Introduction: Sport-related concussion (SRC) has emerged as a major public health problem. Brain imaging studies have raised several questions about long-term neurologic effects after SRC, but the clinical importance of these findings remains unknown. Our goal was to summarize the brain imaging studies after acute SRC in American football players.
Methods: A systematic review was performed with the following inclusion criteria: football players, brain imaging within 4 weeks of SRC, and sample size >5. Studies were assessed for: 1) methodology (control selection, type I error, recall bias, and baseline imaging), 2) imaging outcomes, and 3) number of positive statistical comparisons. Imaging was classified as hyperacute (<1 week post-injury) or intermediate (1 week to 6 months post-injury). Proportion tests were used to assess which methodologies were likely to lead to positive results.
Results: Eleven studies (all case-controls) met inclusion criteria. Median time to initial imaging was 72 hours (range: 24-168 hours). Imaging outcomes included changes in blood oxygenation level dependent (BOLD) and functional MRI (fMRI) (63%), metabolic changes on 1H-MR spectroscopy (18%), and white matter changes on diffusion tensor (DTI) imaging (18%). Eight of the 11 studies made a total of 809 comparisons of brain activity, of which 146 were statistically significant (18%). Nine of the 11 studies (82%) reported positive hyperacute findings, and these studies were more likely to have no baseline imaging (p=0.420) and be subject to recall bias (p=0.023) than negative studies. One of 7 intermediate studies (14%) reported positive findings, and this study was less likely to control for type I error (p=0.420) and have baseline imaging (p=0.495) than negative studies.
Conclusions: The study of acute brain imaging findings after SRC is in its infancy. The transitory nature of positive imaging findings and methodological limitations complicate study interpretation. Further research is required to correlate imaging findings with clinical outcomes.
Patient Care: The current literature on acute imaging findings after sport-related concussion is heterogeneous and difficult to correlate with clinical outcomes. Our research aims to summarize the reported findings while critically analyzing the methodology of these studies. Such research will help clinicians understand the utility of various imaging modalities for acute sport-related concussion and their correlation with clinical outcomes. Our overarching goal is to improve our knowledge of these technologically advanced imaging studies in a way that athletes and families can understand the neurologic implications of playing contact sports.
Learning Objectives: By the conclusion of this session, participants should be able to:
1. Identify the wide array of imaging modalities used in the acute evaluation of sport-related concussion.
2. Summarize the acute imaging findings after sport-related concussion reported in the literature.
3. Discuss the methodological limitations of studies reporting acute imaging findings in football players after sport-related concussion.