Bell's Palsy (Facial Paralysis)
Bell's palsy is a form of temporary facial paralysis resulting from inflammation of the facial nerve. Although it’s actual cause still remains unknown, most investigators believe that it is cause by a viral infection of the nerve. Bell's palsy is named for Sir Charles Bell, a 19th century Scottish surgeon who was the first to describe the condition. The disorder, which is not related to stroke, is the most common cause of facial paralysis. Generally, Bell's palsy affects only one of the paired facial nerves and one side of the face, however, in rare cases, it can affect both sides. When Bell's palsy occurs, the function of the facial nerve is disrupted, causing an interruption in the messages the brain sends to the facial muscles. This interruption results in facial weakness or paralysis.
The facial nerve-also called the 7th cranial nerve-is a paired structure that travels through a narrow, bony canal (called the Fallopian canal) in the skull, beneath the ear, to the muscles on each side of the face. For most of its journey, the nerve is encased in this bony shell.
Each facial nerve directs the muscles on one side of the face, including those that control eye blinking and closing, and facial expressions such as smiling and frowning. Additionally, the facial nerve carries nerve impulses to the lacrimal or tear glands, the saliva glands, and the muscles of a small bone in the middle of the ear called the stapes. The facial nerve also transmits taste sensations from the tongue.
What are the Symptoms?
Because the facial nerve has so many functions and is so complex, symptoms of Bell's palsy can vary from person to person and range in severity from mild weakness to total paralysis. Symptoms may include twitching, weakness, or paralysis on one or both sides of the face, drooping of the eyelid and corner of the mouth, drooling, dryness of the eye or mouth, impairment of taste, and excessive tearing in one eye. Most often these symptoms, which usually begin suddenly and reach their peak within 48 hours, lead to significant facial distortion.
Other symptoms may include pain or discomfort around the jaw and behind the ear, ringing in one or both ears, headache, loss of taste, hypersensitivity to sound on the affected side, impaired speech, dizziness, and difficulty eating or drinking.
What Causes Bell's Palsy?
Bell's palsy occurs when the nerve that controls the facial muscles is swollen, inflamed, or compressed, resulting in facial weakness or paralysis. Exactly what causes this damage, however, is unknown.
Most scientists believe that a viral infection such as the common cold sore virus - herpes simplex - causes the disorder. They believe that the facial nerve swells and becomes inflamed in reaction to the infection, causing pressure within the Fallopian canal and leading to an infarction (the death of nerve cells due to insufficient blood and oxygen supply). In some mild cases (where recovery is rapid), there is damage only to the myelin sheath of the nerve. The myelin sheath is the fatty covering-which acts as an insulator-on nerve fibers in the brain.
The disorder has also been associated with influenza or a flu-like illness, headaches, chronic middle ear infection, high blood pressure, diabetes, sarcoidosis, tumors, Lyme disease, and trauma such as skull fracture or facial injury.
Who Gets it?
Bell's palsy afflicts approximately 40,000 Americans each year. It affects men and women equally and can occur at any age, but it is less common before age 15 or after age 60. It disproportionately attacks pregnant women and people who have diabetes or upper respiratory ailments such as the flu or a cold.
How is it Diagnosed?
A diagnosis of Bell's palsy is made based on clinical presentation-including a distorted facial appearance and the inability to move muscles on the affected side of the face-and by ruling out other possible causes of facial paralysis. There is no specific laboratory test to confirm diagnosis of the disorder.
Generally, a physician will examine the individual for upper and lower facial weakness. In most cases this weakness is limited to one side of the face or occasionally to the forehead, eyelid, or mouth. Electrical tests called electromyography (EMG) and electroneurography (ENOG) can confirm the presence of nerve damage and determine the severity and the extent of nerve involvement. A magnetic resonance imaging (MRI) ) scan can eliminate other causes of facial paralysis.
How is it Treated?
Bell's palsy affects each individual differently. Some cases are mild and do not require treatment as the symptoms usually subside on their own within 2 weeks. For others, treatment may include medications and other therapeutic options.
Studies have shown that steroids are an effective treatment for Bell's palsy. Prednisone is the most commonly used medication in the treatment of Bell’s palsy. It is effective in improving facial function by limiting or reducing damage to the nerve. Antiviral drugs such as acyclovir are used to fight viral infections are also frequently used in cases of Bell’s palsy. Analgesics such as aspirin, acetaminophen, or ibuprofen may relieve pain. Because of possible drug interactions, patients taking prescription medicines should always talk to their doctors before taking any over-the-counter drugs.
Another important factor in treatment is eye protection. Bell's palsy can interrupt the eyelid's natural blinking ability, leaving the eye exposed to irritation and drying. Therefore, keeping the eye moist and protecting the eye from debris and injury, especially at night, is important. Lubricating eye drops, such as artificial tears or eye ointments or gels, and eye patches are effective.
Physical therapy to stimulate the facial nerve and help maintain muscle tone may be beneficial to some. Facial massage and exercises may help prevent permanent contractures (shrinkage or shortening of muscles) of the paralyzed muscles before recovery takes place. Moist heat applied to the affected side of the face may help reduce pain. Electrical stimulation may help nerve regrowth.
Facial nerve decompression is a surgical treatment for Bell's palsy to relieve pressure on the compressed nerve. The surgery sometimes considered in severe cases of complete facial paralysis that has occurred within 3 weeks of onset of the palsy. Careful electrical testing of the facial nerve is undertaken before considering surgery.
The surgery is performed under general anesthesia. The surgery is fairly extensive, requiring access through the middle cranial fossa (craniotomy) to completely decompress the nerve at its most constricted point along its course. Hospitalization for 1 or 2 days is usually required.
What is the Prognosis?
The prognosis for individuals with Bell's palsy is generally very good. The extent of nerve damage determines the extent of recovery. Improvement is gradual and recovery times vary. With or without treatment, most individuals begin to get better within 2 weeks after the initial onset of symptoms and most recover completely, returning to normal function within 3 to 6 months. For some, however, the symptoms may last longer. In a few cases, the symptoms may never completely disappear. Early evaluation is therefore essential if the face becomes totally paralyzed within 2 weeks of the onset. Electronic testing is required to predict the prognosis for recovery, and if poor, surgical decompression can be considered. In rare cases, the disorder may recur, either on the same or the opposite side of the face.