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Objective : To investigate the cerebral glucose metabolism of subjects who had a Clinical Dementia Rating (CDR) of 0.5, we studied 40 subjects whose CDR was 0.5 and 40 age-matched healthy subjects. Methods : Cerebral glucose image of each subject was obtained by [ 18 F]-2-fluoro-deoxy- d -glucose (FDG) positron emission tomography (PET). The anatomically standardized images were produced with NEUROSTAT. Then, the two groups were compared with the Statistical Parametric Mappings (SPM) 99. Results : A comparison with the SPM 99 revealed that relative cerebral glucose metabolism was lower in the posterior cingulate gyri and parietal lobules in the CDR 0.5 group than in the healthy subjects group. Conclusion : These findings are very similar to those in patients with probable Alzheimer's disease (AD) and suggest that the majority of subjects with CDR 0.5 are suffering from very mild AD or at least a prodromal state of AD.

Progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) are neurodegenerative disorders that may be accompanied by dementia and parkinsonism as clinical symptoms. The purpose of this study was to elucidate cerebral metabolic differences of these two diseases with cognitive impairments by [18F] fluorodeoxyglucose (FDG) and positron emission tomography (PET).A total of 12 patients with PSP (age: 62.8+/-6.0 years old, m: 7, f: 5, Mini-Mental State Examination (MMSE): 23.4+/-2.6), 12 patients with CBD (age: 64.8+/-6.3 years old, m: 6, f: 6, MMSE: 22.9+/-4.5), and age-matched healthy subjects (normal control (NC)) (age: 63.8+/-7.7 years old, m: 7, f: 5) were subjected to FDG-PET to obtain glucose metabolic images. We compared regional cerebral metabolic images by a voxel-by-voxel analysis with statistical parametric mapping (SPM) among PSP, CBD, and NC subjects, and evaluated differences of hypometabolic regions.The patients with PSP showed reduced cerebral glucose metabolism in the medial and lateral frontal gyri, basal ganglia, and midbrain compared with NC, whereas the patients with CBD showed significant reduction in the parietal lobes (p0.001). SPM also revealed parietal hypometabolism in CBD patients compared with PSP patients (p0.001).The predominant parietal glucose metabolic reduction in CBD patients was different from previously reported findings. This finding would be the characteristic substance of patients with CBD accompanying cognitive impairments. Our findings suggest that measurement of glucose metabolism by PET and a voxel-based analysis is useful to understand the pathophysiology of these two diseases with cognitive impairments.

The purpose of this study was to delineate the specific patterns of cerebral glucose metabolism with regard to the time of onset of Alzheimer's disease (AD). Methods : Two groups of 20 AD patients with different ages of onset were examined. The early onset (EO) and late onset (LO) groups had mean ages of onset of 53.9 and 72.7 years. Groups of age-matched normal subjects were used as controls. A regional relative cerebral glucose metabolic image of each subject was obtained by 2-[ 18 F] fluoro-2-deoxy- d -glucose (FDG) positron emission tomography (PET). NEUROSTAT program was used for spatial normalization and voxel-based statistical parametric mapping (SPM) 99 was used for statistical analyses. Results : Both AD groups had significant hypometabolic regions in the bilateral parieto-temporal regions compared with the age-matched groups. The EO group had more severe hypometabolism in the bilateral parietal and posterior cingulate cortices and precuneus region than the LO group. However, LO group showed no significant hypometabolic regions compared to the EO group. Conclusion : The effects of time of AD onset were delineated as a double dissociation, that is, EO AD patients have a more severe reduction of glucose metabolism. Our finding suggests the existence of biological subtypes of AD.