Bell palsy (a type of facial nerve palsy) is sudden weakness or paralysis of muscles on one side of the face due to malfunction of the 7th cranial nerve (facial nerve). This nerve moves the facial muscles, stimulates the salivary and tear glands, enables the front two thirds of the tongue to detect tastes, and controls a muscle involved in hearing.
The cause may be a viral infection or an immune disorder that causes the facial nerve to swell.
People may feel pain behind the ear, then one side of the face may become weak or completely paralyzed, and they may be unable to taste with the front of the tongue on the affected side.
Doctors usually base the diagnosis on symptoms.
Corticosteroids are used to reduce swelling of the nerve.
With or without treatment, most people recover completely within several months.
When the facial nerve is paralyzed (called facial nerve palsy), doctors can find a cause (such as Lyme disease or sarcoidosis) in about half the cases. When no cause is obvious, Bell palsy is diagnosed.
Doctors used to think that the cause of Bell palsy was unknown (idiopathic). However, recent evidence suggests that in some cases, a cause (such as a viral infection or an immune disorder that causes the facial nerve to swell) can be identified.
Common causes of Bell palsy include
Other viruses, such as coxsackievirus, cytomegalovirus, and the viruses that cause mumps, rubella, mononucleosis, or influenza, may also cause Bell palsy. Infection causes the nerve to swell. When the nerve is swollen, it is squeezed (compressed) by the narrow passageways in the skull that it passes through.
Other disorders can cause facial nerve palsy. Lyme disease can cause facial nerve palsy, but unlike Bell palsy, it may affect both sides of the face. In African-Americans, sarcoidosis is a common cause of facial nerve palsy. Sometimes tumors and skull fractures cause facial palsy.