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V2 - Maxillary Nerve
Figure 16. Cranial Nerve V2 – Maxillary Nerve (shown in purple)
The maxillary nerve like the ophthalmic nerve is sensory only in function. It is one of the crucial nerves to learn in dentistry as it provides the sensation of the middle face which includes all of the upper teeth and their supporting structures (Figure 17). It follows a complicated course and has many important branches so hang on tight and make sure you refer to the diagram often.
It terminates like the ophthalmic at the trigeminal ganglion but to get there passes through the foramen rotundum. After passing through the foramen but before joining the trigeminal ganglion the maxillary nerve is joined by the meningeal branch that carries sensory information from the meninges that surround the brain.
Figure 17. Cranial Nerve V2 – Maxillary Nerve
Anterior to the foramen rotundum is the sphenopalatine fossa. In this space the nerve has an appendage known as the pterygopalatine ganglion which is a parasympathetic ganglion associated with pre-ganglionic fibers from the facial nerve that arrive at the ganglion on the greater petrosal nerve. The post-synaptic fibers exit the ganglion on the ganglionic branches to join the maxillary nerve. Additionally post-synaptic sympathetic fibers feed through the ganglion to also pass into the maxillary nerve V2. All of these visceral motor fibers join the maxillary nerve and then pass into the zygomatic nerve from which they connect via a communicating branch to the lacrimal nerve to innervate the lacrimal gland as mentioned in the section on the ophthalmic nerve.
In addition, sensory fibers from a number of sensory branches pass through the ganglion without synapsing. The first of these is the greater palatine nerve which passes from the palate through the greater palatine foramen and provides sensory innervation to much of the hard palate. The second is the lesser palatine nerve which passes through the lesser palatine foramen and provides the same service to the soft palate. The next is the nasopalatine nerve which passes from the anterior palatal tissue first through the single incisive foramen then the left and right fibers pass through individual nasopalatine foramina. It then joins with branches from the nasal septum and joins the maxillary nerve at the pterygopalatine ganglion. This final pair of nerves does the remaining area of the hard palate sensation anterior to the canine teeth along with the mucosa in the inferior part of the nasal septum.
Figure 18. Cranial Nerve V2 – Maxillary Nerve (shown in purple)
There are also branches that are less important in dentistry whose areas of innervation can be gleaned from their names. These are the pharyngeal, posterior inferior nasal and posterior superior nasal branches. These all join the nerve and proceed to follow it back to the trigeminal ganglion along with palatal branches.
Anterior to the ganglion is another important sensory nerve that joins the maxillary after passing into the space via foramina in the posterior part of the maxillary tuberosity. This nerve, known as the posterior superior alveolar, provides sensory innervation to the posterior maxilla including the maxillary sinus and the molar teeth and their supporting structures including soft tissue on the facial side except the mesiobuccal root of the first molar in some individuals. This nerve is often targeted for obtaining anesthesia in the posterior maxilla. One can also see in the diagram that this nerve joins with the middle superior alveolar nerve and the anterior superior alveolar nerve to form a continuous network. However, this does not seem to be clinically significant.
To complicate matters further the middle superior alveolar and the anterior superior alveolar do not join directly to the maxillary nerve but rather to a large branch of the nerve that is found in the floor of the orbit. This nerve is known as the infraorbital nerve and begins in the skin of the face inferior to the eye in several locations. There is an inferior palpebral branch that carries sensations from the lower eyelid. There are internal and external nasal branches, a branch known simply as the nasal branch and a branch that runs to the upper lip known as the superior labial branch. The infraorbital nerve thus does most the sensation to the middle face.
The infraorbital nerve passes through a foramen named for it just below the orbital rim. It gathers the anterior and middle superior alveolar branches within the orbit before passing through the inferior orbital fissure into the pterygopalatine space. This is where it meets the posterior superior alveolar to form the maxillary nerve.
The middle superior alveolar nerve is not always present but if it is it supplies sensory innervation to the premolar teeth plus the mesial buccal root of the first molar, their supporting tissue and the facial soft tissue. The anterior superior alveolar serves the same function for the anterior teeth and surrounding tissues. The infraorbital nerve is therefore very important in dental pain control also. Block anesthesia of the infraorbital nerve numbs a large area of the face from the lower eyelid to the lip along with all of the teeth except the molars.