The symptoms were headaches, blurred vision and involuntary muscle twitches. Bright lights, loud noises and babies crying made him irritable. Memory lapses made his job in live television a nightmare.
In 1990, two years after he retired from the NFL, former New York Giants linebacker Harry Carson picked up the tab for his 13-year, Hall of Fame career.
A neuropsychologist's diagnosis: mild post-concussion syndrome. Carson didn't know what to think.
"My only question was, 'Am I going to live?' " he recalled. "PCS didn't mean anything to me."
It didn't mean much to anyone in the NFL then. But in the next 10 years, after quarterbacks Steve Young and Troy Aikman retired with multiple head traumas, post-concussion syndrome forced its way into the league's medical vocabulary.
Today, the NFL still is trying to come to grips with an that injury sports agent Leigh Steinberg describes as an "undiagnosed health epidemic" and a "ticking time bomb."
Research by the league's mild traumatic brain injury (MTBI) committee has suggested there is no evidence multiple concussions have a cumulative, chronic effect and that players who suffer one brain trauma are not at significant risk of a second one either in the same game or during the season. These findings have been disputed by brain injury experts around the country.
Today, the science of concussions will go under the microscope. NFL commissioner Roger Goodell has summoned physicians and athletic trainers from every team to Chicago today to attend a one-day conference on MTBI. He also wants the dissenting voices of outside critics to be heard.
Expectations range from enthusiastic to suspicious.
Dr. Andrew Tucker, the Ravens' physician and a member of the MTBI committee, said the meeting would allow opposing sides to "hash things out and develop some strategies moving forward."
"I'd be very surprised if there's not a greater appreciation for the other side," said Tucker, also director of Union Memorial Sports Medicine. "If we can hear the concerns of people portrayed as critics of our work, hopefully they will have greater appreciation for everything that comes out of the committee."
Dr. William Barr, the chief of neuropsychology at the New York University School of Medicine, welcomes the chance to reach consensus, but he isn't convinced the committee is as willing.
"That's the big worry that a lot of us have," Barr said. "I believe I'm invited because I've had a dissenting view on the way the brain injury committee conducted its studies.
"They might expect me to go off and say it's all worthless. [But] I want to be constructive. I believe a lot of us have put a lot of work into collecting this data and we could still turn it around and learn something useful for the NFL and the players."
Dr. Ira Casson, an attending neurologist at Long Island Jewish Medical Center and co-chairman of the NFL's MTBI committee, rejected the idea his group will attempt damage control in Chicago.
"We want to hear what people have to say," Casson said. "We want our physicians to hear what they have to say."
Barr served on the committee as a consultant until 2004, when he was dismissed by then-chairman Elliot Pellman. Barr has been critical of the NFL studies on concussions because the neuropsychological tests of several hundred players were omitted under Pellman.
"That was a poor sampling," Barr said. "Whether it was laziness, ignorance or malevolence, I don't know. That's not how research should be done. There were so many contradictions in it.
"They don't use [all] the data, but acknowledge every one of the neuropsychologists who were consultants. My name is on that study. I never would have allowed my name on the study if I knew what it said."
Pellman, who runs ProHealth Care Associates in Lake Success, N.Y., declined to respond to Barr's charges. Although he stepped down as chairman in February, he remains on the NFL committee and will participate today.
"I don't believe that negotiating this out through the media does [anyone] much good," Pellman said. "That's the reason for this conference. ...
"No doubt Barr and others have taken an emotional position. I do not want to defend this one way or another. This is about taking care of players and our patients, and everything else is secondary."
Former Maryland quarterback Boomer Esiason was Pellman's patient in 1995 when he suffered a serious concussion playing for the New York Jets. Esiason was out cold on the field for four minutes and gone from the Jets' lineup for five weeks. Pellman was the Jets' physician then and now.
"All I can tell you is, Elliot Pellman always treated me with the utmost professionalism that I could ask of any doctor," Esiason said. "He put me through a battery of tests no other player had gone through. Elliot was all over this."
Dr. Tony Strickland, a neuropsychologist and director of the Sports Concussion Institute in Marina del Ray, Calif., also defends the NFL by pointing to research that has advanced knowledge of concussion recognition and treatment.
"We have learned more about concussion in the past five years than we knew in the previous 50," Strickland said. "You can only be accountable for that of which you know. If scientists and clinicians were unclear regarding when actual concussion would occur, then I don't think it's necessarily fair for the NFL to be held to a standard that was and is still evolving."
When Goodell scheduled the conference, he detailed new league standards in concussion management. He will require neuropsychological baseline testing for every player, to be done at the start of the season for comparative purposes once an injury has occurred.
These tests were introduced in 1984, when Dr. Jeffrey Barth, the director of the University of Virginia brain injury and sports concussion institute, tracked 116 Virginia football players. Barth wanted to conduct research into concussion from car accidents.
He expanded his study to 10 college teams and 2,450 players a year later. Although slow to embrace the idea initially, most of the sporting world has followed Barth's lead. He said if the NFL wants to avoid controversy in its concussion policies, it should turn "evaluation and institution of programs over to an academic university that has experience with traumatic brain injury."
Steinberg, the sports agent, said mistakes made dealing with concussion have implications for both the player and the team. Rosters have become diluted in the salary-cap era. For practical and ethical reasons, Steinberg said, the NFL will be motivated to find solutions to the concussion issue.
"If players are lost for a season or career through incorrect diagnosis or treatment, it can have devastating effects for a franchise, both for a Super Bowl race and long-term," he said.
"This problem and the number and severity of concussions only promises to get worse because training and nutrition have produced a generation of bigger, faster and stronger players. ... For the NFL, it's not simply a moral, ethical issue, it's good business [to find answers]."
Steinberg arranged a series of concussion seminars in the 1990s, when Young and Aikman endured head traumas. He participated in another one recently with Strickland's company where long-term health issues were raised.
Although the NFL committee is embarking on a study of retired players, the only research done on the subject comes from a survey by the Center for the Study of Retired Athletes at the University of North Carolina.
The center warned that players who have suffered at least three concussions are at greater risk for dementia, early onset of Alzheimer's and bouts of depression later in life. The NFL's MTBI committee says the study is flawed for its methodology.
Steinberg said the concussion threat "goes to the very essence of what it means to be human."
"It's one thing to understand and accept risk that ... a player in his 50s may suffer aches and pains reaching down to pick up a child," Steinberg said. "It's another thing not to be able to recognize that child."
Carson has learned to deal with post-concussion syndrome. But he fears for others.
"Truth be known, there are players who have played in the NFL who are walking around suffering from the effects of concussions and don't even know it," he said.
Steinberg believes today's conference signals a new day in treatment of concussions.
"The NFL is the trigger point for all collision sports," he said. "As goes this conference, as goes this policy, others will follow - collegiate sports, high school sports, youth sports and ultimately all collision sports."