Branches of the Petrous Carotid Artery. A–D, Stepwise dissection of a left middle fossa. A, Lateral view. A short segment of the petrous carotid artery is exposed under the dura at the lateral margin of the V3. The geniculate ganglion and facial nerve have been exposed. The greater petrosal nerve exits the geniculate ganglion and passes anteromedial above the petrous carotid. B, The trigeminal nerve has been reflected forward to expose the petrolingual ligament. This petrolingual ligament is formed at the point where the dura lining the carotid canal is reflected laterally to cover the middle fossa floor. Reflecting the trigeminal nerve forward exposes the abducens nerve coursing around the lateral margin of the cavernous carotid above the petrolingual ligament. C, The dura lining the floor of the middle fossa has been removed while preserving the upper part of the petrolingual ligament and the periosteal lining of the carotid canal. A venous plexus that courses between the periosteal lining of the canal and the artery can be seen through the dura lining the carotid canal. The greater petrosal passes obliquely across the upper surface of the petrous carotid and turns downward along the anterior surface to cross above the foramen lacerum located below the anterior genu of the petrous carotid. D, The region bordering the anterior genu of the petrous carotid has been exposed. The abducens nerve passes lateral to the proximal part of the cavernous carotid. The vidian artery arises from the distal horizontal segment and passes forward to enter the vidian canal with the vidian nerve. The anterior genu passes above, and not through, the foramen lacerum, which has been opened. E, Another specimen. The area bordering the anterior genu and vidian canal has been exposed. A vidian artery arises from the horizontal segment of the petrous carotid and joins the vidian nerve in the vidian canal. The vidian artery anastomoses with the maxillary artery in the pterygopalatine fossa. The vidian nerve ends in the pterygopalatine ganglion. The V2 also passes through the pterygopalatine fossa and has multiple anastomoses with the pterygopalatine ganglion. (Images courtesy of AL Rhoton, Jr.)