Background: Repetitive head impacts experienced during competitive sports contribute to neurologic changes over the course of a season. Internal jugular vein compression, by means of an externally worn neck collar device has shown efficacy in mitigating white matter (WM) alterations following repeated head impact exposure. However, its relative effectiveness in high versus low head impact exposures is unknown. Hypothesis/Purpose: The purpose of this study was to investigate the effectiveness of an externally worn neck collar device in limiting WM alterations over a season of high school football in players who receive high and low cumulative head impact exposures over 90 g. Methods: 213 male high-school football athletes were prospectively assigned to two study groups: a control group (non-collar; n=106) and an experimental group who wore the jugular vein compression collar during all practices and games (collar; n=107). MRI data was collected from all participants pre- and post-season. Fractional anisotropy (FA), and mean, axial and radial diffusivity (MD/AD/RD) were calculated to assess WM integrity at both time points. Cumulative head impact exposure was monitored by accelerometers attached to each athlete’s left mastoid process during every exposure. Participants were dichotomized into subgroups based on accumulated exposures to hits over 90 g, which divided the entire cohort into four subgroups, using a cut-off of 40 hits : (1) non-collar group (≥40 hits, n=57); (2) collar group (≥40 hits, n=51); (3) non-collar group (<40 hits, n=49); (4) collar group (<40 hits, n=56). Results: As seen in Table 1, in athletes with ≥40 hits, both the non-collar and collar group showed significant pre- to post- season reductions in MD, AD, and/or RD. The non-collar group with ≥40 hits also showed a significant increase in FA, MD, and AD. RD, FA, and MD changes were greater in the non-collar group compared to the control group with ≥40 hits, while AD changes were greater in the collar group compared to the non-collar group with ≥ 40 hits. The non-collar group with <40 hits presented significant pre- to post-season reductions in MD, AD, and RD that were greater than the collar group with < 40 hits (whom did not show pre-to post-season changes). Discussion & Conclusion: The present results provide support for internal jugular vein compression to protect the brain from both low- and high-level repeated head impact exposure. However, less consistent changes were observed for athletes exposed to repeated, high-level head impacts, warranting further investigation. [Table: see text]
Abnormal White Matter Integrity Related to Head Impact Exposure in a Season of High School Varsity Football