Weakness or paralysis of the facial muscles on one side of the face due to damage to one of the facial nerves
The facial nerve controls the muscles of expression and emotion in the face and carries taste sensations from the front of the tongue to the brain. In facial palsy, one of the two facial nerves is damaged, compressed, or inflamed, and this results in weakness of the facial muscles, causing the eyelid and corner of the mouth to droop on one side of the face. People with facial palsy are often concerned that they have had a stroke, but this is unlikely if only the face is affected because a stroke is usually also associated with muscle weakness in other parts of the body.
Facial palsy is usually temporary, but a full recovery may take several months. The disorder affects about 1 in 4,000 people in the UK each year.
The most common form of facial palsy is Bell’s palsy, which in most cases is thought to arise as a result of infection with the herpes simplex virus, the virus that causes cold sores. In other types of facial palsy, causes of facial nerve damage include the viral infection shingles (see Herpes zoster) and the bacterial infection Lyme disease. In addition, the facial nerve sometimes becomes inflamed as a result of a middle-ear infection (see Otitis media). In rare cases, the facial nerve may be compressed by a tumour called an acoustic neuroma. Facial palsy can also result from injury or from damage to the nerve from a tumour of the parotid salivary gland.
In some cases, such as in Bell’s palsy, the symptoms of facial palsy appear suddenly over about 24 hours. In other cases, including facial palsy caused by an acoustic neuroma, symptoms may develop slowly. The symptoms include:
Partial or complete paralysis of the muscles on one side of the face.
Pain behind the ear on the affected side of the face.
Drooping of the corner of the mouth, sometimes associated with drooling.
Inability to close the eyelid on the affected side and watering of the eye.
Impairment of taste.
If facial palsy is very severe, you may have difficulty in speaking and eating, and, occasionally, sounds may seem unnaturally loud in the ear on the affected side. If the eyelid cannot be closed, the eye may become infected, leading to ulceration of the cornea, the transparent front part of the eye. In facial palsy due to shingles, you will also have a rash of crusting blisters on your ear.
Your doctor will probably be able to diagnose facial palsy from your symptoms alone. A rapid onset over about 24 hours suggests Bell’s palsy. Symptoms that develop more slowly usually indicate another cause.
If your doctor suspects a tumour may be compressing the facial nerve, he or she may arrange for you to have CT scanning or MRI. Nerve and muscle electrical tests may also be arranged to assess nerve damage. If you live in a part of the UK where Lyme disease is common, you may have a blood test to look for evidence of this disorder.
If your symptoms have appeared in the last 48 hours, your doctor may prescribe corticosteroids for up to 2 weeks to reduce inflammation of the nerve, and an antiviral drug such as aciclovir. He or she may also recommend that you take painkillers. To prevent damage to the cornea, you may be given artificial tears (see Drugs acting on the eye), and you will probably be advised to tape the affected eye shut when you go to sleep.
Bell’s palsy usually clears up without further treatment. For other types of facial palsy, the underlying cause will be treated, if possible. For example, if it is due to shingles, aciclovir or another antiviral drug will be prescribed. To be effective, treatment with aciclovir should begin as soon as the rash appears. If you have an acoustic neuroma, it will be removed surgically to relieve compression of the facial nerve.
If muscle paralysis persists, surgery may be used to graft nerve tissue or reroute another nerve to the face. Facial exercises or massage may help to maintain tone (see Physiotherapy).
With appropriate treatment, facial palsy usually improves within about 2 weeks. However, a full recovery may take up to about 12 months. Some people are left with residual weakness.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.