Trigeminal nerve – location, structure, functions and diseases

Proven content

The trigeminal nerve is one of the cranial nerves and its main role is to convey sensory information from the face and head, although it also provides motor control to the chewing muscles. It is both large and complex, and has many branches and connections to other cranial nerves.

Trigeminal nerve – what is it?

There are 12 cranial nerves in our body, all of them originating in the brain. They come in pairs and connect different areas of the body and organs to the brain.

The cranial nerves can transmit two kinds of information:

1. Sensory information includes details about smells, sights, tastes, touch and sounds reaching the brain.
2. Motor (movement) information refers to signals that affect the movement or activity of muscles and glands.

The nerves that send sensory information are said to have sensory functions. Those that send motor information have motor functions. While some nerves only have sensory or motor functions, others may have both.

The trigeminal nerve (Latin nervus trigeminus, English trigeminal nerve) is one of the cranial nerves that performs both a sensory and a motor function. It is worth adding that cranial nerves are also classified using Roman numerals based on their location. The trigeminal nerve is also called the V cranial nerve.

See also: Nervous system – structure and ailments

Trigeminal nerve – testicles

There are four types of trigeminal fibers: three sensory and one motor.

The sensory fibers are arranged in a column that extends from the midbrain, through the pons and medulla, to the top of the cervical spine.

1. nucleus of the intracerebral tract: is responsible for proprioceptive feeling; it extends along the entire length of the midbrain;
2. main sensory nucleus: located in the upper part of the bridge, on the side of the motor nucleus; is responsible for epicritical feeling (precise feeling of touch and pressure);
3. nucleus of the spinal cord: located at the bottom of the bridge; it is responsible for the protopathic feeling (pain, heat, cold).

The motor fibers start in the trigeminal motor nucleus in the pons and go exclusively to the mandibular V3 nerve.

See also: Neck spine

Trigeminal nerve – branching

Fibers of the trigeminal nerve leave the brain in the anterolateral part of the bridge, where the two roots of the V nerve exit, called the larger part (these are the sensory fibers) and the smaller part (made up of motor fibers).

In the area of ​​the temporal bone pyramid, the mentioned roots form a trigeminal ganglion, from which three branches of the trigeminal nerve begin:

1. optic nerve (V1);
2. maxillary nerve (V2);
3. mandibular nerve (V3).

Trigeminal nerve – the optic nerve

The optic nerve is classified as the sensory nerve. It innervates the lateral part of the nose and the facial skin (from the eyelid fissure upwards) and receives sensory sensations from the cornea, conjunctiva or frontal sinus. It runs through the cavernous sinus and the superior orbital fissure.

The following branches depart from the optic nerve:

1. tear nerve;
2. frontal nerve (subdivides into the supraorbital and supremic nerves);
3. nasociliary nerve (from which the short branches depart to the ciliary ganglion, short and long ciliary nerves, and the subtotal and posterior ethmoid nerve, and the anterior ethmoid nerve).

Trigeminal nerve – maxillary nerve

The maxillary nerve also belongs to the sensory nerves and is responsible for receiving sensory sensations from the face, in fact from the area extending between the gap in the eyes and the gap in the mouth. In addition, the maxillary nerve is also responsible for the innervation of the maxillary sinus, upper teeth and gums, throat, hard palate and nasal cavity.

This nerve runs through the cavernous sinus, through the central fossa of the skull, where it captures the middle meningeal branch innervating the meningeal and leaves the skull through the circular foramen.

The following branches depart from the maxillary nerve:

1. zygomatic nerve (dividing into zygomatic-temporal and zygomatic-facial nerves);
2. infraorbital nerve (it captures numerous alveolar nerves);
3. pterygoid palatine nerves.

See also: Skull bones – everything you need to know

Trigeminal nerve – mandibular nerve

The mandibular nerve, in turn, contains both sensory fibers and motor fibers. It is responsible for the sensory innervation of the temple area and the area below the mouth gap, as well as areas such as the lower teeth and gums, and the auricle. The mandibular nerve also innervates the masticatory muscles in motion. However, it does not run through the cavernous sinus, but exits the skull through the foramen ovale.

The mandibular nerve captures the following branches:

1. the dural branch;
2. deep temporal nerves (supply the temporal muscle);
3. lateral pterygoid nerve (innervates the pterygoid muscles: lower lateral and upper lateral);
4. medial pterygoid nerve (responsible for the innervation of the medial pterygoid muscle);
5. masseter nerve (supplies the masseter muscle);
6. cheek nerve;
7. ear-temporal nerve;
8. lingual nerve;
9. inferior alveolar nerve.

