Robert Monges, a coach for James Lick High School, checks tight end Dominic Brewster for a concussion during a football game played in Morgan Hill, Calif., in 2006. Patrick Tehan/San Jose Mercury News/MCT/Landov hide caption

itoggle caption Patrick Tehan/San Jose Mercury News/MCT/Landov

Randy Moss of the 49ers glides down the field, under an arcing football, on his way to a touchdown against the Patriots on December 16, 2012. Jared Wickerham/Getty Images hide caption

itoggle caption Jared Wickerham/Getty Images

Linebacker Ray Lewis announced Wednesday that he will retire after the Baltimore Ravens' season ends. Most media coverage of Lewis' legacy has omitted his part in a 2000 double-homicide case. Harry How/Getty Images hide caption

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Dr. Ann McKee, professor of neurology and pathology of Boston University School of Medicine and co-director of the Veterans Affairs Center for the Study of Traumatic Encephalopathy, inspects a brain in the Bedford Veteran Medical Center last year. Stan Grossfeld/Boston Globe via Getty Images hide caption

itoggle caption Stan Grossfeld/Boston Globe via Getty Images