Brain pulsations enhance cerebrospinal fluid flow in perivascular spaces

Cerebrospinal fluid (CSF) flow is modelled in human perivascular spaces (PVSs) that surround brain penetrating arteries. It is proposed that the outer PVS boundary oscillates due to brain pulsations, and the arterial wall motion is driven by a blood pressure wave. Lubrication theory is employed to derive a mathematical model for the CSF flow, which is then solved numerically. A parametric analysis is undertaken to investigate the effect of the brain pulsations, which shows that pulsations magnify the net axial CSF flows created by the arterial wall motion. The findings suggest that net axial CSF flows are almost entirely positive (deeper into the brain), with arterial wall motion highly dependent on PVS-penetrating artery configurations. Given the glymphatic hypothesis, the findings support the clinical practice of treating dilated PVSs as indicators of an increased likelihood of neurodegenerative conditions, such as dementia.