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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 viral meningitis or 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, there is damage only to the myelin sheath of the nerve and recovery is rapid. The myelin sheath is the fatty covering-that insulates-the 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.

This answer is based on source information from the National Institute of Neurological Disorders and Stroke.

In general, the cause of Bell’s palsy is unknown. It may result from problems in the body’s immune system (its system for fighting disease).

It may occur if blood flow to the nerve is blocked or constricted, or it may involve inflammation caused by viral infections.

Bell’s palsy occurs more frequently in people who have diabetes, in those who have a family history of Bell’s palsy, and in pregnant women.

Very rarely, a tumor (an abnormal growth) can produce symptoms like those of Bell’s palsy. If facial paralysis does not begin to improve after several weeks, your doctor may recommend an MRI test to rule out the rare possibility of a tumor.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.