Pterygopalatine Fossa Anatomy
The pterygopalatine fossa lies between the pterygoid process of the sphenoid bone posteriorly, the palatine bone medially and the maxilla anteriorly (Fig. 7.43). It is slit-like and opens laterally through the pterygomaxillary fissure into the infratemporal fossa.
It contains part of the maxillary (V2) division of the trigeminal nerve, the pterygopalatine ganglion and its branches and the termination of the maxillary artery, together with accompanying veins and lymphatics. The pterygopalatine fossa communicates with the middle cranial fossa through the foramen rotundum, with the foramen lacerum through the pterygoid canal, with the orbit through the inferior orbital fissure, with the walls of the nasal cavity through the sphenopalatine foramen and with the palate via the greater and lesser palatine canals.
Maxillary (V2) division of the trigeminal nerve
The maxillary division (Fig. 7.44) leaves the cranial cavity through the foramen rotun- dum, crosses the pterygopalatine fossa and continues forwards through the inferior orbital fissure into the orbit. It terminates as the infraorbital nerve, which traverses the infraorbital canal to reach the face. The maxillary division has several branches arising in the pterygopalatine fossa and the floor of the orbit. In the pterygopalatine fossa (Fig. 7.45), two branches suspend the pterygopalatine ganglion from the parent nerve. Also arising in the fossa are the posterior superior alveolar nerves (Figs 7.44 & 7.45), which descend in the posterior wall of the maxillary air sinus to reach the upper molar teeth. In the floor of the orbit, the middle and anterior superior alveolar nerves (Fig. 7.44) arise and descend in the lateral and anterior walls of the maxilla. Collectively, the superior alveolar nerves supply the maxilla and its air sinus, the alveolar ridge and all the upper teeth. The zygomatic nerve (Fig. 7.44) also arises in the floor of the orbit and ascends on the lateral wall, dividing into zygomaticotemporal and zygomaticofacial nerves. These branches pierce the zygomatic bone to supply the overlying facial skin. A branch from the zygomaticotemporal nerve conveys postganglionic parasympathetic fibres from the pterygopalatine ganglion to the lacrimal gland. The infraorbital nerve (Fig. 7.44) emerges onto the face through the infraorbital foramen and supplies the skin of the cheek, lower eyelid, upper lip and lateral surface of the external nose.
The pterygopalatine ganglion (Fig. 7.45) is suspended from the maxillary division in the pterygopalatine fossa and transmits sensory, parasympathetic and sympathetic nerve fibres. Sensory fibres originating in the palate, nose and nasopharynx pass through the ganglion without synapsing to enter the maxillary division. Preganglionic parasympathetic fibres destined for the ganglion leave the brain in the facial (VII) nerve and travel via the greater petrosal nerve. These fibres emerge from the petrous temporal bone and pass along the floor of the middle cranial fossa to enter the foramen lacerum, where they accompany postganglionic vasomotor sympathetic fibres from the carotid plexus as the nerve of the pterygoid canal to reach the pterygopalatine ganglion. In the ganglion the parasympathetic fibres synapse, and postganglionic fibres are distributed through the appropriate branches of the ganglion to the mucous glands in the nose and palate. Secretomotor parasympathetic fibres destined for the lacrimal gland enter the maxillary division and travel in its zygomatic branch. The ganglion earns its nickname, the ‘hay fever ganglion’, by virtue of its parasympathetic component. Sympathetic fibres are also distributed in the branches of the ganglion.
There are five groups of branches from the pterygopalatine ganglion (Fig. 7.45): posterior lateral nasal, pharyngeal, nasopalatine, and greater and lesser palatine. Posterior lateral nasal nerves, entering via the sphenopalatine foramen, supply the lateral wall of the nasal cavity. The pharyngeal branch innervates the nasopharynx. The nasopalatine nerve (Fig. 7.46) crosses the anterior surface of the body of the sphenoid bone to enter the nasal septum, then angles anteroinferiorly in a groove on the upper edge of the vomer, eventually passing through the incisive canal onto the lower surface of the anterior part of the hard palate. The nerve conveys sensation from the front of the palate and the inferior part of the nasal septum. The greater and lesser palatine nerves traverse the palatine canal to emerge from the appropriate palatine foramina on the lower surface of the hard palate. The greater palatine nerve supplies the hard palate, while the lesser innervates the soft palate.
The maxillary artery (Figs 7.44 & 7.45) enters the pterygopalatine fossa from the infratemporal fossa and divides into its terminal branches which accompany the branches of the ganglion and bear corresponding names. Venous blood drains into the pterygoid plexus, which continues into the infratemporal fossa and communicates with the cavernous sinus via the inferior and superior orbital fissures.