dr. ben anamalu, the real-life physician who diagnosed cte, a brain disease caused by brain trauma affecting a number of pro players. in a statement released today about the movie the nfl said in part, the nfl has made numerous changes to the game to enhance player health and safety at all levels of football. we are seeing measurable results including a 34% decrease in concussions in nfl games since the 2012 season." "nightline" first reported on cte in the early days of dr. amalu's findings. >> i slept in the car probably a year and a half out of the last five years. >> reporter: the pittsburgh steelers mike webster won four super bowls. famous, wealthy, revered. he died homeless, broke, and alone. >> mike webster died today. a heart attack took his life at the age of 50. >> reporter: believing that behavioral changes were caused by trauma to the brain, the webster's extensive autopsy. >> the heart attack cannot explain his life after football. i had to provide an explanation for that. i was extremely disappointed when i opened up his skull and his brain looked normal. >> reporter: determin