Chronic Traumatic Encephalopathy in Contact Sports: A Systematic Review of All Reported Pathological Cases

Abstract

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease associated with head trauma. Although initially believed to affect only boxers, the at-risk population has expanded to encompass a much wider demographic, including American football players, hockey players, wrestlers, and military veterans. This expansion has garnered considerable media attention and public concern for the potential neurodegenerative effects of head trauma. The main aim of this systematic review is to give a complete overview of the common findings and risk factors for CTE as well as the status quo regarding the incidence and prevalence of CTE. This systematic review was performed using PubMed and MEDLINE and includes all neuropathologically confirmed cases of CTE in the medical literature to date, from the first published case in 1954 to August 1, 2013 (n = 153). The demographics, including the primary source of mTBI (mild Traumatic Brain Injury), age and cause of death, ApoE genotype, and history of substance abuse, when listed, were obtained from each case report. The demographics of American football players found to have CTE are also presented separately in order to highlight the most prevalent group of CTE cases reported in recent years. These 153 case reports of CTE represent the largest collection to date. We found that a history of mTBI was the only risk factor consistently associated with CTE. In addition, we found no relationships between CTE and age of death or abnormal ApoE allele. Suicide and the presence of premorbid dementia was not strongly associated with CTE. We conclude that the incidence of CTE remains unknown due to the lack of large, longitudinal studies. Furthermore, the neuropathological and clinical findings related to CTE overlap with many common neurodegenerative diseases. Our review reveals significant limitations of the current CTE case reporting and questions the widespread existence of CTE in contact sports.

Editorial: Do Orthopaedic Surgeons Belong on the Sidelines at American Football Games?

“…Discoveries about CTE didn't begin with football-the condition first was described nearly 100 years ago as ''dementia pugilistica'' among boxers-and it probably won't end with football, either. Wrestling and ice hockey show up as bit players in the scant research on CTE that is available, and boxing of course is on the list [9]. But because of the combination of the muchhigher number of football players exposed at every skill level and age group (boxing does not even make the top-10 list in that regard [11]), the number of orthopaedic surgeons who cover footballrelated events compared to the muchsmaller number who are involved with boxing and other concussion-producing sports, and the dominance of football in terms of CTE risk in all high-quality analyses on the topic that we have found [8,17], we perceive the problem in that sport merits special attention.…”

Retirement-from-sport considerations following pediatric sports-related concussion: case illustrations and institutional approach

“…96 Athletes with the cognitive variant present primarily with memory and executive function impairments, while those with the mood/behavioral variant often present with symptoms of depression and anxiety as well as aggressive, violent, or disinhibited behavior. To date, the majority of published cases of CTE have occurred in collegiate and professional athletes who have retired from careers in boxing, American football, and hockey; 44,65 however, a limited number of cases of CTE have been also reported among adolescents with a history of repetitive head trauma. 71 While some authors continue to point out the lack of empirical evidence supporting a causal relationship between TBI and CTE, 29,44,94 there does appear to be empirical justification to actively limit individuals' exposure to concussions and subconcussive head injuries during a period of active brain development in children and adolescents.…”

“…68,69 More recently, however, increasing attention has focused on the more serious effects of concussion and subconcussive injuries including abnormalities documented on advanced structural neuroimaging studies and the longterm risk of developing cognitive impairment, mood disorders, and neurodegenerative diseases including chronic traumatic encephalopathy (CTE). 7,29,44,48,49,51,65,70,71,80,94,98,99 To mitigate the risks of more serious brain injury following SRC, experts offer consensus statements containing supervised return-to-play (RTP) guidelines that promote the safe return of athletes to the field of play after concussion symptoms have fully resolved. 4,68,69 These guidelines may reduce the risk of second-impact syndrome, a very rare and poorly defined condition thought to arise from loss of cerebral autoregulation and resultant diffuse cerebral edema.…”

SMART - a tool for assessing patients with discordes of consciousness

“…Jednymi z lżejszych następstw urazu mózgu są zespoły wstrząśnienia albo stłuczenia mózgu [9]. Jeżeli w okresie naprawy układu nerwowego po pierwotnym urazie nie dojdzie do kolejnego, to zazwyczaj uszkodzenia te nie zostawiają po sobie śladu [10]. W przypadku cięższych urazów może dojść do uszkodzenia większych obszarów mózgu włączając w to struktury korowo-podkorowe, międzymózgowie czy śródmó-zgowie [9].…”

“…Some minor brain injuries include concussion and cerebral contusion [9]. If there is no subsequent injury in a period when the nervous system is healing after the primary injury, usually full recovery is observed [10]. In the case of more serious injuries, greater areas of the brain can be damaged, including cortex and subcortex structures as well as diencephalon or mesencephalon [9].…”