September 2021

Concussion Series: Part Two

In part two of the concussion series we're looking at CTE, head knocks and how concussion is currently being treated in the sporting world.

This is the second part of our in-depth series on concussion. You can sign up as a subscriber to receive full access to not just this series, but to all of our premium content. You can access part one here.

In part one we looked at the history of concussion and how it has been treated in the past. 

As explained, head knocks, concussion and the effects are not new to researchers and scientists. It has been 100 years since “dementia pugilistica” was coined and over the years doctors from different sports have all raised their concerns about long term damage to the brain.

In rugby league it was raised by former Parramatta Eels doctor Dr Peter Manollaras during the 1980s. 

In part two of this concussion series we will be looking at the modern fascination with CTE, its links to concussion and head knocks, as well as how it is being treated at the moment.

This starts with the research of Dr Bennet Omalu in 2005 and his research reports on two deceased former American football players, diagnosing them both with chronic traumatic encephalopathy.


Dr Omalu

Dr Omalu’s two research papers on deceased athletes affected by CTE were recognised as the first two cases of the disease in former NFL players.

In the first case, the background of the athlete was evaluated as suffering from “symptoms of cognitive impairment, a mood disorder, and Parkinsonian symptoms. There was no family history of Alzheimer’s disease or any other head trauma outside football”.

In the second case, the athlete’s history consisted of “severe major depressive disorder without psychotic features after retirement, attempted suicide multiple times and finally committed suicide 12 years after retirement by ingestion of ethylene glycol”.

Despite both former players displaying symptoms of neurological issues, Dr Omalu’s paper pointed out that neither had suffered multiple recorded concussions during their careers.

No conclusion as to the cause of CTE in these two players was immediately reached at this point. Instead both papers called for further research into the causes, symptoms and prevalence of the condition in athletes.

The NFL’s initial response to the research was to try and quash it. What eventually resulted was a billion dollar lawsuit against the game for trying to hide the disease.

Since then the threat of litigation and concerns for player safety has prompted other sporting codes to approach concussion and head impacts much more seriously than before.

But, what actually does the damage? What happens to the brain as a result of repeated impacts to the head?

Tau Proteins

One of the key indicators of a brain disease such as CTE, but can also be present in other disorders, is the presence of tau proteins.

Dr Omalu had found large, tangled groups of these proteins which had damaged the brain. Tau proteins are also found in dementias including Alzheimer’s, although they normally show up later in life. Dr Omalu had found them in former athletes in their 50s, which is what caused his initial concern and the subsequent diagnosis of CTE.

Dr Chris Levi explains that research following Dr Omalu’s initial reports, was better able to categorise and diagnose diseases caused by those tau proteins.

“It’s what we call a tauopathy which is a neuropathological marker of neurodegeneration based around a particular protein called tau. There is a neuropathological consensus around what it looks like but the criteria are not specific necessarily to traumatic brain injury because we see it in other areas. 

“But the thing that distinguishes it from other tauopathies is this, what we call, perivascular distribution of the tau and the fact that it sits in a particular area of the brain, deep in the little crevices, the so-called cortical sulci,” says Dr Levi.

What he is pointing out is that tau proteins will present in a range of conditions, not just CTE, but where the proteins are located in the brain can indicate if they were contributing to CTE symptoms.

He adds that this knowledge isn’t completely new, just that science is now able to provide a clearer picture of what is happening.

“It is a real entity but we’ve known about this for a long time. It’s just that medical science has evolved and we’re now able to categorise this better.”

The Current Debate

The biggest differences between research groups when it comes to CTE are the causes of related diseases and how prevalent they are in playing groups.

One research paper published in the Journal of the American Medical Association in 2017 found CTE present in 110 out of 111 professional football players’ brains or roughly 10 per cent of the approximately 1,400 brains in the brain bankl.

It was a concerning paper, but one that Dr Nowinski says shouldn’t be blown out of proportion given how that type of research is often conducted. However, he still cautions that it is prevalent in a large chunk of the playing population.

“So that sample was 10 percent of NFL players that died over the study period. So that’s the floor. And now we’re getting more NFL players, so we know the floor is much higher. And so depending on how you analyse the data, it’s likely that the number is closer to 50 per cent. But it’s definitely not 99 percent, it’s not 90 per cent. It’s an extraordinary number because this disease is not seen in the normal population.”

