Inferior View of a Stepwise Dissection of an Axial Section of the Cranial Base. E, The cartilaginous tissue has been removed from the foramen lacerum to expose the anterior genu of the petrous carotid sitting above the foramen lacerum. The vidian nerve passes above the petrous apex, courses at the lateral edge of the foramen lacerum, and enters the vidian canal in the base of the pterygoid process of the sphenoid bone. F, The floor of the vidian canal, which courses in the base of the pterygoid process, has been drilled to expose the vidian nerve. The medial and lateral pterygoid plates and the pterygoid process were removed to expose the pterygopalatine fossa where the vidian nerve enters the pterygopalatine ganglion. G, The part of the petrous apex below the carotid canal has been removed to expose the horizontal segment of the petrous carotid. Some of the posterolateral portion of the eustachian tube has been preserved. The branches of the third trigeminal division are exposed below the foramen ovale in the infratemporal fossa. H, Inferior view of skull base showing the course of the petrous carotid and vidian nerve. The petrous carotid enters the carotid canal and exits the skull base in the area above the foramen lacerum. The vidian nerve passes above the petrous apex to enter the vidian canal and forward to join the pterygopalatine ganglion in the pterygopalatine fossa. (Images courtesy of AL Rhoton, Jr.)