From the Departments of Radiology (Maged Goubran, B.D.M., Marios Georgiadis, M.K., N.M., C.A., L.M., D.D., P.S.D., J.R., M.W., M.Z.), Neurosurgery (G.G.), and Bioengineering (D.B.C.), Stanford University, CA; Department of Medical Biophysics (Maged Goubran) and Physical Sciences Platform & Hurvitz Brain Sciences Research Program (Maged Goubran), Sunnybrook Research Institute, University of Toronto, ON, Canada; Stanford Center for Clinical Research (S.S.), CA; Department of Neurology (E.L.D.), University of Utah School of Medicine, Salt Lake City; Department of Radiology (B.B.), Uniformed Services University of the Health Sciences, Bethesda, MD; and Department of Radiology (B.B.), Madigan Army Medical Center, Tacoma, WA.
Neurology. 2023 Aug 29;101(9):e953-e965. doi: 10.1212/WNL.0000000000207543. Epub 2023 Jul 21.
Repeated impacts in high-contact sports such as American football can affect the brain's microstructure, which can be studied using diffusion MRI. Most imaging studies are cross-sectional, do not include low-contact players as controls, or lack advanced tract-specific microstructural metrics. We aimed to investigate longitudinal changes in high-contact collegiate athletes compared with low-contact controls using advanced diffusion MRI and automated fiber quantification.
We examined brain microstructure in high-contact (football) and low-contact (volleyball) collegiate athletes with up to 4 years of follow-up. Inclusion criteria included university and team enrollment. Exclusion criteria included history of neurosurgery, severe brain injury, and major neurologic or substance abuse disorder. We investigated diffusion metrics along the length of tracts using nested linear mixed-effects models to ascertain the acute and chronic effects of subconcussive and concussive impacts, and associations between diffusion changes with clinical, behavioral, and sports-related measures.
Forty-nine football and 24 volleyball players (271 total scans) were included. Football players had significantly divergent trajectories in multiple microstructural metrics and tracts. Longitudinal increases in fractional anisotropy and axonal water fraction, and decreases in radial/mean diffusivity and orientation dispersion index, were present in volleyball but absent in football players (all findings |T-statistic|> 3.5, value <0.0001). This pattern was present in the callosum forceps minor, superior longitudinal fasciculus, thalamic radiation, and cingulum hippocampus. Longitudinal differences were more prominent and observed in more tracts in concussed football players (n = 24, |T|> 3.6, < 0.0001). An analysis of immediate postconcussion scans (n = 12) demonstrated a transient localized increase in axial diffusivity and mean/radial kurtosis in the uncinate and cingulum hippocampus (|T| > 3.7, < 0.0001). Finally, within football players, those with high position-based impact risk demonstrated increased intracellular volume fraction longitudinally (T = 3.6, < 0.0001).
The observed longitudinal changes seen in football, and especially concussed athletes, could reveal diminished myelination, altered axonal calibers, or depressed pruning processes leading to a static, nondecreasing axonal dispersion. This prospective longitudinal study demonstrates divergent tract-specific trajectories of brain microstructure, possibly reflecting a concussive and repeated subconcussive impact-related alteration of white matter development in football athletes.
在美式橄榄球等接触频繁的运动中，反复的冲击可能会影响大脑的微观结构，这可以通过弥散磁共振成像（diffusion MRI）来研究。大多数影像学研究是横断面的，不包括低接触运动员作为对照组，或缺乏先进的束流特异性微观结构指标。我们旨在使用先进的弥散 MRI 和自动纤维定量方法，研究高接触（橄榄球）和低接触（排球）大学生运动员的纵向变化。
我们对多达 4 年随访的高接触（橄榄球）和低接触（排球）大学生运动员的脑微观结构进行了检查。纳入标准包括大学和团队的注册。排除标准包括神经外科史、严重脑损伤以及主要的神经或物质滥用障碍。我们使用嵌套线性混合效应模型研究了束流长度上的弥散指标，以确定亚急性和急性冲击的急性和慢性影响，以及弥散变化与临床、行为和运动相关测量之间的关系。
共纳入 49 名橄榄球运动员和 24 名排球运动员（共 271 次扫描）。橄榄球运动员的多个微观结构指标和束流的轨迹明显不同。在排球运动员中，出现了各向异性分数和轴突水分数的纵向增加，以及径向/平均弥散度和方向离散度指数的下降（所有发现|T 统计量|>3.5， 值<0.0001）。这种模式在胼胝体压部、上纵束、丘脑辐射和扣带回海马体中都存在。在脑震荡的橄榄球运动员中，纵向差异更为明显，观察到更多的束流（n=24，|T|>3.6，<0.0001）。对 12 例急性脑震荡后扫描的分析显示，在钩回和扣带回海马体中，轴向弥散度和平均/径向峰度的局部一过性增加（|T|>3.7，<0.0001）。最后，在橄榄球运动员中，那些基于位置的高冲击风险的运动员，其细胞内体积分数纵向增加（T=3.6，<0.0001）。
在橄榄球运动员中观察到的纵向变化，特别是在脑震荡运动员中观察到的变化，可能表明髓鞘减少、轴突直径改变或轴突修剪过程抑制导致轴突分散的静态、非递减。这项前瞻性纵向研究表明，脑微观结构的束流特异性轨迹不同，这可能反映了橄榄球运动员的脑震荡和反复的亚急性冲击与白质发育的改变有关。
