The Glymphatic System: A Review of the Challenges in Visualizing its Structure and Function with MR Imaging

The central nervous system (CNS) was previously thought to be the only organ system lacking lymphatic vessels to remove waste products from the interstitial space. Recently, based on the results from animal experiments, the glymphatic system was hypothesized. In this hypothesis, cerebrospinal fluid...

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Bibliographic Details
Published in:Magnetic Resonance in Medical Sciences 2022, Vol.21(1), pp.182-194
Main Authors: Naganawa, Shinji, Taoka, Toshiaki
Format: Article
Language:English
Subjects:
Alzheimer's disease
Animals
Aquaporin 4
Brain - diagnostic imaging
Central Nervous System
Cerebrospinal fluid
endolymphatic hydrops
gadolinium
Glaucoma
glymphatic system
Glymphatic System - diagnostic imaging
Glymphatic System - physiology
Hydrocephalus
In vivo methods and tests
Lymphatic system
Magnetic Resonance Imaging
Medical imaging
Meninges - diagnostic imaging
Neurodegenerative diseases
Neuroimaging
Parenchyma
Review
sleep
Structure-function relationships
Subarachnoid space
Superior sagittal sinus
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Summary:The central nervous system (CNS) was previously thought to be the only organ system lacking lymphatic vessels to remove waste products from the interstitial space. Recently, based on the results from animal experiments, the glymphatic system was hypothesized. In this hypothesis, cerebrospinal fluid (CSF) enters the periarterial spaces, enters the interstitial space of the brain parenchyma via aquaporin-4 (AQP4) channels in the astrocyte end feet, and then exits through the perivenous space, thereby clearing waste products. From the perivenous space, the interstitial fluid drains into the subarachnoid space and meningeal lymphatics of the parasagittal dura. It has been reported that the glymphatic system is particularly active during sleep. Impairment of glymphatic system function might be a cause of various neurodegenerative diseases such as Alzheimer’s disease, normal pressure hydrocephalus, glaucoma, and others. Meningeal lymphatics regulate immunity in the CNS. Many researchers have attempted to visualize the function and structure of the glymphatic system and meningeal lymphatics in vivo using MR imaging. In this review, we aim to summarize these in vivo MR imaging studies and discuss the significance, current limitations, and future directions. We also discuss the significance of the perivenous cyst formation along the superior sagittal sinus, which is recently discovered in the downstream of the glymphatic system.
ISSN:1347-3182
1880-2206
DOI:10.2463/mrms.rev.2020-0122