Mass Transfer Via Multiple Modes of Convection in Perivascular Space*

Alzheimer's disease is a progressive degenerative condition that has various levels of effect on one's memory. It is thought to be caused by a buildup of protein in small fluid-filled spaces in the brain called perivascular spaces (PVS). The PVS often takes on the form of an annular region around arteries and is used as a waste-clearing system for the brain; therefore when there is no protein clearance in the PVS, the other waste cannot be cleared from the brain. To analyze the effects of the protein clearances in the PVS, a digitized scan of a vein from a mouse's brain was investigated. This scanned geometry was then meshed and used for computational fluid dynamics (CFD) studies. Tandem analyses were then carried out and compared between the mouse PVS section and a cylinder with matching dimensionless parameters and hydraulic resistance. The pair was used to validate the CFD model and then assess mass transfer during periods of various types of convection: no flow, constant flow, sinusoidal flow, sinusoidal flow with zero net flux, and an anatomically correct asymmetrical periodic flow. The results showed that, for all the flows in question, there was no protein clearance benefit by the anatomically correct PVS geometry.