SPORTS MEDICINE
August 16, 2016

Athletes and Concussion

The brain tsunamis that concussions set in motion can change the structure of athletes' brains.

Athletes — from football players to equestrians to cyclists — get concussions. They aren't the only ones, of course, but for people who put their bodies on the line daily, the odds of sustaining a brain injury are higher than for the rest of us.

When the brain is jarred by a fall or a hit, it can create a brain tsunami in which large groups of brain cells become depolarized. The waves of depolarizations spread slowly but persistently throughout the brain, causing widespread brain dysfunction.

Athletes who had a greater number of past concussions also had a greater decrease in cerebral blood flow and a larger reduction in the size of one specific area deep inside the frontal cortex.

That is why, even years after a concussion, changes can still be seen in the brain of an athlete, and the brains of young athletes may be particularly vulnerable because they are still developing. The changes seen in a recent study include reduced blood flow and shrinkage of the brain's frontal lobe.

Comparing Athletes With and Without Concussions

Even though the headaches and other obvious symptoms from a concussion generally disappear within 7-10 days, some studies, especially those on combat veterans and professional football players, show that concussions can have long-lasting effects.

None of the athletes had suffered any recent injury. Their last concussion had occurred anywhere from nine months to 10 years in the past.

Male and female varsity athletes from the University of Toronto were given an advanced type of MRI scan called multi-modal MRI at the beginning of their season. The scans of 22 who had no known concussions were compared to 21 who had from one to five previous concussions. None of the athletes had suffered any recent injury. Their last concussion had occurred anywhere from nine months to 10 years in the past. The athletes were drawn from seven different contact and non-contact sports: basketball, football, hockey, lacrosse, rugby, soccer and volleyball.

More Concussions, More Brain Changes
The brains of athletes with a concussion history showed a 10-20% reduction in the size and a 25-35% reduction in blood flow to substantial portions of the brain's frontal lobe when compared to athletes with no concussion history. Changes were also visible in the structure of the brain's white matter. And there were increases seen in the size of certain areas at the back of the brain, including the right hippocampus.

The frontal lobe may be affected even in young, healthy adults with few concussions.

The frontal lobe is the center for behaviors such as impulse control and problem-solving, and these are often impaired in older athletes with a history of repeated head injury. The study findings suggest that the frontal lobe may be affected even in young, healthy adults with few concussions.

While it's not clear what the increased size of other brain regions means, the authors do point out that similar growth is seen as an adaptation after other brain injuries such as stroke and may signal new regions attempting to take over functions previously provided by regions that are now injured.

Impulse Control Problems and Depression

Athletes who had a greater number of past concussions also had a greater decrease in cerebral blood flow and a greater reduction in the size of one specific area deep inside the frontal cortex known as the insula. Those who had longer recovery times (clearance to play) from the last concussion were associated with a greater decrease in the size of the frontal lobe.

“We found that in specific regions of the brain (including parts of the frontal lobes), estimates of grey matter volume were significantly lower in athletes with a history of concussion, compared to those without,” Nathan Churchill, the study's lead author, told TheDoctor. “Sport concussion is still considered to be a short-term injury, but this study provides further evidence of brain changes that may lead to long-term health consequences, including the risk of re-injury, depression and cognitive impairments.”

In the past, most MRI scans have been taken between one week and one month after a concussion. There's been very little chance to see scans taken later on, much less to interpret them. And while the precise meaning of all the changes seen in the current study may not yet be clear, it provides more evidence that concussions can change the brain permanently. Hopefully, the information will help us find ways to prevent the ongoing damage concussions can do, perhaps by interrupting the depolarization of the brain before it gains too much momentum.

The study appears in the Journal of Neurotrauma and is freely available.

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