At the University of Sydney Dr Michael Buckland is an associate professor in neuropathy and head of the department of neuropathy at Sydney’s Royal Prince Alfred Hospital.

He says that if the rate of CTE was the same as the 10 per cent of cases in that 2017 study, there would be cause for grave concern.

“In any other workplace, if they said “do this but there’s a 10 per cent chance of this horrible later in life disease”, no one would put up with that… I don’t think it’s insignificant (the rate of CTE) and what we’ve seen so far in Australia with the Australian sports brain bank, there’s no reason to believe that rugby league is going to be particularly different to the NFL when it comes to the incidence and estimated prevalence of this disease.”

Here is where the first real differences between researchers come in.

While Dr Nowinski believes CTE prevalence is around 50 percent, some studies on boxers have found prevalence at 17 percent, while Dr Levi believes the number is lower.

In addition to this, much of the research concerning CTE has been conducted using brains donated by players who were already displaying some symptoms of CTE.

Independent experts have called for more longitudinal studies, allowing for a wider sample group of retired players to be analysed.

That’s exactly what Dr Levi has called for and is currently working on.

“The science has to be a number of things, but especially it has got to look at, in a well-designed, longitudinal study, what the absolute and relative risks are.

“If you put the first big research question as being, what is the true risk of long term brain and mental health problems associated with playing collision sports? Huge question and some of the research that I’m doing with Andrew (Dr Andrew Gardner) is focussing on that,” says Dr Levi.

The study Dr Levi is working on is currently following 150 former professional rugby league players, tracking incidences of brain diseases and causes of death to try and find a risk profile for CTE and other neuro-degenerative diseases.

“There’s certainly more going on than just concussion”

As touched on in part one, there is a distinction to be made between “head knocks”, which are blows to the head that don’t result in concussion, and actual concussions.

What often seems to be lost in the reporting of concussion and cases of CTE is the role that head knocks or “sub-concussive blows”, as they are sometimes termed, play in the development of those diseases.

Dr Buckland says the focus on sub-concussive blows came out of studies completed at the Boston brain bank, as the rates of concussion reported and the amount of CTE cases didn’t match up.

“The concept of sub concussive blows really came about because, in the Boston studies, they couldn’t correlate the number of reported concussions with the risk or severity of CTE and what correlates, is years of play,” he says.

“There’s certainly more going on than just concussion.”

The “years of play” Dr Buckland mentions is in reference to the research being conducted in America into the correlation between the length of time an individual plays a contact sport at any level, and their risk of developing a neurodegenerative disease later in life.

Dr Buckland adds that in some Australian studies changes in the brain have been detected in athletes that have not had a diagnosed concussion but have been playing a contact sport.

“I am also aware of the literature out there, including some from a group from Monash (University) showing that contact sports athletes, after a season with no documented concussions, still show changes in their brains on imaging and have detectable changes in their blood, on the levels of circulating biomarkers.”

Dr Nowinski agrees and says studies in the US are trying to ascertain to what degree an athlete’s risk rises each year.

“In American football with a sample of hundreds of football players, your odds of developing CTE in our original study showed it went up 30% per year you played. So you start with basically nothing, but once you start to get into high single digits and double digits, that’s where we start to pick up a very significant number of people having CTE.

“The same thing was found in the 1960s in boxers. The more matches you had (the higher your risk), and so it’s basically whatever is sparking CTE is likely sub-clinical,” says Dr Nowinski.

“Be conservative”

With the research into CTE and its related causes continuing to evolve, and risk profile still being assessed, doctors Levi, Buckland and Nowinski all prefer to err on the side of caution.

“When you do not know what the absolute and relative risk is then the default position is to be conservative. I think they (the NRL) have quite appropriately adopted a conservative position, as have the other codes and fuelling this is occupational health and safety, legal concerns and risk of litigation. 

“So you’ve got an appropriate, responsible response in terms of what the science currently tells us and I think you’ve got a major drive in parallel with that being that occupational health and safety and litigation issue,” says Dr Levi.

“I think it sort of points to that concussion, return to play is as much of a medical question as a social question. The science hasn’t changed. The social consequences of returning people faster or within a few days of concussion, has changed. 

