The year was 2013, the Maple Leafs were an okay team in the lockout-shortened season and were about to head to a first-round playoff matchup with the Boston Bruins. Randy Carlyle, the head coach, was two years away from being fired — the move that began the great changes in Toronto.

Randy Carlyle had a theory

In a game in April, Joffrey Lupul took a hit to the head and left the ice. In discussing his status, Carlyle said the following:

“I have a theory on concussions,” he said. “I think the reason there’s so much more of them — obviously the impact and the size of the equipment and the size of the player — but there’s another factor: everyone wears helmets, and under your skull when you have a helmet on, there’s a heat issue.

“Everyone sweats a lot more, the brain swells. The brain is closer to the skull. Think about it. Does it make sense? Common sense?” said Carlyle, who said he’d never talked to a doctor about his premise.

“I don’t know if it’s true, but that would be my theory. Heat expands and cold contracts. The brain is like a muscle, it’s pumping, it swells, it’s a lot closer to the outside of the skull.”

Sportsnet had a doctor debunk that theory at the time:

“That wouldn’t be possible in my view — scientifically it is unsound to think that the temperature underneath the head and the helmet is going to reflect the temperature of the brain. There are too many layers of tissues in between,” [Dr. Charles Tator, project director of the Canadian Sports Concussion Project at the Krembil Neuroscience Centre at Toronto Western Hospital] said. “The circulation of blood and other factors that dissipate temperature would prevent any outside change of temperature of a few degrees from getting the brain from getting into the brain. The theory doesn’t hold water — or you could say the theory doesn’t hold brain — scientifically.

“And I don’t think there’s any evidence that exercise makes the brain swell; I have not seen that.”

And five years later, the NHL is still guilty of taking very little action taken on reducing head hits — the chief cause of traumatic brain injuries (TBI). Tom Wilson had a hearing on October 18 for the appeal of his 20-game suspension for an illegal hit to the head of Oskar Sundqvist. That suspension is dramatically long compared to the punishment most players get for hitting someone in the head.  If the appeal, or potential arbitration subsequent to it, succeeds in lowering the suspension, we may see this rare attempt to treat the problem seriously fail on the basis of past indifference by the NHL.

But while Carlyle was ill-informed and foolish in 2013, and he rightly became a symbol of wilful ignorance in the NHL, the debunking of his statements might have been a bit misleading.

Cooling the brain works?

The Swedish news site Expressen is reporting that a treatment for concussions involving external cooling of the brain is being studied in the SHL and Allsvenskan.

The product being used is from a Swedish company called PolarCool, who have produced a sort of helmet that contains a gel designed to lower the temperature in the brain after a head hit. Their theory is not just about swelling, as you might imagine, but about metabolism. A similar product offered by another Swedish company, Braincool, includes this explanation:

Multiple mechanisms can explain the beneficial effects of cooling. For each degree Celsius by which the brain temperature is reduced, its metabolism decreases roughly 6-10%. This entails less consumption of oxygen and blood glucose, thus reducing the risk of cell death. In addition, cerebral edema (accumulation of blood fluid inside the brain) is diminished, resulting in decreased intracranial pressure.

The CEO of PolarCool appears to still be employed by Braincool as well at this time, and is their former product manager.

The Polarcap device, as shown in Expressen’s story looks like this:

This all seems a bit absurd and even Carlyle-esque, but the story indicates that 12 clubs in Sweden have used the product with many players from junior, women’s and men’s hockey making up the cohort of users. This is in part a research project as well as treatment, and they have findings showing an improved recovery time when the device is used immediately after injury.

The idea of using hypothermia (a lowering of the core temperature) to treat brain injury is not new, and in 2012, a systemic review of studies on the idea was conducted. It found two key things:

Two of the studies showed no effect of head cooling on temperature. … But otherwise the data showed that liquid head-cooling devices and an intranasal cooling device could reduce temperature by around 1 °C or more, within 1 hour. This is promising and, in particular, suggests that there may be a role for liquid head-cooling devices for induction and maintenance of modest temperature reduction in TBI and stroke (the intranasal cooling device was not designed for prolonged use). It was noteworthy that even in the presence of active body warming (applied to prevent head cooling having a ‘knock-on’ effect on body temperature), intracranial temperature was reduced with a liquid head-cooling device and could be reduced below core body temperature.

The doctor who debunked Carlyle was not absolutely correct that brain temperature cannot be affected externally, but I think we’re still really safe in assuming helmets don’t cause concussions.


