Figure 7.

Schematic representation of the CSF compartment. Tracer injected in the cisterna magna distributes via the CSF and reaches the SAS and paravascular space, which extents along arteries into the parenchyma. Leptomeningeal vessels are bathed by the CSF. However, the space around artery and vein may be different due to the particular shape of these vessels: bigger around the circular arteries and smaller around the flattened veins (see sketched cross-section). Cerebral cisterns connect to the subarachnoid space and embed major branches of leptomeningeal arteries. Pressure oscillations produced by respiration and heart beat cause mixing within the CSF compartment. Insert: at the level of the microcirculation, the PVS disappears and fuses with the basement membrane of smooth muscle cells, pericytes, and endothelial cells. Green: CSF; red: artery; blue: vein; purple: glia limitans; light blue: basement membrane; pink: parenchyma.