Magnetic Resonance Imaging of the Glymphatic System in the Human Brain

Our conventional understanding of fluid transport across the brain has significantly changed over the last decade after introduction of the concept of the glymphatic system and discovery of meningeal lymphatics. The glymphatic system is not a true anatomical structure but merely a functional system for cerebrospinal fluid (CSF) and interstitial fluid exchange, whereby the CSF enters the brain through the periarterial space. This movement is driven by a few potential driver mechanisms. The CSF thereafter travels to the interstitium facilitated by aquaporin 4 channels in the astrocytic end feet and subsequently through the interstitium via diffusion and convection/advection and finally exits through the perivenous space. In this review, we describe magnetic resonance imaging (MRI) techniques that have been used or may potentially be useful to analyze the glymphatic system, together with a brief summary and discussion of limitations. MRI, a widely used clinical modality, may potentially provide deeper understanding of the pathophysiology of various diseases based on the concept of the glymphatic system.