High contact sports put athletes at a higher risk of sustaining a concussion. This work focused on assessing regional brain health in aging, retired Canadian Football League (rCFL) players years to decades after retirement. Advanced, quantitative magnetic resonance imaging (MRI) techniques were implemented to identify and quantify microstructural brain white matter damage, cognitive functional signal characteristics (fractal dimension (FD) and amplitude of low frequency fluctuations (ALFF) and fractional ALFF (fALFF)), and cerebral blood flow (CBF) dysregulation.
Due to the high reproducibility of diffusion tensor imaging (DTI) and resting state functional MRI (rsfMRI), a Z-scoring approach exploring outliers relative to a large normative dataset was implemented to examine each rCFL subject individually. However, arterial spin labelling (ASL) data is more sensitive to scanner inconsistencies, therefore a group-wise analysis was performed with the CBF and ASL spatial coefficient of variance (ASL sCoV) data.
Minimal microstructural damage was detected in the rCFL subjects, but a substantial amount of functional and CBF abnormalities were present. The FD was significantly reduced in 48 of 91 regions-of-interest (ROIs) examined, and the four rCFL subjects with the highest number of abnormal ROIs all exhibited worse motor speed, social functioning and general health scores than the other rCFL subjects. Furthermore, the ALFF analysis identified the cerebellum, parietal lobe ROIs, and central sub-cortical ROIs to be consistently abnormal. Finally, the temporal occipital fusiform cortex, superior parietal gyrus, caudate nucleus, and the cerebellum were significantly abnormal bilaterally based on CBF and ASL sCoV values, which also correlated with worse physical functioning and elevated daily chronic pain.
This work adds to the growing literature that brain changes are present later in life that may be related to concussions and repetitive sub-concussive head impacts sustained years earlier. Several consistently damaged ROIs also correlated with adverse clinical presentations to indicate areas of future research. / Dissertation / Doctor of Philosophy (PhD) / Clinical concussion assessment has a limited ability to identify brain injury location and severity. Therefore, there is a need for more advanced diagnostic tools to provide meaningful, objective information to concussion patients and clinicians. The work presented in this thesis aimed to assess brain health using magnetic resonance imaging (MRI) techniques of retired professional football players with a complex history of concussions and repetitive sub-concussive impacts. Our research found concussion-related functional and cerebral blood flow brain abnormalities past that of normal aging, but minimal white matter damage, present in the retired athletes that also correlated with clinically testable health metrics such as motor speed, emotional well-being, and pain. Through personalized subject-specific analyses, this work provides further evidence of the effects of concussions later in life.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/27763 |
| Date | January 2022 |
| Creators | Danielli, Ethan |
| Contributors | Noseworthy, Michael D, Biomedical Engineering |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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