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). Conclusion: The findings do not support 18F-flortaucipir having differential affinity to any 4-repeat tau lesion type.