Mild Concussions Don't Often Lead to Permanent Brain Damage

Each year as football season approaches, a common topic in sports media coverage is the impact of multiple concussions on the long-term brain function of high school, college and professional players. Stories abound about well-known players whose careers are cut short to protect against permanent brain damage.

Against the background of those prominent and severe cases, though, continuing research at the Medical College of Wisconsin indicates that most mild-to-moderate sports related concussions are recovered from fully, with minimal likelihood of permanent brain damage unless another concussion occurs before symptoms from the first have gone away.

"I think the jury's still out on whether multiple mild concussions over time lead to permanent brain damage. Indeed, with a couple of exceptions, it's probably more likely that is not the case," said Thomas A. Hammeke, PhD, Medical College Professor of Neuropsychology. Dr. Hammeke practices at the Froedtert & Medical College Neurosciences Center and the Neuropsychology Clinic.

Dr. Hammeke has been principal investigator in the Department of Neurology for research into concussions among area high school football players for the past six years. In general terms, the effort is designed to develop better ways to quickly diagnose concussions and their severity on the field, while helping coaches and doctors later determine when it is safe to allow an athlete to return to play.

Recovery Time and Severity
"We see and evaluate people (not just football players) with many concussions in their histories who seem to function very normally, and we cannot find evidence of brain dysfunction," said Dr. Hammeke. "However, we do know-at least in animal models-that overall recovery is not as good if there is a second concussion before full recovery from the first. There's reason to think that that would be true for humans, too.

"There is a condition called the 'Second Impact Syndrome' that also represents a circumstance where an individual suffers a second event before they've recovered from an initial one. Second Impact Syndrome typically has a catastrophic outcome in that the brain swells up very rapidly and the individual typically dies. This is very rare, and we don't know what causes this.

"The sheer number of football players, for example, who have two concussions in a single game is probably pretty high among professionals, and we don't see second impact syndrome very often in professionals. My guess is that there is a genetic predisposition to that kind of swelling in certain people, which may be linked to migraine disorders."

Permanent brain injury from concussive trauma can occur if the injury is so severe that the person wasn't going to fully recover from it to begin with. "For example," said Dr. Hammeke, "boxers who get knocked out may suffer brain bleeds, hemorrhages inside the brain. Hemorrhages do cause cell death in the brain and unquestionably produce permanent effects.

"But a simple, uncomplicated concussion, with no bleeding in the brain, appears to be a relatively benign event for most people as long as the individual is given time to recover."

Concussion Grades in Three Levels
There is a broad range of concussion symptoms, including physical, cognitive and emotional symptoms. As described in Dr. Hammeke's HealthLink article Sports Concussions a Growing Concern, they include "…low-grade headaches that won't go away, difficulty concentrating or 'feeling foggy,' neck pain, ongoing fatigue or lack of energy, change in sleep patterns, increased sensitivity to sound or light, blurred vision, ringing in the ears and mood changes."

The American Academy of Neurology has developed the most commonly used system for grading concussions. This three-grade system is primarily based on the severity and duration of symptoms and whether or not the concussion resulted in a period of unconsciousness.

"'Concussion' means some change in one's mental capacities caused by a blow to the head or simply by acceleration/deceleration of the head," said Dr. Hammeke. "Grade 1 concussion symptoms last no more than 15 minutes and the individual is not knocked unconscious. In Grade 2 the symptoms last longer than 15 minutes but there is still no loss of consciousness. Grade 3 is any concussion with a loss of consciousness.

"Usually, the kind of concussion that occurs with football or other team sports is at the mild end of the severity spectrum. It is rare that bleeding inside the skull occurs, even in Grade 3 concussions. Most individuals seem to recover reasonably well. Indeed, they seem to recover fully within 5 to 10 days, and some even quicker than that."

Guidelines and Recommendations
The Medical College research into football concussions was first funded by grants from the National Academy of Neuropsychology and NFL Charities. Others who have supported the studies include the Green Bay Packers Foundation, Herbert H. Kohl Charities, National Federation of State High School Associations, Waukesha Memorial Hospital Foundation, and several other funding agencies.

Dr. Hammeke is writing a paper on recovery from football concussions and the most recent phase of the Medical College research was completed in April 2007 (not yet published). With little evidence that multiple mild concussions over time result in permanent brain damage, a more immediate concern for coaches and medical staff is to learn more about the criteria for safe return to play.

"We're trying to refine the guidelines for allowing players to go back into the game. The guidelines are there based on expert consensus, meaning experts getting together and thinking about what is a reasonable thing to do. But they're not really based so much on science as there haven't been studies to address these issues. We're trying to anchor those guidelines in science.

"We're doing that by measuring mental capacities after a concussion, measuring how many symptoms the individual reports and for how long they report them, measuring how long they're able to maintain balance when they're standing in awkward positions, as we think that might be a useful measure of recovery.

"And we're also doing measures with functional magnetic resonance imaging (fMRI) to see if there are biological markers that we can anchor to changes in brain function related to the concussion. There may well be a subset of individuals who have a genetic predisposition to not recover nearly as well. It will take us a lot more time to tease that out. More time and research is needed to identify that."

Dan Ullrich
HealthLink Contributing Writer

MCW Health News presents up-to-date information on patient care and medical research by the physicians of the Medical College of Wisconsin.