Group-Wise Evaluation and Comparison of White Matter Fiber Strain and Maximum Principal Strain in Sports-Related Concussion

Abstract

Sports-related concussion is a major public health problem in the United States and yet its biomechanical mechanisms remain unclear. In vitro studies demonstrate axonal elongation as a potential injury mechanism; however, current response-based injury predictors (e.g., maximum principal strain, ε(ep)) typically do not incorporate axonal orientations. We investigated the significance of white matter (WM) fiber orientation in strain estimation and compared fiber strain (ε(n)) with ε(ep) for 11 athletes with a clinical diagnosis of concussion. Geometrically accurate subject-specific head models with high mesh quality were created based on the Dartmouth Head Injury Model (DHIM), which was successfully validated (performance categorized as "good" to "excellent"). For WM regions estimated to be exposed to high strains using a range of injury thresholds (0.09-0.28), substantial differences existed between ε(n) and ε(ep) in both distribution (Dice coefficient of 0.13-0.33) and extent (∼ 5-10-fold differences), especially at higher threshold levels and higher rotational acceleration magnitudes. For example, an average of 3.2% vs. 29.8% of WM was predicted above an optimal threshold of 0.18 established from an in vivo animal study using ε(n) and ε(ep), respectively, with an average Dice coefficient of 0.14. The distribution of WM regions with high ε(n) was consistent with typical heterogeneous patterns of WM disruptions in diffuse axonal injury, and the group-wise extent at the optimal threshold matched well with the percentage of WM voxels experiencing significant longitudinal changes of fractional anisotropy and mean diffusivity (3.2% and 3.44%, respectively) found from a separate independent study. These results suggest the significance of incorporating WM microstructural anisotropy in future brain injury studies.

Head-Impact–Measurement Devices: A Systematic Review

“…Researchers have reported average rotational values of 4030 rad/s 2 for females 107 and values ranging from 1307 to 5419 rad/s 2 for males. 43,61,62 The recorded linear magnitude of the only youth ice hockey concussion reported in the literature was 31.8g, and the rotational value was 2911 rad/s 2 . This impact represented the lowest recorded linear magnitude in the sample and was in the lowest 50% for recorded rotational accelerations.…”

“…Most research has involved male athletes, predominantly in football (n ¼ 40),* ice hockey (n ¼ 12), 16,[42][43][44][45]61,62,[76][77][78][79][80] soccer (n ¼ 4), 87,[93][94][95] and boxing (n ¼ 1). 89 Males sustained more impacts in ice hockey and boxing than females did.…”

“…7 g t o 145g, 16,17,47,58,61,62,70,72 with a 95th percentile of 7688 rad/ s 2 . 26 Among football injuries, acceleration and impact location increased the specificity of injury prediction.…”

“…40,72 A total of 6 collegiate ice hockey concussions were captured using the HITS. Linear values ranged from 30.7g to 31.7g in an all-male sample 61,62 (n ¼ 2) and 30.4g to 52.2g in an all-female sample 43 (n ¼ 4). Researchers have reported average rotational values of 4030 rad/s 2 for females 107 and values ranging from 1307 to 5419 rad/s 2 for males.…”

White Matter Injury Susceptibility via Fiber Strain Evaluation Using Whole-Brain Tractography

“…To address this inconsistency, recent studies have begun to use strains along WM fibers to characterize elongation of axonal bundles (termed ''axonal'' or ''fiber'' strain, e n ). 11,[16][17][18][19][20][21][22] Initial evidence suggests that fiber orientation-dependent e n improves injury prediction relative to its isotropic counterpart, e ep :…”