Chronic traumatic encephalopathy, or CTE, is a neurodegenerative disease that has been found at an alarming rate among former professional football players. A 2017 study from JAMA found 110 of 111 deceased NFL athletes had CTE. The disease also affects military veterans who suffered brain injuries since Sept. 11, 2001.
The conversation surrounding CTE has primarily focused on the role concussions play in the accumulation of the tau protein in blood vessels in the brain, which can cause cell death, dementia and cognitive impairments.
But researchers from the Boston University School of Medicine have found evidence of CTE in young athletes’ brains without signs of concussion, indicating the condition is directly tied to head impacts—but not necessarily concussive hits.
The results were published online Thursday, Jan. 18, in Brain.
First, researchers—including Lee Goldstein, MD, PhD, and Ann McKee, MD—examined four brains from teenage subjects who had sustained head injuries one, two, 10 and 128 days before death. Analysis showed early-stage CTE in one and abnormal accumulation of tau in two others. Brains from four control-matched athletes without recent head injury did not show such pathology.
The team then used dynamic contrast-enhanced MRI to study mice with head injuries. They discovered such impacts caused leaky blood vessels and brain inflammation.
"The same brain pathology that we observed in teenagers after head injury was also present in head-injured mice. We were surprised that the brain pathology was unrelated to signs of concussion, including altered arousal and impaired balance, among others. Our findings provide strong causal evidence linking head impact to TBI and early CTE, independent of concussion," wrote Goldstein, the corresponding author of the study. "The results may explain why approximately 20 percent of athletes with CTE never suffered a diagnosed concussion."
Researchers then used computer simulations and mechanical models to show factors that cause concussion may be distinct from those that result in CTE.
"To prevent the disease, you have to prevent head impact—it's hits to the head that cause CTE," Goldstein added.
Such a study could have far-reaching implications in sports—for professionals, children and parents—and for medicine as it grapples with properly treating brain injury. The NFL Players Association released a statement Thursday.
“We stood firm against an [expanded] 18-game schedule and insisted on changes to the work rules in 2011 to limit contact of all types to protect players, and this study reinforces we made the right decision,” according to the NFLPA. “We have been in close touch with the researchers at Boston University, who are also members of our Mackey-White Health and Safety committee, and we will review this study carefully to consider future changes to improve the health and safety of our players.”
But head trauma is a real concern for many people who don’t play contact sports.
"Intimate partners who are having repetitive head injuries—domestic violence victims, homeless, children at risk, people in our prison systems. [With] all of these people, we need to take the focus off concussion and find out if they have injured brains," Goldstein said, in an interview with NPR.
The full study is available here.