Concussion, once seen as ‘part of the game’, especially in contact sports, is now treated with caution and stringent return-to-field protocols to ensure further damage isn’t incurred. Depending on the sporting league, there may be defined concussion protocols with medical and allied health professionals to assess their athletes. However, not all sporting leagues have these procedures.
So, what about athletes who don’t have access to concussion protocols? And what about non-sports related concussions? How many concussive or sub-concussive impacts have these athletes experienced before they reach their pinnacle?
In short, how many bumps is too many?
Another broader and pertinent aspect of concussion is the fact that a majority of them do not occur on a field of play. Nearly 15% of concussions can be attributed to sports, while falls, car accidents, recreational activities and domestic violence account for the majority of reported cases.
The concussive impact is just the beginning of the journey with the majority of cases experiencing continuing symptoms for up to three weeks before resolution. Then there is about 15% of concussion cases that express a plethora of persistent symptoms for weeks, months and sometimes years after the concussion. These chronic cases, once categorised as post-concussion syndrome, are now clinically named persistent post-concussion symptoms.
Diagnosing a concussion for athletes has progressed with the development of tools such as the Sport Concussion Assessment Tool 5 (SCAT-5), while GPs will diagnose based on their patients’ medical history, a physical examination including a focused neurological assessment, balance and cognitive testing. Even with these tools and procedures, a concussion remains a clinical diagnosis.
So, how are clinicians meant to diagnose and treat concussions without a way of quantifying the severity of the trauma and the individual differences between cases?
Some individuals can absorb a concussive impact without short or long-term consequences, while others can sustain a concussion from the same level of impact and experience significant short and long-term consequences.
Further complicating diagnosis is the lesser known sub-concussive impact, where an individual sustains an impact that is below the threshold of expressing symptoms that can potentially cause damage.
There is increasing evidence pointing towards long-term exposure to concussive and sub-concussive impacts being causal to chronic traumatic encephalopathy (CTE), a nascent neurodegenerative disease. Think of a football player taking a hit from a tackle and continuing to play without any issue or symptoms, then continuing to take similar knocks throughout the game, then multiply this over the lifetime of their career and the cumulative damage can be causal to CTE.
What is not known is how many bumps is too many, and what is the threshold before the damage is irreversible. As a CTE diagnosis is only possible by post-mortem autopsy, to definitively identify causality is difficult.
The fundamentals of a concussion are relatively simple. A mild form of traumatic brain injury (mTBI) caused from an impact to the body or head with enough force to shake the brain and cause it to impact the skull, damaging nerve fibres and small blood vessels. While changes to the brain from an isolated concussion will be resolved without intervention, in the majority of cases, this is dependent on the impact itself and the individual’s susceptibility and resilience to the concussive force.
Yet, concussion severity is difficult to measure as there is a multitude of variables that contribute to the injury, such as the force of the impact, and the neurological and physiological susceptibility or resilience of an individual to the impact.
There is, however, a broad symptomology that goes some way to provide clinicians with enough diagnostic markers to identify if an individual is presenting with concussive symptoms, such as the SCAT-5 tool.
Melbourne neurophysiologist Associate Professor Alan Pearce is a researcher focused on neurophysiology of sports-related concussion. He uses transcranial magnetic stimulation to observe the central nervous system integrity, comparing concussion injuries in both acute settings and in the long-term potential chronic effects of repeated head trauma.
According to A/Prof Pearce, identifying a concussion is problematic because of individual differences between cases.
“There is a constellation of signs or symptoms that won’t necessarily be the same across two individuals. And these range from being knocked out – which occurs in 10% of concussions – to signs of unstable gait or being dizzy or unbalanced,” he said.
“Then you have symptoms such as headaches, nausea, confusion, slurring of words, inability to focus, inability to maintain eye contact or focus. Generally, in that very acute space, people can get quite anxious about what’s going on. It could be a set of signs and symptoms relating to the actual observed insult to the brain.”
