Impact? The Ongoing Investingation of Concussion and Neurodegenerative Disease

Author: Olivia Kehoe
Artist: Zach Ng
Editor: Rachel Grosberg

Contact sports are increasingly attracting attention: not from spectators, but from the scientific community. Once considered an injury you could “rub some dirt on” and return to the field, repetitive head impacts are now considered to be the cause of a neurological disease afflicting many contact sports athletes. What has emerged over the last decade of research is a contentious link between repetitive head injury, and the development of early symptoms of dementia. At the heart of this issue are ex-professional athletes who have voiced their experiences of developing symptoms in the years after their retirement, some ultimately leaving their brains to research. While at first lone voices, stifled by the stigma of their conditions and denial by powerful sports governing bodies, this issue stands at a tipping point. The largest biomedical research agency, the US National Institute of Health, has now formally recognised a causal link between repetitive head injuries and Chronic Traumatic Encephalopathy (CTE), a distinct neurodegenerative disease.

Where it all began

Concern about the long-term effects of repetitive brain injury has existed in medical literature for at least a century. Tracing back to 1920s boxing, the term ‘punch drunk’ was coined in relation to prize fighters who presented with altered behaviour. Memory loss, confusion, a Parkinsonian gait and dramatic changes in personality, such as higher levels of aggression, were among the symptoms progressively observed in individuals sustaining ‘considerable head punishment’ during matches. However, there remains debate about whether historical reports of repetitive brain injury, and modern CTE characterisations refer to the same condition. 

Modern CTE has its roots in a ground-breaking paper published by Dr Bennet Omalu and colleagues in 2005, detailing the autopsy of a retired professional American football player with distinct neuropathological features in their brain that were similar, but not identical, to features observed in Alzheimer’s patients. Among the cases published since then include athletes from internationally popular sports such as rugby, football, ice hockey, boxing and wrestling, as well as non-athlete groups such as military veterans with blast exposure and victims of physical abuse. An array of clinical symptoms and associated neuropathology have followed to characterise this novel disease. 

Written in pathology

The hallmark of CTE in brains post-mortem is the abnormal phosphorylation and accumulation of the protein tau into neurofibrillary tangles that clog up neurons and astrocytes. General atrophy (shrinkage) of the cortex and enlargement of the brain’s ventricles are also characteristic, and similar to the shrinking seen in other forms of dementia. Altered mood, movement and behavioural disorders have also been reported and related to CTE. Yet crucially, these individuals developed cognitive symptoms much younger than is typical for age-related dementias, such as Alzheimer’s disease.   

What makes CTE particularly intriguing, is that it is emerging as a neurodegenerative disease with an environmental aetiology. This means that external events, such as head impacts, could be the trigger for disease, rather than genetic origins. 

Ongoing Research

One of the biggest debates in the area of CTE is if it’s even a concept at all. Many ask the question: “Can head injuries from contact sports really lead to early onset neurodegeneration?” Those driving the research, such as Dr. Anne McKee of Boston’s CTE Centre, maintain that there is an irrefutable correlation, while others stand strongly in denial. Sceptics cite the lack of reliable control groups, confounding factors in the studies that may introduce bias, the fact that diagnosis is so far only possible post-mortem (often meaning a reliance on retrospective interviews with next-of-kin), and the lack of a clear mechanism between head trauma and the onset of clinical symptoms. Despite the announcement from the NIH, alongside efforts to understand the nature and prevalence of the disease, uncertainty remains on many other fronts. How do later-life symptoms progress? What is the relationship between pathology in the brain and clinical presentation? Is there overlap with other neurodegenerative diseases and comorbidities?

Media Controversy

Characterising CTE has become not merely the pursuit of medical understanding, but an increasingly high-profile political battle fought between researchers, athletes and governing bodies such as the National Football League (NFL). The spotlight has been on the latter, not least for the book, League of Denial, and its film adaptation starring Will Smith. Told as the story of a public health crisis, such narratives have shaped societal understanding of CTE in relation to sport. Given the influence of NFL as a multi-million dollar industry, it would appear necessary to ensure that research remains independent of external bodies, so that political or financial interests do not bias future studies or the researchers working on them.

A caution for more balanced and unbiased reporting was not made more forthcoming than in an article in The Lancet, Neurology, titled ‘Primum non nocere’ (Latin= do no harm). In the article, researchers of brain injury and neurodegeneration voiced concerns about the narratives and tone of the coverage on CTE cases by media outlets in the past decade. Moreover, they emphasised that where much of the characterisation so far of clinical and pathological outcomes is still in its infancy, this nuance and uncertainty is often neglected in media reporting. Clarity in communicating the nature of this relationship is crucial for public safety, by developing a better understanding of risk, prevention strategies and the possibility for future therapeutic targets.

In Harm’s Way

In the absence of any disease-modifying treatments, prevention remains the most effective strategy for managing CTE. Public perception and popular reporting of the disease will thus prove increasingly important for developing and implementing preventative measures and policy changes in contact sport. Suggestions for protecting at-risk groups include introducing safe practice techniques in game play, while also penalising dangerous tackles or manoeuvres. More broadly, this requires a cultural shift in the way that sports and activities involving repetitive head impacts are perceived, which can be achieved through consideration of the socio-political and financial implications surrounding diagnosis. Most importantly, an environment among players, coaches, physicians and the public that prioritises players’ safety above all may promote better transparency in reporting symptoms. This must start in school and youth league sports, all the way to understanding the incentives around injured professional athletes wanting to return to the field.

Given how common concussive injuries and head impacts are, those in the line of fire deserve to know the risks they face when stepping onto the field. With a causal link now recognised, it is undeniably important for research to push on, to prevent future cases of CTE.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s