The importance of modeling the human cerebral vasculature in blunt trauma

Abstract

Background Multiple studies describing human head finite element (FE) models have established the importance of including the major cerebral vasculature to improve the accuracy of the model predictions. However, a more detailed network of cerebral vasculature, including the major veins and arteries as well as their branch vessels, can further enhance the model-predicted biomechanical responses and help identify correlates to observed blunt-induced brain injury. Methods We used an anatomically accurate three-dimensional geometry of a 50th percentile U.S. male head that included the skin, eyes, sinuses, spine, skull, brain, meninges, and a detailed network of cerebral vasculature to develop a high-fidelity model. We performed blunt trauma simulations and determined the intracranial pressure (ICP), the relative displacement (RD), the von Mises stress, and the maximum principal strain. We validated our detailed-vasculature model by comparing the model-predicted ICP and RD values with experimental measurements. To quantify the influence of including a more comprehensive network of brain vessels, we compared the biomechanical responses of our detailed-vasculature model with those of a reduced-vasculature model and a no-vasculature model. Results For an inclined frontal impact, the predicted ICP matched well with the experimental results in the fossa, frontal, parietal, and occipital lobes, with peak-pressure differences ranging from 2.4% to 9.4%. For a normal frontal impact, the predicted ICP matched the experimental results in the frontal lobe and lateral ventricle, with peak-pressure discrepancies equivalent to 1.9% and 22.3%, respectively. For an offset parietal impact, the model-predicted RD matched well with the experimental measurements, with peak RD differences of 27% and 24% in the right and left cerebral hemispheres, respectively. Incorporating the detailed cerebral vasculature did not influence the ICP but redistributed the brain-tissue stresses and strains by as much as 30%. In addition, our detailed-vasculature model predicted strain reductions by as much as 28% when compared to current reduced-vasculature FE models that only include the major cerebral vessels. Conclusions Our study highlights the importance of including a detailed representation of the cerebral vasculature in FE models to more accurately estimate the biomechanical responses of the human brain to blunt impact.

Mechanical Behavior of Blood Vessels: Elastic and Viscoelastic Contributions

“…However, a new generation of FEHM consider the nonlinear behavior and viscoelasticity of brain structures, as it has been explicitly pointed out by the developers of YEAHM (University of Aveiro) [50]. Interestingly, some FEHM model CBVs as nonlinear elastic materials [51][52][53], and some of these models use curves and fittings based on [19,31]. These new models include geometric details of the vasculature and even consider the internal pressure inside the CBVs.…”

Cerebral Vasculature Influences Blast-Induced Biomechanical Responses of Human Brain Tissue

“…We previously developed and validated a 3-D high-fidelity FE model of a 50th percentile United States male head to simulate blunt impact ( Subramaniam et al, 2021 ). Here, we extended that model to simulate blast loading.…”

“…For the human-head FE model, we used the same mesh described in our recent study ( Subramaniam et al, 2021 ). Briefly, we used OpenFlipper 3.1 ( Möbius and Kobbelt, 2012 ) to mesh the individual components by creating triangular surface meshes without losing important anatomical features.…”

“…While several human-head FE models ( Sharma, 2011 ; Singh et al, 2014 ; Garimella et al, 2018 ) excluded the brain-surface convolutions (i.e., the ridges and grooves on the human-brain cerebral cortex), Yu et al (2020) , who represented the gyri and the sulci to account for brain-geometry effects, found that the gyri influenced the blast-induced brain-tissue strain rates. Similarly, while the human brain is comprised of over 643,738 m of vasculature, including veins, arteries, venules, and arterioles ( Begley and Brightman, 2003 ), with a few exceptions ( Hua et al, 2015 ; Cotton et al, 2016 ; Zhao and Ji, 2020 ; Subramaniam et al, 2021 ), most FE models do not represent the cerebral vessels ( Taylor and Ford, 2009 ; Nyein et al, 2010 ; Sharma, 2011 ; Panzer et al, 2012 ; Singh et al, 2014 ; Tan et al, 2014 ; Wang et al, 2014 ; Salimi Jazi et al, 2016 ; Tan et al, 2017 ; Garimella et al, 2018 ; Yu et al, 2020 ). Using a 3-D surrogate FE model that approximated the human head as a sphere and the blood-vessel network as tessellations, Hua et al (2015) showed that the cerebral vasculature redistributed blast-induced brain-tissue strains by as much as 612%.…”

“…Recently, using a high-fidelity rat-head FE model, we showed that the inclusion of a detailed network of cerebral vessels stiffens the brain tissues, decreasing the brain-tissue strains by as much as 33% for blast-loading conditions ( Unnikrishnan et al, 2019 ). More recently, using a high-fidelity human-head FE model, we showed that inclusion of a detailed network of cerebral veins and arteries decreased brain-tissue strains in the human brain by as much as 28% for blunt impacts ( Subramaniam et al, 2021 ). Here, we hypothesize that inclusion of such a comprehensive network of cerebral veins and arteries, not represented in any of the human-head blast models discussed above, can further enhance model-predicted blast-induced biomechanical responses of human brain tissues and help identify correlates of blast-induced brain injury.…”