Reports in the past few years on the devastating effects of head injuries among football players have raised awareness of chronic traumatic encephalopathy, or CTE.

This neuro-degenerative disease is believed to be caused by repetitive, severe brain injuries. In such cases, a protein called tau forms clumps that slowly spread throughout the brain and eventually kill brain cells. There is no cure.

“It was colloquially known as being ‘punch drunk,’ and was previously, more formally known as dementia pugilistica,” says Daryl W. Thompson, a neurologist and medical director of Ascension St. John Heyman Stroke Center in Tulsa. “The onset is typically insidious and it may have behavioral and psychological manifestations, like memory deficits and paranoia, as well as difficulty with speaking and coordination.

“The two groups … at risk are professional athletes in contact sports as well as individuals in the military.”

Thompson notes that people with the genetic risk factor of the APOE gene (apolipoprotein e4 allele) are also particularly vulnerable.

Zohny S. Zohny, a neurosurgeon with Saint Francis Health System’s Warren Clinic in Tulsa, says several risk factors are associated with CTE, but determining who will develop the disease isn’t possible.

“At this time, there is no blood test or neuro-imaging test, such as a CT scan or MRI of the brain, that can diagnose CTE,” Zohny says. “CTE can only be diagnosed … after death with an autopsy.”

Many people experience concussions during their lifetimes, but the consistency of trauma has been found to be the main cause of the disease.

“CTE occurs as a result of repetitive head injuries over a number of years from contact sports such as football or soccer, or activities that expose an individual to repetitive head injuries (such as military service or domestic violence), not after just one or two concussions in life,” Zohny says.

At the forefront of research is Boston University’s CTE Center, which examines long-term consequences of repetitive brain trauma in athletes and military personnel. The CTE Center, which has garnered national attention for investigating the prevalence of CTE in football players, recently reported that the risk and severity of developing CTE increases with the number of years playing football.

 “For every year of absorbing the pounding and repeated head collisions that come with playing American tackle football, a person’s risk of developing CTE … increases by 30 percent,” the CTE Center states. “And for every 2.6 years of play, the risk of developing CTE doubles. These new findings from an analysis of the brains of 266 deceased amateur and professional football players – reported in Annals of Neurology by a team of researchers from the CTE Center – are the first to quantify the strength of the link between playing tackle football and developing CTE.”

In 2017, the Journal of the American Medical Association reported the CTE Center’s study on the brains of 202 deceased football players, 111 of whom played in the National Football League. All but one of those NFL players had CTE.

Jesse Mez, a lead author of the CTE Center study and director of Boston University’s Alzheimer’s Disease Center, says these findings can help players, family members and physicians to make informed decisions about certain sports. The study also moves doctors a step closer to diagnosing CTE while a patient is alive, which Mez says is “critical for testing potential therapies and for guiding clinical care.”