A
perivascular space, also known as a
Virchow–Robin space, is an
immunological space between an
artery and a
vein (not
capillaries) and the
pia mater that can be expanded by
leukocytes. The spaces are formed when large
vessels take the pia mater with them when they dive deep into the
brain. The pia mater is reflected from the surface of the brain onto the surface of blood vessels in the
subarachnoid space.
Perivascular cuffs are regions of leukocyte aggregation in the spaces, usually found in patients with
viral encephalitis.