A, Inferior view of the frontal lobe and anterior perforated substance with the optic chiasm reflected downward. The anterior cerebral veins pass above the optic chiasm and are joined across the midline by an anterior communicating vein. The anterior cerebral veins join the veins draining the posterior part of the orbital surface of the frontal lobe and the superficial and deep sylvian veins to constitute the anterior end of the basal vein. B, Enlarged view of the anterior cerebral and anterior communicating veins. Paraterminal veins, draining the cortical areas below the genu of the corpus callosum, join the anterior cerebral veins near the junction with the anterior communicating veins. C, Enlarged view of the right deep sylvian and anterior cerebral veins joining below the anterior perforated substance to form the anterior end of the basal vein. D, Enlarged view of the large left superficial sylvian and smaller deep sylvian veins joining the anterior cerebral and olfactory veins to empty into the anterior end of the basal vein. (Images courtesy of AL Rhoton, Jr.)