Concussions, also known as mild traumatic brain injuries (mTBI), have long captivated the interest of medical researchers and the general public alike. These injuries, often caused by a sudden blow to the head, have historically been viewed as transient and relatively benign. However, with advancements in neuroscience and technology, our understanding of concussions has evolved significantly. In this blog, we will explore the top 5 most important discoveries in neuroscience related to concussions, shedding light on the paradigm shifts that have occurred in recent years.
Recognition of Sub-concussive Hits and Cumulative Effects
Traditionally, concussions were understood as acute injuries with immediate and noticeable symptoms. However, the first major paradigm shift in concussion neuroscience occurred with the realization that it's not just the major blows to the head that pose a risk. Researchers began exploring the effects of repetitive sub-concussive hits, which are minor impacts that do not result in clinical symptoms but can still cause damage to the brain.
Studies conducted in the early 2000s, such as the work by Guskiewicz et al. (2007), and Baugh et al. (2012), were instrumental in highlighting the cumulative effects of sub-concussive hits over time. These studies focused on athletes participating in contact sports like football and soccer, where repetitive head impacts are common. The findings revealed that even without apparent symptoms, repeated sub-concussive hits could lead to neurodegenerative changes in the brain later in life.
For example, Guskiewicz et al. (2007) studied retired professional football players and found an association between recurrent concussions during their playing careers and late-life cognitive impairment. Similarly, Baugh et al. (2012) reported on chronic traumatic encephalopathy (CTE), a progressive neurodegenerative condition associated with repeated concussions and sub-concussive hits.
This discovery raised concerns about the long-term consequences of participating in contact sports and sparked further research into prevention and management strategies. As a result, athletes, coaches, and sports organizations now have a heightened awareness of the importance of reducing all types of head impacts to protect brain health.
Biomarkers for Concussion Diagnosis and Management
Diagnosing concussions has long been a challenge, as it relied heavily on subjective symptoms reported by the injured individual. However, another ground breaking discovery in concussion neuroscience came with the identification of reliable biomarkers for diagnosing and managing concussions.
Researchers started investigating specific molecules in the blood or cerebrospinal fluid that could indicate the presence and severity of brain injury. Studies like Papa et al. (2012) and Shahim et al. (2017) played a crucial role in establishing the significance of biomarkers in the field of concussion management.
Papa et al. (2012) conducted a systematic review of clinical studies examining biomarkers of brain injury in athletes after sports-related concussions. They found that biomarkers such as tau protein, glial fibrillary acidic protein (GFAP), and neurofilament light chain (NFL) could be detected shortly after a concussion, allowing for objective measures to assess brain injury.
Similarly, Shahim et al. (2017) conducted a study with professional ice hockey players and demonstrated the usefulness of blood biomarkers in diagnosing brain injury following a sports-related concussion. The ability to objectively measure brain injury through biomarkers has transformed the way concussions are diagnosed, monitored, and managed. It has also facilitated safer return-to-play decisions and led to a more comprehensive understanding of concussion recovery.
Neuroimaging and Structural Changes in the Brain
Concussions involve complex physiological changes in the brain, and neuroimaging techniques have played a crucial role in visualizing these alterations. Advanced imaging methods such as magnetic resonance imaging (MRI), diffusion tensor imaging (DTI), and functional MRI (fMRI) have enabled researchers to observe structural and functional changes in the brain following a concussion.
Ling et al. (2012) conducted a study to investigate biomarkers of increased diffusion anisotropy in semi-acute mild traumatic brain injury. Their findings showed that concussions could lead to alterations in white matter integrity, especially in regions responsible for cognitive functions and emotion regulation. This discovery opened new avenues of research into understanding the underlying mechanisms of concussion-related symptoms and cognitive deficits.
Furthermore, Shenton et al. (2012) conducted a comprehensive review of MRI and DTI findings in mild traumatic brain injury. Their study shed light on the long-term effects of concussions, demonstrating persistent abnormalities in white matter even after the acute phase of the injury. This highlighted the importance of continued monitoring and management of concussed individuals to prevent long-term consequences.
Resting-state fMRI studies have also contributed to the understanding of concussions by examining altered connectivity patterns in the brain following injury. These studies have shown disrupted functional connectivity between brain regions involved in cognition, memory, and emotion, providing further insight into the cognitive and emotional sequelae of concussions.
