Combining the Finite Element Method with Structural Connectome-based Analysis for Modeling Neurotrauma: Connectome Neurotrauma Mechanics

Abstract

This article presents the integration of brain injury biomechanics and graph theoretical analysis of neuronal connections, or connectomics, to form a neurocomputational model that captures spatiotemporal characteristics of trauma. We relate localized mechanical brain damage predicted from biofidelic finite element simulations of the human head subjected to impact with degradation in the structural connectome for a single individual. The finite element model incorporates various length scales into the full head simulations by including anisotropic constitutive laws informed by diffusion tensor imaging. Coupling between the finite element analysis and network-based tools is established through experimentally-based cellular injury thresholds for white matter regions. Once edges are degraded, graph theoretical measures are computed on the “damaged” network. For a frontal impact, the simulations predict that the temporal and occipital regions undergo the most axonal strain and strain rate at short times (less than 24 hrs), which leads to cellular death initiation, which results in damage that shows dependence on angle of impact and underlying microstructure of brain tissue. The monotonic cellular death relationships predict a spatiotemporal change of structural damage. Interestingly, at 96 hrs post-impact, computations predict no network nodes were completely disconnected from the network, despite significant damage to network edges. At early times () network measures of global and local efficiency were degraded little; however, as time increased to 96 hrs the network properties were significantly reduced. In the future, this computational framework could help inform functional networks from physics-based structural brain biomechanics to obtain not only a biomechanics-based understanding of injury, but also neurophysiological insight.

The influence of dynamic response and brain deformation metrics on the occurrence of subdural hematoma in different regions of the brain

“…As a result, the metrics used here indicate a global, or macro level, response of the brain in those regions, and for further analysis a local, or micro, model of the vasculature of the SDH ROI may be warranted. 18 In addition, as it was important to discern if the SDH ROI deformations were significantly different from those in the rest of the cerebellum, a t-test was conducted to establish if there were any significant differences between the responses. An ANOVA was conducted across different lobes of the brain for each response variable.…”

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 :…”

“…Both Cloots and coworkers 17 and Wright and Ramesh 19 employed a multiscale approach to couple a macroscale three dimensional (3D) or two dimensional (2D) head model, respectively, with a microscale element embedding a single axon. Work from Wright and colleagues, 21 Kraft and associates, 20 Sahoo and coworkers, 26 , and Giordano and Kleiven 27 assigned average FA values and fiber directions to each element from coregistered DTI for strain evaluation. Instead of averaging on elements, Ji and associates 22 evaluated fiber strain at each DTI voxel transformed into the corresponding FE model space using strain tensors from the closest FE element on a subject-specific basis.…”

“…Because axons and their bundles are neural processes that connect neuronal cell bodies and transmit information between them, 28,29 it is reasonable to assume that any damage along the axons, regardless of the location (within or outside the boundary of any traversing ROI), would constitute potential functional impairment. 20 The goal of this study was to develop a technique to evaluate e n along voxel-or anatomically constrained whole-brain tractography, which has not been performed before. An ''injury susceptibility index'' was developed to quantify injury vulnerabilities with a finer, graded ''likelihood'' of injury of discrete WM voxels or individual neural pathways, extending previous efforts where typically a dichotomous injury status was instead assigned.…”

A finite-element reciprocity solution for EEG forward modeling with realistic individual head models

“…The meshing pipelines provided here may also prove useful for other types of finite-element simulations, such as those evaluating neurotrauma mechanics [40]. The finite element solution used during leadfield creation may also be adaptable for other types of simulations, such as the modeling of transcranial direct current stimulation.…”