Six Degree-of-Freedom Measurements of Human Mild Traumatic Brain Injury

Abstract

This preliminary study investigated whether direct measurement of head rotation improves prediction of mild traumatic brain injury (mTBI). Although many studies have implicated rotation as a primary cause of mTBI, regulatory safety standards use 3 degree of freedom (3DOF) translation-only kinematic criteria to predict injury. Direct 6DOF measurements of human head rotation (3DOF) and translation (3DOF) have not been previously available to examine whether additional DOFs improve injury prediction. We measured head impacts in American football, boxing, and mixed martial arts using 6DOF instrumented mouthguards, and predicted clinician-diagnosed injury using 12 existing kinematic criteria and 6 existing brain finite element (FE) criteria. Among 513 measured impacts were the first two 6DOF measurements of clinically-diagnosed mTBI. For this dataset, 6DOF criteria were most predictive of injury, more than 3DOF translation-only and 3DOF rotation-only criteria. Peak principal strain in the corpus callosum, a 6DOF FE criteria, was the strongest predictor, followed by two criteria that included rotation measurements, peak rotational acceleration magnitude and Head Impact Power (HIP). These results suggest head rotation measurements may improve injury prediction. However, more 6DOF data is needed to confirm this evaluation of existing injury criteria, and to develop new criteria that considers directional sensitivity to injury.

Mechanistic Insights into Human Brain Impact Dynamics through Modal Analysis

“…In time, with the advances in imaging techniques, axonal injury, which requires excessive regional stretching of axons [19,20], has become one of the leading hypotheses behind the mechanism of concussions. Confirming this hypothesis, strain in the brain and specifically strain in the periventricular region of the brain-with the highest density of axon fibers-have been shown to correlate best with acute concussion and longterm neurological deficits [21][22][23][24]. However, dynamical behavior of the brain during rapid head motions with various amplitudes, durations, and directions, as well as the reason for higher susceptibility of these deep regions of the brain to strain are still largely unknown [22,25].…”

“…Confirming this hypothesis, strain in the brain and specifically strain in the periventricular region of the brain-with the highest density of axon fibers-have been shown to correlate best with acute concussion and longterm neurological deficits [21][22][23][24]. However, dynamical behavior of the brain during rapid head motions with various amplitudes, durations, and directions, as well as the reason for higher susceptibility of these deep regions of the brain to strain are still largely unknown [22,25].As a complex dynamical system with an intricate geometry, nonuniformly compliant boundary conditions and significantly inhomogeneous material properties, understanding the mechanical characteristics of the brain requires a multifaceted approach that takes into account both the spatial and temporal aspects of this system. A force impulse on the head creates nonlinear traveling shear waves inside the brain, which propagate at different speeds and attenuate at different rates, and can create localized strain concentrations at different regions of a linear [26] and nonlinear [27] viscoelastic medium.…”

“…This is an important gap in knowledge especially since impact biomechanics of the brain is by-and-large a transient phenomenon, spanning a few to a hundred milliseconds [22,31]. Previous studies have shown a strong dependence of brain motion and deformation on the PHYSICAL REVIEW LETTERS 120, 138101 (2018) Editors' Suggestion Featured in Physics 0031-9007=18=120(13)=138101 (7) 138101-1…”

Protective Capacity of Ice Hockey Helmets against Different Impact Events

“…[12][13][14]17,20,28,31,32,49,52,57,58,74,85,87 Falls in ice hockey are typically characterized by the mass of the head impacting a rigid impact surface, 25 resulting in high magnitude and short duration linear and rotational acceleration. 12,53,54,59 Such an event is reflected in the current ice hockey certification standard as it aims to replicate the injurious impact events examined by Gurdjian et al 18 which involved an animal model and cadaver head drops to a rigid surface.…”

Default mode network, connectivity, traumatic brain injury and post-traumatic amnesia

“…Interactive pdfs derived from the FreeSurfer platform are available online ( Supplementary Figs 1 and 2). (E) Taken from Hernandez et al (2015). Regions where peak principle strain occurred during TBI that resulted in loss of consciousness (LOC).…”