Bell's palsy

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at January 22, 2016
StartBell's palsy

Named for Sir Charles Bell, a Scottish anatomist who discovered the illness in the 1800s, Bell’s palsy is a temporary condition that affects approximately 40,000 Americans every year. A temporary weakening or paralysis of muscles on one side of the face, the disorder is equally common in women and men but usually occurs among those between the ages of 15 and 60.

Contents

Definition & Facts

Caused by trauma to the facial nerve that carries messages from the brain, Bell’s palsy may affect facial expression, eye movement, taste, and production of saliva and tears. Severity may range from mild to acute and is not related to the kind of paralysis commonly caused by strokes. Around 50 percent of sufferers will recover in a short period of time; another 35 percent will get better in less than a year. In less than one percent of cases, both sides of the face may be affected.

Bell’s palsy is caused by trauma or damage to the facial nerve, also known as the seventh cranial nerve. This nerve, mostly enclosed in a narrow, bony channel called the Fallopian canal, runs from the skull to the ear and then to the muscles on either side of the face. Once the seventh cranial nerve separates, it tells the muscles on that side of the face what to do: when to blink or close the eyes, when to smile or frown, and when to produce tears or saliva. It also carries taste sensations from the tongue to the brain and connects to a small bone in the middle of the ear that transmits sound vibrations.

Symptoms & Complaints

Because Bell’s palsy results from defects in the complex nerve that extends from the brainstem to the face, warning signs vary widely from person to person. Most, however, begin abruptly and peak within two days. Symptoms include the following and usually involve one side of the face or specific area around the eye or mouth:

Causes

Scientists know that Bell’s palsy is triggered by inflammation, but they are not certain how this happens. Research suggests that viruses play a role by causing swelling and restricting the flow of blood and oxygen to cells in the nerve. In mild cases of Bell’s palsy, the inflammation affects only the fatty covering of the nerve, its myelin sheath, and recovery occurs quickly. Muscle atrophy usually does not occur in this short period of time.

Bell’s palsy is more common among older people, people with autoimmune disease, and women in the third trimester of pregnancy. Some scientists suspect a correlation between Bell’s palsy and the herpes virus, cytomegalovirus, or Lyme disease. Those who have migraines might be twice as likely to suffer from this kind of paralysis.

Diagnosis & Tests

There is no definitive laboratory test for Bell’s palsy. The diagnosis is based on the clinical presentation of symptoms, including distorted facial features and muscle weakness usually limited to one side of the face, and the elimination of other possible causes of paralysis.

A test called an electromyography (EMG), can be used to measure the degree and severity of nerve damage. Computed tomography (CT) scan, MRIs, and X- rays may also be used to rule out other causes of pressure on the facial nerve. Other possible diagnoses include tumors, Lyme disease, blunt trauma, and strokes. Doctors also use blood tests to diagnose coexisting problems, such as diabetes and infectious illnesses, that may cause paralysis.

Treatment & Therapy

Mild cases of Bell’s palsy often require no treatment and go away on their own within a couple of weeks. More severe cases may be treated with medication or therapeutic interventions. When the cause of the palsy is known, therapy targeted to its source can be helpful. Recent studies show that steroids, like prednisone, reduce swelling and inflammation. Drugs used to fight viral infections may shorten recovery time, and pain relievers help to relieve discomfort. As in all illnesses, care should be taken to avoid adverse interactions between drugs.

Alternative therapies include injections of botulinum toxin approved for commercial use which is marketed as Botox®, physical therapy, massage and acupuncture. Because Bell’s palsy can interrupt the eyes’ blinking reflex, lubricating drops, gels, or ointments may be used to keep the eyes moist and safe.

Occasionally, surgery may be used to relieve pressure on the facial nerve or to correct deformities like crooked smiles or eyelids. The facial nerve regenerates at a speed of one to two millimeters per day and can continue to renew itself for up to 18 months, or longer. Appearance can continue to improve even longer than that.

Prevention & Prophylaxis

Although researchers agree that people who suffer from Bell’s Palsy are more likely to get the disorder again, the numbers are uncertain. Recent studies estimate the rate of reoccurrence at 5 to 9 percent, with an average of ten years between occurrences.

Because the cause of the condition is a mystery, there is no known prevention. People at risk may be able to prevent complications from the disorder by actively monitoring concurrent illnesses and seeking treatment as soon as symptoms of Bell’s palsy occur.