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The trigeminal nerve belongs to the cranial nerves. Thanks to it, we feel when someone touches us on the face, the fibers of the trigeminal nerve also control the muscles, thanks to which we can chew our food. The scope of the innervation of the trigeminal nerve, however, is much greater - what other structures are innervated by it? Apart from the best known neuralgia, what are the diseases of the trigeminal nerve?

The trigeminal nerve(Latinnervus trigeminus , English trigeminal nerve) is the fifth and largest of the cranial nerves. Its functions include both receiving sensory stimuli from the face and head, as well as controlling the activities of certain muscles within the skull.

These tasks, however, are de alt with by the end fibers of the trigeminal nerve - they begin in the so-called testicles of the trigeminal nerve.

Trigeminal nerve: testicles

The trigeminal nerve contains two types of fibers: sensory and motor. The first of these have their origins in three different nuclei - they are:

  • nucleus of the intracerebral band (responsible for propioceptive sensation)
  • main sensory nucleus (located in the upper part of the bridge, hence the nerve fibers that deal with perceiving tactile stimuli)
  • core of the spinal cord (responsible for the perception of sensations such as pain, cold or heat)

Sensory fibers that begin in all three of the aforementioned nuclei later go to all three major branches of the trigeminal nerve.

As for the motor fibers, all of the trigeminal nerves begin in a single nucleus. It is the motor nucleus of the trigeminal nerve, which is located in the pons. Unlike sensory fibers, motor fibers are only part of one branch of the V nerve, the mandibular nerve.

Trigeminal nerve: course and branches

The fibers that make up the trigeminal nerve leave the brain in the anterolateral part of the bridge - this is where the two roots of the V nerve leave, called the larger part (these are the sensory fibers) and the smaller part (made up of motor fibers).

In the vicinity of the temporal bone pyramid, both roots form a tricuspid ganglion, from which three branches begintrigeminal nerve:

  • optic nerve (V1)
  • maxillary nerve (V2)
  • mandibular nerve (V3)

Trigeminal nerve: first branch, i.e. the optic nerve

The optic nerve is a sensory nerve which innervates the side of the nose and the skin of the face (from the palpebral fissure upwards). It runs through the cavernous sinus and the superior orbital fissure.

The following branches extend from the optic nerve:

  • lacrimal nerve
  • frontal nerve (divides into supraorbital and supra-block nerves)
  • nasociliary nerve (from which short branches extend to the ciliary ganglion, short and long ciliary nerves, and sub-block nerve, posterior ethmoid nerve, and anterior ethmoid nerve)

Ultimately, the optic nerve is responsible for the sensory innervation of the above-mentioned areas, but it also receives sensory experiences from the cornea, conjunctiva or frontal sinus. One of its branches - the lacrimal nerve - is responsible for the innervation of the lacrimal gland.

Trigeminal nerve: second branch, or maxillary nerve

The second branch of the trigeminal nerve, i.e. the maxillary nerve, just like the optic nerve is a sensory nerve - it receives sensory experiences from the face, and more precisely from the area stretching between the eye gap and the mouth gap.

The maxillary nerve runs through the cavernous sinus until - through the central fossa of the skull, where it captures the middle meningeal branch innervating the meningeal - it leaves the skull through the circular opening.

The following branches depart from the maxillary nerve:

  • zygomatic nerve (divides into zygomatic-temporal and zygomatic-facial nerves)
  • infraorbital nerve (it captures numerous alveolar nerves)
  • pterygoid palatine nerves

The maxillary nerve donates some of its fibers to the pterygo-palatine ganglion. At the same time, it also gets fibers from this coil - these fibers are parasympathetic fibers.

Ultimately, the maxillary nerve sensitively innervates the aforementioned area of ​​the face, and besides, it also sensually supplies the maxillary sinus, upper teeth and gums, as well as the throat, hard palate and nasal cavity.

Trigeminal nerve: third branch, or mandibular nerve

The mandibular nerve, unlike the two previously described branches of the trigeminal nerve, is a mixed nerve - it contains both sensory fibers and motor fibers. It sensitively innervates the area of ​​the face in the area of ​​the temples and the area below the mouth space, while the mandibular nerve supplies the masticatory muscles in motion. It does not run through the cavernous sinus, but exits the skull through the foramen oval.

