Neuro-biomechanics of Chiari malformation: Modelling CSF flow and soft tissues of the central nervous system in the normal setting and Chiari 1 malformation

The cerebrospinal fluid (CSF) surrounds and protects the brain and spinal cord offering a cushion against shock and aiding in maintaining physiological balance. Understanding CSF dynamics is crucial for insights into neurological disorders like Chiari 1 Malformation (CM1) and hydrocephalus. CM1 involves the downward displacement of brain tissue through the skull opening, which obstructs the CSF flow. Theories suggest that this altered CSF distribution due to CM1 might contribute to related disorders like syringomyelia, where fluid accumulates within the spinal cord and which has been associated with severe motor and sensory symptoms. However, the source of syringomyelia remains debated. This thesis aims to investigate the effect of an artificial 3D obstruction as present in CMI using both a Computational Fluid Dynamics (CFD) and a poroelastic Fluid Structure Interaction (FSI) approach. The artificial 3D herniation has the advantage to be the same in the different simulation leading to not impact of the difference in person specific geometry between healthy and with obstruction which can lead to a bigger impact that the obstruction itself. First, the 3D circulation of CSF is investigated in a CFD model of the cranial and upper spinal CSF. Following this, the effects of a 3D idealized volume that mimics CM1-related obstruction within a section of the SAS are investigated at varying levels of obstruction: 40%, 60% and 100%. First, in CFD simulations, the CSF space is considered rigid without interaction with the spinal cord. Subsequently, the spinal cord is modelled as a poroelastic material which can mechanically interacts and allow fluid exchange with the CSF in the spinal SAS. The simulation outcomes indicate that obstructed CSF flow within the cervical spinal canal leads to increased pressure gradients and velocities. The heightened velocities are predominantly observed within the obstruction region. Particularly the substantial obstruction appears to alter the spinal cord's deformation behaviours and seems to enhance fluid exchange between the spinal SAS and the spinal cord. However, the precise mechanisms driving this relationship remain unclear, warranting further investigation. The study's results reveal that implementing the FSI approach did not significantly improve the understanding of CSF flow in the spinal SAS. However, it did offer extra insights into fluid exchange and stresses in the spinal cord. In conclusion, this study has provided enhanced insights into the implications of an artificial three-dimensional obstruction using the CFD and the FSI. The findings might facilitate the selection of the most suitable approach for subsequent simulations.