Let’s imagine a once astute, world-renowned fighter, a decade past his prime, struggling to recall the names of his family members, whilst simultaneously suffering from unexplainable mood swings. Once referred to as being “punch drunk”, this tragic condition is now known as Chronic Traumatic Encephalopathy (CTE). Previously thought to affect boxers solely, CTE is now recognised as a degenerative brain condition affecting a wide range of individuals exposed to repeated head trauma. As our knowledge of CTE expands, uncovering its mysteries and protecting those at risk is vital.
HOW DOES CTE AFFECT THE BRAIN?
The structure and function of a healthy brain rely on a delicate balance of neurons (nerve cells) and their connections, supported by glial cells. These cells work together to transmit signals and maintain brain health. 1 In contrast, the repeated trauma to the brain found in CTE triggers a sequence of harmful effects. 2
These injuries cause immediate damage, such as bruising and torn blood vessels. Over time, however, the more insidious effects emerge. One of the major characteristics of CTE is the accumulation of abnormal proteins called tau. 2 Tau proteins normally stabilise microtubules (tiny tubes in the brain), which are essential for the transport of nutrients and other substances within neurons. 2
In CTE, tau proteins become abnormally altered. 2 This causes them to clump together inside neurons, forming neurofibrillary tangles. These tangles disrupt the normal function of neurons, impairing their ability to communicate and eventually leading to their death. As more neurons are affected, widespread brain tissue degeneration occurs, particularly in areas vulnerable to trauma, such as the frontal and temporal lobes. 2
These pathological changes are distinct from other neurodegenerative diseases like Alzheimer's disease, despite some overlap in symptoms, and are a key focus in understanding and diagnosing CTE. 3
WHAT ARE THE SYMPTOMS OF CTE?
CTE causes a wide range of symptoms that can significantly impact daily life. These include memory loss, problems with thinking, impulsive behaviour, aggression, depression, emotional instability, personality changes, suicidal thoughts or behaviours, issues with walking and balance and trouble with speech. 4 Symptoms of CTE typically start gradually and tend to take years before becoming severe. In most cases, symptoms of CTE typically manifest several years after the initial head injuries. 4
WHAT ARE THE RISK FACTORS OF CTE?
Current research indicates that the main risk factor for CTE is repetitive hits to the head. 5 This is more prevalent in people who partake in contact sports such as boxing, martial arts, and hockey. 6 CTE is also seen in individuals who are a part of the military as a result of blasts or combat-related trauma to the head. 6 This risk also extends to people with a history of multiple concussions or repetitive head injuries regardless of the environment. It is thought that genetics may potentially play a role in determining susceptibility to CTE, however, more research is needed before a genetic risk factor can be concluded. 7
DISCOVERY OF CTE
CTE was first described in the 1900s when it was observed in boxers and described as 'punch drunk' syndrome. 8 The condition was initially characterised by symptoms of cognitive and motor decline following repeated head injuries. However, the modern understanding of CTE began to form in the early 2000s, largely due to the pioneering work of Nigerian-American forensic pathologist Dr. Bennet Omalu. 8 Dr. Omalu identified distinct brain changes in American football players, particularly the accumulation of tau protein, and published his findings in 2005. His work highlighted the link between repeated head trauma and progressive brain disease, bringing widespread attention to CTE and sparking a broader investigation into its prevalence in other sports and activities. His discoveries have since led to significant research and debate, raising awareness about the long-term consequences of repeated head injuries. 8
DIAGNOSIS OF CTE
The diagnosis of CTE remains a challenge as a definitive diagnosis is currently only available through a post-mortem autopsy of the brain. 9 Although CTE cannot be confirmed before death, experts can make presumptive diagnoses based on symptoms and physical and neurological examination. 9 Neurological and cognitive assessments may be conducted to assess memory, behavioural change and thinking ability. 9 Imaging techniques such as computed tomography (CT) scans, magnetic resonance imaging (MRI) scans, and positron emission tomography (PET) scans are being used to explore the brain changes found in CTE to find potential biomarkers. 9
SUMMARY
CTE is a brain condition caused by repeated head injuries, causing symptoms such as memory loss, cognitive decline, and emotional instability. Initially observed in boxers, CTE is now known to affect athletes in contact sports, military personnel, and more broadly anyone exposed to repeated head trauma. The diagnosis of CTE remains challenging, requiring post-mortem examination, however, ongoing research aims to identify biomarkers for earlier detection.
REFERENCES
National Institute of Neurological Disorders and Stroke. Brain Basics: Know Your Brain | National Institute of Neurological Disorders and Stroke [Internet]. www.ninds.nih.gov. 2023. Available from: https://www.ninds.nih.gov/health-information/public-education/brain-basics/brain-basics-know-your-brain
McKee AC, Stein TD, Kiernan PT, Alvarez VE. The Neuropathology of Chronic Traumatic Encephalopathy. Brain Pathology [Internet]. 2015 Apr 23;25(3):350–64. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4526170/
Turner RC, Lucke-Wold BP, Robson MJ, Lee JM, Bailes JE. Alzheimer’s disease and chronic traumatic encephalopathy: Distinct but possibly overlapping disease entities. Brain Injury [Internet]. 2016 [cited 2020 Oct 22];30(11):1279–92. Available from: https://pubmed.ncbi.nlm.nih.gov/27715315/
Antonius D, Mathew N, Picano J, Hinds A, Cogswell A, Olympia J, et al. Behavioral Health Symptoms Associated With Chronic Traumatic Encephalopathy: A Critical Review of the Literature and Recommendations for Treatment and Research. The Journal of Neuropsychiatry and Clinical Neurosciences [Internet]. 2014 Jan;26(4):313–22. Available from: https://pubmed.ncbi.nlm.nih.gov/26037854/
NHS. Chronic Traumatic Encephalopathy [Internet]. NHS. 2019. Available from: https://www.nhs.uk/conditions/chronic-traumatic-encephalopathy/
Chronic Traumatic Encephalopathy (CTE) [Internet]. Alzheimer’s Disease and Dementia. 2023. Available from: https://www.alz.org/alzheimers-dementia/what-is-dementia/related_conditions/chronic-traumatic-encephalopathy#:~:text=Those%20at%20greatest%20risk%20for
Abdolmohammadi B, Dupre A, Evers L, Mez J. Genetics of Chronic Traumatic Encephalopathy. Seminars in Neurology [Internet]. 2020 Jul 26 [cited 2020 Dec 20];40(04):420–9. Available from: https://pubmed.ncbi.nlm.nih.gov/32712945/
Cantu RC, Bernick C. History of Chronic Traumatic Encephalopathy. Seminars in Neurology. 2020 Aug;40(04):353–8.
Cleveland Clinic. Chronic Traumatic Encephalopathy (CTE) | Cleveland Clinic [Internet]. Cleveland Clinic. 2022. Available from: https://my.clevelandclinic.org/health/diseases/17686-chronic-traumatic-encephalopathy-cte
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