Simulation of fluid transport in a porous media model of the brain interstitium using the Lattice Boltzmann Method

Brain parenchyma is a complex porous medium consisting of numerous cell types, surrounded by interstitial fluid that composes 20 percent of the total brain volume. Like other parts of the human body, these cells produce waste that must be cleared from the interstitial fluid. Recent experiments demonstrate that the glymphatic system, a fluid circulation pathway analogous to the lymphatic system found in the body, contributes to the removal of such waste. Cerebrospinal fluid (CSF) surrounds the brain and flows into the brain along perivascular spaces (channels surrounding the brain's vasculature) to exchange with interstitial fluid and remove waste via advection and diffusion. Failure in glymphatic system function is hypothesized to cause waste accumulation, leading to neurodegenerative diseases such as Alzheimer's. In this work, we developed a Lattice Boltzmann Method (LBM) code which is a powerful tool for solving fluid flow in complicated geometries, such as porous media. We simulate advective-diffusive transport in an idealized porous media model of the brain tissue. Our approach is very general and allows us to rapidly test different hypothesized geometries and driving pressures, all of which are very difficult to measure in vivo. We will present preliminary simulations that offer novel insight into solute exchange between perivascular and interstitial spaces in the brain, with the goal of developing new hypotheses that can be tested against experiments. Our simulations provide an innovative approach to resolving fundamental details of mass transport through the interstitial spaces of the brain, which has been called the final frontier of neuroscience. Gaining a deeper understanding of solute exchange has tremendous implications for the prevention and treatment of neurological disorders like Alzheimer's disease.