Quadrigeminal plate and cistern. Prominent midbrain eminences including the superior and inferior colliculi medially and the middle cerebellar peduncle just below the trochlear nerve. The trochlear nerve courses along with branches of the superior cerebellar artery and posterior cerebral artery within the ambient cistern posterolateral to the midbrain. The quadrigeminal artery, also known as the collicular artery, is a branch of the posterior cerebral artery irrigating the colliculi of the quadrigeminal plate. The cerebellar vermis is midline and has venous drainage into the superior cerebellar vein and the precentral cerebellar vein. (Image courtesy of AL Rhoton, Jr.)