Bell's palsy is a form of temporary facial paralysis resulting from damage or trauma to the 7th cranial nerve, one of the facial nerves. It is the most common cause of facial paralysis. Generally, Bell's palsy affects only one side of the face, but it can affect both sides.
Symptoms vary among individuals and include sudden weakness on one side of the face, drooping eyelid or corner of the mouth, drooling, inability to close the eye or mouth, altered taste, and excessive tearing in the eye. Symptoms appear suddenly and reach their peak within 72 hours. Bell's palsy can range in severity from mild weakness to total paralysis, and can cause significant facial distortion.
The exact cause of Bell's palsy isn't known, but many scientists believe that reactivation of a dormant viral infection can cause the facial nerve to swell and become inflamed. Several other conditions can cause facial paralysis that might be diagnosed as Bell's palsy.
The disorder can affect anyone at any age. Risk factors include pregnancy, preeclampsia, obesity, hypertension, diabetes, and upper respiratory ailments.
Steroids can increase the probability of facial nerve function recovery. Antiviral drugs (in addition to steroids) might help with the recovery of facial nerve function. Analgesics such as aspirin, acetaminophen, or ibuprofen may relieve pain. Keeping the eye moist and protecting it from debris and injury, especially at night, is important. Lubricating eye drops can help.
Other therapies such as physical therapy, facial massage, or acupuncture may provide a potential small improvement in facial nerve function and pain.
The prognosis for individuals with Bell's palsy is generally very good. The extent of nerve damage determines the extent of recovery.
With or without treatment, most individuals begin to get better within two weeks after the initial onset of symptoms and most recover some or all facial function within six months.
Some individuals may show moderate to severe side effects. In some cases, residual muscle weakness may last longer or may be permanent.
The NINDS conducts and supports an extensive research program of basic science to increase understanding of how the nervous system works and circumstances that lead to nerve damage. Knowledge gained from this research may help scientists find the definitive cause of Bell's palsy.
Scientists are studying two genes to identify the molecular mechanisms involved in the regeneration of nerve projections (axons) to their original targets. An understanding of how to regenerate peripheral nerves may lead to ways to prevent nerve damage and injuries from occurring.