Relationship between ¹⁸F-flortaucipir uptake and histologic lesion types in 4-repeat tauopathies

Progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) are 4-repeat tauopathies with overlapping, but also morphologically distinct tau immunoreactive lesions that vary in count by brain region. ¹⁸F-flortaucipir positron emission tomography uptake has been reported to correlate with overall tau burden, and in one CBD case to have greater affinity to threads than tangles. We determine whether ¹⁸F-flortaucipir uptake is associated with histologic lesion type in 4-repeat tauopathies. Methods: We performed semi-quantitative regional lesion counts on pretangles/neurofibrillary tangles, threads, oligodendroglial coiled bodies, tufted astrocytes, and astrocytic plaques in 29 autopsied 4-repeat tauopathies (PSP=16; CBD=13). Regression models were used for statistical analyses. Results: ¹⁸F-flortaucipir uptake marginally correlated with threads in the precentral cortex (p=0.04) and with astrocytic lesions in the red nucleus (p=0.05). Conclusions: The findings do not support ¹⁸F-flortaucipir having differential affinity to any 4-repeat tau lesion type.