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Review
. 2022 Apr 30;71(2):199-208.
doi: 10.33549/physiolres.934802. Epub 2022 Mar 28.

Brain Fluid Channels for Metabolite Removal

M Maloveská  1 , F Humeník, Z Vikartovská, N Hudáková, V Almášiová, L Krešáková, D Čížková
Affiliations
Review

Brain Fluid Channels for Metabolite Removal

M Maloveská et al. Physiol Res. .

Abstract

The adult human brain represents only 2% of the body's total weight, however it is one of the most metabolically active organs in the mammalian body. Its high metabolic activity necessitates an efficacious waste clearance system. Besides the blood, there are two fluids closely linked to the brain and spinal cord drainage system: interstitial fluid (ISF) and cerebrospinal fluid (CSF). The aim of this review is to summarize the latest research clarifying the channels of metabolite removal by fluids from brain tissue, subarachnoid space (SAS) and brain dura (BD). Special attention is focused on lymphatic vascular structures in the brain dura, their localizations within the meninges, morphological properties and topographic anatomy. The review ends with an account of the consequences of brain lymphatic drainage failure. Knowledge of the physiological state of the clearance system is crucial in order to understand the changes related to impaired brain drainage.

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Conflict of interest statement

Conflict of Interest

There is no conflict of interest.

Figures

Fig. 1
Fig. 1
The ISF and CSF flow paths in brain tissue (top of the image) and routs of CSF outflow from SAS (bottom of the image). ISF - perivascular drainage channel /IPAD system (shown by dotted lines) – elimination of ISF along the basement membrane of brain penetrating capillaries and arteries, CSF - paravascular drainage channel/ glymphatic system (shown by thick lines) - CSF flows into the paravascular space around arteries, is combined with ISF and parenchymal solutions in brain parenchyma and subsequently it exits the brain in paravascular space around veins, CSF outflow from SAS via: 1. the arachnoid granulations of the dural sinus; 2. connections between the olfactory nerves and nasal lymphatics; 3. by means of the meningeal lymphatic vessels.
Fig. 2
Fig. 2
Detail of CSF inflow along the Pial – Glial basement membrane and ISF outflow via Intramural peri-arterial drain-age (IPAD) system. CSF enters the brain between the pia mater and glia limitans. ISF and solutes pass out the brain along basement membranes surrounding smooth muscle cells in the tunica media of arteries, what is referred to as the Intramural Peri - Arterial Drainage (IPAD) system.
Fig. 3
Fig. 3
Possibility of meningeal lymphatic vessels localization within the subarachnoid space. The meningeal lymphatic vessels are located within the subarachnoid space: (i.) they are directly “bathed” by CSF, therefore the products of brain metabolism (yellow stars) could easily diffuse into the meningeal lymphatic vasculature, (ii.) the lymphatic vessels are located at the interface between the brain dura and arachnoid layer, (iii.) they are positioned directly inside in brain dura. The figure is modified image of Raper [44].
See this image and copyright information in PMC

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