More than 40 percent of retired NFL players in a new study showed evidence of traumatic brain injury on sensitive MRI scans (diffusion tensor imaging), the researchers reported. The findings were released in conjunction with a presentation scheduled for the American Academy of Neurology’s 68th Annual Meeting in Vancouver, Canada, April 15–21, 2016.
This large study of living, retired National Football League (NFL) athletes provides objective evidence that a substantial portion have brain changes consistent with traumatic brain injury (TBI). Lead author Francis X. Conidi, MD, DO, of the Florida Center for Headache and Sports Neurology and Florida State University College of Medicine, emphasized that the rate of TBI detected by advanced imaging in these former players was notably higher than what is typically seen in the general population.
The research combined detailed cognitive testing with magnetic resonance imaging (MRI) techniques in 40 retired NFL players. Participants were aged 27 to 56, with an average age of 36. Most had retired from the league less than five years earlier. On average the players had seven NFL seasons (range two to 17 seasons) and reported an average of 8.1 diagnosed concussions. In addition, 31 percent described repeated “sub-concussive” impacts—blows to the head or body that did not meet the threshold for a diagnosed concussion but may nonetheless affect the brain over time.
The team used diffusion tensor imaging (DTI), an MRI method that maps the movement of water molecules in brain tissue to assess the integrity of white matter pathways. White matter consists of the nerve fibers that connect different brain regions and support communication between cells. DTI can detect microstructural disruption of these pathways that may not be visible on routine MRI scans.
Seventeen of the players (43 percent) had DTI measures that were 2.5 standard deviations below age-matched healthy controls—an objectively defined cutoff the investigators used to indicate likely traumatic brain injury with a low error rate. In addition, traditional MRI showed evidence of axonal injury—the disruption of nerve cell axons that carry signals between brain cells—in 12 players (30 percent). These structural findings were accompanied by notable cognitive changes: about half the sample had significant deficits in executive function, 45 percent had problems with learning or memory, 42 percent had impaired attention and concentration, and 24 percent had deficits in spatial and perceptual skills.
One clear pattern emerged: longer NFL careers were associated with a higher likelihood of showing DTI abnormalities. Players who spent more seasons in the league were more likely to have DTI evidence of white matter disruption. Interestingly, the number of reported concussions did not correlate with DTI findings, and the duration of an NFL career did not predict abnormalities on conventional MRI. These distinctions suggest that cumulative exposure to head impacts over time—even impacts that are sub-concussive and not diagnosed as concussions—may contribute to detectable microstructural brain changes that conventional imaging can miss.
Dr. Conidi noted that the findings in living players “shed light on the possible pathological changes consistent with chronic traumatic encephalopathy (CTE) that may be taking place.” While CTE can currently be diagnosed definitively only through postmortem examination, advanced neuroimaging such as DTI combined with neuropsychological testing can reveal patterns of injury and cognitive dysfunction that warrant further study and monitoring.
Source: Rachel Seroka – AAN
Image Credit: The image is in the public domain.
Original Research: The researchers planned to present their findings at the 2016 American Academy of Neurology 68th Annual Meeting in Vancouver during the week of April 15–21, 2016.