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Advanced Dissections

A. Sphenopalatine and Vidian Foramen and Pterygomaxillary Fossa (Figures 37-41)

Identification of the sphenopalatine foramen and pterygomaxillary fossa may be indicated in cases when posterior epistaxis requires endoscopic cauterization or ligation of the sphenopalatine or internal maxillary vessels (51-53). Exposure and control of these vessels may also be necessary during an endoscopic resection of a juvenile angiofibroma or other nasopharyngeal neoplasms (54-57).

The sphenopalatine foramen is circular or oval, and is usually found a few millimeters superior to the tail of the middle turbinate. Occasionally it consists of two separate openings: a larger superior opening, with the neurovascular pedicle supplying the superolateral nasal wall and septum, and a smaller inferior opening, with the neurovascular pedicle supplying the inferolateral nasal wall and inferior turbinate (58). The septal (nasopalatine) neurovascular pedicle can be seen coursing toward the posterior nasal septum and rostrum just inferior to the ostium of the sphenoid sinus and tail of the superior turbinate. Because this branch is often transected in the course of a sphenoid sinusotomy, it requires cauterization. The remaining branches of the sphenopalatine artery supply the lateral nose and anastomose with terminal branches of the labial artery (from the external carotid artery) and the anterior and posterior ethmoid arteries (from the internal carotid artery).

The vidian nerve carries parasympathetic fibers to the nose and paranasal sinuses. The vidian nerve is found coursing along the floor of the lateral sphenoid sinus in a posteroanterior direction.

Figure 37 Sagittal (a) and endoscopic (b) views representing the approximate level of the sphenopalatine (SP) and vidian (V) foramina slightly superior to the insertion of the middle turbinate tail (MT). The sphenopalatine foramen may also be found posteromedial to the vertical antrostomy ridge and approximately half the distance between the posterior MOF and the lamellar insertion of the inferior turbinate into the lateral nasal wall (dotted lines).

Figure 37 Sagittal (a) and endoscopic (b) views representing the approximate level of the sphenopalatine (SP) and vidian (V) foramina slightly superior to the insertion of the middle turbinate tail (MT). The sphenopalatine foramen may also be found posteromedial to the vertical antrostomy ridge and approximately half the distance between the posterior MOF and the lamellar insertion of the inferior turbinate into the lateral nasal wall (dotted lines).

The easiest way to visualize the nerve is to expose the sphenopalatine foramen first. A wide sphenoid sinusotomy is then performed to determine the level of the sphenoid floor. The vidian foramen may be found along the inferior bony face of the sphenoid immediately posterior and perpendicular to the sphenopalatine foramen. Nerve fibers enter directly into the pterygomaxil-lary fossa immediately lateral to the vidian foramen.

The pterygomaxillary fossa can be exposed by removing the vertical ridge of the antrostomy and adjacent thin posterior bony wall of the maxillary sinus through the middle meatal antros-tomy. The internal maxillary artery and its branches, the sympathetic and parasympathetic nerve plexus, veins, and buccal fat can be seen within the pterygomaxillary fossa. Superiorly, the infraorbital nerve may be seen coursing toward the foramen rotundum superolateral to the vidian foramen.

Figure 38 Endoscopic view showing the sphenopalatine foramen (arrows) posteromedial to the vertical antrostomy ridge. S = sphenoid sinus. M= posterior wall of the maxillary sinus.

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