The venous circle of trolard

A venous anastomotic network is occasionally found at the base of the brain, which closely resembles the vicinal arterial circle of Willis. When present, this venous polygon is composed of the anterior cerebral and communicating veins, the basal vein of Rosenthal and the posterior communicating and lateral mesencephalic veins. We propose that this anastomotic ring be termed the venous circle of Trolard. This venous circle might cause bleeding with such procedures as an endoscopic third ventriculostomy. We believe that information regarding this venous circle may be useful to neuroradiologists or neurosurgeons operating at the base of the brain (Fig. 1, Ref. 10).