Peristaltic flow in the glymphatic system: insights from elastohydrodynamic effects

The flow of cerebrospinal fluid (CSF) through the glymphatic system is linked to metabolic waste clearance and nutrient delivery within the brain. Consequently, the decreased functionality of this system is associated with neurodegenerative diseases such as Alzheimer’s disease and dementia. Despite broad applications in medicine including drug delivery, the driving mechanisms behind CSF flow are still not fully understood. The flow of CSF through annular perivascular spaces (PVSs) surrounding cranial arteries is investigated using a stream function approach to parametrically study the flow physics. The 2D model employs a submerged infinite sheet which carries a prescribed traveling wave, representing the pulsing action of the arterial wall. The flow induced by the wall-wave motion is coupled with a passive, elastically deformable semi-infinite wall on the top boundary of the fluid, which aims to model the brain tissue. The flow of CSF, induced pressure gradients and brain tissue deformation are found analytically using perturbation methods over a large parameter space of physiologically relevant quantities. We determine the influence of the wavelength, amplitude and frequency of the peristaltic motion as well as the brain tissue elasticity on the induced CSF flow. Results lead to key insights regarding the circulation and transport of CSF through the PVS, such as flow rate dependence on the elastic properties of the brain and vascular system as well as the necessity of having a constant pressure gradient in the direction of flow.