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We evaluated cerebellar subregional metabolic alterations in patients with cerebellar ataxia, a representative disease involving the spinocerebellum. We retrospectively analyzed 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) images in 44 patients with multiple system atrophy of the cerebellar type (MSA-C), 9 patients with spinocerebellar ataxia (SCA) type 2, and 14 patients with SCA type 6 and compared with 15 patients with crossed cerebellar diaschisis (CCD) and 89 normal controls. Cerebellar subregional metabolism was assessed using 13 cerebellar subregions (bilateral anterior lobes [ANT], superior/mid/inferior posterior lobes [SUPP/MIDP/INFP], dentate nucleus [DN], anterior vermis [ANTV], and superior/inferior posterior vermis [SUPV/INFV]) to determine FDG uptake ratios. MSA-C and SCA type 2 showed severely decreased metabolic ratios in all cerebellar subregions compared to normal controls (ANT, 0.58 ± 0.08 and 0.50 ± 0.06 vs. 0.82 ± 0.07, respectively, p < 0.001). SCA type 6 showed lower metabolic ratios in almost all cerebellar subregions (ANT, 0.57 ± 0.06, p < 0.001) except INFV. Anterior-posterior lobe ratio measurements revealed that SCA type 2 (Right, 0.81 ± 0.05 vs. 0.88 ± 0.04, p < 0.001; Left, 0.83 ± 0.05 vs. 0.88 ± 0.04, p = 0.003) and SCA type 6 (Right, 0.72 ± 0.05 vs. 0.88 ± 0.04, p < 0.001; Left, 0.72 ± 0.05 vs. 0.88 ± 0.04, p < 0.001) showed preferential hypometabolism in the anterior lobe compared to normal controls, which was not observed in CCD and MSA-C. Asymmetric indices were higher in CCD and MSA-C than in normal controls (p < 0.001), whereas such differences were not found in SCA types 2 and 6. In summary, quantitative analysis of cerebellar subregional metabolism ratios revealed preferential involvement of the anterior lobe, corresponding to the spinocerebellum, in patients with cerebellar ataxia, whereas patients with CCD and MSA-C exhibited more asymmetric hypometabolism in the posterior lobe. [ABSTRACT FROM AUTHOR]

Background: Although cognitive impairment is not a consistent feature of multiple system atrophy (MSA), increasing evidence suggests that cognitive impairment is common in MSA with predominant parkinsonism (MSA-P). It is assumed that the cognitive impairment in MSA-P is caused by the striatal dysfunction and disruption of striatofrontal connections. The aim of this study was to evaluate the relationship between regional glucose metabolism in the frontal cortex and striatum in patients with MSA-P using [18F]FDG brain PET. Methods: Twenty-nine patients with MSA-P and 28 healthy controls underwent [18F]FDG brain PET scan. The [18F]FDG brain PET images were semiquantitatively analyzed on the basis of a template in standard space. The regional glucose metabolism of the cerebral cortex and striatum were compared between MSA-P and healthy control groups. The correlations between age, symptom duration, H&Y stage, UPDRS III score, MMSE score, and glucose metabolism in the cerebellum and striatum to glucose metabolism in the frontal cortex were evaluated by multivariate analysis. Results: The glucose metabolism in the frontal cortex and striatum in MSA-P patients were significantly lower than those in healthy controls. Glucose metabolism in the striatum was the most powerful determinant of glucose metabolism in the frontal cortex in MSA-P. Only age and glucose metabolism in the cerebellum were independent variables affecting the glucose metabolism in the frontal cortex in healthy controls. Conclusion: The decrease in frontal glucose metabolism in MSA-P is related to the decrease in striatal glucose metabolism. This result provided evidence of striatofrontal deafferentiation in patients with MSA-P. [ABSTRACT FROM AUTHOR]

Purpose: To assess the in vivo whole-brain relationship between uptake of [18F]THK-5351 on PET and cortical atrophy on structural MRI according to the presence and severity of Alzheimer's disease (AD). Materials and methods: Sixty-five participants (21 normal controls, 32 mild cognitive impairment [MCI] subjects, and 12 AD patients) were enrolled from a prospective multicenter clinical trial (NCT02656498). Structural MRI and [18F]THK-5351 PET were performed within a 2-month interval. Cortical volume and standardized uptake value ratios (SUVR) were calculated from MRI and PET images, respectively, for 35 FreeSurfer-derived cortical regions. Pearson's correlation coefficients between SUVR and cortical volume were calculated for the same regions, and correlated regions were compared according to disease severity and β-amyloid PET positivity. Results: No significantly correlated regions were found in the normal controls. Negative correlations between SUVR and cortical volume were found in the MCI and AD groups, mainly in limbic locations in MCI and isocortical locations in AD. The AD group exhibited stronger correlations (r = −0.576–0.781) than the MCI group (r = 0.368–0.571). Hippocampal atrophy did not show any correlation with SUVR in the β-amyloid PET-negative group, but negatively correlated with SUVR (r = −0.494, P =.012) in the β-amyloid PET-positive group. Conclusions: Regional THK-5351 uptake correlated more strongly with cortical atrophy in AD compared with MCI, thereby demonstrating a close relationship between the neuro-pathologic process and cortical atrophy. Hippocampal atrophy was associated with both β-amyloid and THK-5351 uptake, possibly reflecting an interaction between β-amyloid and tau deposition in the neurodegeneration process. [ABSTRACT FROM AUTHOR]