The Maxillary Branch of the Trigeminal Nerve
Understanding cranial nerves can easily be a problem that is hard to overcome in the process of studying anatomy. Since the matter is complex, students can easily forget why they even have to know all of that information.
The maxillary nerve is one of the branches of the trigeminal nerve, otherwise known as the fifth cranial nerve (CN V). Supplying sensory innervation to certain parts of the face, the mucosa of the nose, together with the teeth, this nerve allows you to feel that annoying fly landing underneath your eye or that annoying pain caused by your dentist.
This article discusses everything you have to know about the anatomy, course, and the damage of the maxillary nerve. .Clinical importance will also be discussed to tie everything together.
|Course||Trigeminal ganglion -> cavernous sinus -> foramen rotundum -> pterygopalatine fossa -> infratemporal fossa -> inferior orbital fissure -> infraorbital nerve (terminal branch) -> respective anatomical structures|
|Branches||Meningeal, zygomatic, zygomaticofacial, zygomaticotemporal, infraorbital, anterior, middle, and posterior superior alveolar nerves, nasopalatine, greater palatine, lesser palatine nerves ('My Zippy Zebra Zoe Is A Majestic Princess, Naturally Gorgeous Lady')|
|Innervation||Dura mater of the middle cranial fossa; mucosa of the nasopharynx, palate, nasal cavity, and nasopharynx; teeth and upper jaw; skin over the side of the nose, lower eyelid, cheek, and upper lip|
- Efferent fibers are actually descending motor fibers that innervate all of the four masticatory muscles, as well as the muscles related to them, such as the anterior belly of the digastric muscle, mylohyoid muscle, tensor veli palatini muscle and the tensor tympani muscle.
- Afferent fibers are part of the general somatic afferent system. They provide sensory innervation to the skin of the face and the frontal part of the scalp, mucosa of the nasal and the oral cavity, frontal two-thirds of the tongue, part of the ear and external acoustic meatus, part of the tympanic membrane, conjunctiva and the dura mater in the anterior and middle cranial fossae.
The trigeminal nerve leaves the pons via two roots:
- Large sensory root
- Smaller motor root
After leaving the pons, these roots continue coursing forward to exit from the posterior cranial fossa. The fibers enter the middle cranial fossa by passing over the medial tip of the petrous part of the temporal bone. In the depression on the anterior surface of the petrous part of the temporal bone, the trigeminal ganglion can be found. For this reason, this depression is called the trigeminal depression, and the ganglion itself is wrapped within the dura mater in a cave-like appearance; it is called the trigeminal cave. This ganglion is the expansion of the sensory root; it contains the bodies of the sensory neurons whose fibers contribute to the making of the trigeminal nerve. Functionally, this ganglion is comparable to a spinal ganglion.
From the anterior edge of the trigeminal ganglion arise the three branches of the trigeminal nerve in the following descending (superior to inferior) order:
The maxillary nerve is exclusively sensory, although its branches receive certain autonomous fibers that reach the maxillary nerve through the pterygopalatine ganglion.
This nerve carries sensory fibers from:
- The dura mater of the middle cranial fossa
- The mucosa of the nasopharynx, the palate, the nasal cavity and maxillary sinus
- The teeth and the upper jaw
- The skin that covers the side of the nose, the lower eyelid, the cheek and the upper lip
Course and Relations
The maxillary nerve arises from the anterior edge of the trigeminal ganglion. It courses forward through the lateral dural wall of the cavernous sinus, inferiorly and laterally to the ophthalmic nerve. The nerve leaves the middle cranial fossa after it passes through the foramen rotundum and enters the upper part of the pterygopalatine fossa.
In this fossa, the nerve extends the most of its branches. The fibers of the maxillary nerve leave the fossa by coursing forward through the pterygomaxillary fissure and then enter the infratemporal fossa. In the infratemporal fossa, the nerve is located adjacent to the maxillary tuberosity. From that position, the nerve turns medially and enters the orbit through the inferior orbital fissure, where it is recognized by the name infraorbital nerve. This nerve represents the terminal branch of the maxillary nerve.
