San Francisco 49ers linebacker Chris Borland, center, during an NFL football game in Santa Clara, Calif. Borland announced that he will retire after just one season to protect himself from brain injuries.
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Kansas City Chiefs linebacker Jovan Belcher's body has been exhumed more than a year after he killed his girlfriend and himself so that his brain can be examined for signs of a degenerative condition linked to repeated concussions.
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.
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