Figure 1.

Anatomy of the paravascular and perivascular spaces. The arterial paravascular space is bounded internally by the pial sheath (4) and externally by the basement membrane of glia limitans (5). The venous paravascular space is bounded internally by the vein wall (6) and externally by the glia limitans. The perivascular space is found within the middle layers of the basement membrane of arterial smooth muscle cells (3). No perivascular space is present in venous vasculature. In each space, the direction of fluid flow and waste clearance, such as amyloid beta (Aβ), is depicted with arrows. Reprinted with permission © Bakker et al. (2016).