Brain Health | A Focus on The Glymphatic System

The glymphatic system denotes a brain-wide, glial-dependent pathway mediating convective exchange between cerebrospinal and interstitial fluids. Organized along perivascular spaces, it aids in enabling macroscopic clearance of metabolic by-products from neural tissue. The term “glymphatic” underscores both its reliance on glial cells and its kinship to lymphatic transport. Accordingly, it is often regarded as the central nervous system’s functional analogue of the peripheral lymphatic system.

In expanding upon this notion, the brain’s fluids may be organized into four compartments: blood (inside cerebral vessels); cerebrospinal fluid (CSF) in the ventricles and what is referred to as the subarachnoid space; interstitial fluid (ISF) bathing brain cells; and intracellular fluid within neurons and glia. Two interfaces aid in keeping these environments distinct: the blood–brain barrier (BBB), formed by tight-junction–linked endothelial cells of brain capillaries with support from pericytes and astrocyte endfeet, and the blood–CSF barrier (BCSFB) at the choroid plexus, where epithelial cells joined by tight junctions aid in regulating exchange between blood and CSF.

The glymphatic system describes perivascular routes that aid in distributing CSF into brain tissue and clearing interstitial solutes. CSF from the subarachnoid space enters periarterial (Virchow–Robin) spaces, mixes with ISF within the parenchyma, and returns along perivenous spaces.

The Glymphatic System & Sleep

Sleep is a fundamental biological process necessary for overall health, as it influences nearly every system in the body, from the brain and metabolism to immunity and tissue repair. When it comes to the glymphatic system, some human studies have emphasized the importance of sleep in relation to glymphatic function, demonstrating that some measures of sleep quality may track with indices of fluid transport in the brain.