Soccer is one of the world’s most popular sports. It is also the only sport where the head, unprotected, is a primary point of contact for the ball when playing. In other contact sports, the negative effects of repetitive traumatic brain injury are well recognized; however, the effects of frequent blows to the head below the threshold of concussion, as seen in soccer players, remains controversial.
In the first study to show alterations in white matter in professional soccer players, HMS researchers and colleagues at Ludwig-Maximilians-University in Munich investigated the brains of 12 soccer players using high-resolution diffusion tensor imaging to investigate structural changes in the brain, specifically white-matter architecture. White matter is the communication network responsible for communicating messages between neurons (gray matter) in the brain.
This research was published in a letter in the Journal of the American Medical Association on Nov. 14.
“Our study found differences in integrity of the white matter of the brains of soccer players compared with swimmers,” said Inga Katharina Koerte, lead author and a visiting research fellow in the Psychiatry Neuroimaging Laboratory at Brigham and Women’s Hospital. “Although only participants without previous symptomatic self-reported concussion or physician-diagnosed concussion were included, we found changes in the brain that are consistent with findings observed in patients with mild traumatic brain injury.”
Researchers evaluated 12 right-handed male soccer players from elite soccer clubs in Germany and compared them to eight swimmers, a sport with low exposure to repetitive brain trauma, from competitive clubs. Aside from their professional sport, the groups were otherwise similar in age, handedness and gender.
In this study, conventional magnetic resonance images used routinely in clinical settings showed no abnormalities when read by a neuroradiologist, suggesting the importance of using more sensitive measures to detect subtle changes in the brain. Researchers then employed high-resolution diffusion tensor imaging, and observed widespread differences between the 12 soccer players and the eight swimmers.
High-resolution diffusion tensor imaging non-invasively provides information about the diffusion of water molecules in biological tissue and can therefore reveal microscopic details about tissue architecture. In the brain’s white matter, diffusion of water molecules reflects the coherence, organization and density of fibers, which makes this imaging technique highly sensitive to changes in white matter architecture.
The alterations were observed in the white matter of the frontal, temporal and occipital lobes in the soccer players when compared to the swimmers. These regions of the brain are known to be responsible for attention, visual processing, higher order thinking and memory.
“The origin of these results is not clear. One explanation may be the effect of frequent subconcussive brain trauma, although differences in head injury rates, sudden accelerations, or even lifestyle could contribute,” said Martha Shenton, senior author and professor of psychology and radiology at Brigham and Women’s and a researcher at the VA Boston Healthcare System. “Additional research is needed to confirm these results we observed in this small sample of soccer players and to help clarify the effects that alterations of white matter have on behavior and health.”
Co-authors, including Ross Zafonte, vice president of medical affairs at Spaulding Rehabilitation Network, echo the importance of following up on this finding as key to understanding the meaning of the changes observed in this group of athletes.
This research was funded by the Else Kröner-Fresenius-Stiftung, Germany (IKK) and the Deutsche Akademischer Austauschdienst (IKK). This work was also supported in part by the INTRuST Posttraumatic Stress Disorder and Traumatic Brain Injury Clinical Consortium funded by the Department of Defense Psychological Health/Traumatic Brain Injury Research Program (X81XWH-07-CC-CS-DoD; RZ, MES), and by an NIH NINDS funded R01 (R01 NS 078337 MES
This story was adapted from a Spaulding Rehabilitation Hospital news release.