Lateral Dissection of the Atlanto-Occipital Joint
5562
Surgical Correlation
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Right posteroinferior dissection of the head near its articulation with the atlas. For orientation, note the styloid process, and posterolateral to this, the facial nerve descending in the facial canal. Medial to these structures are the jugular foramen, transmitting the internal jugular vein and glossopharyngeal, vagus, and spinal accessory nerves, and the internal carotid artery entering the carotid canal. A portion of the petrous bone has been removed to expose the petrous segment of this artery. Paracondylar bone removal reveals the sigmoid sinus and, similarly, removal of a portion of the occipital condyle has opened the hypoglossal canal to reveal the hypoglossal nerve and venous plexus. Medial to this is the vertebral artery ascending through the foramen magnum adjacent to the medulla oblongata (spinal dura has been removed). (Image courtesy of AL Rhoton, Jr.)