What is Bell's palsy?

Bell's palsy

What is Bell's palsy?

If you have Bell's palsy, the muscles of your face suddenly become weak. This usually happens on just one side of the face. It means you can't move your face properly. You may find only half of your face moves when you smile, and you can't move one eyelid to open or close it.

Bell's palsy happens because one of the nerves sending messages from your brain to your face muscles has stopped working properly.

The most common symptom of Bell's palsy is not being able to move the muscles on one side of your face.

Some people who have a

stroke
You have a stroke when the blood supply to a part of your brain is cut off. This damages your brain and can cause symptoms like weakness or numbness on one side of your body. You may also find it hard to speak if you've had a stroke.

stroke also get weakness in the muscles of the face. But this is different from Bell's palsy. If you have a stroke, other parts of your body are affected, too. And after a stroke you can usually move your forehead and eyelids.

Bell's palsy happens when a nerve in your face is damaged.

Source:
National Institute of Neurological Diseases and Stroke (NINDS)
Bell's palsy fact sheet.
July 2008. Available at http://www.ninds.nih.gov/disorders/bells/detail_bells.htm (accessed on 18 December 2008).

¹ It's called the facial nerve. There's one on each side of your face.

Each facial nerve comes out from your brain through a small tunnel under your ear, and then divides into many branches. These branches are connected to the muscles that you use to blink, smile and frown.

The nerves also go to the

gland
A gland is any group of cells in the body that makes and releases something for use by another part of the body. For example, the thyroid gland makes a hormone called thyroxine. This acts on receptors within cells. By acting on the receptors it gives the cells a message to speed up their metabolism and work harder.

glands that make your tears and saliva, and they carry the sense of taste from your tongue.

Facial nerves control the movement of the muscles in your face and send messages back to your brain.

We don't know for certain what causes Bell's palsy.

Doctors think there may be swelling (

inflammation
If your skin or some other part of your body becomes red, swollen, hot or sore, we say it is inflamed. It means that your body is trying to protect you from germs, from something in your body tissues that can hurt you (like a thorn or sliver), or from things that cause allergies (allergens). Inflammation is part of the way the body heals an infection or injury.

inflammation) around the facial nerve, which squashes the nerve as it passes through your skull. The nerve can't work properly until the inflammation goes. The messages the brain sends to your face muscles get interrupted. So, the muscles of your face become weak or paralyzed (they can't move).

Doctors think the swelling around the nerve is probably caused the by the same viruses that cause cold sores and

chickenpox
Chickenpox is a common childhood illness caused by a virus. It usually leads to a fever, tiredness and an itchy rash. The virus can easily spread from person to person, and people usually get it about two weeks after they were around someone with the illness. About two days before the rash starts, you can give the virus to others. Chickenpox clears up on its own in most children, but adults and some children may get complications such as pneumonia, kidney problems or heart problems. You can get a chickenpox vaccine to help protect you from this infection.

chicken pox:

Source:
Murakami S, Mizobuchi M, Nakashiro Y, et al.
Bell palsy and herpes simplex virus: identification of viral DNA in endoneurial fluid and muscle.
Annals of Internal Medicine. 1996; 124: 27-30.

The virus that causes cold sores is called herpes simplex virus
The virus that causes chicken pox is called herpes zoster virus. Bell's palsy caused by herpes zoster virus is less common but can be more serious.

Source:
Adour KK, Byl FM, Hilsinger RL Jr, et al.
The true nature of Bell's palsy: analysis of 1,000 consecutive patients.
Laryngoscope. 1978; 88: 787-801.

³

You might have had cold sores or chicken pox in the past. But some people carry these viruses in their bodies for a long time without getting any symptoms. Getting Bell's palsy does not mean you will go on to get cold sores or chicken pox.

Not everyone who has weak face muscles has Bell's palsy. About a third of people have another reason for their muscle weakness.

Source:
Holland NJ, Weiner G.
Recent developments in Bell's palsy.
BMJ. 2004; 329: 553-557.

⁴ These include:

A stroke
An injury
An ear disease
Lyme disease
This is an infection transmitted by some tick bites. It can lead to severe, flulike symptoms, including fatigue, fever, headache, muscle pain and a rash. Lyme disease can be treated with antibiotics. In rare cases, if the infection is not treated, people can develop more serious problems, such as arthritis in their joints and problems with their nervous system and heart. Lyme disease is typically seen in the Northeast and North Central United States.

Lyme disease (caused by a tick bite)
A type of cancer (but this is rare).

Your doctor will examine you and ask you questions to rule out other possible reasons for your face muscles becoming weak. You won't be diagnosed with Bell's palsy until other problems have been ruled out. There isn't a test that can tell you for certain you have Bell's palsy. But you can have investigations to look for other things that might make your face muscles weak. You might need to go to the hospital for an

MRI scan
The magnetic resonance imaging (MRI) machine uses a magnetic field to create detailed pictures of the inside of the body. These pictures allow doctors to look at parts of the body in three-dimensional images.

MRI scan or a

CT scan
A CT scan is a type of X-ray. It takes several detailed pictures of the inside of your body from different angles. CT stands for computed tomography. It's also called a CAT scan (computed axial tomography).

CT scan. And you might also need a test called electromyography (EMG) to see how badly your nerve is damaged.

To read more, see Tests and scans if you have Bell's palsy.

Sources for the information on this page:

National Institute of Neurological Diseases and Stroke (NINDS)Bell's palsy fact sheet.July 2008. Available at http://www.ninds.nih.gov/disorders/bells/detail_bells.htm (accessed on 18 December 2008).

Murakami S, Mizobuchi M, Nakashiro Y, et al.Bell palsy and herpes simplex virus: identification of viral DNA in endoneurial fluid and muscle.Annals of Internal Medicine. 1996; 124: 27-30.

Adour KK, Byl FM, Hilsinger RL Jr, et al.The true nature of Bell's palsy: analysis of 1,000 consecutive patients.Laryngoscope. 1978; 88: 787-801.

Holland NJ, Weiner G.Recent developments in Bell's palsy.BMJ. 2004; 329: 553-557.

This information was last updated on Jan 09, 2009

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