limbic regions except the ant erior cingulate cortex. The greatest percentage volumetric losses occurred in the septal area (34%), hippocampus (28%), amygdala (21%), parahippocampa l cortex (21%), and posterior cingulate cortex (20%). Combining volumetric measures of amygdala and septal area distinguished patients with AD from no rmal control subjects with 93% accuracy. Conclusions: These results verify that system-wide limbic degeneration occurs in patients with AD. In additio n, atrophy in selected limbic structures was used to distinguish patients w ith AD from normal elderly individuals with over 90% accuracy in this selec t clinical sample. The measures require further exploration in samples more representative of those seen by primary care physicians before their utili ty can be accurately assessed.