The Anatomy of the Maxillary Nerve

Tasked with carrying important information to the central nervous system (CNS), the maxillary nerve runs from upper gingiva (the upper set of teeth), along the surface of the middle of the face, through the palate and nasal cavity, before terminating in the upper lip and cheek. It is a branch of the trigeminal nerve (the fifth cranial nerve) which serves both a sensory (afferent) and motor (efferent) function. The maxillary branch is involved mostly in the sensory function. It helps relay sensation and pain messaging from the upper teeth, jaw, the mucosa (membranes) of the nasal cavity, as well as part of the tongue and face.

As a branch of the trigeminal nerve, the maxillary nerve is often implicated in trigeminal neuralgia, a rare condition characterized by severe pain in the face and jaw. In addition, lesions of this nerve can cause intense hot and cold sensations in the teeth. When infected by the varicella zoster virus (also known as shingles), persistent neuropathic (nerve-associated) pain is far more common than loss of sensation.

Anatomy

Structure & Location

The maxillary nerve is the second of three branches of the trigeminal nerve. It arises between the trigeminal's ophthalmic and mandibular divisions in a region called the trigeminal ganglion, a cluster of nerves involved in relaying sensory information to the brain as well as chewing motor function.

Medium-sized when compared to the other branches, this nerve runs forwards from each side of the head at the level of the brainstem (around the ears) through the walls of the sinus just beneath and to the side of the ophthalmic nerve. It then accesses the upper gingiva via the pterygopalatine fossa (a depression on each side of the skull). After giving off most of its branches it courses to the orbit of the eye via the inferior orbital fissure.

Significantly, this nerve gives off a number of important branches that play a role in conveying sensory information. These branches are grouped based on their location along the course:

Cranial nerves: Close to the origin of the maxillary nerve in the middle cranial fossa, its smallest branch arises—the middle meningeal nerve. This brings sensory information to the dura mater (the tough, outer membrane of the brain and spine).

Pterygopalatine fossa: The middle course of the nerve, at the pterygopalatine fossa on each side of the skull, the maxillary nerve accesses the pterygopalatine ganglion and gives off a vast majority of its branches. These are:

• Orbital branches: Several small branches arise here and innervate the orbital wall, the sphenoidal sinus (a space behind the eye), and ethmoidal sinus (located between the eyes).
• Palatine nerves: Originating from the lower (inferior) surface of the pterygopalatine fossa, the greater and lesser palatine nerves cross through the palatine canal. The greater palatine nerve accesses the hard palate of the top of the mouth, travelling forward via a groove there to innervate the mucosa glands as well as the nearby upper set of teeth. In contrast, the lesser palatine nerve emerges through its own foramen to run sensory information from the tonsils, soft palate, and uvula.     
• Nasal nerves: From the pterygopalatine ganglion, these branches—most notably the medial and lateral posterior superior nasal nerves as well as the nasopalatine nerve—access the nasal cavity via the sphenopalatine foramen. The lateral posterior superior nasal nerve runs to the side of the cavity, innervating the mucosa of the sidewall of the nasal cavity. The medial posterior superior nasal nerve moves towards the middle, across the nasal roof. The longest of these branches, the nasopalatine nerve crosses the nasal roof and continues along the septum to emerge on the roof of the oral cavity. 
• Pharyngeal nerve: This nerve originates in the pterygopalatine ganglion and crosses to the mucosa and the nasopharynx glands via a structure called the palatovaginal canal.
• Ganglionic branches: These two nerves emerge directly from the lower (inferior) surface of the maxillary nerve, connecting it to the pterygopalatine ganglion, conveying sensory information. 
• Posterior superior alveolar nerve: Also arising directly from the maxillary nerve, the posterior superior alveolar nerve progresses out of the side of the pterygopalatine ganglion to access the infratemporal fossa, a complex area at the base of the skull that allows many nerves to enter and leave the brain. From there, it runs down and towards the side to reach the maxilla or upper jaw bone.   
• Zygomatic branch: This branch is another one that arises directly from the maxillary nerve, exiting the pterygopalatine fossa through the inferior orbital fissure. It travels on the outer sidewall of the orbit to then subdivide into the zygomaticotemporal and zygomaticofacial branches, both of which run on the lower and lateral side of the orbit. The former of these passes through the temporal fossa—a depression on the side of the skull—to enervate the skin of the parts of the face. The latter accesses the skin of the cheek through multiple gaps in the zygomatic bone.

The orbit floor: As the maxillary nerve exits the pterygopalatine fossa via the inferior orbital fissure, it enters the orbit and becomes the infraorbital nerve. In turn, it splits into two branches:

• Middle superior alveolar nerve: Arising in the infraorbital groove, running down the sidewall of the maxillary sinus to enervate the mucous membrane. Smaller branches of this nerve enervate the premolars in the mouth.
• Anterior superior alveolar nerve: This branch splits off from the infraorbital nerve and travels along the sidewall of the maxillary sinus to convey sensory information from the mucous membranes. Its branches supply the canine and upper incisor teeth, and then give rise to a nasal branch, which also accesses the mucous membrane of the sidewall as well as the nasal cavity.

