Pauline Anderson

April 13, 2016

Mounting evidence underlines just how risky playing professional football can be. Preliminary study results show that almost 43% of retired National Football League (NFL) players showed traumatic brain injury (TBI) according to sophisticated neuroimaging. The longer they played, the more at risk they were.

This is the first time that so many living ex-football players have been assessed using diffusion tensor imaging (DTI), said lead researcher, Francis X. Conidi, MD, Florida Center for Headache and Sports Neurology, Port St Lucie.

An advanced form of neuroimaging, DTI enables three-dimensional visualization and characterization of white matter and is an objective biomarker of TBI, Dr Conidi said.

"This is big, really big; it's another piece of this large puzzle," he said. "It's really the first objective type of evidence of TBI that we're seeing in large numbers of living players — not CTE [chronic traumatic encephalopathy] data when they're dead."

The results were released April 11. Dr Conidi will present his findings in full at the upcoming American Academy of Neurology (AAN) 2016 Annual Meeting in Vancouver, British Columbia, Canada.

Alternative Explanation

There's growing concern among professional football players and parents of kids participating in the sport that the hits, tackles, and resulting concussions that have for years been accepted as part of the game may lead to dementia or CTE later in life.

These new findings give players an "alternative explanation" for their neurocognitive deficits and behavioral problems, said Dr Conidi. They also could provide "an actual link to CTE because there is evidence out there that tau deposition occurs in white matter," he added.

But that's not to say that all players with TBI will go on to develop CTE or other neurodegenerative disorders, such as Alzheimer's disease (AD) and Parkinson's disease (PD), he stressed.

The new analysis included 40 retired players, mean age 35.85 years. They had put in an average of 7 years in the NFL and had an average of just over 8 concussions, with 31% reporting numerous subconcussive hits. All had normal neurologic examinations.

The mean Mini-Mental State Examination (MMSE) score of these players was 27.3 and their mean Clinical Dementia Rating (CDR) score was 0.5 (the CDR scale goes from 0 to 3, with 3 indicating severe dementia).

Of the total, 42.5% of the former players had positive DTI MRIs — objective evidence of traumatic brain injury.

DTI, which shows movement of water through white matter, is a powerful tool that can visualize this brain region and indicate damage. "DTI is now considered the standard neuroimaging technique for TBI," said Dr Conidi.

Researchers also looked at conventional MRI. They found that 30% of the participants had evidence of traumatic axonal injury, another biomarker for TBI.

Intensive "paper and pencil" neuropsychological testing uncovered several significant deficits, said Dr Conidi. These included abnormalities in attention and concentration (42%), executive function (50%), learning/memory (44.7%), and spatial/perceptual function (23.7%).

Although it appeared that most players with positive DTI findings had neuropsychological deficits, the researchers could not statistically correlate the DTI MRI findings with the neuropsychological data.

There was a weak statistical correlation with the number of years played in the NFL and the likelihood of having a positive DTI finding (P = .0491).

Interestingly, there was an inverse correlation between the number of years played and the number of concussions, and no correlation was seen between the number of concussions and positive DTI.

Dr Conidi stressed that "there is no such thing as a mild concussion" and that "a concussion is a concussion is a concussion." But he noted that players with the highest number of positive DTI results were offensive and defensive linemen.

"We see that the individuals who are in the trenches, who are the blue collar guys, banging each other, play in and play out, are really having issues."

It's not clear from the study whether early exposure to football — that is, in high school or before — had any influence on TBI risk. "These players have evidence of TBI; when it occurred, we don't know, and we will never know unless we followed them longitudinally," said Dr Conidi.

But he said other research has shown that athletes who start playing the game earlier have a higher likelihood of experiencing memory problems later in life.

For players who now know they have TBI, Dr Conidi takes an optimistic approach. "Statistics say that maybe 35% of people with TBI will go on later in life to have neurodegenerative diseases like AD," he said. He points out to patients that this means there is a 65% chance that they will not progress.

These players are being sent for neurocognitive rehabilitation. They get one-on-one speech therapy or occupational therapy, and their sleep and headache issues are addressed. It's not clear yet whether these efforts affect their test scores, he said.

For parents of kids still keen to play football, Dr Conidi suggested considering flag football teams that don't involve tackling, or leagues that limit hitting to games — not in practices — until the child is at least in the mid-teens.

He noted that some schools are even banning hitting during practices for young adults aged 18 to 22 years. "That's probably what needs to happen," he said. "There's just more evidence that probably it's the cumulative effects of these hits more than the big hits."

Key Connection

For comment, Medscape Medical News turned to Mohan Kottapally, MD, assistant professor of clinical neurology & neurocritical care, University of Miami Miller School of Medicine, Florida, who was not involved in the study.

Although he said he was "super excited" about the study, he urged caution in interpreting the data.

First of all, said Dr Kottapally, relatively little is known about concussion because doctors don't have the benefit of many decades of investigation in the field. "It's like this is the tip of the iceberg; we don't know how deep or how big it is."

All that the abstract really objectively tells us, said Dr Kottapally, is that longer exposure to contact sports is correlated with increased lesions on DTI.

It doesn't, however, directly link the lesions with clinical symptoms. Problems with learning, remembering, and focusing can occur in someone who is under the influence of alcohol or has a migraine as well as someone who has had concussions, he said.

Some patients who sustain a concussion go on to develop post-traumatic migraine headaches, which can be reversible, said Dr Kottapally.

"It would be interesting to see how many of the over 40% who had positive imaging findings were suffering from diseases that might confound or complicate the interpretation" of the results, he said.

"It's important to know if they have been successfully evaluated and treated for reversible causes before we just say 'this is because of the concussion'."

Making a connection between the DTI lesions and severity of clinical symptoms is "key," he stressed.

"What the study shows us overall is that longer exposure to repetitive contact sports may predispose you to the development of this type of structural lesion, but the next thing we need to find out is if the development of these structural lesions causes the clinical symptoms."

Dr Kottapally said he was struck by the lack of correlation between the number or severity of lesions on DTI and the number of concussions. "This highlights a problem clinicians face, as one patient with significant imaging findings of TBI may be asymptomatic, whereas another with milder imaging findings may have more severe symptoms. So it's important to always get the whole picture for a patient."

The fact that participants who had been playing longer had fewer concussions may be due to players retiring early if they had significant postconcussive symptoms, noted Dr Kottapally. "It might be reflective of the fact that patients who had a more serious concussion early on didn't play for as long."

The number of concussions someone sustains doesn't necessarily connect to the development of CTE, Dr Kottapally agreed.

"We're all trying to find out what is a true cause and effect relationship, and what are just associations," he added. "What everyone is looking for is a magical test that you can use statically, at one moment in time, to be able to determine should a person play or not."

Dr Conidi reports he has received personal compensation for activities with Scientific Advisory Board Boston Scientific, has received personal compensation in an editorial capacity for Advisory board Med Link, and has received research support from Research Funding Seeing Stars Foundation.

American Academy of Neurology (AAN) 2016 Annual Meeting. Abstract 9071. To be presented April 19, 2016.


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