A New Model Comparing Impact Responses of the Homogeneous and Inhomogeneous Human Brain

Abstract

A new three-dimensional human head finite element model, consisting of the scalp, skull, dura, falx, tentorium, pia, CSF, venous sinuses, ventricles, cerebrum (gray and white matter), cerebellum, brain stem and parasagittal bridging veins has been developed and partially validated against experimental data of Nahum et al (1977). A frontal impact and a sagittal plane rotational impact were simulated and impact responses from a homogeneous brain were compared with those of an inhomogeneous brain. Previous two-dimensional simulation results showed that differentiation between the gray and white matter and the inclusion of the ventricles are necessary in brain modeling to match regions of high shear stress to locations of diffuse axonal injury (DAI). The three-dimensional simulation results presented here also showed the necessity of including these anatomical features in brain modeling. Although both the homogeneous and inhomogeneous brain models predicted almost the same intracranial pressure response of the brain, they predicted a different shear stress response. Simulation results suggest that coup/contrecoup injures are pressure induced, while brain-stem injuries are caused by shear stress/strain. Furthermore, shear strains at the genu of the corpus callosum can be a predictor of DAI. The impact response of parasagittal bridging veins, simulated by using one-dimensional string element, appeared to be reasonable and consistent with experimental results. The model predicted that the bridging veins in the central part of the superior sagittal sinus were at higher risk of rupture as they could be subjected to higher tensile strains during the rebound phase. This could be an important injury mechanism for subdural hematoma which also depends on the direction of impact.