A, The veins on the anterior surface of the pons and medulla and the veins of the cerebellopontine fissure and their tributaries empty into the superior petrosal veins. The median anterior medullary vein and median anterior pontomesencephalic veins course in the midline, but often do not extend along the full length of the pons and medulla. The vein of the pontomesencephalic sulcus and the transverse pontine veins are transversely oriented. The veins of the cerebellomedullary fissure join the veins of the middle cerebellar peduncle, which ascends to join the veins of the cerebellopontine fissure. B, The veins in the crural and ambient cistern join the basal vein, which empties into the vein of Galen in the quadrigeminal cistern. The basal vein also drains the walls of the temporal horn, which has been opened on the right. An internal occipital vein passes from the calcarine sulcus and occipital lobe to the vein of Galen. C, Enlarged view of the basal cisterns. The inferior ventricular vein from the temporal horn and the lateral atrial vein join the basal vein, which also drains the walls of the crural and ambient cisterns. The cerebellomesencephalic fissure, an inferior extension of the quadrigeminal cistern, is drained by tributaries of the vein of Galen. D, Lateral view of the cerebellomesencephalic fissure. The veins in the medial portion of the cerebellomesencephalic fissure empty into the vein of Galen and those from the lateral part may join the superior petrosal veins. In this case, the vein of the cerebellomesencephalic fissure is small, resulting in most of the fissure’s drainage being directed laterally through a pontotrigeminal vein, which passes above the trigeminal nerve to empty into a superior petrosal vein formed by a superior hemispheric and transverse pontine vein and the vein of the cerebellopontine fissure. (Images courtesy of AL Rhoton, Jr.)