Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease that is most often associated with contact sports and military service. CTE is separate from the post-concussive symptoms that are common after a mild brain injury or concussion, as it typically does not present until several years after the injury. CTE is not the accumulation of symptoms from injury, but an accumulation of pathology such as brain atrophy, increased cerebral fluid, and increased protein deposits and tangles. CTE is similar to, but distinct from, other neurodegenerative disorders such as Alzheimer's disease or frontotemporal dementia.
A research review of CTE emphasized that, although all cases of CTE (which can only be confirmed through autopsy) were confirmed to have multiple brain traumas, there is evidence that multiple traumas and CTE can occur even in those without a reported history of concussion. This can include those who are exposed to a large number of hits to the head without symptomatic concussion.
In addition, concussion that occurs during childhood may put an individual at greater risk of developing CTE later. Although this theory has not been confirmed, there is evidence that a blow to a developing brain can produce longer lasting deficits and more catastrophic consequences than in adults.
Baugh CM, Stamm JM, Riley DO, et al. Chronic traumatic encephalopathy: Neurodegeneration following repetitive concussive and subconcussive brain trauma. Brain Imaging and Behavior. (May 2012).