Mild Chronic Traumatic Encephalopathy Neuropathology in People With No Known Participation in Contact Sports or History of Repetitive Neurotrauma

Iverson GL, Luoto TM, Karhunen PJ, Castellani RJ. J Neuropathol Exp Neurol. 2019 Jul 1;78(7):615-625.

Take Home Message: CTE is present in people without a history of contact sports, repeated concussions, or subconcussion head impacts.

The media has propagated a claim that chronic traumatic encephalopathy (CTE) afflicts people with a history of contact sports and repetitive concussions, subconcussion head impacts, or both. These claims are largely based on case studies/series of athletes or military veterans. However, there is growing evidence that CTE may be present among people with and without a history of contact sport participation. Therefore, the authors applied the consensus criteria for neuropathology of CTE to an autopsy case series of 8 men (age range 54 to 82 years) without a history of participation in contact or collision sports (2 had a history of a traumatic brain injury). From each case, organ samples were collected to determine the primary cause of death. A neuropathologist who was unaware of the person’s age, personal history, and clinical history examined the brain samples to assess macroscopic (ischemic contusions, hemorrhage) and microscopic (extent of abnormal tau protein and neurofibrillary tangle accumulation) abnormalities. Lastly, electronic medical records and family surveys were collected to determine family and general medical history (drug problems, brain injury, sport participation history). The macroscopic assessment revealed no specific irregularities in 7 of the 8 patients. One out of the two cases with a history of a single traumatic brain injury had CTE pathology. Furthermore, 5 out of 6 cases without a history of brain injury meet the criteria for CTE.

The authors found that 75% of the small case series met the neuropathological criteria for CTE, but none of the men had a known history of participation in contact sports or had a history of multiple concussions. This is important because some researchers have asserted that CTE is a pathology that only afflicts those involved in contact sports; however, CTE may affect those with neurodegenerative diseases or drug addictions. Finding CTE among people without a history of contact sport participation is consistent with two larger studies that have found CTE among 1 to 6% of people (see below). It remains uncertain if these signs of CTE have any affect on the patient (dementia, neurocognitive dysfunction), or if this is a common sign of aging in the brain. Larger prospective studies are needed to understand the risk factors for CTE and how we should design prevention strategies before we make haphazard recommendations. Currently, medical professionals should continue to educate athletes, parents, and coaches about the risks of not reporting concussions and proper management and return to play protocols, but also address concerns about CTE that could lead them to make unhealthy decisions about not participating in sport. It is vital that athletes and parents understand that CTE is found in the general population and despite common media attention we are only beginning to understand who is at risk for CTE and why.

Questions for Discussion: How can we best educate athletes, parents, and coaches about CTE?

Written by: Jane McDevitt

Reviewed by: Jeffrey Driban

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