Nervemandibular gives the following branches:

  • tire branch
  • deep temporal nerves (supply the temporal muscle)
  • lateral pterygoid nerve (innervates the pterygoid muscles: lower lateral and upper lateral)
  • medial pterygoid nerve (responsible for the innervation of the medial pterygoid muscle)
  • masseter nerve (supplies the masseter muscle)
  • buccal nerve
  • ear-temporal nerve
  • lingual nerve
  • inferior alveolar nerve

The mandibular nerve is also related to two ganglia: the ear ganglion and the submandibular ganglion, from which parasympathetic fibers are delivered to the branches of this nerve.

Finally, apart from receiving sensory stimuli from the aforementioned range of the face, the mandibular nerve also innervates, among others, and the mucosa of the cheek, lower teeth and gums or the auricle.

As for the motor fibers of the mandibular nerve, it is thanks to them that we can chew our food - because they supply the muscles that are involved in the process of chewing the food we eat.

Trigeminal nerve: examination

The assessment of cranial nerve function is included in the standard neurological examination. When examining the trigeminal nerve, facial sensation is primarily assessed.

The neurologist may use some pointed objects (in order to assess the perception of pain stimuli), in addition, he may also use cool and warm devices (this serves to check whether the examined person feels the thermal stimuli correctly).

In a situation where sensation is disturbed in some parts of the body, it is possible to make assumptions as to which branch of the trigeminal nerve may have been damaged.

For example, when a patient does not feel anything in the side of the nose, it may indicate damage to the maxillary nerve, and if he has a suppressed feeling in the forehead area, then he may have damaged the optic nerve.

The assessment of the trigeminal nerve also includes the following assessment:

  • of the corneal reflex: the optic nerve (reflex centripetal arm) and the facial nerve (reflex centrifugal arm) are involved; in a situation where, after irritation of the cornea (e.g. with a cotton swab), the subject does not reflex eyelid squinting, it may be due to damage to the optic nerve
  • mandibular nerve: the subject is asked to open his mouth and move the lower jaw to the sides; it is then observed whether there are any problems with performing such an activity, and it is also checked whether, for example, the mandible does not deviate one way or the other
  • mandibular reflex: the patient is therewhen asked to open his mouth, the examiner gently hits the patient's chin with a hammer - the masseter muscles should contract properly and the mouth should close; the absence of such a reaction may indicate damage to the mandibular nerve

Trigeminal nerve: diseases

One of the most famous conditions that affect the V nerve is trigeminal neuralgia. Patients who suffer from it are definitely aware of the burden of this problem - it is associated with attacks of violent, very persistent pain, which patients sometimes even describe as "the worst pain in life".

The cause of trigeminal neuralgia may be inflammation involving this structure, but also pressure on the nerve by blood vessels. The problem with this disease is not only that its symptoms can be very severe, but also that they can be provoked by factors such as speaking, brushing teeth, touching the areas innervated by the trigeminal nerve (even very delicate) or also … a gust of wind.

Trigeminal neuralgia is not the only problem that may be related to the fifth cranial nerve, however.

Another disease that can affect this structure is the trigeminal neuroma, a benign tumor that originates in Schwann cells (these cells are part of the sheath of the nerves).

In addition to this, the trigeminal nerve may also be involved in pathological processes related to multiple sclerosis, and it is suspected that the occurrence of cluster headaches may be related to the dysfunction of the trigeminal nerve.

  • Facial nerve palsy
  • Paralysis of cranial nerves
  • Bell's Palsy

Sources:

  1. Human anatomy. A textbook for students and doctors, ed. II and supplemented by W. Woźniak, ed. Urban & Partner, Wrocław 2010
  2. Neurology, scientific editor W. Kozubski, Paweł P. Liberski, ed. PZWL, Warsaw 2014
  3. Tewik T.L., Trigeminal Nerve Anatomy, Nov 28 2022, Medscape
  4. Materials from Radiopaedia.org, on-line access: https://radiopaedia.org/articles/trigeminal-nerve

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Category:

Neurology