Diffusion measures indicate fight exposure-related damage to cerebral white matter in boxers and mixed martial arts fighters
Shin W, Mahmoud SY, Sakaie K, Banks SJ, Lowe M, Phillips M, Modic MT, Bernick C. AJNR Am J Neuroadiol. 2013; ahead of print.
Take Home Message: The number of knockouts, among boxers and mixed martial arts fighters predicted structural damage in the brain. This finding suggests that the number of knockouts a fighter endures in their career can predict how much microstructural damage the brain suffered.
Chronic traumatic encephalopathy is a degenerative brain tissue disease caused by cumulative head trauma that can only be definitively diagnosed postmortem. Due to the frequency of blows to the head, boxers and mixed martial arts fighters are prone to this syndrome. There are limited studies that investigate structural changes in brain tissues in fighters, and diffuse tensor imaging may be able to detect subtle structural changes that may reflect microstructural damage to the brain. Therefore, the authors assessed previous fight history and diffusion magnetic resonance (MR imaging to evaluate the relationship between microstructural brain damage and fight-related exposure. A total of 155 male fighters (74 boxers and 81 mixed martial arts fighters),who had no visible abnormalities in the central nervous system on typical MR images had a baseline diffusion tensor imaging scan, and were followed up annually with diffusion tensor images for 4 years. For this initial study, the authors focused on the baseline MR images of the brain. The number knockouts among boxers and mixed martial arts fighters predicted damage within the white matter of the brain. There were more regions of the brain affected amongst boxers (e.g., corpus callosum, cingulate, amygdala) compared with mixed martial arts fighters (i.e., corpus callosum & posterior cingulate); however, there was a larger level of decreased diffusion (connectivity) within the region of the brain affected within mixed martial arts fighters. The number of fights did not predict structural changes in the brain of boxers or mixed martial arts fighters.
The number of knockouts, most predominantly among the boxers, predicted microstructural damage in the brain. This finding suggests that the number of knockouts a fighter endures in their career may predict how much microstructural damage the brain suffered. Specifically, it is not just how often they take on a professional fight, but how often they receive a severe blow. The style of fighting may reflect why more regions of the brain were affected in boxers compared to mixed martial arts fighters, since boxers specifically target the head. It was also interesting to note that in both groups the corpus callosum was affected. The corpus callosum is involved in allowing the right- and left-brain hemispheres to communicate; therefore, damage to this region could lead to cognitive dysfunction, which is one of the symptoms that characterize chronic traumatic encephalopathy. Future studies should include cognitive testing to evaluate if cognition is impaired down the line with future fights and potential knockouts. Health care providers should note that the number of knockouts the fighter has received when caring for them after a brain injury, and should educate the fighter about the possible repercussions of future knockouts.
Written by: Jane McDevitt PhD
Reviewed by: Jeffrey Driban
Questions for discussion: Do you think the length of their fights or concussion history would be predictors of structural damage? Do you think there should be a cut-off for how many knockouts a fighter can endure in their career?