“You can’t diagnose a concussion without a set of symptoms and the heterogeneity of symptoms are huge in concussion. The added difficulty is trying to diagnose when an individual is not presenting with any concussions or symptoms.”
The difficulty, he said, was in what was assumed as a concussive impact, such as an athlete taking a heavy hit on the field then continuing playing without expressing any overt symptomology.
“Do you pull them off to try and assess, or, do you not? Particularly if they’re saying, ‘I’m fine’. The other added complexity is that concussion is what we call an evolving injury. You can get concussed but symptoms may not show up until several minutes or several hours later, or even the next day.”
An area of concern is sub-concussive impacts where an individual can experience multiple impacts over time.
“We really don’t yet know whether sub-concussive hits, for example, heading a soccer ball over a career, is going to lead to longer term problems. While there doesn’t seem to be the severity of concussion symptoms reported following repeated sub-concussive hits, it’s not yet clear whether there may be longer term outcomes as a consequence of those kind of repeated lower level impacts,” A/Prof Pearce said.
His research has focused on contact sports athlete cohorts that are commonly expected to experience a multitude of sub-concussive impacts over a career.
“We’re seeing neurological impairments that correlate to cognitive impairments and some fine motor control changes as well, but they are quite subtle. These people are not advanced in their impairments. What I’ve been looking at is the effect on the brain and central nervous system of having multiple concussions, or hundreds or thousands of smaller sub-concussive hits, 20 years later.”
According to A/Prof Pearce, the more concussions the brain experiences, the easier it is to be concussed, with less impact force required for concussion symptoms to present. Each subsequent concussion generally requires a longer recovery too, yet why this is the case isn’t clear.
Perth sports doctor Dr Gill Cowen told Medical Forum that while there was ongoing research focused on sub-concussive impacts, the evidence was not clear as to the long-term consequences. Even defining what a sub-concussive impact is, was problematic.
Dr Cowan is a senior lecturer at Curtin Medical School and chair of the Sports and Exercise Medicine Network in the RACGP Faculty of Specific Interests. She has worked as a club doctor for numerous teams and sporting leagues.
“It’s a difficult area because there isn’t a clearly established definition. Determining if an injury has occurred without clear identification of what sub-concussive impacts have actually been sustained during a person’s life-time or sporting career is problematic,” she said.
Perth neuroscientist Professor Melinda Fitzgerald is a neurotrauma researcher and Deputy Director of the Curtin Health Innovation Research Institute at Curtin University, jointly appointed by the Perron Institute. She is focused on understanding the mechanisms of damage which occurs following a traumatic brain injury and predicting outcomes following a concussion.
Prof Fitzgerald said self-reporting of concussions is an initial barrier to care as people did not necessarily seek medical attention following what was probably a concussive impact.
“We don’t yet know if only the more severe cases go to the emergency department. We don’t actually have data on that and it’s hard to get that data because you don’t know what you don’t know. One of the things we really want to get a better handle on is concussion in the community. How many people are suffering from a blow to the head that results in continuing symptoms? That is potentially not diagnosed properly as a concussion and people are not necessarily seeking medical aid.”
Until there is clear population-level data, it is difficult to ascertain the incidence of concussion in Australia and ensure that people really do go and see their GP and that they are appropriately managed following such an injury, according to Prof Fitzgerald.
Ultimately, a national database to track concussion cases would be the best way to capture data to see what statistically significant short-term and long-term effects are happening at a population-level, Dr Cowen said.
“Historically, there have been problems with people not reporting symptoms and that’s why in sport the SCAT-5 is useful as you have objective assessment tools, as well as subjective reporting of symptoms,” says Dr Cowen
Complicated long-term effects
Although concussions, as far as the broad symptomology is concerned, are relatively well known, the long-term effects are not. What happens after a concussive impact is where the ambiguity lies.
A concussive impact can occur in milliseconds and the long-term effects can be seemingly relatively benign in the short-term, lasting for hours or days, yet the long-term consequences can also be pervasive, unpredictable and last for years. In some cases, one concussive impact can be sufficient to cause permanent damage, depending on individual susceptibility and the severity of the impact.
