I asked Dr. McKee how CTE was determined. In this study, a single pathologist made the diagnosis, but she let me know that an upcoming study with independent pathologic review shows "very good inter-rater reliability". In lay terms, that suggests that CTE, as seen here with characteristic phosphorylated tau deposits, is a distinct pathological entity.

Risk of CTE was higher with more years of football playing and with playing at a higher level. 110 of 111 – that's 99% - of former NFL players had CTE.

The question everyone is asking, of course: how prevalent is CTE in these athletes?

This autopsy study was not a random sample of football players. Far from it. 81% of the brain donations reviewed were the result of a family member approaching the center near the time of death. They did this precisely because there were concerning symptoms.

86% of these individuals had memory problems, 72% had dementia in their last year of life, 91% had behavioral or mood symptoms, 68% had motor symptoms. The authors, to their credit, state that this study can not impute or imply the prevalence of CTE in footballers.