Date of Award

12-2016

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biomedical Engineering

First Advisor

Thomas M. Talavage

Committee Chair

Thomas M. Talavage

Committee Member 1

Eric A. Nauman

Committee Member 2

Larry J. Leverenz

Committee Member 3

Zhongming Liu

Committee Member 4

Andrew O. Brightman

Abstract

As participation in women’s soccer continues to grow and the longevity of female athletes’ careers continues to increase, prevention of mTBI in women’s soccer has become a major concern for female athletes as the long-term risks associated with a history of mTBI are well documented. Among women’s sports, soccer exhibits the highest concussion rates, on par with those of men’s football at the collegiate level. Head impact monitoring technology has revealed that “concussive hits” occurring directly before symptomatic injury are not predictive of mTBI, suggesting that the cumulative effect of repetitive head impacts experienced by collision sport athletes should be assessed. Neuroimaging biomarkers have proven to be valuable in detecting brain changes that occur before neurocognitive symptoms in collision sport athletes. Quantifying the relationship between changes in these biomarkers and the cumulative mechanical load experienced by female soccer athletes may prove valuable in developing measures to prevent mTBI. This work pairs functional magnetic resonance imaging with head impact monitoring to assess changes in cerebrovascular reactivity and resting state functional connectivity in female soccer athletes and to test whether the observed changes can be attributed to the cumulative mechanical load experienced by female athletes participating in high school soccer both transiently over a season and chronically over several years of play. Marked cerebrovascular reactivity changes over a season of play were observed in female soccer athletes, relative both to non-collision sport control measures and pre-season measures. These changes persisted 4-5 months after the season ended and recovered by 8 months after the season. Segregation of the total soccer cohort into cumulative loading groups revealed that population-level cerebrovascular reactivity changes were driven by athletes experiencing high cumulative loads in short periods of time and that focusing on impacts 50g or higher helped increase identification of individuals with cerebrovascular reactivity decreases using head impact data. Resting state functional connectivity assessments revealed hypoconnectivity in soccer athletes as compared to non-collision sport control athletes. This hypoconnectivity was more pronounced in between network connections as opposed to within network connections. However, resting state functional connectivity was not altered over a season of play in soccer athletes, suggesting that the observed differences between soccer athletes and control athletes were due to long term exposure to chronic exposure to mild repetitive head trauma over several years of play.

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