The trigeminal nerve constitutes the fifth cranial nerve. It is involved in the sensitivity and motor skills of the head.

Mixed nerve. The trigeminal nerve (V) is made up of sensory and motor nerve fibers, giving rise to three nerves (1):

• ophthalmic (V1), sensitive;
• the maxillary nerve (V2), sensitive;
• the maxillary nerve (V2), sensitive;

Origin. The trigeminal nerve is the largest of the cranial nerves. These sensitive fibers come from the trigeminal ganglion (2), located at the base of the skull, while these motor fibers come from the masticatory nuclei. All fibers meet, cross and emerge from the bridge, brainstem region (1).

Distribution. Each nerve is prolonged and gives rise to multiple branches to be able to reach specific areas of the face (1) (2).

• The ophthalmic nerve enters at the orbit level to reach the forehead, the back of the nose, the upper eyelid, the cornea and conjunctiva of the orbit, and the cranial dura.
• The maxillary nerve crosses the round foramen of the skull and joins the cranial dura mater, the pharynx, the anterior region of the temple, the lower eyelid, the cheek, the nose, the upper lip, the mucosa located on the upper part of the oral cavity, the gums, teeth of the upper jaw, and the palate.
• The sensory fibers of the mandibular nerve cross the foramen oval of the skull and reach the cranial dura mater, the external auditory meatus, the tympanic membrane and the pinna of the ear, the posterior zone of the temple, the temporomandibular joint, the lining of the cheeks of the oral floor, an anterior part of the tongue, and the teeth of the lower jaw.
• Motor fibers of the mandibular nerve pass through the foramen ovale and innervate the tensor muscles of the eardrum and palate, the masticatory muscles, the anterior belly muscle of the digastric, and the mylohyoid muscle. These fibers then extend to the pterygoid muscles and the mandible.

Role in sensitive and sensory communication of the face. The trigeminal nerve and its three branches play an important role in the sensitive and sensory transmission of information perceived at the level of the face, such as sight, hearing, taste or even touch.

Role in chewing and swallowing. The motor fibers of the mandibular nerve play an essential role in the movement of the mandible, in particular by allowing the opening of the mouth and by innervating the masticatory muscles (2). They are also involved in the movements of the jaw during swallowing.

Trigeminal reflexes. The trigeminal nerve is involved in different reflexes (2)

• corneal reflex thanks to the ophthalmic nerve;
• jaw reflex through the mandibular nerve;
• tearing reflex thanks to the ophthalmic nerve;
• oculo-cardiac reflex through the ophthalmic nerve.

Trigeminal neuralgiaThis pathology is manifested by sharp pain on one side of the face (4). It is due to contact between a branch of the trigeminal nerve and a vascular loop. This neuralgia mainly occurs in people over the age of 50 and more commonly in women (3) (4).

Headache (headache). A frequent symptom in adults and children, it manifests as pain in the face, and more frequently in the forehead and temples. There are many causes of a headache. A doctor can be consulted in case of sharp and sudden pain.

Migraine. A particular form of headache, it often begins with very localized pain and manifests as seizures (4).

Medical treatment. Certain medications may be prescribed to relieve pain such as pain relievers.

Surgical treatment. As a last resort, surgery may be performed in the event of trigeminal neuralgia.

Physical examination. A study of the patient’s history is performed to identify risk factors, especially in cases of migraines.

Angio-IRM/Angioscanner. These tests allow the blood vessels to be analyzed by medical imaging.

Medical imaging. Additional examinations may be performed to identify the causes of trigeminal neuralgia such as CT or MRI.

In connection with the three branches of the trigeminal nerve supplying different parts of the face, François Chaussier, a French physician of the 5th and XNUMXth centuries, gave the name of the trifacial nerve, which was then transformed into the trigeminal nerve (XNUMX).