Concussions make lasting changes to the brain, even after you feel fine

We don’t know what those changes actually mean.

brain scan
Three months after concussion, the brains of adolescent hockey players still don’t look normal Deposit Photos

In Canada, many kids are on ice skates before they can walk. But they don’t get to start slamming into each other until they’re around 11, when they can sign up for full contact hockey. Unsurprisingly, that’s also the age when the baby Wayne Gretzky’s start getting their first concussions.

If they take a knock, the puck-hungry preteens are sidelined until they pass through a standard return-to-play protocol: after the initial symptoms subside, the recommended approach is for athletes to gradually ramp up activity, making sure headaches and dizziness don’t return at each step of the way. Once they pass through that incremental increase without issue, doctors will clear them to return to the rink.

But a new study shows that even when young hockey players who suffer concussions appear fully recovered, and doctors and trainers return them to the ice, scans still show abnormalities in the brain. The findings were published today in the journal Neurology, and add to a growing number of studies showing that neurological changes linger even after clinical symptoms of a concussion clear up. Athletes may appear back to normal on a battery of cognitive and physical tests, but not on an MRI scan.

“The problem is those tests don’t seem to be very sensitive in the long run,” says study author Ravi Menon, director of the Centre for Functional and Metabolic Mapping at Western’s Robarts Research Institute in Ontario. “They return to normal quickly, but the MRI data shows the brain is still healing.”

Menon’s study followed a group of male hockey players, aged 11 to 14. Fourteen players suffered a concussion during the season, and went through a functional MRI scan, cognitive, memory and balance test both one to three days after the injury and again three months later. Their tests were compared with those of 26 injury-free players, who served as controls.

On average, the injured kids took 24 days to return to play, and they were all back in the game by the time the three month mark rolled around. At that point, they tested normally on the cognitive, memory and balance tests—but they still had changes to some structures in the brain and changes to the connectivity patterns between brain regions. The types of abnormalities are consistent with those seen in previous studies done in other, older populations, Menon says, but it’s a particular concern for young athletes, whose brains are still developing.

It’s not clear what, exactly, the impact of the neurological changes could be—after all, the athletes appear to act and feel normally. But the changes to the activation and wiring patterns, Menon says, could be compensating for underlying damage. He thinks they might be similar to the way the brain tries to work around accumulating damage from diseases like Alzheimer’s disease: the changes are asymptomatic, until they’re not. “It may be perfectly fine, until you exhaust the ability to compensate,” Menon says.

Despite the dozen or so studies with similar findings, the recommendations for concussion recovery aren’t likely to change any time soon. A review paper published in April, which took a close look at most of the existing research on neurobiology during concussion recovery, noted that the bulk of available data indicates that changes to the body and the brain stick around after symptoms clear. However, the authors concluded that there is still not enough information about what those changes mean to warrant a shift in the current standards of a gradual return to sports based on clinical symptoms.

Matt Gammons, the former president of the American Medical Society for Sports Medicine, says the same. “I don’t think anyone is ready to say that we should change our usual practice,” he says. Gammons worked on the AMSSM position statement on concussions in 2013.

Gammons stressed that the concussion recovery process is not one size fits all, and the decision to return to play can vary from athlete to athlete. Conversations with athletes and their parents often include discussions of some of the less well understood elements of concussion recovery, like long-term neurological changes, and these factors can play into decision making.”When you tell a kid they can’t go back to participating in a sport, there are consequences to that,” he says. “But it’s common sense to say that if we’re able to take more time, let’s take some more.”

Even though the research might enter the conversation in some decisions, Gammons says the evidence isn’t strong enough to indicate changes to concussion recovery protocols or institutional recommendations. That’s primarily because researchers don’t know how or if the neurological changes seen on the scans in these studies are harmful in the long run. “We’re quite a ways off from being to look at imaging showing persistent changes without any symptoms and being able to say why that matters,” he says.

One of the complicating factors, Gammons says, is that the scanning technology is incredibly powerful. If you break your arm, for example, it’ll heal in about six weeks. But if you do an MRI six weeks out, he says, the scan will still show changes at the spot of the break. “The question is [whether] those persistent changes matter.”

Menon recognizes that the actual impacts of the neurological changes seen in his study, and others, are still up in the air. However, he says he’d still like to see the next round of concussion recommendations change to reflect a more conservative approach to return to play.

“I think it would be important for them to, at least for kids, look at these studies and maybe err on the side of caution until we understand more,” he says.