The trigeminal nerve is a cranial nerve. It arises from the brainstem, and its branches cover your face and head. The trigeminal nerve is a paired nerve — you have one on each side. Its chief function is to carry sensations of pain, touch, heat, and cold from the face to the brain. One part of this nerve also controls the muscles used for chewing. Injuries or disorders of the trigeminal nerve can have several symptoms that affect daily life.
What Is the Trigeminal Nerve?
The trigeminal nerve is also known as cranial nerve 5 or the fifth cranial nerve. It provides sensations to your scalp and face. It also controls some muscles involved in chewing and swallowing. The trigeminal nerve has three branches:
The ophthalmic nerve. This branch of the trigeminal nerve covers the scalp and upper part of the face, including the eye, eyelids, and forehead. It is a purely sensory nerve and carries sensations to the brain.
The maxillary nerve. This branch covers the middle part of the face and is also a purely sensory nerve. It carries sensations from your nose, cheeks, lower eyelids, upper lip, and gums. This nerve also carries sensations from the inside of the mouth, the palate, the upper jaw teeth, and the sinuses.
The mandibular nerve. This branch of the trigeminal nerve has both sensory and motor parts. It carries sensations from the lower part of your face, including the jaw, lower lip, and gums. It carries sensations other than taste from the front part of your tongue. The motor part of this nerve controls the muscles involved in chewing, biting, and swallowing.
Trigeminal Nerve Function
The trigeminal nerve is the sensory nerve of the head and face. It provides sensations of touch, heat, cold, and pain from structures inside the skull (the coverings of the brain, or the meninges), the scalp, face, corneas of the eyes, the sinuses, and the insides of the mouth and nose. It also carries proprioceptive sensations from the temporomandibular joint (the hinge of the jaw). This input lets your brain know if your mouth is open or closed without checking in a mirror.
The mandibular branch of the trigeminal nerve has motor nerve fibers too. It controls the muscles involved in chewing (masseter, temporal, pterygoid, mylohyoid, and digastric muscles). These muscles allow you to move your lower jaw (mandible) up, down, and side to side. The mandibular nerve also controls muscles in the palate and temple.
Where Is the Trigeminal Nerve Located?
Trigeminal nerve anatomy begins in the brain and extends all over the head and face. The sensory component of this nerve emerges near the part of the hindbrain called the pons. After leaving the skull, these nerve fibers collect to form the trigeminal ganglion near the temple. The three branches arise from this ganglion and spread to cover the head and face.
The motor part of the trigeminal nerve arises separately from the brain. It joins the mandibular nerve after it separates from the trigeminal ganglion. The ophthalmic nerve enters the orbit, the skull cavity that holds the eyeball. Here, it splits into branches that supply different parts of the eye. The maxillary nerve passes through the orbit and branches out to supply the nose, teeth, and midface. The mandibular nerve runs along the lower jaw before entering the tongue.
Signs Something Could Be Wrong With Your Trigeminal Nerve
The trigeminal nerve is the sensory nerve of the face and scalp. A disorder of the sensory nerve fibers can produce excessive sensations (hyperesthesia) or loss of sensations (anesthesia) on your face. You may also lose the sense of the opening or closure of your jaw.
The motor part of the trigeminal nerve supplies the muscles for chewing. You may notice difficulty chewing, clenching your teeth, and moving your lower jaw to one side. Your jaw may deviate to one side when you open it.
If you notice any of these symptoms, you should see your doctor. They'll test your trigeminal nerve by touching various parts of your face and head. They may also test for pain sensation using a pin. The corneal reflex protects your eyes — it causes you to blink when your cornea is touched. This reflex is absent if your trigeminal nerve is not working. Your doctor may test this by touching your cornea with a wisp of cotton.
Conditions Affecting the Trigeminal Nerve
Trigeminal neuralgia. This is a painful condition affecting the distribution of the trigeminal nerve. The pain appears suddenly and is electric shock-like. It is limited to one side of your head or face and lasts for a second to several minutes at a time.
Compression of the nerve by blood vessels causes about three-fourths of trigeminal neuralgia cases. About 15% of cases are caused by neurological disorders like multiple sclerosis, cerebellopontine angle tumors, and arteriovenous malformations. About 10% of cases have no known cause.
The pain of trigeminal neuralgia most often occurs in the area covered by the maxillary and mandibular nerves. The pain usually lasts less than two minutes, but some people have episodes lasting up to 10 minutes. The pain is often triggered by simple touch on the face and inside the mouth, such as by talking, chewing, brushing, shaving, washing, or drying.
Your doctor will ask for a detailed description of the distribution, frequency, and duration of pain to make a diagnosis and plan treatment. They may ask for a magnetic resonance imaging (MRI) scan or a computed tomography (CT) scan to find the reason for the neuralgia. Your doctor will then prescribe medicines to reduce the severity and frequency of the painful episodes.
Trigeminal nerve injury. The mandibular nerve is most often injured during tooth extraction. Other causes are injury, tumor surgery, placing dental implants, and local anesthesia injections. Mild injury causes pain in the distribution of the nerve. If the nerve has been cut, the area supplied is numb. If you feel either of these symptoms, consult your doctor soon. Nerve repair is most successful when done soon after the injury.
How Can You Keep Your Trigeminal Nerve Healthy?
There aren't any measures that specifically improve trigeminal nerve health. But some general measures help keep your nervous system healthy:
- Eat a balanced, nutritious diet.
- Have a physically active lifestyle.
- Reduce stress.
- Avoid smoking and harmful drugs.
- Get adequate, restful sleep every night.
- Diseases like high blood pressure (hypertension) and diabetes are bad for nerve function. Keep them under control with regular treatment.