A, The infratemporal fossa is surrounded by the maxillary sinus anteriorly, the mandible laterally, the sphenoid pterygoid process anteromedially, and the parapharyngeal space posteromedially, and contains the mandibular nerve and maxillary artery and their branches, the medial and lateral pterygoid muscles, and the pterygoid venous plexus. B, Part of the lateral pterygoid muscle has been removed to expose the branches of the trigeminal nerve coursing in the infratemporal fossa below the greater sphenoid wing. The pterygopalatine fossa is located between the posterior maxillary wall anteriorly, the sphenoid pterygoid process posteriorly, the nasal cavity medially, and the infratemporal fossa laterally. The pharyngeal recess (fossa of Rosenmüller) projects laterally from the posterolateral corner of the nasopharynx with its lateral apex facing the internal carotid artery laterally and the foramen lacerum above. The posterior nasopharyngeal wall is separated from the lower clivus and the upper cervical vertebra by the longus capitis, and the nasopharyngeal roof rests against the upper clivus and the posterior part of the sphenoid sinus floor. C, The sphenoid pterygoid process has been removed to expose the maxillary nerve passing through the foramen rotundum to enter the pterygopalatine fossa where it gives rise to the infraorbital nerve, which courses in the roof of the maxillary sinus. The maxillary nerve within the pterygopalatine fossa gives off communicating rami to the pterygopalatine ganglion. The vidian nerve, formed by the union of the deep petrosal nerve from the carotid sympathetic plexus and the greater petrosal nerve, courses forward through the vidian canal to join the pterygopalatine ganglion. The terminal part of the petrous carotid is exposed above the foramen lacerum. D, Enlarged view with highlighting of the pre- (red) and poststyloid (yellow) compartments of the parapharyngeal space. The styloid diaphragm, formed by the anterior part of the carotid sheath, separates the parapharyngeal space into pre- and poststyloid parts. The prestyloid compartment, a narrow fat-containing space between the medial pterygoid and tensor veli palatini, separates the infratemporal fossa from the medially located lateral nasopharyngeal region containing the tensor and levator veli palatini and the eustachian tube. The poststyloid compartment, located behind the prestyloid part, contains the internal carotid artery, internal jugular vein, and the cranial nerves IX through XII. (Images courtesy of AL Rhoton, Jr.)