Stern, et. al/New England Journal of Medicine
Experimental brain scans of more than two dozen former N.F.L. players found that the men had abnormal levels of the protein linked to chronic traumatic encephalopathy, the degenerative brain disease associated with repeated hits to the head.
Using positron emission tomography, or PET, scans, the researchers found “elevated amounts of abnormal tau protein” in the parts of the brain associated with the disease, known as C.T.E., compared to men of similar age who had not played football.
The authors of the study and outside experts stressed that such tau imaging is far from a diagnostic test for C.