Definition
Bell's palsy describes the acute onset of an unexplained weakness or paralysis of the muscles on one side of the face. Afflicted individuals may be unable to close the eye on the affected side of the face, and may also experience tearing, drooling, and hypersensitive hearing on the same side. The onset can be quite sudden, sometimes occurring overnight. The weakness and paralysis resolve completely in the majority of cases. Although it cannot be considered a serious condition from a health standpoint, it can cause extreme stress, embarrassment, and inconvenience for those affected.
Description
Bell's palsy has been described as a diagnosis of exclusion because several other disorders exhibit similar symptoms. Facial palsies have been linked to conditions such as Lyme disease, ear infection, meningitis, syphilis, German measles (rubella), mumps, chicken pox (varicella), and infection with Epstein-Barr virus (e.g., infectious mononucleosis). True Bell's palsy is an idiopathic facial palsy, meaning the root cause cannot be identified. Although Bell's palsy is not life-threatening, it can present symptoms similar to serious conditions such as stroke, ruptured aneurysm, or tumors.
Demographics
Every year, approximately 40,000–65,000 Americans are stricken with Bell's palsy. Worldwide, there is an annual incidence of 20–30 cases per 100,000 individuals. An individual can be affected at any age, but young and middle-aged adults are the most likely to be affected. It is unusual to see Bell's palsy in people less than 10 years old. Bell's palsy can affect either side of the face. Gender does not seem to factor into risk, though pregnant women and individuals with diabetes, influenza, a cold, or an upper respiratory infection seem to be at a greater risk.
In the large majority of cases (80–85%), the facial weakness or paralysis is temporary. However, individuals who experience complete paralysis seem to have a poorer recovery rate with only 60% returning to normal. Approximately 4–6% of all Bell's palsy cases result in permanent facial deformity, and another 10–15% experience permanent problems with spasms, twitching, or contracted muscles. Between 2% and 7.3% of individuals who have had Bell's palsy could experience a recurrence: on average, the first recurrence happens 9.8 years after the first episode; the second, 6.7 years later. One recurrence is very infrequent, and a second is extremely rare.
Causes and symptoms
The symptoms of Bell's palsy arise from an inflammation of the seventh cranial nerve, otherwise called the facial nerve. Each side of the face has a facial nerve that controls the muscles on that side of the face. Inflammation leads to the interference with conduction of nerve signals, and that in turn results in the loss of muscle control and tone.
Why the facial nerve becomes inflamed in Bell's palsy is a matter of considerable debate. Some evidence implicates the herpes simplex virus (HSV), which is responsible for cold sores and fever blisters. HSV infection has been suggested in up to 70% of Bell's palsy cases. Most people harbor this virus, although they may not exhibit symptoms. A number of other conditions have also been associated with the development of Bell's palsy, including facial or head injuries, headache, repeated middle ear infections, high blood pressure, diabetes, sarcoidosis, tumors, influenza, and other viral infections, as well as Lyme disease.
The major symptom of Bell's palsy is one-sided facial weakness or paralysis. Muscle control is either inadequate or completely missing. Patients frequently have difficulty shutting the affected eye and may not be able to close it at all.
Other symptoms can include pain in the jaw or behind the ear on the affected side, ringing in the ear, headache, decreased sense of taste, hypersensitivity to sound on the affected side, difficulty with speech, dizziness, and problems eating and drinking.
Diagnosis
Although Bell's palsy is not life-threatening, it has similar symptoms to serious conditions such as stroke. The fact that Bell's palsy is a diagnosis of exclusion becomes apparent in the course of the medical examination—it is imperative to rule out other disorders. Disorders that need to be excluded include demyelinating disease (e.g., multiple sclerosis), stroke, tumors, bacterial or viral infection, and bone fracture. Therefore, emergency medical attention is a wise and necessary precaution.
During the evaluation, the affected individual is asked about recent illnesses, accidents, infections, and any other symptoms. A visual exam of the ears, throat, and sinus is done, and hearing is tested. The extent of the symptoms is assessed by grading the symmetry of the face at rest and during voluntary movements such as wrinkling the forehead, puckering the lips, and closing the affected eye. Involuntary movements are assessed in combination with the voluntary movements. Neurologic exam is done to rule out involvement of other parts of the nervous system.
Blood tests and sometimes a cerebrospinal fluid (CSF) analysis may be needed. The results of these tests help determine the presence of a bacterial or viral infection or an inflammatory disease. Electrophysiological tests such as electromyography and nerve conduction study, in which a muscle or nerve is artificially stimulated, may be used to assess the condition of facial muscles and the facial nerve. Radiological tests may also be included, such as an x ray, magnetic resonance imaging (MRI), and computed tomography (CT).
Once all other possibilities are exhausted, a diagnosis of Bell's palsy is made. During the next few weeks, the patient is carefully assessed. If facial movement, even a small amount, has not returned within 3–4 months, the diagnosis of Bell's palsy may need to be reevaluated.
Treatment team
The patient's primary care provider may be the initial contact; further consultation may be obtained from a neurologist and/or an ophthalmologist. Physical therapists may help with pain issues and regaining function.
Treatment
Many doctors prescribe an antiviral drug and/or a steroid for Bell's palsy, but there is some controversy about whether these drugs actually help. The consensus opinion seems to be that, although drugs might not be necessary, they are not dangerous, and they may help in some cases. If drugs are used, they need to be taken as soon as possible following the onset of symptoms. The use of antiviral drugs such as acyclovir, famciclovir, or valacyclovir is recommended to destroy actively replicating herpes viruses. Steroids such as prednisone are thought to be useful in reducing inflammation and swelling.
In the past, surgery was performed to relieve the compression on the nerve. However, this treatment option is now used very infrequently because its benefits are uncertain, and it carries the risk of permanent nerve damage.
The need to protect the affected eye is universally promoted. Since the individual may not be able to lower the affected eyelid, the eye may become dry, particularly at night. Excessive dryness can damage the cornea. Daytime treatment includes artificial tears and may include an eye patch or other protective measures. Nighttime treatment involves a more intense effort at keeping the eye protected. Eye lubricants or viscous ointments, along with taping the eye shut, are frequently recommended.
In cases of permanent nerve damage, cosmetic treatment options such as therapeutic injections of botulism toxin or surgery may be sought or suggested.
Prognosis
Most individuals with Bell's palsy begin to notice improvement in their condition within 2–3 weeks of the symptoms' onset. At least 80% of them will be fully recovered within three months. Among the other 20% of afflicted individuals, symptoms may take longer to resolve or they may be permanent. Individuals suffering permanent nerve damage may not regain control of the muscles on the affected side of the face. These muscles may remain weak or paralyzed. As the nerve recovers, muscles may experience involuntary facial twitches or spasms that accompany normal facial expressions.
Resources
PERIODICALS
Billue, Joyce S. "Bell's Palsy: An Update on Idiopathic Facial Palsy." The Nurse Practitioner 22, no. 8 (1997): 88.
Kakaiya, Ram. "Bell's Palsy: Update on Causes, Recognition, and Management." Consultant 37, no. 8 (1997): 2217.
ORGANIZATIONS
Bell's Palsy Research Foundation. 9121 E. Tanque Verde, Suite 105-286, Tucson, AZ 85749. (520) 749-4614.
Julia Barrett
Rosalyn Carson-Dewitt, MD
