>> which is nathan stiles, right. ♪ >> hi. >> hello. >> welcome. s n owinski. >> this is the stiles' first visit to the brain bank. >> what we've learned in the last three years is that it's a progressive disease, and then as the individual ages, if they're susceptible to this disease, it really becomes a widespread disease affecting large regions of the brain. >> so all of this was because of a concussion? >> probably more than one concussion. probably some concussive hits too. >> no one believed there was a problem until they were able to show -- >> until it was too late. yeah. for nathan, yeah. >> the stiles met with me afterwards. >> what was that like to sit there and talk to dr. mckee? what was -- >> you know, it's my son. to see the pictures of his brain, that's -- >> that's a lot. >> yeah. yeah, that's a lot. something you don't wish on your worst enemy. >> which i think the good thing is you can see every effort is being made to learn from it. i think nathan is helping to come up with a plan to maybe what to do with concussions. >> hmm. can

. >> number 44, senior nathan stiles, is a springhill broncos star running back. >> if you would watcheful. >> nathan's also a starter on the varsity basketball team, a sing singer. >> the 2010 homecoming king is nathan stiles. >> he's the toast of springhill, kansas. the broncos lost that game. and the next day nathan had headaches. no big deal. until five days later when his mom connie received a phone call. >> and i got a call from the trainer at school saying, nathan's telling me he's still having headaches. you need to go take him to the emergency room. so i did. had a cat scan. nothing. >> the doctor kept nathan out of play for three weeks. but he was ready to return, his mom was worried. >> and i remember him looking at me and he goes, "now mom, are you okay with this?" and i'm like -- with him going back to football. i'm like no, but it's his choice. nathan, you want to play? yeah, i'm all right. yeah. i only got two games left. >> but in the last game of the season, right after halftime, nathan went down. >> he had collapsed on the sideline. and the coaches were telling me to

nathan's doctor, thought it had healed. >> did you get angry at all, ron? >> no. no, i was just -- you're in shock. >> i couldn't look at this the book for a long time. >> i know. >> the stilesmeaning in nathan's tragic death because of this woman. >> i think the last time you were here, we had maybe five brains, and now we're in the 90s. >> dr. ann mckee runs the world's largest brain bank. it's a joint project between the veterans administration and boston university. i first met her years ago when she began finding evidence in the brains of deceased nfl players of unnatural protein deposits, the same kind of proteens found in alzheimer's patients. it's called chronic traumatic encephalopathy. these symptoms are usually found in people in their 80s, not their 40s. >> is this definitely caused by blows to the head? >> it's never been seen in any reported case, except for a case of blows to the head. >> that's exactly what the styies wanted to know when they donated nathan's brain to mckee's center. did repeated blows to the head cause that kind of damage in young nathan's brain? and the answer was yes. under the microscope -- >> that's really obvious. >> we saw telltale sig

nathan back. >> this is looking at it under the microscope and seeing all that dark brown. >> but the stiles hopere gift will tell us more about brain conditions than ever before. >> we have all the confidence that there's something to be learned from it. >> i think i want it to be my life's mission to make sure this doesn't happen to other kids. >> mckee knows how much more vulnerable these young kids may be. when the young developing brain is hit during football, no matter how hard, the brain is rocked. it's like an egg inside a shell. it stretches, the delicate fibers pulled, fluids violently sloshed around the brain, trying to absorb the blow. >> youth are at risk for any changes in that fluid balance, and they may not be able to handle it as well. >> sounds like you're saying they're more at risk than adults. >> oh, absolutely. >> and this is important, no matter how good a helmet is, it can't completely protect a brain from this sort of trauma. >> some of the helmets can slow down the impact, but i think, ultimately, a helmet won't completely solve this problem. i think we're going to have