Osseous anatomy of the posterior skull base. The petrous portion of the temporal bone joins the petrous portion of the sphenoid bone and the clival portion of the occipital bone medially to form the petroclival fissure, and it joins the greater wing of the sphenoid laterally to form the petrosphenoidal fissure. The foramen lacerum is a natural gap formed at the sphenopetroclival junction, and it forms the continuation of the petrous carotid canal with the sphenoidal carotid canal. The lingual process of the sphenoid bone forms the lateral aspect of the foramen lacerum. The petrous portion of the temporal bone forms the anterior aspect of the jugular foramen. The inferior petrosal sinus typically runs at the level of the petroclival fissure to interconnect the cavernous sinus with the jugular foramen. (Image courtesy of JC Fernandez-Miranda)