For years, doctors have known repeated blows to the head can have consequences long after athletes leave the field.
“I think our main concern is the cumulative effect over time, and how much cumulative effect is necessary is what we don't know,” said Dr. Vamsi Chavakula, a neurosurgeon with Sharp HealthCare.
He said chronic traumatic encephalopathy, or CTE, is a progressive brain disease associated with repeated head trauma and it can affect more than football players.
“Combat sports like MMA or boxing, professional football, even soccer with head strikes, as well as members of the military, service members who have been involved in shocks or blasts repeatedly," Chavakula said.
Sarah Banks, a neuropsychologist at UC San Diego Health, has studied CTE for more than a decade. She uses brain autopsies to learn more about the disease.
“We really do rely on the families of these individuals who sadly die with repetitive head injury and dementia to donate their brain so that we can learn more about what happens,” Banks said.
That means diagnosing CTE in a living person is a process of elimination.
“A lot of times, it is kind of a wait and see," Chavakula said. "It takes a minimum of a year to even establish the fact that we've ruled out every other condition. Before we really settle on this type of a diagnosis.”
Doctors first have to rule out brain tumors, Alzheimer's and Parkinson's disease, he said.
Researchers are looking for other ways to detect CTE, including through blood and spinal fluid, but there is no reliable test yet.
Another big question scientists still can't answer is why some players get CTE and some do not, Banks said. A long history of playing contact sports is just one piece of the puzzle.
“It's a risk factor, but it doesn't mean that you will get it,” she said.
The uncertainty is raising questions about how early in life repeated head impacts may matter.
“It's actually a big question that's happening nationally, especially in kids' sports, is, 'Do we let our kids continue to engage in contact sports? Should we delay the age at contact?'” Chavakula said.
For now, researchers are working toward a better understanding of who is most vulnerable. Next year, experts will meet at the National Institutes of Health to discuss new criteria and possible biomarkers that could help make diagnosing CTE during life more certain, Banks said.
