In Vivo Assessment of Tau Deposition in Alzheimer Disease and Assessing Its Relationship to Regional Brain Glucose Metabolism and Cognition

Aim In this study, we investigated the relationship of cerebral tau deposition (F-18-tau-AD-ML 104 PET/CT) with glucose metabolism (F-18-FDG PET/CT) and cognitive function in patients with Alzheimer disease (AD). Patients and Methods Seventy subjects (Mini Mental State Examination [MMSE] score <18 = 37 [AD]; MMSE score, 18-24 = 16 [early AD]) and 17 controls were included in this study. All participants underwent detailed neurological and neuropsychological evaluation, followed by F-18-tau-AD-ML 104 and F-18-FDG PET/CT imaging. Region-wise SUVmax ratios at 50 to 60 minutes postinjection were calculated for F-18-tau-AD-ML 104 and F-18-FDG, using the cerebellar cortex as the reference region. Linear models were used to investigate the association of regional F-18-tau-AD-ML 104 retention with F-18-FDG uptake and cognition (MMSE scores). Results F-18-Tau-AD-ML 104 retention was observed in the parietal lobe, temporal lobe, hippocampus, parahippocampus, frontal lobe, anterior and posterior cingulate, and precuneus in advanced and early AD patient as compared with normal controls with regional hypometabolism in overlapping regions on F-18-FDG PET. Significant negative association was found between F-18-tau-AD-ML 104 regional retention and glucose metabolism in the parietal lobe, temporal lobe, hippocampus, parahippocampus, frontal lobe, anterior and posterior cingulate, and precuneus among patients with advanced and early AD. In advanced and early AD patients, a negative association was found between F-18-tau-AD-ML 104 regional retention (precuneus) and cognition (MMSE score), whereas a positive association was observed between F-18-FDG regional uptake (precuneus) and cognition (MMSE score). Conclusions Tau pathology overlapped with areas of hypometabolism on FDG PET in the brains of AD patients. Tau deposition was found to have negative association with cognitive scores in these patients.