What is the facial nerve?

The facial nerve is a nerve which controls the muscles on the side of the face. It allows us to show expression, smile, cry, and wink. Injury to the facial nerve causes a socially and psychologically devastating physical defect; treatment may require extensive rehabilitation or multiple procedures.

The facial nerve is the seventh of the twelve cranial nerves. Everyone has two facial nerves, one for each side of the face. The facial nerve travels with the hearing nerve (the eighth cranial nerve) as it travels in and around the structures of the middle ear. It exits the front of the ear at the stylomastoid foramen (a hole in the skull base), where it then travels through the parotid gland. In the parotid gland it divides into many branches which provide motor function for the various muscles and glands of the head and neck.

What are symptoms of a facial nerve problem?

Facial nerve problems may result in facial muscle paralysis, weakness, or twitching of the face; dryness of the eye or the mouth; or alteration of taste on the affected side. However, the finding of one of these symptoms does not necessarily imply a specific facial nerve problem; your physician needs to make a careful investigation in order to make a precise diagnosis.

What conditions affect the facial nerve?

There are numerous causes of facial nerve disorder:

• Trauma: such as birth trauma, skull base fractures, facial injuries, middle ear injuries, or surgical trauma.

• Nervous system disease: including Opercular syndrome, Millard-Gubler syndrome.

• Infection: of the ear or face, or Herpes Zoster of the facial nerve (Ramsey-Hunt syndrome).

• Metabolic: diabetes mellitus or pregnancy.

• Tumors: acoustic neuroma, schwannoma, cholesteatoma, parotid tumors, glomus tumors.

• Toxins: alcoholism or carbon monoxide poisoning.

• Bell's palsy: Also called idiopathic facial nerve paralysis (see below).

How are the causes of facial nerve dysfunction diagnosed?

Causes of facial nerve disorder vary from unknown to life threatening. Sometimes, there is a specific treatment for the problem. Accordingly, it is important to investigate why the problem has occurred. The specific tests used for diagnosis will vary from patient to patient, but include:

1. Hearing tests: Hearing tests are done to assess the status of the auditory nerve. The stapedial reflex test can evaluate the branch of the facial nerve that supplies motor fibers to one of the muscles in the middle ear.


2. Balance tests: Will help find out if part of the auditory nerve is involved.


3. Tear tests: The loss of the ability to form tears may help to locate the site and severity of a facial nerve lesion.


4. Taste tests: The loss of taste in the front of the tongue may help locate the site and severity of a facial nerve lesion.


5. Salivation test: Decreased flow of saliva may help locate the site and severity of a facial nerve lesion.


6. Imaging studies: help determine if there is infection, a tumor, a bone fracture, or any other abnormality. These studies are usually a CT scan and/or a MRI scan.


7. Electrical tests: Stimulation of the nerve by an electrical current tests whether the nerve can still cause muscles to contract. It can be used to evaluate progression of the disease. For example, if testing indicates equal muscle response on both sides of the face, the patient can be expected to have complete return of facial function in three to six weeks without significant deformity.

What is Bell's palsy?

Bell's palsy is paralysis of the facial nerve of unknown cause. The diagnosis is made when no other cause can be identified. Bell's palsy is thought to be caused by a viral infection of the facial nerve. The most likely virus is the herpes simplex virus. Other names for this condition are "idiopathic facial palsy" or Antoni's palsy.

Bell's palsy is usually a self-limiting, non-life threatening condition that spontaneously remits within six weeks. The incidence is 15-40 new cases per 100,000 people per year. There is no predominant age or racial predilection; however it is 3.3 times more common during pregnancy and slightly more common in menstruating females. In general, the incidence increases with advancing age.

The typical symptoms of Bell's palsy include:

• Unilateral acute paralysis of facial muscles. The paralysis involves all muscles, including the forehead.

• About half the time, there is numbness or pain in the ear, face, neck or tongue.

