Oscillatory and steady streaming flow of cerebrospinal fluid during the cardiac cycle #

Mariia Dvoriashyna, Alain Goriely

12:50 Monday in 4Q56.

Part of the Physiological flows and transport session.

Abstract #

Cerebrospinal fluid (CSF) is a transparent fluid with properties similar to water. It is produced primarily in the choroid plexus and flows from the ventricles into the subarachnoid space (SAS), a fibrous space that covers the brain and spinal cord and is exteriorly lined by the dura membrane. The fluid is drained through the arachnoid villi into the sagittal sinus at the top of the head. In addition to the slow production-drainage flow, there is also a pulsating flow in the SAS driven by arterial pulsation: during systole, CSF flows from the cranial to the spinal SAS, and during diastole, the flow reverses. This flow plays a role in transporting and clearing metabolic waste from the brain. To complement existing numerical models, we use an analytical technique called lubrication theory to investigate flow in the cranial SAS in this study. We model the SAS as a thin region between the two sphere-like surfaces, with the inner surface oscillating periodically with a prescribed function. We use lubrication theory to simplify the Navier-Stokes equations (since the thickness of SAS is much smaller than its length), which allows us to obtain second-order equations for fluid pressure. For the simplified case of a spherical brain surface and spatially uniform thickness, we obtain the analytical solution. In the case of realistic brain shapes, we obtain complex three-dimensional flow fields. As a result of the oscillations, there is a steady streaming flow in both cases, with velocities of about 10um/s, which are comparable to those of production-drainage flow. This suggests that steady streaming is important for solute transport around the brain and waste clearance.