Facial nerves: The final course of the maxillary nerve, after exiting the infraorbital foramen, sees the nerve divide into three sets of terminal branches:

• Inferior palberal branches: These are the two or three branches that supply the skin and conjunctiva of the eye (the membrane that covers and protects the eye) and communicate with branches in the face.
• Nasal branches: Supplying the skin of the side surface of the nose, the internal nasal branch accesses the nasal septum and vestibule (or nostril), while others link up with nerves in the face and coming from the eye.   
• Superior labial branches: There many of these smaller nerves, which serve to enervate the side of the cheek, the upper lip, oral mucosa, and labial glands (which help produce saliva).  

Anatomical Variations

As with many parts of the nervous system, there are sometimes variations seen in the structure of the maxillary nerve, and this is of particular concern for surgeons and dentists. For instance, it can be what is called “bifid,” meaning it is split into two parts. Furthermore, healthcare providers have observed variations in the mapping of associated nerves, such as cases where the superior alveolar nerve supplies regions usually serviced by the buccal nerve, and areas usually supplied by the zygomatic branch are enervated by the infraorbital nerve instead. In addition, the zygomatic branch may pass through the zygomatic bone before splitting up, as opposed to bifurcating prior to that.  

Notably, there have also been cases where people have multiple infraorbital foramina as opposed to just one. This has implications for dentists and healthcare providers tasked with ensuring that the face or upper set of teeth are numbed prior to treatment. Other variations include a greater palatine nerve—rather than maxillary nerve—that services the upper molar and premolar teeth. Finally, the nasopalatine nerve is sometimes observed innervating the incisor teeth.

Function

As noted above, the maxillary nerve is an afferent, meaning it serves a sensory function. This being the case, it’s part of the system that conveys temperature, touch, and pain sensation from the parts of the body it accesses. Primarily, then, it delivers information back from the following:

• The dura mater of the middle cranial fossa: The middle cranial fossa is the butterfly-shaped depression at the base of the skull; like all parts of the brain and skull, this section is enveloped in the dura mater, a thick, outer membrane.
• Mucosa within the face: The nasal branches deliver sensory information from the mucosa that lines the nasopharynx, the palate, the nasal cavity, as well as the maxillary sinus.
• The teeth: This nerve delivers sensory information from the upper set of teeth.
• The face: Sensory information from some regions of the face, such as the skin of the side of the nose, lower eyelid, cheek, and upper lip.

Sensory information from these areas passes via axons to the trigeminal ganglion, located within an area called “Meckel’s cave,” a special pouch within the middle cranial fossa. These branches converge to form the sensory root of the trigeminal nerve and convey the sensory information to the brains at the level of the pons, a section associated with a range of bodily functions, such as sleep, breathing, swallowing, hearing, balance, among many others. Finally, this sensory material passes through the trigeminal nucleus and thalamus before it is processed within the cerebral cortex.

Associated Conditions

Due to its close associations with the trigeminal nerve, issues there will impact the maxillary nerve. Most notably, it may be impacted by trigeminal neuralgia, a disorder at the nerve’s root that causes pain in and around the jaw. Treatments for this condition include everything from pharmacological approaches to surgery. In facial or dental surgery, a maxillary nerve block may need to be applied by an anesthesiologist—numbing the nerve—and this procedure can also help with trigeminal neuralgia. These procedures can be directed to specific teeth as necessary.

Other conditions can also impact the maxillary nerve, including lesions of the zygomatic nerve, which helps produce the liquid layer of film that goes around the eye. This condition can affect the trigeminal nerve and all of its pathways, leading to uncomfortable sensations and sensitivity to heat and cold in the teeth due to inflammation in the nerve.

Rehabilitation

Disorders and conditions affecting the maxillary nerve can have a significant impact on quality of life. And while there is a degree to which nerves can heal on their own, there are limitations. In cases of trigeminal neuralgia, if there is damage here or in the trigeminal nerve, most healthcare providers tend to wait three to six months to see if the case has resolved before considering surgical treatment. During this time, healthcare providers may prescribe anti-inflammatory or other drugs to aid with symptoms.

Surgeries repairing this nerve following trigeminal neuralgia are largely successful, with all three major approaches—microvascular decompression, radiosurgery, and radiofrequency lesioning—having success rates at or above 80%. Recovery varies based on treatment:

• Microvascular decompression: This eases pressure on the nerve by adjusting the position of surrounding veins; a minimally-invasive procedure, recovery takes about four to six weeks (after a couple of days in the hospital).
• Radiosurgery: A completely non-invasive approach, healthcare providers use specialized radiofrequency waves to scramble pain messaging coming from the maxillary nerve at the trigeminal nerve. While this is an outpatient procedure, results take longer, with most seeing reduction in pain within four to six weeks after treatment.
• Radiofrequency lesioning: In severe and high-risk trigeminal neuralgia patients who also suffer from other conditions, this approach is recommended. Like radiosurgery, the aim is to scramble pain messaging at the level of the trigeminal nerve. While it provides immediate relief and patients resume normal daily life within two days, this treatment may often need to be repeated within one to two years.

With careful monitoring and timely interventions, maxillary nerve issues—as well as the conditions that can lead to them—can certainly be taken on. It’s always important to talk to your healthcare provider if you’re feeling any related pain or discomfort.