Arterial pulsation vs neurovascular coupling as a driving mechanism of cerebrospinal fluid flow in complex perivascular space geometries

Removal of brain's protein wastes such as amyloid-β is facilitated by cerebrospinal fluid (CSF) transport in perivascular spaces (PVSs), which are annular channels surrounding blood vessels. Buildup of amyloid-β in the brain is connected to neurological disorders such as Alzheimer's disease. Here, we derive a one-dimensional finite volume model (FVM) to study CSF flow in PVSs. FVM lets us simulate complex geometries that are not computationally feasible in higher-dimensional simulations. We model PVSs as an annulus filled with CSF. Two cases are considered: 1) a pial PVS with rigid and impermeable outer walls, 2) a penetrating PVS with compliant and permeable outer walls. In both cases, the inner radius changes periodically in time as a consequence of arterial pulsation or neurovascular coupling, which are hypothesized to drive CSF through PVSs. We use both idealized and realistic waveforms obtained from in-vivo experiments for arterial pulsations and neurovascular coupling waves. This approach will enable new insights into CSF flow behavior in the brain's waste removal system and pave the way for a new understanding of the mechanisms leading to neurological diseases.