Chronic Traumatic Encephalopathy: The Neuropathological Legacy of Traumatic Brain Injury

Abstract

Almost a century ago, the first clinical account of the punch-drunk syndrome emerged, describing chronic neurological and neuropsychiatric sequelae occurring in former boxers. Thereafter, throughout the twentieth century, further reports added to our understanding of the neuropathological consequences of a career in boxing, leading to descriptions of a distinct neurodegenerative pathology, termed dementia pugilistica. During the past decade, growing recognition of this pathology in autopsy studies of non-boxers who were exposed to repetitive, mild traumatic brain injury, or to a single, moderate or severe traumatic brain injury, has led to an awareness that it is exposure to traumatic brain injury that carries with it a risk of this neurodegenerative disease, not the sport or the circumstance in which the injury is sustained. Furthermore, the neuropathology of the neurodegeneration that occurs after traumatic brain injury, now termed chronic traumatic encephalopathy, is acknowledged as being a complex, mixed, but distinctive pathology, the detail of which is reviewed in this article.

Evidence for Acute Electrophysiological and Cognitive Changes Following Routine Soccer Heading

“…With increased awareness of immediate and late complications of head injuries in sport, in particular the proposed association between exposure to repetitive concussion and late neurodegenerative disease (Hay et al, 2016), there have been considerable efforts to reduce risk of injury and better manage concussions when they do arise (McCrory et al, 2013). Soccer (association football) is acknowledged as the most popular participation sport globally, with routine game-play in soccer involving intentional and repeated head impacts through heading the ball; a skill regularly included in training sessions and from a young age.…”

Long-term health outcomes after exposure to repeated concussion in elite level: rugby union players

“…Finally, death rates from neurodegenerative disease in ex-NFL players have been reported to be three times higher than in the general population8 and greater risk of death late after mTBI has in part been found to be associated with repeated brain injury 9. Autopsy studies in former athletes have fuelled anxieties over CTE as a late outcome of exposure to repeated concussion 10 11. However, few studies have addressed long-term health in living, retired athletes and evidence to support a causative link between TBI and CTE is awaited 12…”

The Effect of Traumatic Brain Injury History with Loss of Consciousness on Rate of Cognitive Decline Among Older Adults with Normal Cognition and Alzheimer’s Disease Dementia

“…Moreover, there is an overlap of symptoms between i) combat personnel with a history of TBI and co-occurring post-traumatic stress disorder and ii) contact-sport athletes with chronic traumatic encephalopathy (CTE) diagnosed at autopsy, which raises the possibility of clinical misdiagnosis [21]. In fact, because CTE is often clinically similar to AD and believed to be partially caused by recurrent head trauma, it is possible that CTE is misdiagnosed as AD in the setting of head trauma [22–24]. A further complication of any study investigating the effects of TBI on AD is the possibility of reverse causation, where undiagnosed AD results in TBI [25].…”