Updated

By Steve Keating

DALLAS (Reuters) - Super Bowl memories are meant to last forever, but former Chicago Bears quarterback Jim McMahon worried on Thursday that his could fade away like his ability to remember things as simple as why he walked into a room.

Flamboyant and quirky, McMahon led the Bears to victory in Super Bowl XX in 1986 and added a second championship ring as Brett Favre's backup with the Packers in 1997. But 15 seasons of absorbing punishment, including at least five concussions, has exacted a heavy toll.

McMahon may have provided NFL fans with a lifetime of memories, his are not so vivid, dulled not by time but by a string of debilitating concussions.

"For now I can still kind of remember (winning a Super Bowl) pretty clearly," McMahon, 51, told Reuters. "But I've had some issues with my memory.

"It's nothing drastic right now, it's simple things like I will walk into a room and forget why I walked in there. I have to stop and go back and think why did I come into this room.

"These things add up. The more you let it go and not get checked it can be devastating."

"When we get together we discuss (concussions), 'How you feeling? You forgetting stuff like me?'" said McMahon, who has donated his brain to a concussion study after his death. "And they are. All of them."

DANGEROUS HITS

The NFL had information about concussions posted in the locker rooms of all 32 teams prior to the season and created a concussion awareness website (www.NFLHealthandSafety.com).

The league also increased fines for dangerous hits and introduced rules requiring a player to pass a battery of tests and be cleared by an independent doctor before returning to action after sustaining a concussion.

"The policies that are in place are good," said Packers starting quarterback Aaron Rodgers, who had two concussions this season. "I went through it twice, I wasn't cleared until I was symptom free.

"It is a more important injury because you have got to think about the rest of your life."

Kevin Turner, a bruising fullback who spent nine seasons with the Philadelphia Eagles and New England Patriots, spends a lot of time thinking about his life - or more accurately the life he has left after being diagnosed with amyotrophic lateral sclerosis, also known as ALS or Lou Gehrig's disease.

A recent study has linked ALS to brain trauma with NFL players having an eight times higher risk of contracting the disease.

BRAIN BANK

While SLI is using NFL players to highlight the devastating cumulative damage caused by repetitive brain trauma, the institute's focus is on research and education.

The institute is also heavily involved in research that is supported by the NFL players union and the NFL, which donated $1 million to help setup the CSTE, the world's largest brain bank that studies post-mortem human brain tissue to better understand the effects of trauma on the human nervous system.

SLI founder Chris Nowinski, who played football at Harvard University before embarking on a professional wrestling career that was ended by concussions, is among the 300 athletes who have donated their brains for study after their death.

"It (CET) appears very wide spread in athletes who have played a lot of contact sports, especially football," said Nowinski. "Of the 13 NFL cases that we've completed post-mortem brain studies 12-of-13 had the disease.

"In pilot studies my brain is not even in the normal category.

"I'm not the same guy. I am probably on borrowed time."

(Additional reporting Simon Evans; Editing by Frank Pingue; To query or comment on this story email sportsfeedback@thomsonreuters.com)