What Are the 12 Cranial Nerves and Their Functions?

During a physical exam your healthcare provider may ask you to raise your eyebrows, blink your eyes, or puff out your cheeks. They’ll probably ask you to stick out your tongue, too. All of these actions can help to check your cranial nerves. These tests may seem simple and even silly, but they’re a useful way to screen for underlying medical conditions. 

Read on for a description of your 12 cranial nerves, what they do, and what it can mean if they’re not working as they should.

What are cranial nerves?

Cranial nerves are a special set of 12 nerve pairs that work in the head and neck. They control your main senses — seeing, smelling, hearing, and tasting. Cranial nerves also control some head, face, and neck movements, along with the feeling in your face and scalp. 

The 12 pairs of cranial nerves link your brain to the rest of your head and neck. Some even reach the trunk of the body. These nerves are different from the nerves in the rest of your body. They don’t travel through the spinal cord. Their location makes traveling through the spinal cord inconvenient. Instead, each cranial nerve pair has a unique path it travels to get through the skull to the head and neck. Each nerve can also be mapped to a unique control center in the brain (a nucleus).

Some cranial nerves communicate both ways with the brain. This means they send and receive messages. Other cranial nerves only send out messages. And others just receive messages. More on this below. 

The 12 cranial nerves and their functions

Each cranial nerve has a name and a number. Traditionally, cranial nerves are numbered 1 through 12 with Roman numerals. But for simplicity we’ll stick to regular numbers here. Each cranial nerve has one nerve on the left and a matching nerve on the right: 

1. Cranial nerve 1, or olfactory nerve: This nerve allows you to smell. 

2. Cranial nerve 2, or optic nerve: This nerve communicates between the eye and the brain, allowing you to see. It also opens and closes the pupil to help your eye adapt to different lighting and distances. 

3. Cranial nerve 3, or oculomotor nerve: This nerve helps the optic nerve open and close your pupils. It’s also one of three cranial nerves that move your eyeballs in your eye sockets. The other nerves that control eyeball movement are cranial nerves 4 and 6. 

4. Cranial nerve 4, or trochlear nerve: This nerve also helps cranial nerves 3 and 6 with eyeball movement. 

5. Cranial nerve 5, or trigeminal nerve: This cranial nerve has several jobs. It has three branches that gather information about sensation from the face. One branch (V3) also helps with chewing.

6. Cranial nerve 6, or abducens nerve: This nerve helps cranial nerves 3 and 4 with eyeball movement. 

7. Cranial nerve 7, or facial nerve: This nerve moves the muscles of the face and controls facial expression. It also helps the tongue to taste.

8. Cranial nerve 8, or vestibulocochlear nerve: This nerve controls hearing and balance.

9. Cranial nerve 9, or glossopharyngeal nerve: This nerve allows you to swallow. It also helps the tongue to taste and to move. 

10. Cranial nerve 10, or vagus nerve: This cranial nerve is long and complex. You’ve probably heard of it since it does a lot for us. It works in the head and neck, where it helps with swallowing and speaking. But it also travels to the chest and abdomen, where it helps control the heart, breathing, and digestion. It plays an important role in calming the body and countering the freeze-fight-flight response. 

11. Cranial nerve 11, or accessory nerve: This nerve moves your back and neck muscles.

12. Cranial nerve 12, hypoglossal nerve: This nerve controls most tongue movement. To speak clearly, you need cranial nerves 9, 10, and 12 to be in good working order.

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Disorders linked to cranial nerve damage

If there’s damage to any one of your cranial nerves, it leads to a specific set of symptoms or disorder. Some of the more common cranial nerve disorders include:

• Bell’s palsy: Injury to cranial nerve 7 makes one side of the face unable to move.

• Trigeminal neuralgia: Cranial nerve 5 senses pain in the face when there’s no physical damage.

• Third, fourth, or sixth cranial nerve palsies: Depending on the nerve(s) injured, one or both eyes will be unable to move in certain directions.

What are symptoms of cranial nerve damage?

The symptoms of cranial nerve damage depend on which nerve is damaged. The functions of cranial nerves vary, and so can their signs of damage. The following can be symptoms of damage:

• Loss of smell

• Difficulty moving one or both eyes in certain directions

• Blurred vision

• Loss of hearing

• Dizziness or loss of balance

• Changes in taste

• Drooping or weakness in parts of the face

• Face pain 

What injuries and diseases cause cranial nerve damage?

Some people are born with cranial nerve damage. And any injury to the brain or cranial nerves can cause cranial nerve damage: 

• Strokes can damage the part of the brain where a cranial nerve is based. 

• Traumatic brain injury (TBI) can lead to cranial nerve damage. This can happen after a car accident or fall. TBI can also occur in veterans after combat. 

• Brain inflammation can occur as part of a viral or bacterial infection, or it can be related to autoimmune disease. 

• Brain tumors or an aneurysm can damage the cranial nerves, depending on their location. 

There are also specific nerve diseases that can affect the cranial nerves:

• Meniere’s disease: Fluid buildup in the ear can make it difficult for cranial nerve 8 to help with hearing and balance.

• Multiple sclerosis (MS): MS is an autoimmune disease that affects the brain and spinal cord.

• Amyotrophic lateral sclerosis (ALS): ALS is a progressive disease where nerve cells die.

How do providers test for cranial nerve damage?

Cranial nerve testing is one of the first physical exam skills doctors and other healthcare providers learn in school. Luckily, it doesn’t need many tools — just a willing participant who doesn’t mind making a few silly faces. Here are some basics of cranial nerve testing:

• Check how your pupils get bigger or smaller in response to a small light.

• Make sure your eyes can move in all directions.

• Confirm you can sense touch all over your face.

• Watch you move all the muscles in your face. A big wide smile proves this.

• Test how you hear quiet sounds close to both ears, like two fingers rubbing together.

• Confirm the strength of your neck and upper back muscles.

• Make sure you can move your tongue from side to side.

When should I see a doctor about cranial nerve damage?

You should get medical help for any sudden changes that may relate to your brain and cranial nerves. This might be a sudden change in how you move a part of your face, or you may suddenly see double. A quick and painless physical exam can screen for cranial nerve problems and help your healthcare provider figure out if you need more testing. 

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Written by:

Meg Burke, MD

Meg Burke, MD, is a practicing primary care geriatrician in the Denver, Colorado area. She is board-certified in internal medicine and geriatric medicine, and received her undergraduate and medical degrees from Georgetown University in Washington, D.C. After graduating from medical school, Dr. Burke completed her internal medicine residency at Johns Hopkins Bayview Medical Center and her two years of subspecialty training in geriatric medicine at the Johns Hopkins Hospital in Baltimore, Maryland.

Edited by:

Sophie Vergnaud, MD

Sophie Vergnaud, MD, is the Senior Medical Director for GoodRx Health. An experienced and dedicated pulmonologist and hospitalist, she spent a decade practicing and teaching clinical medicine at academic hospitals throughout London before transitioning to a career in health education and health technology.

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