Navigating the Skull Base



   Two parallel lines can be drawn lateral to the petro-occipital fissure for locating other structures. In the petrous temporal bone, a petrous line traverses the carotid canal terminating posteriorly in the middle ear and anteriorly at (or just above) the foramen lacerum. In the greater wing of the sphenoid, a sphenoid line begins posteriorly immediately above the sphenoid spine and traverses the foramen spinosum and the foramen ovale. Following the sphenoid line to the body of the sphenoid bone and then proceeding anteriorly, the foramen rotundum is located one to two sections higher. The foramen rotundum opens into the pterygopalatine fossa immediately above and lateral to the pterygoid canal.