macroscopic waste clearance system that utilizes a unique system of perivascular tunnels, formed by astroglial cells, to promote efficient elimination of soluble proteins and metabolites from the central nervous system. [ http://www.informatics.jax.org/accession/sbello https://doi.org/10.1007/s11064-015-1581-6 https://github.com/obophenotype/uberon/issues/1260 ]