Introduction: Lasting neurocognitive deficits after participation in football is a growing public health concern. Brain imaging studies have suggested that long-term neuroanatomical changes occur in football athletes, but the clinical importance of these findings remains unknown. Our objective was to summarize the brain imaging studies after long-term SRC in American football players.
Methods: A systematic review was performed with the following inclusion criteria: football players, brain imaging at least 2 years from prior concussion or retirement, and sample size >5. Studies were assessed for methodology (selection of controls, type I error, recall bias, and baseline imaging) and imaging outcomes. Proportion tests were used to assess which methodologies were likely to lead to positive results.
Results: Sixteen studies (all cross-sectional studies) met inclusion criteria. Highest level of play was high school (1), college (3), and professional (12). Thirteen of the 16 studies made a total 456 comparisons of brain activity, of which 171 were statistically significant (38%). Nine of 16 studies (56%) had appropriate controls. Five of 16 studies (31%) had appropriate control of type I error. All studies (16/16) had recall bias when obtaining player concussion history or had unclear methodology. Imaging outcome measures included patterns of connectivity on functional MRI (fMRI) (25%), metabolic changes on 1H-MR spectroscopy (6.3%), and white matter changes on diffusion tensor (DTI) imaging (31.2%). Zero of 16 studies (0%) had baseline imaging performed.
Conclusions: Studies of long-term structural and functional brain imaging findings in American football players are heterogeneous in both methodology and findings. Understanding the clinical significance of statistically positive findings is complicated by methodological limitations and study design. Further research is required to correlate imaging findings with clinical outcomes.
Patient Care: This research will help clinicians understand the utility of long-term neuroimaging findings in American football players. Specifically, this research identified strengths and weaknesses of structural and functional neuroimaging modalities in assessing long-term effects of football participation. Ultimately, further investigation is warranted to understand how neuroimaging may reveal chronic sequelae of football participation and guide clinical decisions in the population of football players.
Learning Objectives: By the conclusion of this session, participants should be able to:
1) Describe the strengths and weaknesses of current long-term neuroimaging studies of football players.
2) Understand common long-term neuroimaging findings in football players.
3) Describe neuroimaging modalities used to study long-term effects of football in players.