Prof Fitzgerald is conducting a study investigating the long-term consequences of concussion and, in particular, “being able to identify whether someone will recover normally from a concussion or not.”
“One in five people have continuing symptoms from concussion that last longer than you would normally expect. Currently we don’t know what predicts that kind of continuance of symptoms,” she said.
Further complicating concussion recovery and potentially protracting the long-term effects is a multitude of biopsychosocial factors, such as the severity of the underlying brain injury, premorbid coping style and previous head injury. Prof Fitzgerald says factors such previous concussion or a neuropsychological condition such as depression, anxiety or migraine might have an impact.
If post-concussive symptoms extend beyond three months a diagnosis of persistent post-concussion symptoms (PPCS) may be applicable but it can be challenging to diagnose.
Research has found adult females, but not female minors, to be more susceptible to PPCS after a sport-related mTBI than adult males and minors. Why there is a statistically significant difference in mTBI sequelae between ages and genders is not completely understood but hormonal influences have been theorised as causal> However, there is an issue of sampling sizes with a large disparity between high number of male participants being studied, compared to females.
Severity of impact
One of the difficulties of predicting long-term consequences was that the severity of the impact did not always correlate with worse long-term outcomes.
“It doesn’t necessarily follow that a heavier hit leads to a greater chance of prolonged symptoms following concussion. Factors such as a previous concussion, a pre-existing neuropsychological condition such as depression or anxiety, or migraines may play roles and influence how an individual recover and if they were to experience a concussion. We haven’t yet looked at genetic factors, but it is possible that they may also play a role in determining vulnerability to longer term problems after a concussion,” Prof Fitzgerald said.
Individual tolerance to impact forces is another variable but there are new technologies able to measure the g-force of impacts.
“The kind of g-forces experienced by concussive impact is very high – up to 100 g-force, which is just extraordinary. It’s difficult to measure and we can’t yet connect that to clinical outcomes and whether people are experiencing a worse concussion as a result of increased g-forces. It’s likely, but we certainly don’t know the longer-term outcomes of particular g-forces experienced by the brain,” she said.
Although concussions are often seen as a consequence of sports-related impacts, the at-risk cohorts, according to Prof Fitzgerald, spread beyond the athlete.
“Younger people are more likely to have impact from sporting activity and perhaps more motor vehicle accidents. But we do see a spike in the elderly with falls. Concussion can be across all populations, but spikes particularly in these cohorts,” she said.
Dr Cowen says the perception of concussions being primarily sports related is challenging because non-sports concussions account for up to 85% of total diagnoses.
“It’s really important that this fact is flagged with clinicians and also the general public. Concussion isn’t just sport related.”
Concussion due to domestic violence is another area in which Dr Cowen highlighted the need for vigilance.
On the field of play
When presented with a concussion on the field of play, the SCAT-5, designed by the Concussion in Sport Group (CSG), is widely used as a standardised tool for concussion assessment and is integrated into concussion protocols, yet the tool does have limitations. A player could report no symptoms and have a relatively normal clinical assessment, but still be of concern to a clinician, so the medical professional may need to make the diagnosis, or take the player out of the game, based on their clinical judgement. The SCAT-5 however, is “an excellent adjunct to routine medical assessment,” according to Dr Cowen.
For children between the ages of 5-12 years, CSG has developed the Child Sport Concussion Assessment Tool (Child-SCAT-5) and for non-medical professionals CSG has the Concussion Recognition Tool 5 (CRT-5).
“Concussion is a clinical diagnosis,” Dr Cowen continued. “At present, we haven’t got an available blood marker or a specific imaging test to assist us, despite ongoing research in this area, and a diagnosis of concussion is down to a clinical assessment. This includes exclusions of cervical spine injury and focal neurology as well as subsequent assessment of the patient for evidence that they may have sustained a concussive injury.”
Measuring the impact
Taking the subjective measurement out of concussion and replacing it with quantitative data points is potentially game-changing for concussion diagnosis. Western Australian start-up HitIQ hopes to achieve that with their smart mouthguard, the Nexas A9, which monitors impacts in real-time.
