VANCOUVER – Many retired National Football League (NFL) players seeking care for neurocognitive symptoms have MRI evidence of traumatic brain injury, according to the largest study of this issue among living players.
Data reported at the annual meeting of the American Academy of Neurology show that 43% of a cohort of 40 symptomatic NFL retirees had abnormal results on diffusion tensor MRI and 30% had evidence of traumatic axonal injury on conventional MRI.
Susan London/Frontline Medical News
Dr. Francis X. Conidi
The likelihood of abnormal diffusion tensor MRI results was correlated, albeit weakly, with the length of the player’s NFL career, but not with the number of concussions sustained.
“It appears that subconcussive hits – that is, the cumulative effects and longer playing careers – place retired alumni at risk for abnormal diffusion tensor MRI,” commented lead author Dr. Francis X. Conidi, director of the Florida Center for Headache & Sports Neurology in Palm Beach and team neurologist for the Florida Panthers of the National Hockey League.
“This could be a possible link to chronic traumatic encephalopathy, as consensus is you need to have repetitive head trauma,” he proposed. “Or this could be a separate entity whereby, in NFL players, the symptoms we are seeing are actually related to the traumatic brain injury itself and [in a subset] with some genetic predisposition, they will go on to have progressive neurological decline.”
Although the cohort was quite young, only 39 years old on average, some had likely played football since youth, and that has implications for prevention, Dr. Conidi added in an interview. “One thing we need to consider is limiting the amount of contact that these people receive on a cumulative basis, starting when they are young and starting in practice, because that’s where most of the contact occurs,” he recommended.
“It is important to note that diffusion tensor imaging is not a routine part of a brain MRI study,” session moderator Dr. José E. Cavazos, professor of neurology and assistant dean at the University of Texas Health Science Center in San Antonio, said in comments provided by email. “The significant correlation between duration of years played and abnormalities in diffusion tensor imaging is of concern given the popularity of the sport.”
Dr. Jose E. Cavazos
“The next step is to replicate the findings, but more importantly, it is to find surrogate markers for early detection for these abnormalities, aiming to intervene (sideline) those players at greater risk for developing cognitive deficits or other impairments,” he added.
In the study, the retired players had a battery of neuropsychological and imaging examinations and tests over a period of 2 days. They were classified as having abnormal diffusion tensor MRI results if they had fractional anisotropy (FA) values at least 2.5 standard deviations below those of age-matched peers in a normative database for specific regions of interest in the brain.
The players ranged in age from 27 to 56 years. On average, they had played 7 years in the NFL and sustained eight concussions during that time. Most had retired in the past 5 years.
Results showed that, overall, 43% had abnormal diffusion tensor MRI results, Dr. Conidi reported. Prevalence, however, varied according to player position: It was highest for defensive linemen (64%) and wide receivers (60%); intermediate for running backs (43%), defensive backs (33%), and offensive linemen (29%); and lowest for quarterbacks (0%) and linebackers (0%).
The number of years played was significantly correlated with abnormal results (P = .049), but the number of concussions was not.
In other findings, sizable proportions of the players had significant abnormalities in attention and concentration (43%), executive function (54%), learning and memory (46%), spatial and perceptual function (24%), and language (5%).
“These guys have played these positions probably since they were young. This isn’t just NFL. We don’t make any claims that professional football caused this,” Dr. Conidi emphasized.
As for future research, the investigators plan to undertake PET scanning to assess clinical and laboratory evidence of Alzheimer’s disease, study sleep pathology, and look for tau protein (a marker for chronic traumatic encephalopathy) in cerebrospinal fluid. Additionally, they will assess treatment outcomes.
The study is not without limitations, Dr. Conidi acknowledged. “With every study that has ever been done on these guys, it is a skewed population: They are coming to us and they are looking to be evaluated,” he elaborated. “The other issue is we don’t have a normative comparison database for the neuropsychological testing.”
Dr. Conidi disclosed that he is a consultant for the NFL, NHL, USTA, PGA, and NCAA and that he receives research support from the Seeing Stars Foundation.