Facial Nerve (Cranial Nerve 7): Everything to Know

Cranial nerve 7, which is also called the facial nerve, controls movement of the face, including the forehead, eyelids, cheeks, mouth, and jaw. The facial nerve can be damaged due to trauma, inflammation, infections, or disease.

Damage to this nerve can cause facial weakness, as well as insufficient tears and saliva, a diminished sense of taste, and decreased sensation behind the ears. Depending on the cause, treatment of cranial nerve 7 damage can include medication, physical therapy, electrical stimulation techniques, and surgery.

This article will discuss the structure and function of cranial nerve 7, injuries and impairments to this nerve, and when to see a healthcare provider.

Structure

Cranial nerve 7 emerges from the brain stem at the level of the pons, which is the middle section of the brain stem. The left and right cranial nerve 7 are symmetric in structure and function. 

From the brain stem, which is at the back of the neck, the nerve winds around toward the face. Cranial nerve 7 has many branches, which lead to the small muscles of the face, glands of the eyes and mouth, and sensory fibers behind the ear.

If one cranial nerve 7 is damaged, it will cause weakness of the whole side of the face, including the forehead.

Function

Cranial nerve 7 has several functions. The most prominent function is movement of the face. Facial movements include blinking, opening the eyes, raising the eyebrows, smiling, puffing out the cheeks, and pursing the lips.

Some of these movements are voluntary (on purpose) and some are involuntary (not on purpose). Involuntary movements include blinking when something is coming toward your eyes. Movement is controlled in the following ways:

• The left cranial nerve 7 controls movement on the left side of the face.
• The right cranial nerve 7 controls movement on the right side of the face.

This nerve also helps produce tears and saliva, contributes to taste sensation, and has some sensory function behind the ears.

Injury or Impairment

Sometimes, medical problems or injuries can cause diminished function of cranial nerve 7, either permanently or temporarily. This causes paralysis (weakness) of some facial movements. Impairment of cranial nerve 7 can cause partial paralysis (paresis) or complete paralysis (plegia) of the affected parts of the face.

Bell’s palsy is the most common condition that affects cranial nerve 7. This condition causes weakness on one side of the face. It is believed to be associated with inflammation or infection, but it is usually considered idiopathic—which means that it has no identifiable cause.

Bell’s palsy can be distressing, but it isn’t dangerous, and it often resolves after weeks or months. Other causes of facial weakness (such as a stroke or infection) often need to be considered and ruled out before Bell’s palsy is diagnosed. Treatment with oral steroids may speed up recovery.

Other problems that can affect cranial nerve 7 include trauma, which can be a result of an accident, a dental condition, or a surgical complication. Sometimes these injuries can lead to permanent facial weakness. In some instances, a surgical procedure may be done to repair the nerve and associated muscle damage.

A tumor, abscess, viral infection, nerve disease, or inflammatory disease can also cause damage to cranial nerve 7. These conditions can be treated, and the nerve function may recover with treatment. 

Complications of facial nerve damage may include difficulty eating. Also, because problems with cranial nerve 7 can affect a person's ability to blink, damage may result to the conjunctiva (the surface of the white part of the eye) or the cornea (the surface of the colored part of the eye and the pupil).

These issues require attention, such as eye patching to protect the eye from dryness and damage or swallowing therapy to help with safe chewing and eating. 

Rehabilitation to improve facial nerve function after an impairment or injury can include physical therapy or electromyographic feedback techniques. In this process, electrical impulses of the facial muscles are measured and displayed, and the person learns what stimulates movement.

When to See a Healthcare Professional

If you develop any symptoms of cranial nerve 7 impairment, it’s important that you get prompt medical attention. 

Symptoms include: 

• Droopy eyelid or decreased ability to open the eye
• Inability to fully close the eye
• Flat or droopy appearance of any part of the face, on one side or both sides  
• A lopsided smile 
• Trouble speaking, chewing, or swallowing
• Trouble moving the tongue 

These symptoms can be caused by a health problem involving cranial nerve 7 or by a condition affecting the brain, such as a stroke (a blockage of blood flow or bleeding in the brain) or a tumor. 

Summary 

Cranial nerve 7 controls movement of the face, and it also has a role in sensation behind the ear and in making tears and saliva. The most common condition affecting cranial nerve 7 is Bell’s palsy, a distressing condition that isn’t harmful.

However, there are many other conditions that can affect cranial nerve 7, and Bell’s palsy is often a diagnosis of exclusion—meaning that other causes of cranial nerve 7 weakness often need to be ruled out before a diagnosis of Bell’s palsy is made. Complications of cranial nerve 7 problems can include corneal injury and difficulty eating. 

A Word From Verywell 

If you have a condition affecting cranial nerve 7 function, it’s important that you get medical attention. It can be stressful to not be able to move the muscles of your face the way you want to, and it’s distressing to see that your face appears lopsided.

Facial nerve weakness is more than just a cosmetic concern—it can cause harm to your eyes or it can be a choking hazard. Most cranial nerve 7 problems are treatable. As you recover, it’s important to maintain physical therapy so you can regain as much control of your facial movements as possible.