Sex Differences in Concussion Susceptibility and Outcomes
Another pivotal discovery in the realm of concussion neuroscience was the recognition of sex differences in susceptibility to concussions and their subsequent outcomes. Early research had predominantly focused on male athletes, leading to a biased understanding of concussions.
Covassin et al. (2012) conducted a study to examine sex differences in the incidence of concussions among collegiate athletes. Their findings revealed that female athletes may experience higher concussion rates compared to their male counterparts. Additionally, Nelson et al. (2016) conducted a head-to-head study of three computerized neurocognitive assessment tools (CNTs) and reported on the importance of accounting for sex differences when assessing cognitive function after concussion.
Hormonal and anatomical differences between men and women may contribute to variations in concussion susceptibility and recovery. These findings emphasized the need for sex-specific concussion management protocols to ensure tailored care and appropriate return-to-play guidelines for both male and female athletes.
Long-term consequences: Chronic Traumatic Encephalopathy (CTE)
Perhaps, the most groundbreaking and impactful discovery in recent years has been the link between concussions and chronic traumatic encephalopathy (CTE). CTE is a progressive neurodegenerative condition associated with repeated head injuries, commonly found in athletes and individuals with a history of concussions, and was discovered by Dr Bennet Omalu (Omalu et al., 2005; you may have seen the movie of this this story starring Will Smith: ‘Concussion’).
McKee et al. (2009) conducted further work in this area, studying the brains of deceased athletes, including football players, who had experienced multiple concussions during their careers. The researchers discovered a unique pattern of abnormal tau protein accumulation in the brain, leading to the development of CTE. This discovery has raised serious concerns about the long-term effects of concussions and the potential for devastating consequences in later life.
Mez et al. (2017) expanded on this work by conducting a clinicopathological evaluation of chronic traumatic encephalopathy in players of American football. Their study further solidified the link between concussions and CTE, prompting widespread media coverage and public awareness.
The revelation of CTE as a potential consequence of concussions has had profound implications on sports safety regulations, concussion management, and public awareness campaigns. As a result, significant efforts have been made to improve sports safety protocols and encourage early diagnosis and appropriate management of concussions to minimize the risk of long-term brain damage.
Summary
The landscape of concussion neuroscience has undergone remarkable transformations over the past few decades, thanks to ground breaking research and technological advancements. From recognizing the cumulative effects of sub-concussive hits to understanding the long-term consequences of CTE, these discoveries have reshaped our understanding of concussions and their impact on the brain.
As the field continues to evolve, it is essential to remain informed about the latest research, as it holds the promise of improving diagnosis, management, and prevention strategies for concussions in the future. By building on these foundational discoveries, researchers are paving the way for a safer and more comprehensive approach to concussions, benefiting athletes, military personnel, and individuals of all ages who are at risk of sustaining brain injuries.
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Daniel Glassbrook, PhD
Daniel is a sports scientist and researcher, previously working as the first team sports scientist for the Newcastle Falcons Rugby Club, and a postdoctoral researcher in sports related concussion at Durham University.
References
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Covassin, T., Swanik, C. B., & Sachs, M. L. (2003). Sex differences and the incidence of concussions among collegiate athletes. Journal of athletic training, 38(3), 238.
Guskiewicz, K. M., Marshall, S. W., Bailes, J., McCrea, M., Cantu, R. C., Randolph, C., & Jordan, B. D. (2005). Association between recurrent concussion and late-life cognitive impairment in retired professional football players. Neurosurgery, 57(4), 719-726.
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Ling, J. M., Pena, A., Yeo, R. A., Merideth, F. L., Klimaj, S., Gasparovic, C., & Mayer, A. R. (2012). Biomarkers of increased diffusion anisotropy in semi-acute mild traumatic brain injury: a longitudinal perspective. Brain, 135(4), 1281-1292.
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Omalu, B. I., DeKosky, S. T., Minster, R. L., Kamboh, M. I., Hamilton, R. L., & Wecht, C. H. (2005). Chronic traumatic encephalopathy in a National Football League player. Neurosurgery, 57(1), 128–134.
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