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Hit record - Conducting field research - literally - to explain concussions


Hit record

Conducting field research — literally — to explain concussions

On Oct. 5, 1996, Stanford faced the University of Washington on the gridiron at Husky Stadium in Seattle. Toward the end of the first half, Cardinal quarterback Chad Hutchinson threw a short pass. A second later, a defensive back for the Huskies plowed into his chin, helmet-first, and another defender drove him to the ground. “That old turf up at Washington was hard,” Hutchinson recalls.

He picked himself up and walked a few steps before stumbling into a teammate. There was blood on his jersey. Something else was wrong too. “I felt like I was drunk. I was in a fog,” he says.

A doctor checked him on the sidelines. “I was coherent enough to answer his questions correctly,” says Hutchinson. He was subsequently allowed to return to the game.  

Luckily, Hutchinson says, it was the first and last concussion of his career. Today, however, it’s doubtful he would have been permitted to stay in the game; he was at risk for second-impact syndrome, a catastrophic swelling of the brain that can occur if another concussion is sustained shortly after the first one.

Fifteen years ago, concussions, while not treated lightly, did not inspire the kind of worry they do now. That sports-related brain injuries have since become a focus of national concern is largely due to reporting by The New York Times’ Alan Schwarz, who in 2007 began writing about how scientists had linked concussions, as well as recurrent sub-concussions, to long-term cognitive problems such as depression and early onset dementia in current and retired professional football players. “Sub-concussion” is the somewhat nebulous term for a violent head impact that doesn’t cause a concussion, and generally goes unnoticed by players, but that many scientists believe cumulatively can have serious, long-term consequences for cognitive health.

Over the past dozen years, a steady drumbeat of research has correlated concussions with chronic neurologic problems. A 2000 survey of 1,090 retired National Football League players found that those who had suffered at least one concussion during their careers reported more speech difficulties, confusion, headaches and trouble recalling recent events, among other neurologic problems, than those who had not. A 2007 study of 2,552 retired professional players found that those who reported having had three or more concussions were three times more likely to be diagnosed with depression than those with no history of concussion.

Yet even though concussions, also called mild traumatic brain injuries, are commonplace, little is known about them. This is where Stanford’s Dan Garza, MD, comes in. The emergency and sports medicine physician has launched an ambitious study of the mysterious affliction.

Last fall, when I went to visit Garza at his office, in the Lacob Family Sports Medicine and Human Performance Center at Stanford, he took me to the human performance lab, where a dummy head wearing a football helmet was attached to a cable-and-pulley contraption. On closer inspection, you could see that the head also had a mouth guard, the kind used by athletes in contact sports to protect their teeth. But it was no ordinary mouth guard; it contained tiny accelerometers and gyrometers. James Mattson, Garza’s research assistant, pulled a cord, and the head fell about 3 feet, coming to a stop with a crash.

“We’ve dropped the head probably a few thousand times from various angles,” says Mattson, a Stanford graduate in human biology. The purpose was to confirm that the mouth guard would accurately measure the force experienced at the center of a football player’s head when jolted by a collision — either with another player or the ground.

“We discovered that the device measures impacts very, very accurately,” says Garza, who last season equipped two dozen members of the Stanford University football team with the high-tech mouth guards, manufactured by the Seattle-based company X2 Impact.

Over the course of many years, Garza plans to use the devices to measure head impacts and correlate them to events on the field, such as a particular tackle. He and his colleagues also plan to collect head-impact data from the Stanford women’s field hockey and lacrosse teams, which will be outfitted with the devices.

Garza, an assistant professor of orthopaedic surgery and medical director of the San Francisco 49ers, hopes the large quantity of data will help researchers develop a more accurate profile of the kinds of collisions that cause brain trauma, as well as more precise diagnostic criteria. “We need to get a better understanding of the epidemiology of these injuries,” he says. “This study will build toward establishing clinically relevant head-impact correlations and thresholds to allow for a better understanding of the biomechanics of brain injuries. It also will serve as a helpful tool to aid in diagnosis and subsequent management of concussions.”

Nationwide, as many as 3.8 million sports- and recreation-related concussions occur each year, according to the Centers for Disease Control. About 10 percent of all contact-sports athletes have concussions each year, according to the Sports Concussion Institute of Los Angeles.

A study of 1,913 NFL games played between 1996 and 2001 found that the rate of concussion was 0.41 per game, or slightly less than one concussion every other game. The rate is likely higher at the high school and college levels, where players often are still developing physically and don’t have the strength and expertise of NFL players, Garza says.

In addition, he says, the injuries probably go underreported, given the difficulty of diagnosing them and the fact that some athletes may ignore their symptoms, knowing they will be sidelined if they speak up.

“One of the biggest problems is the uncertainty surrounding concussions,” he says. “If you tear your ACL, I can say, ‘Here’s the injury on the MRI, and here’s how we repair it.’ So there’s a confidence around treating those kinds of injuries. But diagnosing concussions is inherently subjective. Even traditional brain imaging will not pick anything up.”

Concussions occur when the brain is violently shaken. The shaking twists and tears connections between cells in the cerebral cortex, causing billions of them to depolarize and fire their neurotransmitters at once. This in turn throws the brain’s chemical balance out of whack, hindering the neurons’ ability to start firing again. Many of these nerve cells then begin to shut down, which is why Hutchinson, the former Cardinal quarterback, said he felt drunk after his concussion.

