Neurofibrillary tangle deposition in primary idiotypic isocortices using flortaucipir PET in histopathologically confirmed Alzheimer’s disease

Tau deposition in Alzheimer's disease (AD) spreads throughout the brain in a stereotypical pattern captured by the Braak neurofibrillary tangle staging scheme. While involvement of primary isocortex defines the highest stage, it is unclear whether flortaucipir PET uptake differs among primary isocortical regions. We determined relationships between flortaucipir uptake in primary visual, auditory, motor, and somatosensory isocortices and Braak stage in 155 autopsy-confirmed participants with AD. Flortaucipir uptake was observed starting at Braak stage V, with visual and auditory isocortices showing greater and faster increases in uptake than somatosensory and motor; age and APOE ε4 influenced uptake. Flortaucipir uptake and change in primary isocortices were similar in the lateral temporal cortex but different in the entorhinal cortex. Findings suggest that tau deposition in primary isocortices in AD occurs earlier than currently emphasized, although there are differences among them. Given these findings, clinical correlations of primary isocortical involvement in AD need to be evaluated.