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Background and purpose: Subcortical structures are affected by neurodegeneration in Alzheimer's disease (AD) and Lewy body disease (LBD). Although the co‐occurrence of AD and LBD pathologies and their possible interaction have been reported, the effect of AD and LBD on subcortical structures remains unknown. The effects of AD and LBD on subcortical atrophy and their relationship with cognitive dysfunction were investigated. Methods: The cross‐sectional study recruited 42 patients with pure AD related cognitive impairment (ADCI), 30 patients with pure LBD related cognitive impairment (LBCI), 58 patients with mixed ADCI and LBCI, and 29 normal subjects. A general linear model was used to compare subcortical volume and shape amongst the groups, to investigate the independent and interaction effects of ADCI and LBCI on subcortical shape and volume, and to analyze the relationship between subcortical volume and cognitive dysfunction in each group. Results: Alzheimer's disease related cognitive impairment and LBCI were independently associated with subcortical atrophies in the hippocampus and amygdala and in the hippocampus and putamen respectively, but their interaction effect was not significant. Compared to the control group, the pure LBCI group exhibited additional local atrophies in the amygdala, caudate and thalamus. Subcortical atrophies correlated differently with cognitive dysfunction according to the underlying causes of cognitive dysfunction. Conclusions: The patterns of subcortical atrophies and their correlation with cognitive dysfunction differ according to the underlying AD, LBD or concomitant AD and LBD. [ABSTRACT FROM AUTHOR]

Background and purpose: Differentiation between parkinsonian type multiple system atrophy (MSA-P) and Parkinson’s disease (PD) is important but often difficult. We investigated the diagnostic value of brain magnetic resonance imaging (MRI) and 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) in differentiating MSA-P from PD. Methods: Twenty-four patients with MSA-P (16 probable and 8 possible) and eight patients with PD were included in this study. Results: For analysis using the putaminal findings, the sensitivities were 58.3% by visual analysis of brain MRI, 95.8% by visual analysis of 18F-FDG PET, and 79.2% by statistical parametric mapping (SPM) analysis of 18F-FDG PET in differentiating MSA-P from PD; the specificity was 100% for each analysis. Using the putaminal findings, visual analysis of 18F-FDG PET had a higher sensitivity compared with brain MRI ( P = 0.004) and SPM analysis of 18F-FDG PET revealed a tendency towards higher sensitivity compared with brain MRI ( P = 0.063). For analysis using both putaminal and infratentorial findings, the sensitivities were 79.2% by visual analysis of brain MRI, 95.8% by visual analysis of 18F-FDG PET, 95.8% by SPM analysis of 18F-FDG PET in differentiating MSA-P from PD; the specificity was 100% for each analysis. Conclusion: Both brain MRI and 18F-FDG PET showed diagnostic usefulness in differentiating MSA-P from PD, with 18F-FDG PET being more sensitive than brain MRI. [ABSTRACT FROM AUTHOR]