A study of the blast‐induced brain white‐matter damage and the associated diffuse axonal injury

Abstract

Purpose -Blast-induced traumatic brain injury (TBI) is a signature injury of the current military conflicts. Among the different types of TBI, diffuse axonal injury (DAI) plays an important role since it can lead to devastating effects in the inflicted military personnel. To better understand the potential causes associated with DAI, this paper aims to investigate a transient non-linear dynamics finite element simulation of the response of the brain white matter to shock loading. Design/methodology/approach -Brain white matter is considered to be a heterogeneous material consisting of fiber-like axons and a structure-less extracellular matrix (ECM). The brain white matter microstructure in the investigated corpus callosum region of the brain is idealized using a regular hexagonal arrangement of aligned equal-size axons. Deviatoric stress response of the axon and the ECM is modeled using a linear isotropic viscoelastic formulation while the hydrostatic stress response is modeled using a shock-type equation of state. To account for the stochastic character of the brain white matter microstructure and shock loading, a parametric study is carried out involving a factorial variation of the key microstructural and waveform parameters. Findings -The results obtained show that the extent of axon undulations and the strength of axon/ECM bonding profoundly affect the spatial distribution and magnitude of the axonal axial normal and shear stresses (the stresses which can cause diffuse axonal injury). Originality/value -The present approach enables a more accurate determination of the mechanical behavior of brain white matter when subjected to a shock.

Evaluation of brain tissue responses because of the underwash overpressure of helmet and faceshield under blast loading

“…The angular and linear accelerations of the head, peak ICP, maximum shear and tensile stresses and strains, skull flexure, cavitation, and the acoustic impedance mismatch have been mentioned as major factors in evaluating the injury risk and level of bTBI [11,13,20,[30][31][32][33][34][35][36]. Hence, two major tissue parameters, ICP and MSS, that are responsible for the concussive and diffuse injuries, respectively [37], were studied in all blast scenarios. Concussive injuries such as contusion mainly occur because of the relative displacement of the brain with respect to skull when the brain collides the skull as the head undergoes acceleration/deceleration [2,3,13,31,38].…”

Molecular Dynamics (MD) and Coarse Grain Simulation of High Strain-Rate Elastomeric Polymers (HSREP)

“…This finding is not completely unexpected considering the fact that the force-field functions used were derived by fitting the quantum mechanical data for the configurational states which are not drastically different than the material reference state (the material state under standard ambient conditions). Specifically, these findings suggest that, while conserving the linear momentum in the longitudinal direction, nanosegregation within polyurea changes the nature of the shock wave-loading on the adjoining structure (e.g., skull, in the case of polyurea-based helmet suspension pads) from a high-stress and shorter-duration to a lower-stress and longer-duration [35]. A comparison of the fully mixed and nanosegregated polyurea computational results displayed in Figure 5.1.7a-c reveals that, under the same imposed particle velocities, the resulting shock acquires a lower speed while the shocked material is subjected to the conditions of lower stress and smaller density in the case of nanosegregated polyurea.…”

Computational biomechanics of human brain with and without the inclusion of the body under different blast orientation

“…The brain is of low shear modulus compared with its bulk modulus and, therefore, cannot tolerate high shear stresses. The brain stem is the area where maximum shear stress is usually expected under blast waves and kinematical motions (Grujicic et al 2012).…”

“…Primary blast may cause linear and rotational accelerations, but the quick blast overpressure, transferred to the brain via the skull, causes complex stress wave motions. When the blast waves impact the head, the waves are partly reflected and partly pass through the skull to brain leading to brain tissue damage (Grujicic et al 2012;Rezaei et al 2014a). Various parameters such as standoff distance from the detonation, blast wave peak overpressure, and positive overpressure duration affect the level of blast injury (Taylor & Ford 2009).…”