Bell's palsy is a temporary form of facial paralysis that occurs with damage to the nerve that controls movement of the muscles in the face.

Bell's palsy is a form of cranial mononeuropathy VII. It is the most common type of this nerve damage. Bell's palsy affects about 2 in 10,000 people.

Bell's palsy involves damage to the seventh cranial (facial) nerve. This nerve controls the movement of the muscles of the face. The cause is often not clear, although herpes infections may be involved.

Bell's palsy is thought to be linked to swelling (inflammation) of the nerve in the area where it travels through the bones of the skull. Other conditions related to Bell's palsy include:

• Diabetes
• Lyme disease
• Sarcoidosis

Symptoms usually start suddenly, and range from mild to severe. They may include:

• Change in facial expression (for example, grimacing)
• Difficulty with eating and drinking
• Drooling due to lack of control over muscles of the face
• Droopy eyelid or corner of mouth
• Dry eye or mouth
• Face feels stiff or pulled to one side
• Facial paralysis of one side of the face, makes it hard to close one eye
• Headache
• Loss of sense of taste
• Pain behind or in front of the ear
• Sensitivity to sound (hyperacusis) on the affected side of the face
• Twitching in face
• Weakness in face

• Blood tests for sarcoidosis or Lyme disease
• Magnetic resonance imaging (MRI)
• Electromyography (EMG)
• Nerve conduction test

Other causes of cranial mononeuropathy VII, such as head injury and tumor, need to be ruled out.

In many cases, no treatment is needed. The goal of treatment is to relieve symptoms.

Corticosteroids or antiviral (acyclovir and valacyclovir) medications may reduce swelling and relieve pressure on the facial nerve. You must take these drugs early (preferably within 24 hours of when symptoms start) for them to be most effective. However, there are no published studies showing that antiviral medications speed up or improve recovery from Bell's palsy.

Your health care provider may recommend lubricating eye drops or eye ointments to protect the eye if you cannot close it completely. You may need to wear an eye patch during sleep.

Surgery to relieve pressure on the nerve (decompression surgery) is controversial and has not been shown to routinely benefit people with Bell's palsy.

About 60 - 80% of cases go away completely within a few weeks to months. Sometimes the condition results in permanent changes. The disorder is not life threatening.

• Abnormal movements, such as tears when laughing or salivation at the wrong times (synkinesis)
• Change in appearance of the face (disfigurement) from loss of movement
• Chronic problems with taste
• Chronic spasm of face muscles or eyelids
• Damage to the eye (corneal ulcers and infections)

Call your health care provider right away if your face droops or you have other symptoms of Bell's palsy. Your health care provider can rule out other, more serious conditions, such as stroke.

Safety measures may reduce the risk of head injury. Many of the other factors that lead to this disorder are not preventable.

Tiemstra JD, Khatkhate N. Bell's palsy: diagnosis and management. Am Fam Physician, 2007;76:997-1002.