Assess the regional relationship between in-vivo ¹⁸F-Flortaucipir (FTP) binding and postmortem tau pathology in a patient with pathologically-confirmed CTE.

Biomarkers for Chronic Traumatic Encephalopathy (CTE) are currently lacking. FTP detects tau pathology in Alzheimer’s disease, and positron emission tomography (PET) with FTP shows elevated binding in individuals at risk for CTE. No study, however, has assessed the correlation between in-vivo FTP PET and postmortem tau in CTE.

At a behavioral neurology tertiary referral center, a male former National Football League player with 17-years of American football exposure was clinically diagnosed with Traumatic Encephalopathy Syndrome. He underwent MRI, ¹⁸F-fluorodeoxyglucose, ¹¹C-PIB and FTP PET 52 months prior to neuropathological examination. FTP Standardized Uptake Value Ratios (SUVR) (inferior cerebellar gray reference region) and W-score (age-adjusted Z-score) maps were qualitatively and quantitatively compared to phosphorylated tau (CP-13) immunostaining.

FTP uptake was distributed in a patchy, frontotemporal predominant pattern, overlapping with regions showing neurodegeneration on MRI and hypometabolism on ¹⁸F-fluorodeoxyglucose PET. ¹¹C-PIB PET was negative. Pathological assessment revealed stage IV CTE, limbic argyrophilic grain disease, Stage 2 limbic-predominant age-related TDP-43 Encephalopathy, and Braak neurofibrillary tangle stage 3. Amyloid β and alpha synuclein immunostaining were negative. FTP W-maps matched areas of high post-mortem tau burden in left fusiform and inferior temporal gyri and juxta-cortical frontal white matter. High FTP W-scores with low tau were found in basal ganglia, thalamus, motor cortex and calcarine cortex. No regions with low FTP W-scores corresponded to areas with high pathological tau burden. A modest correlation, which did not reach statistical significance (rho=0.35, p=0.17), was found between FTP SUVR and tau area fraction at the regional level.  

FTP PET during life showed a modest correspondence with post-mortem pathology in CTE. Although based on a single case, FTP may have limited utility as a tau biomarker in CTE.