As a major cause of death and disability, traumatic brain injury (TBI) creates considerable burdens to society due to high economic costs. Accordingly, investigation into the common causes of TBI such as dynamic head impact problems is of great importance in order to further understand the injury mechanisms, precisely diagnose the level of the injuries, and develop effective prevention methods. Finite element (FE) method has been widely used for gaining insights into the mechanical response of brain tissue during impacts, yet there are still computational challenges to be addressed and severe mesh distortion effect in the cerebrospinal fluid (CSF) is one of them.

In this study, the coupled Eulerian-Lagrangian (CEL) formulation is implemented in the head impact simulations, aiming to overcome the mesh distortion difficulties due to large deformation in the CSF region and provide a biofidelic model of the interaction between the brain and skull. The CEL method, applied in an impact scenario, is first validated using experimental data from a cylindrical surrogate head system. Three different FE head models (cylindrical, transverse section, coronal section) are then constructed successively to investigate the function of certain brain structures during head impacts and compare the injury patterns in different brain regions under different impact conditions. Brain regions susceptible to injury are evaluated based on multiple criteria.

According to the simulation results, the accumulation effect of the CSF and the contact between the brain and skull are realized by using the CEL method. When comparing simulation results using different brain structures, it is found that the sulci structures on the brain delays the intracranial pressure (ICP) wave transmission process and lowers the pressure level in the brain. The arachnoid trabeculae restrain the large movements of the brain, and together with the sulci, help to prevent the CSF accumulation at the contrecoup impact site. By comparing the direct and non-contact head impacts with same brain-skull motion, the results confirm a more apparent injury pattern in the direct impact case. However, the thalamus and midbrain regions are more susceptible to axonal injury in the non-contact impact case, which also shows higher sensitivity to the relative movement between the brain and skull.