To understand the product and its potential, Medical Forum spoke with Mr Damien Hawes from HitIQ.
“We’ve taken a custom-fit mouthguard and put a flexi circuitry board inside of it which has three high resolution accelerometers, a small battery inside and Bluetooth connectivity. The device measures head kinematics specifically as well as linear and rotational forces using the array of accelerometers inside of the mouthguard,” he said.
The device is currently in testing with professional and amateur sports teams and athletes in Australia and the US and, along with similar devices being developed elsewhere, could lead to a breakthrough in real-time concussion diagnosis.
“The process of identifying an athlete with concussion in the field of play comes down to looking for signs and symptoms of a concussion and that’s really difficult in the heat of the battle.”
A device that can measure impact force and bring awareness to coaches and medical staff could also reduce the burden on the athletes to self-report, Mr Hawes said.
“Players often have a warrior mentality and they don’t want to show vulnerability during a game, so they are not in the right frame of mind to self-report after a concussive blow. We want out product to be the safety net for players, so they are removed from the field of play if concussed. They get through the risk and they get the appropriate medical treatment. They can recover and get back out on the field.”
The CTE problem
Chronic traumatic encephalopathy (CTE) is a difficult topic to broach as diagnosis of the neurodegenerative disease is only possible with an autopsy, yet there are growing concerns that the primary risk-factors in developing this tauopathy are repetitive concussive or sub-concussive impacts leading to chronic neurobiological sequelae with pathologically unique disease characteristics; essentially clusters of Tau proteins that disrupt the surrounding brain tissue and change the brain function.
Although CTE is a nascent disease in terms of diagnosis and nomenclature, the precursor diagnosis has been dementia pugilistica – which was, as the name suggests, a disease derived from the side-effects of boxing and the associate head trauma from competing in the sport.
Post-mortem CTE diagnoses are becoming more common among at-risk athletes due to targeted autopsies, whereas, in the past, awareness of the disease meant there were few undertaken on at-risk athletes. Sydney neuropathologist Associate Professor Michael Buckland suggests this was due to the niche cohort of those suspected to be susceptible.
“I was taught, as were probably all doctors of my generation, that there was this interesting sort of diagnostic anomaly of dementia pugilistica that can be found in boxers. But you would have to have a reason to go looking. At that time, it was just an interesting anomaly only found in professional or serious boxers and unless you had that written in the patient history, you would never go looking.”
“When I read what they were describing, I was thinking back over all the brains I had seen and, you know, I’d never seen that before.’ That pathology is distinctive. I don’t see that in my routine practice. I see lots of Alzheimer’s cases and compared to the Tau stains they were publishing; it isn’t Alzheimer’s disease. I don’t see that in my cases.”
Although Tau is present in other neurodegenerative diseases, such as Alzheimer’s disease, Lewy body dementia and frontotemporal dementia, A/Prof Buckland says that it presents with a unique, irregular pattern of accumulation, pathognomonic to CTE.
Dr Buckland runs the neuropathology service for New South Wales. Brains that need to be examined for a coronial or hospital autopsy are sent to him, which is how he came to examine the brains of two former athletes.
“The first, just on the standard hematoxylin and eosin stain, (and not doing the Tau), this brain had a whole lot of pathology in the hippocampus. You could tell just on the standard H&E stain there was something wrong. That then triggered me to do Tau and a variety of other stains and there it was. I picked up the first Tau stain on the frontal cortex.”
According to Dr Buckland, this was a routine assessment, in which he was not specifically looking for CTE.
“We didn’t have a history of dementia in this case, but as soon as I looked at the brain, I could there was a degenerative process going on. The other case, well, I went looking for it and, once again, I didn’t have to go looking very hard to see CTE specific Tau,” he said.
As far as definitively identifying the causality of CTE, A/Prof Buckland says the evidence is not clear but he adds, “I think it’s important to note that we actually don’t understand a lot about any of the neurodegenerative diseases, including Alzheimer’s disease. We still don’t understand what causes it, how to treat it. The CTE sceptics seem to hold it to a different level of proof before they’ll accept it, compared to any other disease that I’m aware of.”
