AUTHOR=Lee Min Kyoung , Cho Se Jin , Bae Yun Jung , Kim Jong-Min 

TITLE=MRI-Based Demonstration of the Normal Glymphatic System in a Human Population: A Systematic Review

JOURNAL=Frontiers in Neurology

VOLUME=Volume 13 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/neurology/articles/10.3389/fneur.2022.827398

DOI=10.3389/fneur.2022.827398

ISSN=1664-2295

ABSTRACT=Background: The glymphatic system has been described as one that facilitates the exchange between the cerebrospinal fluid (CSF) and interstitial fluid, and many recent studies have demonstrated its presence based on magnetic resonance imaging (MRI). We aim to systematically review the studies demonstrating a normal glymphatic system in a human population using MRI and to propose a detailed imaging protocol for the glymphatic system.
Methods: We searched the MEDLINE and EMBASE databases to identify studies with human participants involving MRI-based demonstrations of the normal glymphatic system. We extracted data on the imaging sequence, imaging protocol, and the targeted anatomical structures on each study. 
Results: According to contrast-enhanced MRI studies, peak enhancement was sequentially detected first in the CSF space, followed by the brain parenchyma, the meningeal lymphatic vessel (MLV), and, finally, the cervical lymph nodes, corresponding with glymphatic flow and explaining the drainage into the MLV. Non-contrast flow-sensitive MRI studies revealed similar glymphatic inflow from the CSF space to the brain parenchyma and efflux of exchanged fluid from the brain parenchyma to the MLV. 
Conclusion: We recommended T1-weighted contrast-enhanced MRI for glymphatic system visualization. Our result can increase understanding of the glymphatic system and may lay the groundwork for developing standardized imaging protocols.