. >> reporter: wayne clark had his first major concussion as quarterback of the san diego chargers back 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: but you didn't lose consciousness? >> right. >> reporter: you got clunked 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 all seen the headlines about chronic traumatic encephalopathy, or cte, a disorder that comes from repeated brain injury. up to now, can only be found after death as with star linebacker junior seau who committed suicide. doctors found the telltale abnormal clumps of protein in his brain. now researchers have developed a way to detect the damage early with a chemical that targets those proteins. the injected chemical lights up brain scans of former nfl players. >> it was kind of a common hit and i went down. >> reporter: finding the protein clumps in parts of the brain dealing with emotion, memory

irreversibly damaged so it gives us a pitcher of what sort of a footprint of prior injuries in wayne clarka concussion that he doesn't even recall that may be impacting his memory now in the nfl c t e study first injected with a compound that bynes protein they had each play football for 20 plus years throughout their lives and all showed abnormal levels, the more concussion the more protein signs of cte. potentially widespread considering that the average football player who plays through college receives 8000 hits to the head a pattern that doctors want to block. some people believe that it is a chronic inflammation that may be drugs and dietary supplements psychotherapy and psychiatric care. researchers stand current players if they saw signs, limit exposure offer treatments and reverse the course of the condition neurosurgeons are trying to change the game and limit they have already started. it looks like another very cold morning on tap for chicago land. then after that, snow. h icphac rit is warmer tonight that it was but not for long. look at this incredible satellite shot of the c

wayne clark a back up quarterback with the chargers in the '70s is is one of the players who participated. he has mild memory loss >> when i first saw the scan i thought, whoa, that looks pretty extensive. i know recalling names which i recall used to be pretty easy for me. now i go through stages where i think, oh, how come i can't remember that? and i'm always wondering, are these age-related or are they concussion related >> brown: finding so far are preliminary. they may help doctors identify and treat brain disease before it impacts other players. the issue is a major concern for football at the professional and collegiate level and possibly even younger players. more than 4,000 former players are suing the nfl for head injuries and the risked they face. we get more on this study from its lead author dr. gary small professor of aging and director of the longevity center at ucla and author of the book the alzheimers prevention program. he joins us from new york. doctor, why is it important to be able to look at living players rather than at autopsies? what's the significance? >> gener

. >> reporter: when he was a backup quarterback in the nfl, wayne clark was lucky to call a play.t he spent most of his time on the sidelines. >> so i didn't take the steady contacts that other players did. >> reporter: except for one game. one concussion in 1972. >> i went down in a slump because i didn't know where i was and what was going. >> reporter: he spent several bleary hours confused. and then boarded a plane back home. >> somewhere over new mexico or arizona, i finally became aware of what was going on again. >> reporter: clark's brain was rattled. but it only happened once during his five year career. >> thescan -- >> reporter: and that's what makes this picture of his brain so perplexing. researchers say he has an abnormal protein in his brain. it's pain found in the brains of several former nfl players. dave duerson, junior seau, all had serious cognitive and emotional problems address eventually committed suicide and were diagnosed with cte or chronic traumatic encephalopathy. clark is cognitively normal. let me show you what i'm talking about. that's a normal brain

. >> reporter: when he was a backup quarterback in the nfl wayne clark was lucky to call a play or throwine. >> i didn't take the steady contacts that other players did. >> reporter: except for one game, one concussion in 1972. >> i went down in a slump. i didn't know where i was and didn't know what was going on and so forth. >> reporter: he spent several bleary hours confused and then boarded a plane back home. >> somewhere over new mexico, arizona, i finally became aware of what was going on again. >> reporter: clark's brain was rattled, but it only happened once during his five-year career. >> the scans -- >> reporter: that's what makes this picture of clark's brain so interestingplexerplexing. he has an abnormal protein called tau in his brain. it's been found in the brains of several former nfl players. dave doer son, junior seau. all had cognitive problems and eventually committed suicide. they were diagnosed with cte, chronic traumatic encephalopathy. clark is cognitively normal. let me show you what i'm he talking about. that's a normal brain scan. compare it to two players in t