Researchers are tackling fresh questions about a degenerative brain disease now that it has been detected in the brains of nearly 200 football players after death. The suspected cause is repeated head blows, an almost unavoidable part of contact sports.
As a new NFL season gets underway, here's a look at what's known — and what still needs to be learned — about the condition:
The largest report to date on chronic traumatic encephalopathy included 202 brains from football players at the youth, college and professional level, all donated post-mortem to a Boston brain bank. CTE was detected in all but one of the 111 NFL players studied, 90 percent of the...