While coursing through the middle cranial fossa, the maxillary nerve extends to the meningeal branch that carries the sensory impulses from the dura mater of the middle cranial fossa.
The nerve extends within the pterygopalatine fossa where its branches extend either directly from the body of the maxillary nerve or from its short pterygopalatine nerves that are added to the pterygopalatine ganglion. Finally, after entering the orbit, the maxillary nerve extends to its terminal branch; the infraorbital nerve.
The most important branches of the maxillary nerve are the following:
This nerve arises from the maxillary nerve in the pterygopalatine fossa, and then courses forward and laterally. It passes through the superior portion of the pterygomaxillary fissure and enters the infratemporal fossa. Soon after that, the zygomatic nerve passes through the inferior orbital fissure and enters the orbit. While inside the orbit, the nerve courses along its lateral wall and then enters the canal present in the zygomatic bone.
Like the nerve that extends to two branches inside this canal, the canal itself also has two hallways that correspond to these branches:
- Anterior zygomaticofacial nerve
- Posterior zygomaticotemporal nerve
These terminal branches of the zygomatic nerve exit the zygomatic canal through the proper foramina named according to the branches: zygomaticofacial and zygomaticotemporal foramen. These will innervate the adjacent parts of the skin. On the lateral wall of the orbit, the zygomatic nerve makes anastomosis with the lacrimal nerve through their common connective branch. Thanks to this anastomosis, parasympathetic fibers from the pterygopalatine ganglion reach the lacrimal gland.
There are usually 2-3 of these nerves. They arise from the body of the maxillary nerve inside the pterygopalatine fossa. These nerves are short, and they course inferiorly and medially towards the pterygopalatine ganglion. They reach the ganglion from its anterior side and then send 2-3 sensory afferent branches for the ganglion.
Simultaneously, the pterygopalatine nerves receive 1-2 efferent branches from the ganglion. These efferent ganglionic fibers are parasympathetic and through the pterygopalatine nerves, they reach the zygomatic nerve. These pterygopalatine nerves give rise to the many branches, of which the most important are branches for the nasal cavity and the palatine nerves.
Branches for the Nasal Cavity
These branches extend from the nerves and course medially. The majority of these branches leave the pterygopalatine fossa through the sphenopalatine foramen and then enter the posterior part of the nasal cavity.
One portion of these branches, called lateral superior posterior nasal (LSPN) branches, cross forward over the lateral wall of the nasal cavity and provide sensory innervation to the mucosa of the superior and middle nasal concha, whereas the other portion of the branches, called the medial superior posterior nasal (MSPN) branches, cross to the medial wall of the nasal cavity, or simply the nasal septum which they innervate. The longest branch among the MSPN branches is called the nasopalatine nerve that enters the incisive canal where it makes anastomosis with the incisive nerve of the contralateral side, and with the greater palatine nerve.
Palatine branches extend from the pterygopalatine nerves and course inferiorly. Usually, there are three of them: one greater palatine nerve and two of the lesser palatine nerves.
The major palatine nerve enters the major palatine canal following the same named artery. It leaves the canal through the major palatine foramen and together with the artery, it courses medially and forwards to end in the area of the incisive fossa where it makes anastomosis with the contralateral major palatine nerve and with the nasopalatine nerve. The major palatine nerve innervates the mucosa of the hard palate.
Minor palatine nerves descend together with the major palatine nerve through the pterygopalatine fossa. Then, they separate from it and course posteriorly through the bone canals of the minor palatine nerves to finally reach the soft palate which they innervate.
Posterior Superior Alveolar Branches
There are usually two of these branches where they separate from the body of the maxillary nerve in the infratemporal fossa.
They course forward and inferiorly, cross through the alveolar foramina on the maxillary tuberosity and enter the alveolar canals. They make anastomosis with the other teeth branches and form a plexus that innervates the teeth of the upper jaw.