Yet the fact that Hutchinson says he recovered fairly quickly and reported feeling no post-concussion symptoms in the hours and days following the injury is fairly good evidence that he suffered a mild concussion — what the American Academy of Neurology probably would have classified as grade 1, which often includes some transient confusion, grogginess, dizziness, balance difficulties and possibly other symptoms that resolve in less than 15 minutes. More serious concussions, like a grade 2, may cause post-traumatic amnesia and, in the case of a grade 3, loss of consciousness. Post-concussion symptoms are often experienced in the days and even weeks following the initial injury and may include headaches, fatigue, ringing in the ears, sleep problems, sensitivity to light and noise, poor concentration, and depression or anxiety. Such symptoms are the result of a severely discombobulated brain, one that has not yet regained its chemical equilibrium.

High-impact blows to the head and neck are the most common cause of the injury, says Stanford neurologist Jaime López, MD, who is assisting Garza with the study. “In a simple model — a linear model — your head is moving fast and then rapidly decelerates during impact,” says López, “at which point some of this energy is absorbed by your skin and your skull and your cerebrospinal fluid, but the rest is absorbed by the brain, which is, of course, a quite delicate structure.”

Rotational force is often involved in concussions and, according to some studies, may be an even bigger culprit than linear force, López says. An obvious example of rotational force would be when a player’s head is struck from the side and whips around. To some degree, rotational forces are always at work in football collisions, which rarely occur along a simple linear plane. “Rotational forces tend to affect larger areas of the brain,” López explains. “But the bottom line is there are complex mechanisms occurring, and we don’t understand them completely.”

Evidence suggests that people who already have sustained a concussion are more vulnerable to subsequent concussions, but neurologists aren’t sure why. There is also some evidence to suggest that genes may help determine a person’s susceptibility to concussions.

‘In theory, players can have post-concussive symptoms that don’t allow them to return for a long period of time ...’

For athletes, the practical question is how long they have to stay on the sidelines after a concussion. At Stanford, that answer depends on when they can meet a set of rigorous, exercise-based criteria, López says. After the concussion, athletes must pass a series of physical tests, beginning with low-exertion activities that become more strenuous over a number of days or weeks, depending on the players’ tolerance levels. The exact amount of time a player is out depends on whether he or she can complete these exercises without triggering symptoms related to the concussion. “In theory, players can have post-concussive symptoms that don’t allow them to return for a long period of time — maybe the rest of the season, maybe the rest of their lives,” López says. But generally, players can return in a few days or weeks.

Figuring out when a concussion has occurred is not straightforward. The more force behind a head impact does not necessarily translate into a greater chance of concussion, studies have shown. In the January 2011 issue of Exercise and Sports Sciences Reviews, researchers at the University of North Carolina report that, according to their study, there was “no relationship between impact magnitude or location, and clinical outcomes of symptoms, balance, or neuropsychological performance.” Football players sustained concussions over a wide range of magnitudes — from 60.51g to 168.71g of linear acceleration to the head, the researchers found, based on data collected from accelerometers in the helmets of Division I college football players. (One “g” is the force of Earth’s gravity, so 60.51g is 60.51 times the force of gravity.) So what kinds of impacts are most likely to cause a concussion?

This is exactly the question Garza hopes to help answer with his study. And with Stanford’s football, lacrosse and field hockey teams, he has a large and conveniently located subject pool. “It’s a great opportunity for our student athletes, many of whom conduct scientific research in their academic studies, to contribute to the leading-edge research being done in sports medicine here,” says Earl Koberlein, senior associate athletic director at Stanford. “It’s a good marriage of the university’s strong academics and strong athletics.”

Last season, Scott Anderson, Stanford’s head athletic trainer, and Jesse Free, an athletic training fellow, operated a computer on the sidelines that picked up data transmitted from the devices during football games and practices. Using video, the researchers were able to correlate this impact data to specific moments of a play.

Although there have been previous head-impact studies in football, they have relied on sensors embedded in helmets. Garza says it is possible the mouth guard data will prove more accurate, given that helmets sometimes shift on players’ heads in a collision, which could throw off measurements. In any case, data from the current study will help illuminate earlier findings, he says.

It’s still too early to draw conclusions from the data, the researchers say, and it’s unclear whether any of the findings would serve helmet makers or lead to rule changes in football. Garza says he does not intend his study to diminish football or endanger its future. Rather, he hopes the data will enable physicians to better identify and care for players who have sustained a concussion or perhaps are at risk of long-term cognitive impairment because of cumulative injuries.

“Emotions are charged up around this, but to be honest I don’t think we should jump to too many conclusions until we have larger studies,” he says. “Concussions can happen in soccer, lacrosse and many other sports. My feeling is that as long as you follow best practices in managing concussions, we can still let people compete.”

Hutchinson, who went on to play both professional football and baseball after graduating from Stanford with degrees in economics and political science, says he has seen teammates who took a lot of violent hits get right back up, seemingly unaffected, while others suffered concussions over and over again from less fearsome hits. “It makes me think there must be a genetic component,” Hutchinson says.

He says he doesn’t think the fear of concussions should deter people from sports they enjoy. “You don’t want to live life like that,” he says. “And I’ve known people who never played football get concussions. I know a guy who has had four concussions, and he got them water-skiing and falling off a ledge — things like that.”

But how would he feel about one of his kids playing football?

“I guess that would give me pause,” he says.


E-mail John Sanford





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