Simulated cerebrospinal fluid motion due to pulsatile arterial flow : Master Thesis Project

Sammanfattning: All organs, including the brain, need a pathway to remove neurotoxic extracellular proteins. In the brain this is called the glymphatic system. The glymphatic system works by exchanging proteins from interstitial fluids to cerebrospinal fluids. The extracellular proteins are then removed through the cerebrospinal fluid drains. The glymphatic system is believed to be driven by arterial pulsatility, cerebrospinal fluid production and respiration. Cerebrospinal fluids enters the brain alongside arteries. In this project, we investigate if a simulated pulsatile flow in a common carotid artery can drive cerebrospinal fluid flow running along the artery, using computational simulations of a linearly elastic and fluid-structure multiphysical model in COMSOL. Our simulations show that a heartbeat pulse increases the arterial radius of the common carotid artery by 6 %. Experimental data, assessed using 4D magnetic resonance imaging of a living human, show an increase of 13 %. Moreover, our results indicate that arterial displacement itself is not able to drive cerebrospinal fluid flow. Instead, it seems to create a back and forth flow that possibly could help with the protein exchange between the cerebrospinal and interstitial fluids. Overall, the results indicate that the COMSOL Multiphysics linearly elastic model is not ideal for approximations of soft non-linearly elastic solids, such as soft polydimethylsiloxane and artery walls work for stiffer materials. The long term aim is to simulate a part of the glymphatic system and the present work is a starting point to reach this goal. As the simulations in this work are simplified there are more things to test in the future. For example, using the same geometries a non-linear elastic model could be tested. The pulsatile waveform or the geometry could be made more complex. Furthermore the model could be scaled down to represent a penetrating artery in the brain instead of the common carotid artery.