Views of the Middle Fossa, Trigeminal Nerve, and Pterygopalatine Fossa. A, Superior view of the middle fossa. The middle fossa dura has been removed to expose the trigeminal nerve. The laterotrigeminal venous system is the venous system surrounding the foramen ovale and mandibular division. B, Superolateral view of the right trigeminal nerve. The bone surrounding the foramen rotundum and ovale has been removed to expose the maxillary and mandibular divisions, respectively. Removing bone in the triangular space between the ophthalmic and maxillary nerve opens into the sphenoid sinus. The maxillary nerve enters the pterygopalatine fossa by passing through the foramen rotundum. C, Lateral view of the right pterygopalatine fossa. The temporal bone, mandibular ramus, and pterygoid muscles have been removed to expose the branches of the maxillary nerve in the pterygopalatine fossa. The vascular structures are anterior to nervous structures in the pterygopalatine fossa. D, Inferior view of the pterygopalatine fossa. The pterygopalatine ganglion is located inferior and medial to the maxillary nerve. The ganglionic branch in the pterygopalatine fossa connects between the maxillary nerve and pterygopalatine ganglion. After crossing the upper part of the pterygopalatine fossa, the maxillary nerve inclines laterally and then enters the infraorbital groove and canal. E, Cross section through the ethmoidal and maxillary sinuses and the nasal cavity in front of the posterior maxillary wall. The posterior wall of the maxillary sinus has been removed to expose the pterygopalatine fossa and ganglion. The maxillary arteries enter the pterygopalatine fossa from the laterally by passing through the pterygomaxillary fissure and give rise to its terminal branches in the pterygopalatine fossa. F, Lateral view of the right pterygopalatine fossa. The maxillary nerve is situated superior and lateral to the pterygopalatine ganglion. The vidian nerve, which courses the floor of the sphenoid sinus, is inferomedial to the maxillary nerve and joins the pterygopalatine ganglion. The maxillary nerve also gives rise to the zygomatic and the posterior superior alveolar nerves. G, The trigeminal nerve has been reflected laterally to expose the vidian nerve. The vidian nerve is formed by the union of the GSPN and deep petrosal nerve. H, Coronal section through the orbital apex behind the pterygopalatine fossa. The anterior end of vidian canal, which opens into the medial part of the posterior wall of the pterygopalatine fossa, is funnel shaped. (Images courtesy of AL Rhoton, Jr.)