Venous anatomy of anterior brainstem and cerebellum. The crus cerebri and interpedunucular fossa of the midbrain, basis pons, proximal medulla, and petrosal surface of the cerebellum are in view in this image. The oculomotor nerves emerge from the lateral surfaces of the interpeduncular fossa. The trigeminal nerves emerge from the anterolateral pons, while the abducens and facial-vestibulocochlear nerve bundles emerge, respectively, from the anterior and lateral pontomedullary junction. The nervus intermedius is part of the facial nerve and contains somatic sensory, gustatory, and parasympathetic fibers. The anterior medulla features the paired pyramids along its length. They are bordered medially by the anterior median fissure and laterally by the olives. The anterolateral or preolivary sulcus intervenes between the pyramids and the olives. The pyramids contain motor fibers of the corticospinal tracts. Roots of the hypoglossal nerve emerge from the preolivary sulcus while the roots of the glossopharyngeal, vagus, and spinal accessory nerves emerge in a rostro-caudal sequence from the postolivary sulci. Choroid plexus material can be seen protruding from the lateral foramina of the fourth ventricle anterior to the flocculus of the cerebellum. The medial anterior pontomesencephalic vein and anterior medullary vein (unlabeled, but occupying the anterior median fissure) are longitudinal veins on the anterior surface of the brainstem (located deep to the basilar artery). They typically intersect with transverse pontine, pontomedullary veins (the latter located at the pontomedullary junction), and medullary veins crossing the medulla transversely. The veins of the petrosal surfaces of the cerebellum drain primarily to the vein of the cerebellopontine fissure as generally do transverse coursing brainstem veins. Venous blood from these sites drain into the superior petrosal veins, which empty into the superior petrosal sinus. (Image courtesy of PA Rubino)