A disconcerting new study involving detailed brain scans of 18 high school and college football players ages 15 to 21 in Wisconsin questions this assumption.
In an abstract to be presented at the American Academy of Neurology conference Saturday, researchers report that all of the student athletes who experienced a concussion continued to have visible damage in their brains six months after the injury. All of these players were deemed recovered in seven to 10 days, so the signs of neurological damage persisted long after they stopped having clinical symptoms of concussion.
Michael McCrea, director of brain injury research at the Medical College of Wisconsin in Milwaukee and the senior author of the study, said that although the results are preliminary given the small sample and short follow-up period, "the findings generally add to the growing body of science to suggest that the tail of physiological recovery after concussion extends beyond the time point of clinical recovery."
The study, which was partly funded by the National Institutes of Health and the U.S. Army Medical Research and Material Command, involved the use of advanced MRI scans called diffusion tensor imaging and diffusion kurtosis tensor imaging to look at changes in the brain's white matter. White matter consists of bundles of nerve fibers that are considered the connective tissue of the brain. These fibers help carry messages from one region of the brain to another. Studies have shown that white matter may appear changed in all kinds of diseases and conditions, including stroke and Alzheimer's.
What McCrea and his colleagues noticed in the student athletes with concussions is that they had less water movement, or diffusion, shortly after their injuries as compared to other players who had not had concussions. This suggests that the white matter tracts may be slightly torn and leaky. They also found that these microstructural changes in the concussion group were still there six months after the injury.
Some of the students in the study had a previous history of concussion, but for others it was the first concussion they experienced. McCrea said that the group was too small for an analysis of whether this previous history made a difference, but hopes to explore such questions in follow-up studies. The athletes in the current study will be followed for two years and researchers hope they will be able to recruit more participants.
This research may one day be able to shed some light on whether some athletes may be returning to sports too quickly.
"As odd as this sounds, we want to know not only when is the athlete ready to return to an activity functionally but when is their brain ready to return physiologically," McCrea said in an interview.
The scariest possibility that the study raises is that the effects of even a single concussion could be permanent. But James R. Couch, a professor of neurology at the University of Oklahoma Health Sciences Center, who is known for his studies on brain injury in U.S. military veterans, cautioned that it's too soon to make that leap.
"There is not a direct one-to-one correlation between the anatomical appearance of the brain and the way a person performs," Couch said in an interview. That is, even if images of the brain show white matter changes, the person could feel and act like their old self.
Couch said it's important when considering studies about longer-term effects of concussion to remember that the brain may be fragile but that it's also incredibly resilient. He said that to really look at the permanence of injuries we would need to have studies that look out 20, 30, or even 40 years after an injury.
"The problem here in trying to interpret the study," he said, "is the brain is a tremendously plastic organ in terms of being able to wire around damage and change things rapidly."
He said that if you think of the brain as a type of intelligent, living electronics system, the way it survives is by "constantly reaching out and making new connections."
"The result may be that they sometimes don't produce as good of a result as the original equipment, so to speak, but in other cases it may be it's good enough," Couch said.