Title: Exploring pressure dependent permeability of brain white matter: Poroelastic theory or microstructurally-based FSI modelling?
Authors: Tian Yuan & Daniele Dini
Conference: International Conference on Nonlinear Solid Mechanics (ICoNSoM 2022), 13 - 16 Jun 2022, Alghero, Italy
Fig: Schematic of the anisotropic poroelastic model and microstructural informed model
Abstract:
The flow of interstitial and cerebrospinal fluids in brain white matter (WM) is key to maintain the tissue functions and health. An important class of brain disease treatments has recently emerged that allows to bypass the blood-brain-barrier by infusing drugs directly into the brain tissue via a catheter. Such procedures, which include Convection Enhanced Delivery (CED), also rely on the fluid transport property of the brain tissue. However, the intricate flow in WM is controlled by the presence of axonal bundles and the complex tissue microstructure. Given the extremely soft nature of the axons, the mechanical interaction between the flow and these anisotropic structures affects the local flow status and the overall transport property of the brain tissue, which can be characterised by the tissue hydraulic permeability. Although recent experiments have reported evidence of pressure dependent permeability of the brain, this phenomenon has not received sufficient attention from a modelling perspective. Here, we use (a) a mathematical model based on poroelastic theory, and (b) a more explicit method - named icrostructurally based fluid-solid interaction (MBFSI) - to model this phenomenon and compare their capabilities and accuracy in predicting the pressure dependent permeability of the WM. The results show that both methods can reproduce this phenomenon if the change of permeability is driven by axons deformation (shrinkage); however, the use of poroelastic theory is not capable of accurate predictions when displacements and interactions between axons play an important role in affecting the fluid flow.
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