Dr Buckland considers CTE to have a relationship with repetitive head injury saying, “it may not be the only cause, but clearly it’s highly likely that it’s a significant cause.”
While the causality of CTE is not clear, Dr Buckland told Medical Forum that it, “seems to start in the in the neocortex, particularly the frontal neocortex, then it spreads to the hippocampus in the later stages. Once it’s taken out the hippocampus and associated structures, then it starts to look a lot more similar to Alzheimer’s disease.”
The probability of CTE, particularly for at-risk athletes or soldiers exposed to multiple concussive and sub-concussive impacts, is not clear.
“However, we do know that not everyone that has lots of knocks will get CTE. What we don’t really have a good idea of is the risk. Is it one in 10, one in 100, one in 1000? It’s really hard to say. I always emphasise this to people: just because you’ve had a lot of hard knocks doesn’t mean you’re going to get CTE.”
Primary health assessments
As the majority of concussions are non-sports related, it is surprising that primary health clinicians don’t have a similar standardised tool such as the SCAT5. Although the SCAT5 can be, and is, used in GP consults, Dr Cowen says it is seen as time consuming and only relevant to sports-related concussive injuries.
While the symptomology may be similar to a sporting concussion, the framework for documenting the event is different. As a solution, Dr Cowen is working with HealthPathways WA to develop a guide for assessment of concussion in General Practice.
“The aim of the guideline is to make it relevant to all concussions rather than those that are sports related,” she said.
In lieu of an assessment tool, Dr Cowen has some advice for primary health clinicians dealing with concussion cases.
“Take a history of the impact – is there a clear description of the mechanism of injury available? – and specifically ask for symptoms or third-party observations. Ask about dizziness, headache, nausea, vomiting, neck pain, fogginess or just not feeling right. You should enquire if there was loss of consciousness or a loss of protective action.”
“Where there any observations of posturing, or a blank, vacant or confused look at the time of the event? Has there been any memory impairment? Inquire if they’ve had previous concussions. Ask them to describe themselves before and after the impact.”
The new norms of post-concussion management
The difficulty for patients and clinicians is having to navigate an overabundance of information on concussion and related treatments, many of which are not evidence-based.
“Moreover, it is unclear which treatments are most appropriate for the constellation of concussion symptoms. Thus, evidence-based education as well as treatment and management options are required,” Prof Fitzgerald said.
She added that a graded return to activity after 24 hours was effective for managing and reducing symptoms, then gradually increasing the intensity of the activity, as long as it doesn’t exacerbate the symptoms.
The protocol for managing an individual post-concussion has evolved too. Dr Cowan explains that the previous treatment paradigm of rest until asymptomatic is no longer best practice.
“Sub-symptom threshold exercise can actually help improve symptoms. Historically, we used to say that a patient should rest until completely asymptomatic. Now we know that after 48 hours, we want patients to start doing more activity, but only to a heart rate level that it is below precipitating the worsening of symptoms.”
To measure the ideal heart rate for threshold exercise, an assessment with the Buffalo Concussion Treadmill Test (BCTT) is effective. The BCTT can evaluate post-concussion symptoms and diagnose physiologic dysfunction while differentiating it from other confounding diagnoses.
The BCTT, based upon the Balke cardiac treadmill test, can measure the clinical severity of the concussion and the amount of aerobic exercise that can be safely undertaken. A study that utilised the BCTT found adolescent athletes who sustained concussions while playing sport recovered more quickly when they underwent a supervised, aerobic exercise regimen.
Professor Melinda Fitzgerald and Dr Gill Cowen are investigating the risk-factors leading to delayed recovery from concussion in the Concussion REcovery Study (CREST) at Curtin University and the Perron Institute. They are seeking participants aged 18-65 years; who have sustained a concussion from any cause; have been diagnosed by a medical doctor, and are within seven days of the concussive event.