The asymmetry of tau deposition and its correlation with cerebral metabolic asymmetry in Alzheimer's disease

Background While the correlation between tau deposition and metabolism in Alzheimer's disease (AD) has been observed, the relationship between asymmetric tau deposition and metabolic asymmetry has not been thoroughly studied. Objective To analyze the asymmetry of tau deposition in AD and explore its correlation with cerebral metabolic asymmetry. Methods We retrospectively enrolled 304 AD patients who underwent 18 F-Florzolotau PET imaging, with 238 also receiving 18 F-FDG PET. Standardized uptake value ratios (SUVRs) were obtained, and asymmetry indices (AIs) of tau deposition and metabolism were calculated. AD patients were classified into subgroups of left/right-dominant or bilateral symmetric tau deposition and hypometabolism based on AI thresholds. Clinical differences and correlations between tau and metabolic asymmetry were assessed. Results Among 304 AD patients, 21.7%, 23.3%, and 4.8% exhibited left-dominant, right-dominant, and bilateral symmetric tau deposition, respectively. For the 238 patients with 18 F-FDG PET, 19.3%, 26.9%, and 8.0% had left-dominant, right-dominant, and bilateral symmetric hypometabolism. Longitudinally, tau and 18 F-FDG metabolic asymmetries exhibited different trends. Tau deposition subgroups did not differ significantly in age, disease duration, sex, or MMSE scores. Significant negative correlations between tau and metabolic asymmetry were found in 16 ROI pairs (ρ = −0.639 to −0.192, p < 0.05), while no significant correlations were seen in 4 other ROIs ( p > 0.05). Conclusions Nearly half of AD patients showed asymmetric tau deposition. Although tau asymmetry negatively correlated with metabolic asymmetry, differences in the proportions of asymmetry, variation trends, and clinical characteristics suggest that other factors influence metabolic heterogeneity in AD.