This nerve is the strongest branch of the maxillary nerve and is the ending branch. After it crosses through the inferior orbital fissure, it courses forward and medially, over the inferior wall of the orbit. The infraorbital nerve first goes through the infraorbital sulcus and then to the infraorbital canal. At the anterior side of the maxilla, this nerve exits the infraorbital canal through the infraorbital foramen and then divides into its many ending branches:
- External nasal branches that innervate the skin that covers the side of the nose
- Internal nasal branches which provide sensory innervation to the nasal septum
- Superior labial branches that innervate the upper lip
- Inferior palpebral branches that provide innervation for the lower eyelid
During its pathway through the infraorbital sulcus, this nerve courses closely to the maxillary sinus. In this part of its path, the infraorbital nerve extends to the following branches:
- Anterior superior alveolar branches
- Middle superior alveolar branch
These branches, together with the posterior superior alveolar branches, participate in making the plexus that innervates the teeth of the upper jaw.
This is the parasympathetic ganglion that is located on the posterior wall of the pterygopalatine fossa. It is stuck into the slightly extended anterior foramen of the pterygoid canal, inferiorly and medially to the body of the maxillary nerve.
Preganglionic fibers for this ganglion are:
- Pterygopalatine nerves that carry sensitive fibers for the ganglion from the maxillary nerve
- The greater petrosal nerve, a branch of the facial nerve, that carries the parasympathetic fibers that synapse within the neurons of the pterygopalatine ganglion
- The deep petrosal nerve that extends from the internal carotid plexus and whose fibers just pass through the ganglion without synapsing with its neurons
Before reaching the ganglion, the greater and deep petrous nerves unite to form a single nerve body. Both of them penetrate the fibrous membrane of the foramen lacerum on the base of the skull. Soon after they leave the cranium, they unite by forming the pterygoid canal nerve. This nerve goes through the pterygoid canal from its posterior to anterior foramen. When the nerve leaves the canal, it enters directly to the pterygopalatine ganglion, bringing both sympathetic and parasympathetic fibers to it.
Postganglionic fibers extend through the short pterygopalatine nerves to join the following branches of the maxillary nerve:
- Zygomatic nerve, and then through the communicant branches to the lacrimal nerve to provide parasympathetic innervation for the lacrimal gland.
- Major palatine nerve and minor palatine nerves, giving them the autonomic fibers for the innervation of the salivary palatine glands of the hard and soft palate.
Since the maxillary nerve is a division of the trigeminal nerve, most of the clinical conditions are described together. Trigeminal neuralgia is a complex sensory disorder that affects the sensory root of the trigeminal nerve. The pain is usually in the region of both the mandibular nerve and the maxillary nerves. It can appear suddenly or may be provoked by touching the region of the skin that is innervated by these nerves.
Blocking the maxillary nerve, or as most surgeons say, maxillary nerve block, is a procedure that is performed by the anesthesiologist before the patient undergoes some sort of maxillofacial surgical procedure, or in some cases of the trigeminal neuralgia. A complete maxillary block is not often necessary, so it is mostly limited to the area of a single tooth in order to prevent the uncomfortable sensations for the patient during the procedure.
Lesions of the zygomatic nerve can cause the disorders affecting the lacrimal gland. Many lesions of the terminal maxillary branches can cause uncomfortable sensations in teeth, such as exaggerated sensitivity from cold or hot food, which may indicate some inflammatory process of the nerve (neuralgia).
Infections of the trigeminal ganglion by the herpes zoster virus (shingles) will cause very painful sensations among all sensory areas that are innervated by the trigeminal nerve, including the maxillary nerve. The infection may eventually result in the complete loss of the sensation within the affected parts.
These are only some of the most frequent manifestations of trigeminal and maxillary nerve conditions, but they certainly prove the importance of the maxillary nerve. In order to recognize the source of the symptom, students must learn and understand the anatomy well, to make their lives as the future clinicians a lot easier.