Facial nerve problems and Bell's palsy definitions and facts
- 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.
- The treatment of a facial nerve disorder depends on the cause and severity.
What is the facial nerve?
The facial nerve is a nerve that controls the muscles on the side of the face. It allows us to show expression, smile, cry, and wink. Injury to the facial nerve can cause a socially and psychologically devastating physical defect; although most cases resolve spontaneously, treatment may ultimately 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 that 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, alteration of taste on the affected side, or even excessive tearing or salivation can be seen as well. However, the finding of one of these symptoms does not necessarily imply a specific facial nerve problem; the physician needs to make a careful investigation in order to make a precise diagnosis. Symptoms of a facial nerve problem can vary in severity depending upon the extent of the injury to the nerve. Symptoms may range from mild twitching to full paralysis of the muscles on one side of the face.
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 stroke involving the brain stem
- Infection of the ear or face, or herpes zoster of the facial nerve (Ramsay Hunt syndrome)
- Tumors including acoustic neuroma, schwannoma, cholesteatoma, parotid tumors, and glomus tumors
- Toxins due to alcoholism or carbon monoxide poisoning
- Bell's palsy, which is also called idiopathic facial nerve paralysis (see below); this condition is sometimes associated with diabetes mellitus or pregnancy
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:
- 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.
- Balance tests: Will help find out if part of the auditory nerve is involved.
- Tear tests: The loss of the ability to form tears may help to locate the site and severity of a facial nerve lesion.
- Taste tests: The loss of taste in the front of the tongue may help locate the site and severity of a facial nerve lesion.
- Salivation test: Decreased flow of saliva may help locate the site and severity of a facial nerve lesion.
- Imaging studies: These tests help determine if there is infection, a tumor, a bone fracture, or any other abnormality. These studies usually include a CT scan and/or a MRI scan.
- 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 Bell's palsy?
Bell's palsy (sometimes referred to as 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.
How does a person get 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.
Bell's Palsy Symptom - Abnormal Facial Expressions
One symptom of Bell's palsy is facial expressions that are not normal. In Bell's palsy, the facial nerve that is injured and inflamed causes symptoms like twitching, weakness, or paralysis on one side of the face, sometimes both; drooling; a drooping eyelid or one corner of the mouth droops. Symptoms peak within about 48 hours, which can lead to facial distortions.
Bell's palsy symptoms
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 a majority of patients.
- There is a family history of Bell's palsy in some of patients.
- Very few patients have bilateral problems.
- There may be a change in hearing sensitivity (often increased sensitivity).
Who gets Bell's palsy? How long does it last?
Bell's palsy is usually a self-limiting, non-life-threatening condition that resolves spontaneously, usually within six weeks. There is no predominant age or racial predilection; however, it is 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.
How is Bell's palsy treated? How is facial nerve paralysis treated?
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.
Treatment options for eye problems
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.
Surgical reconstruction options
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.
Is there a cure for Bell's palsy? What is the prognosis for other 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 a majority of persons who experience Bell's palsy will have complete recovery. The best outcomes occur with rapid diagnosis and treatment.
Can Bell's palsy and other 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 a healthy lifestyle to decrease the risk of diabetes, cancer, or infection may help prevent some cases of facial nerve palsy.
A concussion is a traumatic brain injury.
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Previous contributing author: Standiford Helm II, MD.