E, The tip of a nerve hook placed inside the fourth ventricle is seen through the paper-thin inferior medullary velum. F, The left half of the inferior medullary velum has been divided to expose the superolateral recess and the ventricular surface formed by the superior and inferior peduncles. G, The uvula has been retracted to the right to expose all of the floor and much of the roof of the ventricle. H, The right half of the cerebellum was removed by dividing the vermis sagittally and the cerebellar peduncles transversely. The tonsil has been removed and the inferior medullary velum and the cranial loop of the PICA have been displaced downward to expose the opening into the lateral recess. The dentate nucleus forms a prominence, the dentate tubercle, in the superolateral recess of the roof of the fourth ventricle near the site of attachment of the inferior medullary velum. (Images courtesy of AL Rhoton, Jr.)