Multi-scale mechanics of traumatic brain injury: predicting axonal strains from head loads

Abstract

The length scales involved in the development of diffuse axonal injury typically range from the head level (i.e., mechanical loading) to the cellular level. The parts of the brain that are vulnerable to this type of injury are mainly the brainstem and the corpus callosum, which are regions with highly anisotropically oriented axons. Within these parts, discrete axonal injuries occur mainly where the axons have to deviate from their main course due to the presence of an inclusion. The aim of this study is to predict axonal strains as a result of a mechanical load at the macroscopic head level. For this, a multi-scale finite element approach is adopted, in which a macro-level head model and a micro-level critical volume element are coupled. The results show that the axonal strains cannot be trivially correlated to the tissue strain without taking into account the axonal orientations, which indicates that the heterogeneities at the cellular level play an important role in brain injury and reliable predictions thereof. In addition to the multi-scale approach, it is shown that a novel anisotropic equivalent strain measure can be used to assess these micro-scale effects from head-level simulations only.

A computational model coupling mechanics and electrophysiology in spinal cord injury

“…Computational biomechanics simulations making use of finite element schemes have recently allowed for the identification of stress extrema and/or patterns at the tissue (Moore et al 2009;Nyein et al 2010;Cloots 2011;Cloots et al 2013;Gupta and Przekwas 2013) and cell scales (Jerusalem and Dao 2012) during TBI events (see these references for a complete literature review). Conversely, recent work building on the observation of "leaky" voltage-gated sodium ion channel after trauma (Wang et al 2009) has proposed a model of the resulting hyperpolarization-(left-)shifts of the ion channel current (Boucher et al 2012).…”

Multiscale Modelling of Blast-Induced TBI Mechanobiology - From Body to Neuron to Molecule

“…In the last few years a new trend of multiscale models has been recommended in which the macro-scale model of biomechanics and linked to micro-scale models of injury to various brain structures including axons, synapses and microvasculature 6,50 . This paper demonstrates this concept on multisite modelling of blast TBI coupling macro-micro-and molecular-scale models of primary biomechanical injury.…”

Connecting fractional anisotropy from medical images with mechanical anisotropy of a hyperviscoelastic fibre-reinforced constitutive model for brain tissue

“…In this study, the model proposed by Cloots et al [28] is used to account for the anisotropy of the brainstem and the corpus callosum. This material model is capable of integrating information on tissue composition and to describe time-rate dependence in the mechanical response.…”

“…A summary of the viscoelastic properties of the brain tissue can be found in table 1. Numerical values for viscoelasticity are chosen in agreement with Cloots et al [28]; in turn, those parameters were based on a study by Kleiven [5].…”

“…The constitutive variables G, k 1 , k 2 , K are assigned the same values that Cloots et al [28] proposed. A summary of the material properties can be found in table 2.…”