Volumes of medial temporal lobe structures in patients with Alzheimer's disease and mild cognitive impairment (and in healthy controls)

Background: The clinical diagnosis of Alzheimer's disease (AD) can be difficult to make in early stages of disease. Structural neuroimaging offers a potential tool in the clinical diagnosis of AD with mild cognitive impairment. Postmortem studies indicate that early neuropathology in AD occurs in medial temporal lobe limbic structures. Magnetic resonance imaging (MRI) studies that assessed these volumes in mildly impaired AD patients remain inconclusive. Methods: Using MRI, we measured volumes of left and right hippocampus, amygdala, and anterior and posterior parahippocampal gyrus (PHG) in 13 AD patients with mild cognitive impairment defined as greater than or equal to 20 on the Mini-Mental State Exam, and in 21 healthy age-and sex-matched controls. Results: The AD patients had smaller medial temporal lobe volumes, except for the right anterior PHG, Discriminant function analysis using MRI volumes produced 94% correct group classification. Conclusions: These results show that in mildly impaired AD patients atrophy is present in medial temporal lobe structures; that MRI volumes of the anterior PHG, which contains entorhinal cortex, are reduced, but the amygdala and hippocampal volumes show greater reduction; and that discriminant function analysis using all volumes as predictors can correctly classify a high proportion of individuals.