In addition, the mandibular nerve is related to the ear and submandibular ganglia, from which parasympathetic fibers are delivered to the branches of this nerve.

See also: The lower jaw – how is it built and what can pain symptoms mean?

Trigeminal nerve – research

The trigeminal nerve plays a role in many sensations felt in different parts of the face. During the examination, the physician may use various pointed objects to assess the perception of pain stimuli, or use cool or warm instruments to assess whether the subject is properly perceiving the thermal stimuli. If sensation is disturbed in certain areas of the face, it can be determined which branch of the trigeminal nerve may have been damaged.

There are several ways to study the function of the trigeminal nerve.

Common methods include:

Examination with a pin or a cotton swab. One or both sides of the face are touched with a pin or a cotton ball. Then the test subject will be asked if she felt anything, and if so, where she felt it. The doctor may also lightly touch the cornea of ​​the eye with a cotton swab to examine the optic nerve. If the test subject does not blink, it is a sign that the optic nerve may have been damaged.

Study with jaw clenching. The doctor will ask the test person to grit their teeth or try to open the jaw when resistance is applied. This test checks your muscle tone and movement for any signs of damage to the trigeminal nerve.

Trigeminal nerve – diseases

The trigeminal nerve can be a source of intense pain for some people. It is part of a chronic condition called trigeminal neuralgia. This happens when the trigeminal nerve is under pressure or irritated. This can happen when a vein or artery is pressing against a nerve. It is worth adding that trigeminal neuralgia is more common in people over the age of 50.

Several things can cause irritation to the trigeminal nerve, including:

1. hit;
2. facial injuries;
3. a brain tumor;
4. neurological conditions such as multiple sclerosis.

The pain associated with trigeminal neuralgia can be very painful. People often describe it as stabbing or stabbing pain that lasts from seconds to hours. The pain can also be burning. It tends to occur more frequently over time. Many things can make you hurt, including touching your face, shaving, eating, yawning, or even talking. Pain may be in one or both sides of the face.

Trigeminal neuralgia is usually treated with medications for other conditions, including anticonvulsants, antidepressants, and muscle relaxants. But some people may stop responding to medications eventually. Sometimes surgery is needed to remove whatever irritates the trigeminal nerve. In other cases, injecting an anesthetic into the nerve may help. Relaxation techniques such as meditation or yoga can also help relax nearby muscles and relieve pain.

In addition to neuralgia, the disease associated with the trigeminal nerve is trigeminal neuroma, which is a benign neoplasm of Schwann cells (these cells are part of the nerve sheath).

A condition known as trigeminal trophic syndrome is also associated with the trigeminal nerve and is a rare disease caused by disruption of the peripheral or central sensory pathways of the trigeminal nerve. A slowly enlarging, non-inflammatory ulcer may develop in the area where the trigeminal nerve has been damaged; embracing, but not limited to, the cheek next to the wing of the nose. These wounds touch the skin innervated by the sensory part of the trigeminal nerve. Similar changes can also occur in the corners of the eyes, in the ear canal, on the scalp or in the mouth. Ulceration has been found to be caused by the patient’s constant “nibbling”. While this is the case, the “nibbling” behavior is an incomplete explanation of the presentation of the disease: the absence of sensation or pain allows the patient to constantly irritate his skin, and although the patient is not feeling, there is constant neuropathic pain as well.

In addition to the aforementioned diseases, in the case of the trigeminal nerve, one can also speak of pathological processes related to multiple sclerosis.

Interestingly, it is also believed that cluster headaches may be associated with dysfunction of the trigeminal nerve. It is a neurological disorder characterized by recurring severe headaches on one side of the head, usually around the eye. It is often accompanied by watery eyes, nasal congestion or swelling around the eye on the affected side. These symptoms usually last from 15 minutes to 3 hours. Attacks often occur in clusters that usually last weeks or months, and sometimes longer than a year.

Recommended measures include lifestyle changes such as avoiding potential triggers (alcohol, nitroglycerin, and histamine). Treatments for acute attacks include oxygen or fast-acting triptan. The measures recommended to reduce the frequency of attacks include steroid injections, civamide, or verapamil. Occasionally, nerve stimulation or surgery may be used if other measures have not worked. The disease affects approximately 0,1% of the general population and usually appears for the first time between the ages of 20 and 40. Men get sick about four times more often than women.

See also: What does the headache on the right show? The doctor explains