Facial Nerve Problems (cont.)

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: These tests help determine if there is infection, atumor, a bone fracture, or any other abnormality. These studies usually include a CT scan and/or a MRI scan.
7. Electrical nerve stimulation 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 and what causes Bell's palsy?

Bell's palsy (Bell palsy) is paralysis of the facial nerve of unknown cause. The diagnosis is made when no other cause can be identified. Although Bell's palsy is thought to be caused by a viral infection of the facial nerve, this hasn't been proven. 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 resolves spontaneously, usually within six weeks. The incidence is 15 to 30 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. Children under the age of 13 seem less at risk of developing Bell's palsy than older individuals.

What are the symptoms of Bell's palsy?

The typical symptoms of Bell's palsy include:

• Acute unilateral paralysis of facial muscles is present; 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 4% to 10% of patients.
• Less than 1% of patients have bilateral problems.
• There may be a change in hearing sensitivity (often increased sensitivity).

What is the mechanism of injury in Bell's palsy?

While the actual mechanism of injury of the facial nerve in Bell's palsy is unknown, one proposed mechanism of injury includes:

• Primary viral infection (herpes) sometime in the past.
• The virus lives in the nerve (geniculate 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.
• The immune system responds to the damaged Schwann cells, which 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?

There are no medications specifically approved to treat Bell's palsy. Underlying medical conditions that lead to facial nerve disorder are treated specifically according to the specific condition that is responsible for the damage to the nerve. Steroid medications (corticosteroids) are the best treatment for Bell's palsy, and it is recommended that all patients be treated. The usual amount is one milligram per kilogram body weight of prednisone (or steroid alternative) per day for 7 to 14 days. Recently, antiviral medications like acyclovir(Zovirax) given in conjunction with steroids have been demonstrated to increase recovery. Doses of the antiviral agent will vary with the drug chosen.

Although physical therapy and electrotherapy probably have no significant benefit, facial exercises can help prevent contractures of affected muscles. 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; however, there can be a substantial risk of hearing loss with this surgery.

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

Patients with facial nerve paralysis have difficulty keeping their eye closed because the muscles which close the eye cannot work. Serious complications can occur if the cornea of the eye becomes too dry. Treatment consists of:

• protective glasses which can prevent dust from entering the eye;
• manual closure of 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 or ointments to help keep the eye lubricated;
• taping or patching the eye closed with paper tape while asleep; and
• in cases in which recovery is incomplete, 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 then 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 allow 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 in reconstructive surgery following severe facial nerve palsies.

What is the prognosis for facial nerve problems?

The prognosis for facial nerve damage depends on the underlying cause. Many patients who have required surgery to remove tumors may have unavoidable permanent injury to the facial nerve, whereas more than 70% of persons who experience Bell's palsy will have complete recovery. The best outcomes occur with rapid diagnosis and treatment.

Can facial nerve problems be prevented?

At one time it was thought that exposure to cold air or a strong wind were predisposing factors leading to idiopathic facial nerve palsy (Bell's palsy); we now know that these ideas were incorrect. As the majority of causes for idiopathic facial nerve problems are unknown, it is difficult to predict with any accuracy specific items to avoid. Choosing ahealthy lifestyle to decrease the risk of diabetes, cancer, or infection may help prevent some cases of facial nerve palsy.

REFERENCES:

Marsk, E., et al. "Prediction of nonrecovery in Bell's palsy using Sunnybrook grading." Laryngoscope 122.4 (2012): 901-906.

Peitersen, E. "The natural history of Bell's palsy." The American Journal of Otology 4.2 (1982): 107-111.

Sullivan, F. M., et al. "Early treatment with prednisolone or acyclovir in Bell's palsy." The New England Journal of Medicine 357:16 (2007): 1598-1607.

Sullivan, F. M., et al. " A randomised controlled trial of the use of aciclovir and/or prednisolone for the early treatment of Bell's palsy: the BELLS study." Health Technology Assessment 47:iii-iv, ix-xi (2009) 1-130.

Teixeira, L. J., et al. "Physical therapy for Bell s palsy (idiopathic facial paralysis)." Cochrane Database of Systematic Reviews. 3 (2008): CD006283.