The science behind the brain disease CTE is less settled than you might think

With chronic traumatic encephalopathy, or CTE, making news across the country, a pair of MUSC Health doctors want people to know that the science behind the brain disease is evolving. There are still a lot of unknowns. 

And they don’t want people to get CTE mixed up with concussions, which are treatable. MUSC Children’s Health has a Concussion Clinic and a Saturday morning injury clinic for children who were hurt playing sports on Friday night.

“Unfortunately, at least from my perspective, CTE is a bit overhyped in the media. We know relatively little about CTE and the potential symptoms that may be related to it,” said Nick Milano, M.D. He’s a cognitive behavioral neurologist who has treated patients suffering from head injuries.

Overhyped? That may surprise some people. After all:

• A Boston University study of 376 brains from former National Football League players found 345 had CTE – more than 91%.
• A Harvard study found about 1 in 3 living former NFL players believes he has CTE. Those who did have CTE said they had more cognitive problems, depression, suicidal thoughts and other problems than players who didn’t think they had it.
• Other athletes who took hits to the head have been diagnosed after death with CTE, along with military veterans.
• A man with mental illness who’d played high school football recently opened fire at the building housing NFL headquarters. He accused the league of hiding the dangers to athletes’ brains and asked that his brain be checked for CTE. The medical examiner’s office found that he did have the disease.

But Eugene Hong, M.D., a sports medicine specialist and chief physician executive at MUSC Health, agreed with Milano. He said CTE is a serious concern, but people are making assumptions without proper evidence. 

“I think one of our roles is to present the science. Here's what we know; here's what we don't know. Here's what we think we know. And try to add perspective rather than contribute to the hype,” Hong said.

He and Milano have the expertise to back that up. Milano not only treats patients with neurological disorders but also studies brain mechanisms that lead to thinking and behavior. Hong, meanwhile, has an international role in sports medicine as chief medical officer for World Lacrosse and serves in the same role for Clemson Athletics. Both work at the Medical University of South Carolina, an academic medical center serving the entire state. 

What doctors and scientists know

“I'm definitely not saying that CTE doesn't exist or doesn't cause any symptoms. But what I'm really saying, and what I tell my patients is, we don't know what those symptoms are yet, or how to diagnose CTE in a living person. This has only been heavily researched for the last 20 years or so, and there's a lot left to learn about what we call the clinicopathological correlation,” Milano said, referring to links between what’s seen in the brain and a person’s symptoms.

“Chronic traumatic encephalopathy is a pathologic diagnosis, meaning it is based on autopsy findings of specific types of abnormal proteins that are found in the brain. In CTE, these are an accumulation of the abnormal protein tau. And they're in specific spots of the brain in CTE, which is different than the tangles of tau you might see in Alzheimer's disease,” he said.

“The research at the moment suggests that repetitive sub-concussive head injuries may lead to the pathological changes in the brain consistent with CTE. Repeated small hits to the head and brain, over and over again, over many years. This is still a theory or a hypothesis, but that's the idea.”

Sub-concussive injuries

The term he used, sub-concussive, makes an important distinction – one that Hong agreed with. “The current research has not proven a direct cause-and-effect relationship between concussions and CTE, and sports medicine physicians generally agree that more research is needed to better understand this issue,” Hong said.

 

The Centers for Disease Control and Prevention agrees. “Research suggests CTE is associated with long-term exposure to repeated hits to the head (head impacts). There is no strong evidence that shows that getting one or more concussions (or other mild traumatic brain injuries) or occasional hits to the head leads to CTE,” the CDC says on its website.

“If you think about the millions of people that have played football at some point in their lives, we do not have a nation of brain-damaged people walking around,” Hong said. 

“From a public health perspective, we do want people of all ages and abilities to engage in regular exercise and sports activities. There are clear benefits to being active. So one challenge for health care providers is to separate hype from science when it comes to being a source of trusted information for patients, families and communities.”

“I absolutely believe it’s important to protect your brain, trying to minimize the risk of concussions,” Milano said. “Having the proper protocol on when you should go back into play. But concussions are not what is believed to cause CTE. So I think those two things should be split.”

More research needed on symptoms

Something else he said is important to consider is the fact that scientists aren’t sure what symptoms are caused by CTE. There’s anecdotal evidence from family members of people with CTE involving changes to their loved ones’ moods and thinking, but research hasn’t confirmed that link.

 

Research also hasn’t determined whether CTE is progressive, Milano said. “And so there's just a lot of open questions, and I think that's where everything has gotten way ahead of itself. You'll see doctors diagnosing people with CTE just because they played football for five years. In reality, these symptoms people are describing can oftentimes be explained by alternative causes.”

Those alternative causes include Alzheimer’s disease, frontotemporal dementia, substance abuse and other psychiatric disorders, Milano said.

Going forward

He and Hong are glad that more research on CTE is underway. Their hopes include the possibility of being able to diagnose it in living people, and if it is progressive, figuring out how to slow or stop that progression. In the meantime, Milano hopes the public absorbs news coverage of CTE with a better understanding of where the science stands. 

“I think a lot of times when people are said to have CTE, or even if they have an autopsy that shows pathologic findings consistent with CTE, that does not mean that anything they were doing was related to that or not. I think that's something that we're still really learning about.”