Stepwise Dissection of the Nasopharynx and Clivus. A, Anterior view of a coronal section just in front of the pterygoid process. The sphenoid sinus, nasal cavity, and nasopharynx offer corridors to the clivus. The infratemporal fossa, containing the lateral and medial pterygoid muscles, branches of the maxillary artery, mandibular nerve, and pterygoid venous plexus, is located lateral to the nasal cavity and nasopharynx. B, The pterygoid muscles, lower part of the temporalis muscles, and vomer have been removed. The vidian canal is located at the lower lateral corner of the sphenoid sinus floor, where a horizontal line along the sinus floor meets a vertical line along the lateral wall of the sphenoid sinus and the medial pterygoid plate. C, The right pterygoid process, tensor, and levator veli palatini muscles and the nasopharyngeal structures, except the right eustachian tube, have been removed while preserving the vidian canal. The eustachian tube extends from the middle ear, passes along the posterior edge of the medial pterygoid plate, and opens into the nasopharynx. The internal carotid artery and internal jugular vein are positioned behind the foramen ovale and branches of the mandibular nerve. D, The pterygoid processes have been removed on both sides, and the eustachian tubes have been retracted laterally to provide an anterior view of the clivus and the adjacent area. The anterior edge of the exocranial orifice of the jugular foramina is located at almost the same level as the anterior edge of the pharyngeal tubercle. The soft palate sits at the level of the foramen magnum. (Images courtesy of AL Rhoton, Jr.)