Veins that drain regions supplied by arteries branching from the maxillary artery in the infratemporal fossa and pterygopalatine fossa connect with the pterygoid plexus. These tributary veins include those that drain the nasal cavity, roof and lateral wall of the oral cavity, all teeth, muscles of the infratemporal fossa, paranasal sinuses, and nasopharynx. In addition, the inferior ophthalmic vein from the orbit can drain through the inferior orbital fissure into the pterygoid plexus.
Significantly, small emissary veins often connect the pterygoid plexus in the infratemporal fossa to the cavernous sinus in the cranial cavity. These emissary veins, which pass through the foramen ovale, through the cartilage that fills the foramen lacerum, and through a small sphenoidal foramen on the medial side of the lateral plate of the pterygoid process at the base of the skull, are a route by which infections can spread into the cranial cavity from structures, such as the teeth, that are drained by the pterygoid plexus. Also, because there are no valves in veins of the head and neck, anesthetic inadvertently injected under pressure into veins of the pterygoid plexus can backflow into tissues or into the cranial cavity.
The pterygoid plexus connects: posteriorly, via a short maxillary vein, with the retromandibular vein in the neck; and anteriorly, via a deep facial vein, with the facial vein on the face.
The pterygopalatine fossa is an inverted teardrop-shaped space between bones on the lateral side of the skull immediately posterior to the maxilla (Fig. 8.153).
Although small in size, the pterygopalatine fossa communicates via fissures and foramina in its walls with the: middle cranial fossa, infratemporal fossa, floor of the orbit, lateral wall of the nasal cavity, oropharynx, and roof of the oral cavity.
Because of its strategic location, the pterygopalatine fossa is a major site of distribution for the maxillary nerve [V2] and for the terminal part of the maxillary artery. It also contains the pterygopalatine ganglion where preganglionic parasympathetic fibers originating in the facial nerve [VII] synapse with postganglionic parasympathetic fibers and these fibers, along with sympathetic fibers originating from the T1 spinal cord level join branches of the maxillary nerve [V2].
All the upper teeth receive their innervation and blood supply from the maxillary nerve [V2] and the terminal part of the maxillary artery, respectively, that pass through the pterygopalatine fossa.
The walls of the pterygopalatine fossa are formed by parts of the palatine, maxilla, and sphenoid bones (Fig. 8.153):
The anterior wall is formed by the posterior surface of the maxilla.
The medial wall is formed by the lateral surface of the palatine bone.
The posterior wall and roof are formed by parts of the sphenoid bone.
The part of the sphenoid bone that contributes to the formation of the pterygopalatine fossa is the anterosuperior surface of the pterygoid process (Fig. 8.154). Opening onto this surface are two large foramina:
The maxillary nerve [V2] passes through the most lateral and superior of these—the foramen rotundum—which communicates posteriorly with the middle cranial fossa (Fig. 8.154B).
The greater petrosal nerve from the facial nerve [VII] and sympathetic fibers from the internal carotid plexus join to form the nerve of the pterygoid canal that passes forward into the pterygopalatine fossa through the more medial and inferior foramen—the anterior opening of the pterygoid canal.