Since his college days, New England Revolution forward Taylor Twellman has had seven diagnosed concussions. Given all the headers and hits over his career, he's wondering if that number might be drastically higher.
Twellman still deals with the effects of a concussion he sustained during a collision with a goalkeeper two years ago, one that possibly cost him a shot at making the U.S. World Cup team and cut short his 2010 season after going on injured reserve in late June.
Now he's volunteered to join a Boston University medical school program in which researchers are trying to better understand the long-term effects of repeated concussions. He's one of 300 athletes in just the last two years who have agreed to undergo a battery of annual tests and donate their brain after death.
"It's not hard [to donate] in that you want to help people down the road," Twellman told The Associated Press in a telephone interview. "But it is hard since they want your brain because it's been damaged."
The athlete registry is the work of the university's Center for the Study of Traumatic Encephalopathy, a collaborative venture between BU Medical School and the Sports Legacy Institute that's addressing what it calls the "concussion crisis" in sports. The group has been at the forefront of research into head trauma in sports and received a $1 million gift from the NFL, which it has pushed for better treatment of concussions.
In addition to the athlete volunteers, the families of 40 deceased players have donated brain and spinal column tissue of their loved ones to the center. The material has been studied to see if repetitive head injuries possibly led to a degenerative disease known as chronic traumatic encephalopathy.
Chris Nowinski, the co-founder of the Sports Legacy Institute, leads the charge to round up donors.
A former football player at Harvard, Nowinski got involved after his career with World Wrestling Entertainment was cut short because of repeated concussions that were so bad he couldn't even remember the script for the bout.
"I think we all know that this is a significant problem that has been ignored," Nowinski said. "These athletes are like, 'I don't need my brain when I go, especially if something good can come of it."
Still, it's not always an easy sell.
"Even good friends of mine who are former athletes are completely uncomfortable with the idea of donating your brain," Nowinski said. "But we need a registry to accelerate our search for treatment."
So far, the athlete registry consists primarily of pro wrestlers, hockey and football players, including former NHL standout Keith Primeau and current Baltimore Ravens offensive lineman Matt Birk, according to a partial list provided to the AP.
Donors to the brain bank include former Philadelphia Eagles safety Andre Waters and Penn football player Owen Thomas, both of whom committed suicide. The family of pro wrestler Chris Benoit also bequeathed his brain after Benoit killed his wife, son and himself at his suburban Atlanta home in June 2007.
All three athletes showed signs of CTE, a disease that has been connected to depression and impulse control issues in NFL players who have sustained concussions.
Thomas, who would have been a senior, killed himself in April. He had no history of concussions, but an autopsy on Thomas' brain by the center's researchers showed he had the early stages of CTE.
Ideally, Nowinski said the center would like to sign up 50 athletes from each sport. Most of the volunteers are men, but there are women in the registry including soccer player Cindy Parlow and swimmer Jenny Thompson.
Athletes who are enrolled in the registry take a medical history every year, perform cognitive tests and answer an array of questions, such as if they've been dealing with bouts of depression. It's a way to establish a medical baseline, helping researchers watch for signs of CTE, which can eventually lead to dementia.
"We have no idea how much head trauma is necessary to produce [CTE]," said Dr. Robert Cantu, a clinical professor of neurosurgery and co-founder of the institute. "We just know those who play sports and who have higher amounts of head trauma have a higher incident of it. ... This is just the tip of the iceberg in terms of studying this problem."
Cantu said studies have shown a first-string college football player in a given year experiences between 800 and 1,500 blows to the head of a G-force greater than 20. That's the equivalent of about a 20-mph car crash each time.
"Not enough to produce a concussion, but a substantial jolt," Cantu said. "Let's make [sports] as safe as we can because total head trauma in susceptible individuals can lead to some really bad stuff."
Over his 13-year NFL career, Birk has sustained at least three concussions, along with being jarred senseless on numerous occasions. He realizes the importance of the research.
"It's something that needs to be figured out because it's somewhat alarming to me as a player what they've found in a short amount of time," said Birk, who played football at Harvard with Nowinski.
Twellman has been struggling to retain his form since taking a punch to the face while scoring a goal against Los Angeles on Aug. 30, 2008. The 30-year-old striker doesn't know when -- or if -- he will return to the soccer field.
"It's very difficult to not do what you're paid to do, what you're born to do," Twellman said. "I'm starting to feel better, having more good days than bad days. But I haven't gotten over the hump to have all good days yet."
In a nine-year NFL career, offensive lineman Kyle Turley estimates he took hundreds of hits to the head bad enough to possibly give him a concussion. As if that wasn't enough, he also used to fire himself up with hard slaps to the side of his head before every game.
After retiring following a career with the Saints, Rams and Chiefs, the tattoo-laden Turley experienced severe headaches, sensitivity to light, vertigo, depression and memory issues.
So he went searching for answers and ran across Nowinski at a retired players conference in Las Vegas 18 months ago.
Nowinski was someone who helped him make some sense of his situation.
"As a player, you're going to go out there and gladly give your body and your brain and everything else, you go out there risking your life," said Turley, a budding country musician in Nashville, Tenn., and one of the athletes in the ongoing study.
"The reality is you're going to be left with a lifelong battle of severe injuries. They have answers for every other injury but the head."