Relationship Between ¹⁸F-Flortaucipir Uptake and Histologic Lesion Types in 4-Repeat Tauopathies

Progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) are 4-repeat (4R) tauopathies with overlapping, but also morphologically distinct, tau immunoreactive lesions that vary in count by brain region. ¹⁸F-flortaucipir PET uptake has been reported to correlate with overall tau burden, and-in 1 CBD case-to have greater affinity to threads than tangles. We determined whether ¹⁸F-flortaucipir uptake is associated with histologic lesion type in 4R tauopathies. Methods: We performed semiquantitative regional lesion counts on pretangles/neurofibrillary tangles, threads, oligodendroglial coiled bodies, tufted astrocytes, and astrocytic plaques in 29 cases of autopsied 4R tauopathy (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). Conclusion: The findings do not support ¹⁸F-flortaucipir's having differential affinity to any 4R tau lesion type.