Bell’s palsy

What is Bell’s palsy?

Bell's palsy is a weakness that affects the nerve fibres that control the muscles of the face. It is due to a problem with the facial nerve. It develops suddenly, usually on one side of the face.

The cause is not clear, but most cases are due to a viral infection. Most people make a full recovery within two to three months. If a course of steroid tablets begins within 72 hours of the first symptom, the chance of a full recovery improves further.

Who gets Bell's palsy?

Anyone can develop Bell's palsy and it affects men and women equally. It most commonly occurs between the ages of 15 and 60 years. About one in 60 people may experience Bell's palsy at some time in their life.

Does Bell's palsy affect the brain or other parts of the body?

No. Bell's palsy is a local problem confined to the facial nerve and facial muscles. If you have other symptoms, such as weakness or numbness in other parts of your body, tell your doctor. There will be another cause.

Other conditions

Bell's palsy is a common cause of a facial palsy. Yet, it can be confused for other conditions. Less commonly, there are other things that can damage or affect the facial nerve. For example:

• a head injury
• sarcoidosis
• Lyme disease
• growths in the ear
• tumours in the parotid gland
• tumours in the brain
• in some people who have a stroke, facial weakness can develop.

Other conditions and their symptoms

With these conditions you are likely to have other symptoms too. This helps doctors to tell the difference between Bell's palsy and other causes of a facial palsy. For example:

• With a stroke, the forehead muscles are not affected. Also, you are likely to have other nerves that are affected as well as the facial nerve. If you think you are having a stroke, call 000. See the leaflet called Stroke for more details.
• With tumours, the symptoms usually develop over weeks or months. This is unlike Bell's palsy, where symptoms develop quickly – often 'overnight'.
• Conditions such as sarcoidosis and Lyme disease tend to cause various other symptoms as well as nerve palsies.

Bell's palsy is uncommon in children younger than 10. Other conditions should be carefully ruled out in children who develop facial weakness.

Most people with straightforward Bell’s palsy do not need brain imaging with CT or MRI. But if there are any atypical or additional features that do not fit with Bell’s palsy, your doctor may request brain imaging.

Symptoms

The main symptom is weakness of the face, which is usually one-sided. The effects of the weakness vary, depending on whether the nerve is partially or fully affected. These include the following:

• Your face may droop to one side. When you smile, only half of your face may move.
• Chewing food on the affected side may be a problem. Food may become trapped between your gum and cheek. Drinks and saliva may escape from the side of your mouth.
• You may not be able to close an eye. This may cause a watery or dry eye.
• You may not be able to wrinkle your forehead, whistle or blow out your cheek.
• You may have some difficulty with speech because the muscles in the side of the face help in forming some words. For example, words beginning with a P.
• Usually the sensation on your face remains intact but some people may report altered sensation on the affected side of the face.

Causes

It is thought that inflammation develops around the facial nerve as it passes through the skull from the brain. The nerve then partly, or fully, stops working until the inflammation goes. If the nerve stops working so do the muscles connected to that nerve. The cause of the inflammation is not known but, in most cases, it is due to a viral infection.

Treatment

As mentioned, there is a good chance of full recovery without any treatment. But treatment with medication is usually advised to improve the chance of full recovery. Also, you need to protect your eye if your eyelids cannot close (see Eye protection).

Steroid tablets

A course of steroid tablets is usually prescribed for about 10 days. The steroid tablet most used is prednisolone. Steroids help to reduce inflammation, which is why they help. Taking a course of steroids does not guarantee full recovery of the nerve function. But it can increase the chance of full recovery compared to no treatment.

Serious side-effects from the short course of steroids are very unlikely to occur. (The main side-effects from steroids occur if you take them long-term. This is not required for this condition.) You should begin the course of steroids as soon as possible after symptoms start; ideally, within 72 hours. Steroids may not have much effect after this.

There is no strong evidence of the benefits of steroid treatment for children with Bell's palsy.

Antiviral medicines

As most cases of Bell's palsy are probably due to a viral infection, it seems logical that antiviral medicines may help.

Some medicines can stop the chickenpox and cold sore virus from multiplying. It is possible that taking a course of steroids plus a course of antiviral medicine may work a little better than taking a course of steroids alone. However, the research trials give conflicting results about this. If there is any benefit from this combination, it is likely to be small.

An exception would be if the doctor suspects the chickenpox virus is responsible. This would be clinically evident by small blisters around your ear or face. In these cases, the blisters would be swabbed for the virus and antiviral medications would be given.

Eye protection

If you cannot close your eyelids, the front of your eye is at risk of becoming damaged. Also, your tear glands may not work properly for a while and your eye may become dry. Dryness can cause damage, so seek treatment to keep your eye moist. Your doctor may advise one or more of the following until your eyelid and tear production recover:

• an eye pad or goggles to protect your eye
• eye drops to lubricate your eye during the day
• eye ointment to lubricate your eye overnight
• an option of taping your upper and lower lid together when you are asleep. Other procedures are sometimes done to keep your eye shut until the eyelids recover.

What to expect

• Most cases of Bell's palsy are painless or cause a mild ache. However, some people develop some pain near the ear. This often begins before the facial weakness and can last for a few days.
• Loud sounds may be uncomfortable and normal noises may sound louder than usual. This is because a tiny muscle in the ear may stop working.
• You may lose your sense of taste on the side of the tongue that is affected.

How does Bell's palsy progress?

Without treatment, full recovery is still likely and occurs in about 15 in 20 cases. With treatment, the chance of full recovery improves. In most people the function of the nerve gradually returns to normal.

Symptoms usually start to improve after about two to three weeks, and are gone within two months. Sometimes it can take up to 12 months to fully recover. In some cases, symptoms do not completely go. Some weakness may remain. But it is often a slight weakness of part of the face and hardly noticeable.

It is uncommon to have no improvement at all; however, some people are left with permanent facial weakness. Some may develop involuntary twitching of the face after Bell’s palsy. This is a form of hemifacial spasm.

If the facial weakness does not recover

The small number of people who have ongoing facial weakness can consider treatments such as these:

• physiotherapy: a treatment called facial retraining with facial exercises may help
• injections of botulinum toxin (Botox®) may help if spasm develops in facial muscles
• various surgical techniques that can help with the cosmetic appearance.

Will it happen again?

In most cases, a Bell's palsy is a 'one-off'. About one in 14 people who have a Bell's palsy can have further episodes. This is more likely if you have close relatives who have also had Bell's palsy.

Seeking help

In a medical emergency call an ambulance – dial triple zero (000). If you have concerns, see your local doctor or healthcare professional. If this is not possible return to the emergency department or urgent care centre.

For more information

Ask your GP or healthcare professional. You can also call healthdirect 24 hours a day on 1800 022 222 or visit healthdirect.gov.au.