SUMMARY: There is increasing use of neuroimaging modalities, including PET, for diagnosing dementia. For example, FDG-PET demonstrates hypometabolic regions in the posterior cingulate gyri, precuneus, and parietotemporal association cortices, while amyloid PET indicates amyloid deposition in Alzheimer disease and mild cognitive impairment due to Alzheimer disease. Furthermore, the use of combination PET with structural MR imaging can improve the diagnostic accuracy of dementia. In other neurodegenerative dementias, each disease exhibits a specific metabolic reduction pattern. In dementia with Lewy bodies, occipital glucose metabolism is decreased, while in frontotemporal dementia, frontal and anterior temporal metabolism is predominantly decreased. These FDG-PET findings and positive or negative amyloid deposits are important biomarkers for various neurodegenerative dementias.

Aims: To investigate regional morphologic changes in idiopathic normal pressure hydrocephalus (INPH) based on diagnosis with INPH Guidelines using voxel-based morphometry. Method: Three-dimensional magnetic resonance imaging was performed in 34 INPH patients, who met probable INPH criteria, probable 34 Alzheimer disease patients, and 34 normal control subjects. Results: Statistical parametric mapping was used to conduct voxel-based morphometry analysis of the morphologic data and revealed enlarged ventricles and sylvian fissures and stenotic sulci of high convexity, especially in the precuneus in the INPH group, with decreased gray matter density in the insula, caudate and thalamus. Conclusion: In INPH, morphologic change occurs in the frontoparietal high convexity with ventricular dilatations, dilated sylvian fissures and tight sulci in the medial parietal lobes.

The aim of this study was to investigate regional differences between morphologic and functional changes in patients with mild dementia with Lewy bodies (DLB) compared with those with Alzheimer's disease (AD). Methods: Twenty patients with very mild DLB (mean age, 74.5 y; mean Mini-Mental State Examination [MMSE] score, 24.0), 20 patients with very mild AD (mean age, 74.1 y; mean MMSE score, 24.0), and 20 age- and sex-matched healthy volunteers (normal controls [NC]) underwent both ¹⁸F-FDG PET and 3-dimensional spoiled gradient echo MRI. Fully automatic volumetry of the MRI data was used to obtain whole brain, hippocampal, occipital, and striatal volumes, which were compared with the results of a similar analysis of glucose metabolic data. Results: In DLB patients, volumetric data indicated a significant volume decrease in the striatum, whereas ¹⁸F-FDG PET showed significant glucose metabolic reductions in the temporal, parietal, and frontal areas—including in the occipital lobe—compared with those in the NC group. In contrast, in AD patients, both the hippocampal volume and glucose metabolism were significantly decreased, whereas the occipital volume and metabolism were preserved. Conclusion: Comparison of very mild DLB and AD revealed different morphologic and metabolic changes occurring in the medial temporal lobes and the occipital lobe, demonstrating characteristic pathophysiologic differences between these 2 diseases.