Modelling and analysis of cerebrospinal fluid flow in the human brain - is cerebrospinal fluid an effective protective mechanism during high-impact loading?

Purpose: This study investigates cerebrospinal fluid (CSF) flow dynamics to enhance the understanding of brain biomechanics and the importance of CSF during high-impact loading. Methods: Comparative analyses were conducted using the benchmark model with smoothed particle hydrodynamics (SPH), without cerebrospinal fluid, and with an additional element - the arachnoid trabeculae - which functions as rigid connections between the brain and skull. The numerical modelling of cerebrospinal fluid and the derived conclusions were validated and calibrated through experiments performed in the additional research phase. Results: The research emphasises the challenges of accurately modelling cerebrospinal fluid dynamics and brain biomechanics. The results were unexpected in several ways. Initially, a rigid cortex-skull connection was anticipated to yield results nearly identical to those observed in Hardy's experiments. Even more surprising were the results for the models with cerebrospinal fluid modelled as smoothed particle hydrodynamics and the model without cerebrospinal fluid, which showed almost identical results in comparison to each other. The novel physical experiment with a gelatine insert subjected to controlled loading and numerical model simulations revealed that SPH models exhibited closely resembling fluid displacement, while tetrahedral elements imposed unrealistic rigidity. Conclusions: The simulations and the novel experiment provide key insights into cerebrospinal fluid dynamics during traumatic brain injury. The findings suggest that the protective function of CSF might be less pronounced under extreme conditions than previously assumed. The smoothed particle hydrodynamics method demonstrates clear advantages over tetrahedral finite element approaches by offering superior brain-in-skull flexibility and avoiding the excessive rigidity inherent to traditional finite element models. We concluded that mechanism of brain protection by CSF is performed rather by hydraulic damping than the brain immersion in vast volume of CSF.