It is estimated that football players can receive as many as 1,500 hits to the head in one season. Not every blow results in immediate injury, but a growing body of research suggests that repetitive hits can lead to serious, long-term brain damage. More than 20 NFL players have so far been diagnosed with chronic traumatic encephalopathy (CTE), a neurodegenerative disease, after their deaths.
Researchers at Boston University’s Center for the Study of Traumatic Encephalopathy (BU CSTE) are now using sophisticated imaging techniques to detect signs of this damage in living patients, work that could lead to a better understanding of the phenomenon, and help identify at-risk athletes. CTE is currently diagnosed through examining a patient’s brain tissue under a microscope.
In February, the BU researchers examined the brain of Dave Duerson, a retired pro football player who committed suicide after suffering from symptoms tied to repetitive brain trauma, including memory loss, poor impulse control, and erratic behavior. Duerson, who played 11 seasons in the NFL, became the 14th player diagnosed with CTE out of the 15 NFL players the center has studied.
“CTE is becoming a widely recognized disease; it is part of the expanding knowledge of traumatic brain injury that has exploded in the last few years,” says Julian Bailes, professor and chairman of the department of neurosurgery and the director of the Brain Injury Research Institute (BIRI) at West Virginia University, the only other institute studying the disease. “We don’t yet know how big the problem really is—is it a few percent of players that have the disease, or more than that?” Bailes says.
In collaboration with Brigham and Women’s Hospital in Boston, the BU researchers recently conducted a pilot study, which involved imaging the brains of five professional athletes known to have experienced repetitive head trauma, and five age-matched nonathlete subjects without any history of head trauma. A similar, but much larger, three-year study is expected to start this summer.
CTE is marked by the progressive degeneration of brain tissue and the accumulation of tau protein, which provides structural support for the microtubules that transmit molecules between cells and neurons, down the axonal tracks. It’s thought that repetitive hits to the head cause these microtubules to stretch, swell, and fall apart, so the cell can’t function and the tau protein starts clumping together.
The researchers used different imaging techniques to detect these changes in the brain. They used diffusion tensor imaging (DTI), a variation of magnetic resonance imaging (MRI), to examine the complex network of nerve fibers that connect different brain areas. DTI tracks the movement of water molecules through the brain, so researchers can create a detailed picture of the axons by analyzing the direction of water diffusion.
The researchers saw fewer axonal connections between neurons and fibers in the pilot study subjects who had a history of head impacts. “It was very apparent when we put the images side by side that the athletes have advanced atrophy or areas where fiber tracks have disappeared,” says Christopher Nowinski, codirector of CSTE and co-founder and president of the Sports Legacy Institute, a nonprofit organization based in Waltham, Massachusetts, that studies brain injury in athletes and was involved with the project.