Is it possible to protect the adolescent brain with internal mechanisms from repetitive head impacts: Results from a Phase II Single Cohort, Longitudinal, Self-Control Study

 Purpose: To quantify the effects of an externally worn collar device for mitigating the influence of repetitive head impacts on alterations to diffusion tensor imaging (DTI) metrics of white matter. Methods: Fifteen female high-school soccer athletes (age: 14.00-16.98 yrs) completed pre- and post-season DTI over two consecutive years, including measures of diffusivity, changes in which may be associated with brain dysfunction. The collar was worn during year 1 (Yr1) but not during year 2 (Yr2). Athlete exposures (AEs) and head impact exposure were recorded over the competitive seasons. Results: There were no significant differences in AEs or head impact exposures between Yr1 and Yr2 (p >0.05). In Yr2, there was significant pre- to post-season mean diffusivity and/or axial diffusivity reduction in multiple WM regions (corrected p< 0.05). Pre- to post-season mean diffusivity, axial diffusivity, and radial diffusivity decreases were 3.04 ± 2.53%, 2.97 ± 2.194%, and 3.37 ± 3.34%, respectively, significantly greater than pre- to post-season changes in Yr1 (mean diffusivity: -0.31 ± 1.78%, p = 0.0014; axial diffusivity: -0.02 ± 2.25%. p = 0.0014; radial diffusivity: -0.63 ± 2.10%, p = 0.0030). Conclusions: Mild bilateral compression to athletes’ internal jugular vein through collar application may have increased intracranial blood volume and spatially redistributed head-impact-derived brain energy absorption. However, future research is needed to elucidate the potential clinical significance of WM changes of various degrees.