Cranial nerves can transmit two types of information:
- Sensory information includes details about smells, sights, tastes, touch, and sounds to the brain.
- Motor information refers to signals that affect the movement or activity of muscles and glands.
Nerves that send sensory information are said to have sensory functions. Those that send motor information have motor functions. While some nerves have only sensory or motor functions, others can have both.
The trigeminal nerve is one of the cranial nerves that has both sensory and motor function. Cranial nerves are also classified using Roman numerals based on their location. The trigeminal nerve is also called cranial nerve V.
The trigeminal nerve is the largest of the 12 cranial nerves. Its main function is transmitting sensory information to the skin, sinuses, and mucous membranes in the face. It also stimulates movement in the jaw muscles.
The trigeminal nerve has three different divisions. Each division has a slightly different function.
The ophthalmic division conveys sensory information from the:
- upper parts of the sinuses
- upper eyelid and associated mucous membranes
- cornea of the eye
- bridge of the nose
Like the ophthalmic division, the maxillary division of your trigeminal nerve has a sensory component. It transmits sensory information from the:
- lower eyelid and associated mucous membranes
- middle part of the sinuses
- nasal cavity and middle part of the nose
- upper lip
- some of the teeth of the upper jaw and associated mucous membranes
- roof of the mouth
The mandibular division is the only part of the trigeminal nerve that has both sensory and motor functions.
It communicates sensory information from the:
- outer part of the ear
- lower part of the mouth and the associated mucous membranes
- front and middle parts of the tongue
- teeth of the lower jaw and the associated mucous membranes
- lower lip
It also stimulates movement of the muscles in the jaw and some of the muscles within the inner ear.
Explore the interactive 3-D diagram below to learn more about the trigeminal nerve.
The trigeminal nerve plays a role in many sensations that are felt in different parts of the face. As a result, there are several ways to test the function of the trigeminal nerve.
Common methods include:
- Pin or cotton swab test. One or both sides of the face are touched with either a pin or cotton swab. The person will then be asked whether they felt anything, and if so, where they felt it. A doctor may also lightly touch the cornea of the eye with a cotton swab to test the ophthalmic division. If the person doesn’t blink, the ophthalmic division of their trigeminal nerve may be damaged.
- Clenching test. A doctor will ask someone to clench their teeth or try to open their jaw when resistance is applied. They’ll check muscle tone and movement for any signs of trigeminal nerve damage.
The trigeminal nerve can also be a source of intense pain for some people. This is part of a chronic condition called trigeminal neuralgia. It happens when the trigeminal nerve is under pressure or irritated. This can happen when a vein or artery presses against the nerve. Trigeminal neuralgia is more common in people over the age of 50.
Several things can cause irritation of the trigeminal nerve, including:
The pain associated with trigeminal neuralgia can be very painful. People often describe it as a shooting or jabbing pain that lasts anywhere from a few seconds to several hours.
Pain can also be achy or burning. It tends to occur more often over time. Many things can trigger the pain, including touching the face, shaving, eating, yawning, or talking. It can affect one or both sides of the face.
Trigeminal neuralgia is usually managed with medications used for other conditions, including anticonvulsants, antidepressants, and muscle relaxers. But some people may eventually stop responding to medication.
Sometimes surgery is needed to remove what’s irritating the trigeminal nerve. In other cases, injecting a numbing agent into the nerve can help.