Abstract
Background:
Cumulative exposure to repetitive sub-concussive head impacts in contact sports may have deleterious effects on brain function, even in the absence of acute symptoms. Moreover, anatomical and biomechanical factors may predispose female athletes to higher risk compared to males. At present, there is no effective injury prevention strategy to protect female athletes from sports-related head impact.
Hypothesis/Purpose:
(1). We aimed to use resting-state fMRI to investigate the effect of a full season of competitive soccer on brain functional network integrity in female high school athletes. (2). We also aimed to evaluate the efficacy of a jugular vein compression neck collar device, designed to mitigate potential injury by reducing the brain slosh effect.
Methods:
A total of 125 high school female soccer athletes were included in this study. These athletes were assigned randomly to a non-collar (n=55, age=16.06±1.06 yrs) or collar group (n=70, 15.81±0.95 yrs) before the season started. High resolution 3D T1-weighted images and resting-state fMRI data were collected prospectively at pre-season and again at post-season. Data processing and analysis were conducted in the MATLAB-based programs Statistical Parametric Mapping (SPM12) and Connectivity Toolbox (Conn). Functional connectivity was computed between each pair of 105 anatomically delineated regions of interest (ROI). Network Based Statistics were applied to detect coherent patterns of altered connectivity from pre- to post-season.
Results:
The non-collar group showed a significant pattern of altered connectivity (p-FWE = 0.047) spanning 60% of ROIs (63/105) and 1.7% of ROI-ROI connections (94/5,460). 65 of the 94 altered connections were weakened from pre-to-post season and tended to occur in the right hemisphere. 29 of the 94 altered connections were strengthened from pre-to-post season and tended to involve regions in the occipital lobe. The collar group did not show any statistically significant change (p-FWE = 0.223).
Conclusion:
The results of this study indicate that exposure to repetitive sub-concussive head impacts during a single season of competitive female soccer induces changes in brain functional connectivity. The observed increases and decreases of functional connectivity strength comprising the pattern of altered connectivity are congruent with a heterogeneous response to insult wherein some connections are reduced in strength due to neuronal damage and other “detour” connections are strengthened to preserve network function. Comparatively, the absence of alterations in the collar group suggest that the jugular vein compression collar may have generated a potentially protective effect to preserve brain functional network integrity during exposure to head impacts.
Pattern of pre-to-post season altered connectivity in the non-collar group (p-FWE=0.023). Observed changes in functional connectivity strength were bimodal with decreased (blue) connectivity occurring predominantly between right hemispheric regions and increased (red) connectivity often associated with occipital lobe areas.