A, The AICA passes between the facial and vestibulocochlear nerves. A dural septum separates the glossopharyngeal and vagus nerves at the jugular foramen. B, The vestibulocochlear nerve and the flocculus have been elevated to expose the junction of the facial nerve with the brainstem. In the retrosigmoid approach, the facial nerve junction with the brainstem can be exposed below the vestibulocochlear nerve. C, The posterior wall of the internal acoustic meatus has been removed. The cleavage plane between the superior and inferior vestibular nerves is especially prominent. D, The dura lining the internal acoustic meatus has been opened. The transverse crest separates the superior vestibular and facial nerves above from the inferior vestibular and cochlear nerves below. E, Enlarged view of the nerves within the meatus. The cochlear nerve is partially hidden anterior to the inferior vestibular nerve. F, The cleavage plane between the superior and inferior vestibular and cochlear nerves has been started laterally and extended medially to expose the individual nerve bundles. (Images courtesy of AL Rhoton, Jr.)