A, The detail shows the site of the vertical scalp incision and right retrosigmoid craniotomy. The cerebellum has been elevated to expose the nerves in the right cerebellopontine angle. The glossopharyngeal and vagal nerves are separated by the dural septum at the level of the dural roof of the jugular foramen. The glossopharyngeal nerve enters the glossopharyngeal meatus and the vagus nerve enters the vagal meatus with the branches of the accessory nerve. Both meatus are very shallow compared with the internal acoustic meatus. The superior and lateral margins of both meatus project downward and medially over the nerves entering the meatus. The vertebral artery displaces the hypoglossal rootlets of cranial nerve XII posteriorly so that they intermingle with the rootlets of the accessory nerve. B, Another specimen showing the relationship of the rhomboid lip and choroid plexus protruding from the foramen of Luschka to the glossopharyngeal and vagus nerves. The choroid plexus protrudes laterally behind the glossopharyngeal nerves. The rhomboid lip is a thin layer of neural tissue that forms the ventral margin of the foramen of Luschka at the outer end of the lateral recess. C and D, Enlarged view of two jugular foramina. The glossopharyngeal and vagus nerves are consistently separated by a dural septum at the level of the roof over the jugular foramen. The jugular dural fold projects downward and medially over the lateral edge of the glossopharyngeal and vagal meatus and over the site at which the nerves penetrate the dura. (Images courtesy of AL Rhoton, Jr.)