Simulating Cerebrospinal Fluid Flow and Spinal Cord Movement Associated with Syringomyelia

Abstract

Syringomyelia is a progressive disease where fluid filled cavities develop inside the spinal cord, and is frequently seen together with Chiari Malformation I (CMI). CMI is characterized by downwards displacements of the Cerebellar Tonsils obstructing flow in the Subarachnoid space, (SAS) which causes abnormal Cerebrospinal fluid (CSF) flow. Many theories on the pathogenesis of syringomyelia have been proposed, many related to abnormal CSF flow, but a full explanation has not yet been given. In this study we formulate a monolithic mixed finite element formulation to investigate fluid structure interaction (FSI) effects of syringomyelia in idealized geometries of the spinal cord and SAS. Models are implemented with the FEniCS software in Python. Elastic and poroelastic representations of the spinal cord are investigated and compared to each other. We tested the hypothesis that fluid velocities within the syrinx can be explained by FSI or poroelasticity, and that these effects alter CSF dynamics. Our results indicate that FSI and poroelastic approaches yield the same results as rigid wall Computational Fluid Dynamics in healthy subjects. In the presence of a syrinx, greater displacements of the cord are predicted. A Poroelastic representation of the spinal cord added substantial damping of the pressure wave inducing syrinx velocity, and thus lower syrinx velocities were seen in these models.