Employing diffusion tensor imaging (DTI) to evaluate the effects of soccer ‘heading,’ investigators have discovered that players who head the ball with high frequency have brain abnormalities similar to those found in traumatic brain injury (TBI) patients.
The research was presented November 29, 2011, at the annual meeting of the Radiological Society of North America (RSNA), held in Chicago (IL, USA). Heading, in which players field the soccer ball with their head, is a fundamental part of the game and the focus of many training drills.
“Heading a soccer ball is not an impact of a magnitude that will lacerate nerve fibers in the brain,” said Michael L. Lipton, MD, PhD, associate director of the Gruss Magnetic Resonance Research Center at the Albert Einstein College of Medicine (New York, NY, USA) and medical director of MRI services at Montefiore Medical Center (New York, NY, USA). “But repetitive heading could set off a cascade of responses that can lead to degeneration of brain cells.”
DTI, a magnetic resonance imaging (MRI) technique, allows researchers to assess microscopic alterations in the brain’s white matter, which comprises millions of nerve fibers called axons that act similar to communication cables connecting various areas of the brain. DTI generates a measurement, called fractional anisotropy (FA), of the movement of water molecules along axons. In healthy white matter, the direction of water movement is fairly uniform and measures high in FA. When water movement is more random, FA values decrease. “Abnormally low FA within white matter has been associated with cognitive impairment in patients with TBI,” Dr. Lipton noted.
Dr. Lipton and colleagues performed DTI on 32 amateur soccer players (average age: 30.8 years), all of whom have played the sport since childhood. The investigators estimated how frequently each soccer player headed the ball on an annual basis and then ranked the players based on heading frequency. They then compared the brain images of the most frequent headers with those of the remaining players and identified areas of the brain where FA values differed considerably.
“Between the two groups, there were significant differences in FA in five brain regions in the frontal lobe and in the temporo-occipital region,” Dr. Lipton stated. “Soccer players who headed most frequently had significantly lower FA in these brain regions.”
The five regions identified by the researchers are responsible for attention, memory, executive functioning, and higher-order visual functions. To evaluate the correlation between the frequency of heading and white matter changes, the researchers also compared the magnitude of FA in each brain region with the frequency of heading in each soccer player. “Our goal was to determine if there is a threshold level for heading frequency that, when surpassed, resulted in detectable white matter injury,” Dr. Lipton said.
The study’s findings demonstrated a threshold level of about 1,000-1,500 heads per year. Once players in the study exceeded that level, researchers observed a considerable reduction in their FA in the five identified brain regions. “What we’ve shown here is compelling evidence that there are brain changes that look like traumatic brain injury as a result of heading a soccer ball with high frequency,” Dr. Lipton said. “Given that soccer is the most popular sport worldwide and is played extensively by children, these are findings that should be taken into consideration in order to protect soccer players.”
Gruss Magnetic Resonance Research Center at the Albert Einstein College of Medicine