TODAY | January 26, 2013
>>> here's our chief medical editor, dr. nancy snyderman .
>> reporter: wayne clark got his first major concussion as quarterback of the san diego chargers in 1972 . the doctors talked to him on the sidelines. clark didn't even remember his own name.
>> i lost all recollection of that complete day before and after the concussion.
>> reporter: you didn't lose consciousness.
>> reporter: you got conked so hard on the head you had amnesia. now 65 clark wonders about the long-term impact of his injuries. he's not the only one. we've seen the headlines about chronic traumatic encephalopathy or cte that comes from repeated brain injury . up till now could only be found with death such as junior seau who committed suicide. now researchers have developed a way to detect damage early with a chemical that targets those proteins. the injected chemical lights up brain scans of former nfl players.
>> kind of a common hit, and i went down.
>> reporter: finding the protein clumps in parts of the brain dealing with emotion, memory, and behavior.
>> if we can find them early, then we can predict who's going to get symptoms and hopefully try to protect their brains while they're still healthy.
>> touch your nose --
>> reporter: sports physicians say this could be one of the first real objective tools in diagnosing brain damage .
>> telling how severe the damage is is part of the problem today. we don't have a good method of telling who is really at risk for long-term symptoms and who isn't.
>> reporter: wayne clark is a grandfather. he says there will always be risks in football and hopes this research could help make safer the sport he loves so much.
>> tell never be completely risk free. but we can improve. and that's my hope.