Comparison of gray matter and metabolic reduction in mild Alzheimer's disease using FDG-PET and voxel-based morphometric MR studies

Purpose: The aim of this study was to investigate regional differences between morphologic and functional changes in the same patients with mild Alzheimer's disease (AD) using statistical parametric mapping (SPM) and voxel-based morphometry (VBM). Methods: Thirty patients with very mild AD (mean age 66.8 years, mean MMSE score 24.0) and 30 age- and sex-matched normal volunteers underwent both F-18-fluorodeoxyglucose (FDG) positron emission tomography (PET) and three-dimensional spoiled gradient echo (SPGR) magnetic resonance imaging (MRI). Statistical parametric mapping was used to conduct VBM analysis of the morphological data, which were compared voxel by voxel with the results of a similar analysis of the glucose metabolic data. Results: In AD patients, VBM data indicated a significant gray matter volume density decrease in bilateral amygdala/hippocampus complex (p < 0.05, corrected), while FDG-PET analysis showed significant glucose metabolic reductions in the posterior cingulate gyri and the right parietal lobule, compared with those in the normal control group. Conclusion: In very mild AD, morphological change occurs in the medial temporal lobes, while in contrast, metabolic changes occur in the posterior cingulate gyri and parietal lobule.