E, The external auditory canal has been transected and the middle ear structures have been removed, except the stapes, which has been left in the oval window. The lateral edge of the jugular foramen has been exposed by completing the mastoidectomy, transposing the facial nerve anteriorly, and fracturing the styloid process across its base and reflecting it caudally. The rectus capitis lateralis has been detached from the jugular process of the occipital bone. The petrous carotid is surrounded in the carotid canal by a venous plexus. F, A segment of the sigmoid sinus, jugular bulb, and internal jugular vein have been removed. The lateral wall of the jugular bulb has been removed while preserving the medial wall and exposing the opening of the inferior petrosal sinus into the jugular bulb. Removing the venous wall exposes the glossopharyngeal, vagus, accessory, and hypoglossal nerves, which are hidden deep to the vein. The main inflow from the petrosal confluens is directed between the glossopharyngeal and vagus nerves. G, The medial venous wall of the jugular bulb has been removed. The intrajugular ridge extends forward from the intrajugular process, which divides the jugular foramen between the sigmoid and petrosal parts. The glossopharyngeal, vagus, and accessory nerves enter the dura on the medial side of the intrajugular process, but only the glossopharyngeal nerve courses through the foramen entirely on the medial side of the intrajugular ridge. The vagus nerve also enters the dura on the medial side of the intrajugular process, but does not course along the medial side of the intrajugular ridge. H, The intrajugular process and ridge have been removed to expose the passage of the glossopharyngeal, vagus, and accessory nerves through the jugular foramen. The tip of a right-angle probe identifies the junction of the cochlear aqueduct with the pyramidal fossa, just above where the glossopharyngeal nerve penetrates the dura. (Images courtesy of AL Rhoton, Jr.)