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Background: Mild cognitive impairment (MCI) is a well-known precursor of Alzheimer's disease (AD) but often also precedes dementia with Lewy bodies (DLB). The early differentiation of DLB from AD is important to delay disease progression. Olfactory dysfunction is a well-known early sign of both AD and Lewy body disorders, including Parkinson's disease (PD) and DLB. Thus, the aim of the present study was to determine whether olfactory and neuropsychological tests can aid in the differentiation of DLB from AD at the MCI stage., Methods: The present study included 122 MCI patients who were monitored until they developed dementia or until their condition stabilized; the follow-up period averaged 4.9 years (range: 3.9-6.2 years). Baseline olfactory function as measured with the Cross-Cultural Smell Identification (CCSI) test and neuropsychological data were compared., Results: During the follow-up period, 32 subjects developed probable AD (MCI-AD), 18 had probable DLB (MCI-DLB), 45 did not convert to dementia (MCI-stable), and eight developed a non-AD/DLB dementia. The mean CCSI score (95% confidence interval [CI]) in patients with MCI-DLB (4.6; 95% CI: 4.0-5.3) was significantly lower than that of MCI-AD patients (6.4; 95% CI: 6.0-6.7, p<0.001) and MCI-stable patients (7.3; 95% CI: 6.9-7.8, p<0.001). The area under the curve of the receiver operating characteristic to discriminate MCI-DLB from MCI-AD using CCSI scores was (0.84; 95% CI: 0.72-0.97). Frontal-executive function and visuospatial ability was worse in patients with MCI-DLB, while verbal recognition memory impairment was greater in those with MCI-AD., Conclusion: Olfactory and neuropsychological tests can help predict conversion to DLB or AD in patients with MCI., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Background: Recent studies have demonstrated that structural and pathologic changes are more severe in patients with dementia with Lewy bodies (DLB) than in those with Parkinson disease with dementia (PDD). We investigated neuropsychological characteristics of patients with mild cognitive impairment (MCI) stage of DLB (DLB-MCI) and PD (PD-MCI) based on the hypothesis that the pathologic differences between DLB and PDD can influence cognitive profiles in the MCI stage of these diseases., Methods: Baseline demographic characteristics and neuropsychological data obtained from patients with DLB-MCI (n=20) and PD-MCI (n=46) were compared., Results: The patients with DLB-MCI showed poorer cognitive performance in the Stroop, Go-No-Go, and semantic fluency tests compared with those with PD-MCI. In addition, patients with DLB-MCI had lower scores on visual and verbal memory performance and in the visuospatial domain compared with PD-MCI patients., Conclusions: Our results demonstrate that patients with DLB-MCI have more severe cognitive impairment in frontal executive, memory, and visuospatial functions than those with PD-MCI. These data suggest that differences in pathologic substrates between PDD and DLB may begin in the MCI stage of the 2 diseases and may lead to differences in cognitive profiles.

Parkinson's disease dementia (PDD) and dementia with Lewy bodies (DLB) share many similar aspects, and making a clinical diagnosis of one disorder over the other relies heavily on an arbitrary criterion, so-called 1-year rule. This study was designed to search for any difference of metabolic patterns in these two disorders using F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) images. We enrolled 16 patients with PD, 13 patients with PDD, and seven patients with DLB. FDG PET was performed, and images were reconstructed by iterative reconstruction using the computed tomography (CT) images, and were normalized to a standard template. Statistical comparison between groups were performed on a voxel-by-voxel basis using t-statistics (two-sample t-test). Compared with the patients with PD, both PDD and DLB patients showed similar patterns of decreased metabolism in bilateral inferior and medial frontal lobes, and right parietal lobe (P(uncorrected) < 0.001). In a direct comparison, DLB patients had significant metabolic decrease (p(uncorrected) < 0.005) in the anterior cingulate compared with those with PDD. These findings support the concept that PDD and DLB have similar underlying neurobiological characteristics, and that they can be regarded as a spectrum of Lewy body disorders.