Numerical Cerebrospinal System Modeling in Fluid- Structure Interaction

Objective Cerebrospinal fluid (CSF) stroke volume in the aqueduct is widely used to evaluate CSF dynamics disorders. In healthy population, aqueduct stoke volume represents around 10% of the spinal stroke volume while intracranial subarachnoid space stroke volume represents 90%. Amplitude of the CSF oscillations through the different compartments of the cerebrospinal system is function of the geometry and the compliances of each compartments but we suspect that it could also be impacted be the cardiac cycle frequency. To study this CSF distribution, we have developed a numerical model of the cerebrospinal system taking into account cerebral ventricles, intracranial subarachnoid spaces, spinal canal and brain tissue in fluid-structure interaction. Materials and Methods A numerical fluid-structure interaction model is implemented using a finite element method library to model the cerebrospinal system and its interaction with the brain based on the fluid mechanics equations and the linear elasticity equations coupled in a monolithic formulation. The model geometry, simplified in a first approach, is designed in accordance to realistic volumes ratio of the different compartments: a thin tube is used to mimics the high flow resistance of the aqueduct. CSF velocity and pressure, and brain displacements are obtained as simulation results, whence CSF flow and stoke volume are calculated from this results. Results Simulation results show significant variability of aqueduct stroke volume and intracranial subarachnoid spaces stroke volume in the physiological range of cardiac frequencies. Conclusions Fluid-structure interactions are numerous in the cerebrospinal system and difficult to understand in the rigid skull. The presented model highlights significant variations of the stroke volumes under cardiac frequency variations only