Imagine navigating a labyrinth, where each twist and turn represents a piece of the Alzheimer’s puzzle. In this study, researchers sought to understand the connections between neuropsychological performance, tau protein deposits, and glucose metabolism in patients with Alzheimer’s disease (AD). They used positron emission tomography/computed tomography (PET/CT) scans with specialized tracers to visualize these components in the brain. The findings revealed that as cognitive function declined, there was a corresponding decrease in glucose metabolism and an accumulation of tau proteins in specific brain regions like the temporoparietal cortex. These changes occurred gradually, starting in the parietal cortex and spreading to the temporal and frontal cortex. The PET scans also showed that both tau protein levels and glucose metabolism were associated with different cognitive domains, such as memory, language, and attention. Interestingly, the results suggested that FDG PET scans, which measure glucose metabolism, had a stronger correlation with neuropsychological function compared to tau PET scans. This research provides valuable insights into the complex web of Alzheimer’s disease progression and highlights the potential of using PET imaging techniques to better understand and treat this devastating condition.

ObjectiveThis study characterizes glucose metabolism and tau protein deposition distribution in patients with Alzheimer’s disease (AD) and to evaluate the relationships between neuropsychological performance and tau protein deposition or glucose metabolism using 18F-FDG and 18F-AV1451 positron emission tomography/computed tomography (PET/CT).MethodsSixty-four patients with β-amyloid-positive (Aβ+) AD and twenty-five healthy participants were enrolled in this study. All participants underwent 18F-FDG and 18F-AV1451 PET/CT. Clinical data and neuropsychological scores were collected. Patients with AD were divided into mild, moderate, and severe groups according to mini-mental state examination (MMSE) scores. The standardized uptake value ratios (SUVRs) for both FDG and AV1451 PET images were calculated using the cerebellar vermis as reference. The SUVRs of the whole cerebral cortex and each brain region were calculated. The volume of interest (VOI) was obtained using automated anatomical atlas (AAL) and Brodmann regions. Student’s t-test was used to perform intergroup comparisons of SUVR. The partial correlation coefficient between SUVR and neuropsychological scores was computed in an inter-subject manner using age and education as covariates.ResultsThe mild subgroup showed a reduction in glucose metabolism and aggregation of tau protein in the temporoparietal cortex. With a decline in neuropsychiatric performance, the SUVR on FDG PET decreased and SUVR on tau PET increased gradually. The areas of glucose metabolism reduction and tau protein deposition appeared first in the parietal cortex, followed by the temporal and frontal cortex, successively. Both FDG and tau SUVRs significantly correlated with MMSE, Montreal cognitive assessment (MOCA), auditory verbal learning test (AVLT), Boston naming test (BNT), clock drawing task (CDT), and verbal fluency test (VFT) (p < 0.05). The SUVR on FDG PET significantly correlated with activities of daily living (ADL) and the Hamilton depression scale (HAMD). There was no significant correlation between the tau SUVRs and ADL or HAMD.ConclusionThe extension of tau protein deposition was similar but not exactly consistent with the area of glucose metabolism reduction. Both tau and FDG SUVRs correlated with cognitive function in domain-specific patterns, and the results of FDG PET more closely correlated with neuropsychological function than tau PET results did.

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