Varsity athletes who are medically cleared to return to play after a concussion show changes — but not impairments — in their brain structure and functioning on MRI scans, Canadian researchers have found.

Investigators from St. Michael's Hospital in Toronto used advanced MRI to scan 27 athletes playing contact and non-contact sports within a week of their concussion and then when they were cleared to return to play. Those players were compared to an equal number of their varsity peers who weren't injured.

When the athletes no longer had symptoms, felt good and were ready to return, the researchers still found differences in their brains. 

"They still showed evidence of some swelling in the white matter and some hyperactivity in their brain function, which is quite striking because otherwise they seem to be doing fine. This tells us there's something biologically that's likely still going on, even though they don't seem to be showing any impairments," said Nathan Churchill, lead author of the study published in Thursday's Scientific Reports, and a postdoctoral fellow with the hospital's neuroscience research program.

It could be that the researchers are peering at signs of the brain's natural recovery response after a blow to the head, either back to normal or a new normal. 

"Our study shows it's not all doom and gloom just because you see a neuroimaging study with some brain effects of getting a concussion," Churchill said. 

Previously, investigators have focused on professional football players and boxers who experienced repeated concussions over their careers.  

Churchill was drawn to the challenge of trying to understand the spectrum of how brain injury manifests. Some bounce back quickly and others struggle for longer.

Peak performance

When he embarked on the experiments, Churchill figured that scientists knew what the brain looks like at the time of recovery and what the brain of an average athlete who plays contact sports is like. They didn't. 

It means researchers still need to set the groundwork of understanding those differences in a range of people of different ages, sporting abilities, male and female and contact and non-contact athletes, before they can answer pressing clinical questions about why people go on to have long-term effects after a concussion, Churchill said.

In this study, the average age of the varsity athletes was 20. Those in the concussion group played rugby, football, ice hockey, field hockey, volleyball, soccer, water polo, basketball and lacrosse.

Michael Hutchison

The MRI findings on varsity athletes suggest taking a conservative approach to return to play protocols, said Michael Hutchison. (University of Toronto)

Earlier this week, researchers from the same lab published a study in Frontiers in Neurology. It suggested the brains of athletes who play contact sports where body contact is permitted, such as soccer and basketball, also showed some differences previously only studied in collision sports like football. 

"One thing that was telling in both the contact and the concussion papers is we saw areas involved in vision and attending to things when you're looking around was affected by impacts. We saw areas involved in coordinating bodily movement were most affected as well. These are the kind of brain areas that need to be performing at their peak if an athlete wants to avoid future collisions." 

The other study included 23 male and female athletes playing collision sports like football and rugby, 22 in contact sports and 20 in non-contact sports like swimming or golf. None reported health issues, and as in the other study,  the differences that researchers observed in the scans didn't seem to impair their day-to-day functioning.

MRIs will likely remain a research tool rather than one for the larger sporting community, said study co-author Michael Hutchison, director of the concussion program at the MacIntosh Sport Medicine Clinic at the University of Toronto.

Hutchison, an assistant professor of kinesiology, said the findings add to a growing body of emerging research on how brain recovery seems to extend beyond clinical recovery.

"I think it should push us to be conservative in our approach," Hutchison said, such as the graded protocols to ensure people are at their best to return to work, school or play.

In the future, Hutchison said perhaps better tools could be invented to focus on these newly identified areas of concern in the brain after concussion, allowing clinicians to be more confident that people are functioning well.  

Concussions are complex and physicians can't rely on just one tool or test to clear athletes to return to play, said Dr. Shannon Bauman, a sport medicine physician and medical director of Concussion North in Barrie. She was not involved in the research.

"My bottom line is while these tests are very interesting and can tell us some of the anatomy and give us some idea of where [there's] some recovery, it still needs that clinician with experience to decide how to interpret that information and how it would be used to make a clearance decision," said Bauman, a spokesperson for Parachute, a non-profit organization focused on injury prevention.

When making decisions about return to play, Bauman said physicians perform a series of detailed physical and neurological exams over time, looking at what might provoke symptoms both in day-to-day activity and in sport-specific tasks, such as stick handling for a hockey player.