The anastomotic venous circle of the base of the brain

Adjacent to the arterial circle of Willis at the base of the brain, there is an anastomotic circle of veins linking the right and left halves of the cerebral deep venous system. This venous circle is formed by anterior and posterior transverse anastomotic channels (the anterior and posterior communicating veins), and paramedian longitudinal vessels (the basal veins of Rosenthal). This collateral venous network has received considerably less attention than its arterial counterpart, but is its functional homologue. Although inconstant, it can be seen readily with current neuroimaging techniques including three-dimensional digital subtraction venographic phase 3D arteriography (3D-DSV) and CT venography (CTV). The venous circle represents a route of contralateral venous drainage that may become important, particularly when segments of the basal vein are absent (with or without complex DVA), or in high flow states including arteriovenous shunts that access the deep venous system. We review the gross anatomy and provide examples of the radiologic imaging of this venous circle.