Justin Strzelczyk

Strzelczyk was an offensive lineman with the Steelers for eight seasons. In 2004, he died in a car crash after taking police on a high-speed chase, the Pittsburgh Post-Gazette reported.  Toxicology reports showed no evidence of drugs or alcohol in the 36-year-old's body. So what caused his erratic behavior?

Strzelczyk's family donated his brain to the Brain Injury Research Institute. Dr. Ronald Hamilton of the University of Pittsburgh told the New York Times, "If I didn't know anything about this case and I looked at the slides, I would have asked, 'Was this patient a boxer?'"

Credit: Rick Stewart /Allsport