Abstract
Repetitive head impacts (RHI) are a growing concern due to their possible neurocognitive effects, with research showing a season of RHI produce white matter (WM) changes seen on neuroimaging. We conducted a secondary analysis of diffusion tensor imaging (DTI) data for 28 contact athletes to compare WM changes. We collected pre-season and post-season DTI scans for each subject, approximately 3 months apart. We collected helmet data for the athletes, which we correlated with DTI data. We adapted the SPatial REgression Analysis of DTI (SPREAD) algorithm to conduct subject-specific longitudinal DTI analysis, and developed global inferential tools using functional norms and a novel robust p value combination test. At the individual level, most detected injured regions (93.3%) were associated with decreased FA values. Using meta-analysis techniques to combine injured regions across subjects, we found the combined injured region at the group level occupied the entire WM skeleton, suggesting the WM damage location is subject-specific. Several subject-specific functional summaries of SPREAD-detected WM change, e.g., the {L}^{infty } norm, significantly correlated with helmet impact measures, e.g. cumulative unweighted rotational acceleration (adjusted p = 0.0049), time between hits rotational acceleration (adjusted p value 0.0101), and time until DTI rotational acceleration (adjusted p = 0.0084), suggesting RHIs lead to WM changes.
Highlights
We conducted a secondary analysis of diffusion tensor imaging (DTI) data for 28 contact athletes to compare white matter (WM) changes
Using our simulation study to optimize the bandwidth parameter for repetitive head impacts (RHI), we found the optimal bandwidth values to be five for small signal, 10 for medium signal, and 19 for large signal (Table 2)
We discovered that the optimal bandwidth value appears to be positively related to the signal size, i.e. the smaller the signal is, the smaller the optimal bandwidth is, which can help determine optimal bandwidth values based on lesion size created by the disease process
Summary
We conducted a secondary analysis of diffusion tensor imaging (DTI) data for 28 contact athletes to compare WM changes. L norm, significantly correlated with helmet impact measures, e.g. cumulative unweighted rotational acceleration (adjusted p = 0.0049), time between hits rotational acceleration (adjusted p value 0.0101), and time until DTI rotational acceleration (adjusted p = 0.0084), suggesting RHIs lead to WM changes. RHI occur frequently during contact and collision sports at all levels of play including youth, collegiate, and professional competitions. Both animal and human studies have shown acute changes in brain structure and function after RHI that are indicative of axonal injury[2,3,4,5,6,7,8,9,10]. This understanding of the acute impact on the brain has led to questions about RHI’s potential long-term neurocognitive effects
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