• There is a preceding viral illness in 60% of patients.

• There is a family history of Bell's palsy in 10% of patients.

• Less than 1% of patients have bilateral problems.

• There may be a change in hearing sensitivity (often increased sensitivity).

The proposed mechanism of injury of the facial nerve in Bell's palsy is:

• Primary viral infection (herpes) sometime in the past.

• The virus lives in the nerve (trigeminal ganglion) from months to years.

• The virus becomes reactivated at a later date.

• The virus reproduces and travels along the nerve.

• The virus infects the cells surrounding the nerve (Schwann cells) resulting in inflammation.

• There immune system responds to the damaged Schwann cells which and causes inflammation of the nerve and subsequent weakness or paralysis of the face.

• The course of the paralysis and the recovery will depend upon the degree and amount of damage to the nerve.

What are treatment options of facial nerve paralysis?

Underlying medical conditions which lead to facial nerve disorder are treated specifically according to the condition detected. Cortisone medications (corticosteroids) are the best treatment for Bell's palsy, and it is recommended that all patients be treated. The usually amount is one milligram per kilogram body weight of prednisone (or steroid alternative) per day. Recently, antiviral medications like acyclovir (Zovirax) given in a dose of 200-400 milligrams five times per day for five days have been demonstrated to increase recovery. After five days of treatment, if the paralysis improves, the acyclovir is stopped and the steroids can be tapered (gradually discontinued) over the next five days. If the paralysis is still complete after five days, then the same dose of both medications are continued for another five days, then the steroids are tapered over the next five days.

Physical therapy and electrotherapy probably have no significant benefit. Surgical facial nerve decompression is controversial in Bell's palsy. Some physicians recommend surgical decompression during the first two weeks in patients showing the most severe nerve degeneration.

What is the treatment for eye problems from facial nerve disorder?

Patients with facial nerve paralysis have difficulty keeping their eye closed because the muscle which closes the eye (orbicularis oculi muscle) cannot work. Serious complications can occur because the cornea of the eye becomes too dry. Treatment consists of:

• Protective glasses can prevent dust from entering the eye.

• Patients can manually close the eye with a finger to keep it moist.

• Patients should use the back of their finger rather than the tip to insure that the eye is not injured.

• Artificial tears can help to keep the eye lubricated.

• The eye can be taped or patched closed with paper tape while asleep, and an ointment used to keep the eye lubricated.

• A temporary or permanent narrowing of the eye opening (tarsorrhaphy) may be necessary.

What surgical reconstruction options are available?

Reconstructive options for patients with facial muscle weakness or paralysis include one or more of the following:

• Nerve repair or nerve grafts: Facial nerve regeneration occurs at a rate of one millimeter per day. If a nerve has been cut or removed, direct microscopic repair is the best option.

• Nerve transposition: Often the tongue nerve (hypoglossal nerve) or the other facial nerve can be connected to the existing facial nerve. For example, the patient can train themselves to move their face by moving their tongue.

• Muscle transposition or sling procedures: The temporalis muscle or masseter muscle (some of the only muscles on the face not supplied by the facial nerve), can be moved down and connected to the corner of the mouth to provide movement of the face.

• Muscle transfers: Free muscles from the leg (gracilis) can be used to provide both muscle bulk and function. Often a cross facial nerve transposition is done to provide similar nerve supply to the donor muscle flap.

• Ancillary eyelid or oral procedures: In addition to one of the above, often it is necessary to include a brow lift or facelift, partial lip resection, eyelid repositioning, lower eyelid shortening, upper eyelid weights, or eyelid springs.

Facial Nerve Problems and Bell's Palsy At A Glance

• Facial nerve disorders affect the muscles of the face.

• There are many causes of facial nerve disorders.

• A number of tests can be helpful to diagnose the cause of a facial nerve disorder.

• Treatment of facial nerve disorder depends on the cause and severity.

sourceLast Editorial Review: 3/6/2007

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