¹⁸F-Flortaucipir PET/MRI Correlations in Nonamnestic and Amnestic Variants of Alzheimer Disease

Abstract

Nonamnestic Alzheimer disease (AD) variants, including posterior cortical atrophy and the logopenic variant of primary progressive aphasia, differ from amnestic AD in distributions of tau aggregates and neurodegeneration. We evaluated whether ¹⁸F-flortaucipir (also called ¹⁸F-AV-1451) PET, targeting tau aggregates, detects these differences, and we compared the results with MRI measures of gray matter (GM) atrophy. <b>Methods:</b> Five subjects with posterior cortical atrophy, 4 subjects with the logopenic variant of primary progressive aphasia, 6 age-matched patients with AD, and 6 control subjects underwent ¹⁸F-flortaucipir PET and MRI. SUV ratios and GM volumes were compared using regional and voxel-based methods. <b>Results:</b> The subgroups showed the expected ¹⁸F-flortaucipir-binding patterns. Group effect sizes were generally stronger with ¹⁸F-flortaucipir PET than with MRI volumes. There were moderate-to-high correlations between regional GM atrophy and ¹⁸F-flortaucipir uptake. ¹⁸F-flortaucipir binding and GM atrophy correlated similarly to cognitive test performance. <b>Conclusion:</b>¹⁸F-flortaucipir binding corresponds to the expected neurodegeneration patterns in nonamnestic AD, with potential for earlier detection of pathology than is possible with MRI atrophy measures.