Mechanical threshold for concussion based on computation of axonal strain using a finite element rat brain model

Concussion, in spite of being a mild traumatic brain injury, involves serious long term consequences and can adversely affect the life of an individual, their family and the wider society. Since, diffuse axonal injury (DAI) is known to be one of the most frequent pathological features of traumatic brain injury (TBI), knowledge of the mechanical threshold for concussion in terms of axonal strain can help in developing better brain injury prediction tools in the context of head protection system optimization and the management of sport related concussions. This paper presents development, validation and utilization of an anisotropic viscous hyperelastic finite element rat brain model for investigation of the mechanical threshold for concussion in terms of axonal strain. For the investigation, twenty-six well documented cases of experimental concussion were simulated. A thorough statistical analysis of global kinematic parameters (maximum rotational acceleration and duration) and intra-cerebral parameters (maximum axonal strain, maximum strain energy, maximum von Mises stress, maximum von Mises strain, maximum shear stress, maximum shear strain, maximum principal stress, maximum principal strain, minimum pressure and maximum pressure) revealed that intra-cerebral parameters are better suited for the prediction of concussion than the global kinematic parameters. The estimated tolerance level for a 50% risk of concussion was found to be 8.97% of maximum axonal strain. The results are promising and hence, this study is not only a key step towards better understanding of concussion, but it also contributes towards concussion related investigations.

Statement of Significance

A number of studies have identified axonal strain as one of the key metrics for the prediction of concussion through biomechanical simulations. Where infeasibility of experimentation on in-vivo human brain limits the in-depth investigation, animal models have proved to be efficient. None of the existing finite element rat brain models have taken anisotropy, based on the rat brain DTI, into account, which is rather a crucial aspect for the fidelity. The present study provides a validated anisotropic viscous hyperelastic finite element rat brain model, which was successfully applied for the simulations of experimental concussive loadings on the rat brain and furnished promising results that are in accordance with the literature. As such, it is helpful in developing more accurate brain injury prediction tools in the context of head protection system optimization and for the management of sport related concussions.