dr ann mckee has studied over 170 brains ? including michael's... dr ann mckee / bu title: that young, it's surprising, even shocking. cte?which is identified only keck - but experts say moments like these show that even amateurs aren't immune to the perils of contact football. take a look at this video - a hit michael told casandra was one of his hardest - he flies at an opponent slamming into him - colliding with such force ? parts of his helmet break off... sot - cassandra keck: i think he suffered from way more than 10 concussions cassandra says michael abruptly quit college football - after suffering one too many hard hits. sot - cassandra keck / michael keck's wife: he was seeing stars // and then he had sensitivity to light all the time just impulsive they turned to doctors, but cassandra says, test results came up empty... sot - cassandra keck: i was so mad that nobody could help him // it was just upsetting that he felt so alone cassandra's life, now changed forever... her five-year old son? too young to remember his dad? sot - cassandra kec

dr ann mckee has studied over 170 brains ? including michael's... dr ann mckee / bu title: professor of neurology and pathology, boston university school of medicine: when you see this disease in a person that young, it's surprising, even shocking. cte?which is identified only after death, has been found in numerous famers frank gifford and junior seau, and is rarely seen in amateur players like michael keck - but experts say moments like these show that even amateurs aren't immune to the perils of contact football. take a look at this video - a hit michael told casandra was one of his hardest - he flies at an opponent slamming into him - colliding with such force ? parts of his helmet break off... sot - cassandra keck: i think he suffered from way more than 10 concussions cassandra says michael abruptly quit college football - after suffering one too many hard hits. sot - cassandra keck / michael keck's wife: he was seeing stars // and then he had sensitivity to light all the time // he had a lot of anger and it was just impulsive they turned to doc

dr. ann mckee studied over 170 brains, including michael's. >> when you see this disease in a person that young, it's surprising, even shocking. >> reporter: cte which is identified only after death has been found in numerous nfl players like hall-of-famers frank gifford and junior seau, take a look at this video. a hit michael told cassandra was one of his hardest. he flies at an opponent, slamming into him. colliding with such force parts of his helmet break off. >> i think he had way more than ten concussions. he was seeing stars and then he had sensitivity to light. all the time. he had a lot of anger and it was >> reporter: they turned to doctors but cassandra says test results came up empty. >> i was so mad that nobody could help him. it was just upsetting. he felt so alone. >> reporter: she says michael did not die in vain. >> letting people know that this disease is out there. you don't know how many hits or how many concussions away you are from getting a disease like this, that's what is so scary. it could happen to anyone. >> reporter: for "good morning america," ryan smith, ab