We found a larger number of studies than expected but few RCTs [Randomized Control Trials] of confirmable quality and none that allowed us to determine if head cooling improves functional outcome. The review has shown that some methods of head cooling can reduce intracranial temperature, which is an important first step in determining effectiveness, but the evidence is not robust.

This review did conclude that the head cooling technology was the most promising for future research and that it had no meaningful side effects. A second review from a different group of scientists in 2016 came to the same conclusions.

One of the issues with the use of this device by Swedish hockey teams is that the results collected may not be the sort of quality that these reviews said was needed. But no one is getting harmed by the use of the device.  The Expressen article quotes a team doctor reporting one player saying the device felt like going outside in a Moscow winter without a hat.

At the very least, this project may add to the understanding of this treatment option.

Treatment, diagnosis or prevention

What this experiment in Sweden does do is raise the question that if the best we’ve got for treatment is unproven, theoretical techniques, maybe the focus of all hockey leagues should be on prevention of traumatic brain injury in the first place.

What the NHL has chosen is a theatrical and public attempt to improve diagnosis of concussions via their spotters in the stands and watching on video. This focus on diagnosing and then treating players with concussions has some perhaps unexpected drawbacks.

Players may feel motivated to downplay or lie about symptoms of a concussion to avoid spotter detection. Nick Kypreos suggested on air during a game one night last season that goalies in particular will fake being okay after a hit to avoid being pulled. He was reviled for his comments, but that doesn’t mean his read on the motivation and behaviour of hockey players is wrong.

The Washington Post reported on the ease with which athletes can “sandbag” healthy baseline tests in order to test as ready to play more quickly post-concussion.

The more serious issue is that focusing on concussions misses the point. As the Washington Post reported on a study from Boston University, the link between a concussion and a traumatic brain injury isn’t as clear as people think it is. Nor is the connection between concussions and subsequent CTE (chronic traumatic encephalopathy) what matters.

When it comes to head injuries and CTE, [Dr. Lee Goldstein, an associate professor at Boston University School of Medicine and College of Engineering] spoke of three categories that are being jumbled: concussions, TBI and CTE. Concussion, he says, is a syndrome defined “by consensus really every couple of years, based on the signs and symptoms of neurological syndrome, what happens after you get hit in the head. It’s nothing more than that, a syndrome. You take one [symptom] from column A, one from column B.”

A TBI is different. “it is an injury, an event,” he said. “It’s not a syndrome. It’s an event and it involves damage to tissue. If you don’t have a concussion, you can absolutely have brain injury and the converse is true.”

CTE is “a bona fide neurodegenerative disease. It will progress independently of whether you have future hits and a lot of people think that the injury is the disease and it’s not. There is an injury and then it goes on to spread in the brain, like other neurodegenerative diseases.”

Which means that the focus on concussion doesn’t prevent the development of CTE.

“My analogy for this is it’s like having health officials focus on the hacking cough in smokers rather than the lung cancer,” Goldstein said. “A cough can be related to smoking — there can be many other causes of a cough. But the fact that you have or do not have a cough is irrelevant to whether you have cigarette-caused lung cancer. . . . It’s the same with chest pain and a heart attack. We would no more rely on chest pain to be the single indicator of whether you’ve had a heart attack.

What this means for the NHL is that by focusing on the syndrome, the thing that can be seen after the fact in some cases, they can avoid ever looking at the hits to the head which cause injury and subsequent serious disease. But preventing head hits means really facing up to having to change the rules of the game and how they are enforced.

Was the suspension to Wilson a step to prevention? Maybe. But do you think Oskar Sundqvist would have got 20 games for a hit to the head of Tom Wilson? If the answer is no, then all it may have done is affect Wilson’s own future behaviour.

Do we even know what works?

Until some hits to the head stop being excused by everyone from the fan to the Commissioner of the league, the best we can do is find a subset of brain injuries along with some false positives by spotting concussions and pulling players off the ice. The NHL doesn’t ever release any statistics to prove this theatrical practice has value beyond public relations.

As the 2016 Consensus Statement on Conscussion in Sport tells us, the treatment options for TBIs are limited, and there is no sure way of determining when a player should return to the ice, although understanding of how much rest is required is growing more solid. The research into how helmets should be constructed is minimal in some sports, and there is very little good evidence on what prevention techniques work best, although there is hard evidence that removing checking from children’s hockey is effective. There is also some evidence from soccer that changes in how rules were enforced reduced some head hits.

The NHL has the opportunity to be a laboratory for all areas of research that are currently under-served, and they have more money than any other hockey organization in the world. But they appear consumed with winning court battles with former players, and they can’t seem to find the will to do much to keep their current players healthy.

Might as well strap them into a Polarcap. At least it won’t make them worse.