“It’s being called out by the media, it’s having educated players start to question their doctors and so I’m not sure what to make of that other than that we’ve started to recognise that the consequences of brain injuries are much more severe than we realised,” says Dr Nowinski.

“I’m very happy to say that whatever changes there are, the focus should be on reducing cumulative head impacts and also I believe the two ways of doing that, maybe practice (limiting or altering full contact training) and looking at the age of when full contact football is introduced. Because if you can knock off years of exposure to repetitive head injury to those younger people, then you’re buying time at the other end,” says Dr Buckland.

Current Treatments

One of the tricky issues surrounding head knocks and concussion is the lack of a completely objective test to diagnose the injury.

Unlike musculoskeletal injuries such as a torn hamstring or broken arm which can be viewed through imaging such as x-rays or ultrasounds, concussions don’t yet have an objective test.

Instead, diagnosis of a concussion relies on subjective testing methods such as questionnaires, response time and coordination tests and the Sport Concussion Assessment Tool or SCAT which is utilised as part of the NRL’s head injury assessment protocol.

Some concussions are easy to diagnose if a player is knocked unconscious, is unsteady on their feet or has coordination and memory issues.

But there are plenty of concussions which can go unnoticed or where the symptoms are delayed until after a game or training.

Further complicating matters is the recovery time for concussions. Without an effective imaging or diagnostic tool, doctors don’t know for sure when a player has fully recovered.

While they may be completely asymptomatic and physically ready, their brain may still be recovering says Dr Buckland.

“Concussions can be very disabling injuries as a separate issue to CTE and potentially what would be most important I think, is knowing when the brain is healed enough to start going back to play or going back to full exercise.

“There was an Australian study published in The Lancet in the mid-90s and from memory I think they were able to detect white matter damage 90 days post-concussion, so it could be quite a long period of recovery for some people to allow the brain to get back to normal,” explains Dr Buckland.

Dr Nowinski agrees.

“The science is showing that people don’t recover on a physiological level, nearly as quickly as they recover on a clinical or symptomatic level, and I think that’s starting to be baked into how people think (about) how to return. The tools they have might say they’re symptom free and somebody wrote down that if they’re symptom free, you can return them, but we now know (that) probably isn’t a great idea. They need more time to recover than we can see.

“Your brain definitely doesn’t recover on a cellular or molecular level even, though you might feel better. Additional head impacts before your brain has fully recovered can make things considerably worse. The brain is in a vulnerable state,” he says.

As the sporting community’s understanding of concussion has changed, it has begun to adapt. 

In 2021 the NRL introduced a requirement for clubs to have an independent concussion expert consult any player wanting to return within 10 days of a concussion.

Meanwhile a raft of players have begun to sit out for extended periods of time after a concussion to allow themselves more time to recover.

Melbourne Storm prop Christian Welch says he thinks the attitude towards concussion has changed dramatically, and it is becoming more commonplace for players to sit matches out even if they pass their physical tests.

“I think there’s a real change in the stigma surrounding, “you need to tough it out. You’re not tough if you don’t play through it.” I think that’s completely changed, and I think that’s fantastic. And I think it’s getting better, and better, the awareness and to be fair, it’s such a hard thing to work on. The health professionals are still working out best practices so it’s an evolving thing really.

“I actually passed, after game one Origin last year (2020), I passed all of the concussion protocols but I just wasn’t feeling like I wanted to take that risk, so I take it really seriously. I gave up that Origin 2,” Welch says.

The Future

The scientific understanding of concussion in contact sport has come a long way in the past 15 years. 

From an injury that was often played through and a sign of toughness, to now being treated seriously and strict protocols, and rules enforced, concussion and associated head knocks is an injury now treated the world over.

And with that improved understanding comes the development of better diagnostic and evaluation tools.

Dr Buckland says some of those tools are being developed right now.

“What’s not talked about as well is there is actually a body of literature on the pathology of concussion. We hear about the definition, there’s no structural injury on imaging as part of the definition of a concussion. 

“Obviously that’s a moving goal post because the definitions were made up when you used to x-ray people’s heads for brain injury, then it moved to CT scans and now it’s MRIs. We’re getting better and better at picking up more subtle damage.”


Part three will look at the future of diagnostic tools and treatments for concussion as well as possible changes to the rules and structures of contact sports. Subscribe for $5/month to get access to the full series and all other content, while also receiving your first month FREE.

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