Fang, Ping

AbstractIntroductionComparison of tau (flortaucipir) positron emission tomography (FTP‐PET) to autopsy is important to demonstrate the relationship of FTP‐PET to neuropathologic findings.MethodsAutopsies were performed on 26 participants who had antemortem FTP‐PET. FTP‐PET standardized uptake value ratios (SUVRs) were compared to autopsy diagnoses and Braak tangle stage. Quantitative tau burden was compared to regional FTP‐PET signal.ResultsParticipants with Braak stages of IV or greater had elevated FTP‐PET signal. FTP‐PET was elevated in participants with Alzheimer's disease. An FTP‐PET SUVR cut point of 1.29 was determined to be optimal. Quantitative measurements of hippocampal and temporal lobe tau burden were highly correlated to FTP‐PET signal (rho's from 0.61 to 0.70, P ≤ .02).DiscussionElevated FTP‐PET reflects Braak IV or greater neuropathology. Participants with primary age‐related tauopathy and hippocampal sclerosis did not show elevated FTP‐PET signal. Secondary neuropathologic diagnoses of Alzheimer's disease neuropathologic change can lead to borderline elevated FTP‐PET signal.

AbstractIntroductionMedial temporal lobe (MTL) uptake on tau–positron emission tomography (PET) is seen not only in Alzheimer's disease (AD) dementia but also in the aging population. The relationship of these findings to the development of AD dementia needs to be better understood.MethodsTau‐PET with AV‐1451 was performed on 576 cognitively unimpaired (CU) participants aged 50–94 years. The number of CUs with and without abnormal MTL regions and those with or without extra‐MTL abnormalities was determined. Left and right regions were compared within each subject.ResultsOf CUs, 58% (334/576) had abnormal tau‐PET findings. MTL abnormalities were present in 41% (238/576) of subjects.DiscussionMTL tau‐PET signal is often associated with abnormal extra‐MTL tau‐PET signal in CU participants and may represent neurofibrillary tangle development that could identify participants most likely to develop AD dementia. Tau‐PET signal exclusively outside of the MTL is seen in 17% of CU participants and could be the initial findings in participants in different AD dementia pathways. Significant (P < .001) differences in tau–standardized uptake value ratio between sides were noted in 26 of 41 examined brain regions implicating further study of side‐specific deficits.