Family doctor

What is it and who gets it?

Bell's palsy is an isolated paralysis of one side of the face that occurs suddenly and without explanation, due to problems with the facial nerve. Also known as "idiopathic facial paralysis", its exact cause has remained uncertain, although recent research has incriminated Herpes simplex I virus (the virus that causes cold sores).

Bell's palsy is one of the most common disorders of nerves, affecting about 20-30 people per 100,000 population; 1 in 30 people can expect to have Bell's palsy in their lifetime. It can occur in people of any age (including babies, though rarely) but is more likely with increasing age. Both men and women are affected, although there is variation with age: the condition is twice as common in females aged 10-19, and 1.5 times more common in men over 40. It is also more common in pregnancy, in diabetics and in those with underactive thyroid glands.

What causes Bell's palsy?

Until recently, there was little idea as to the cause of Bell's palsy, although it was thought to occur because of inflammation and subsequent damage to the nerve. However, new evidence has shown that reactivation of a Herpes infection is linked to many cases of the condition (just as cold sores occur because of reactivation of Herpes simplex I). Consequently, the treatment of Bell's palsy has changed in the past few years.

How do I know I have it?

The facial nerve has many functions: it supplies the muscles of the face, part of the eardrum, the salivary glands and the tear glands. It also carries taste sensation from the front two-thirds of the tongue back to the brain. Therefore, facial nerve damage can have many symptoms (what you, the patient, notices/describes) and signs (what your doctor finds).

Any of the following signs and symptoms may occur, depending on exactly which part of the facial nerve has been affected.

Symptoms:

Sudden facial weakness (common to all cases, but of varying severity):

• Drooping of the corner of the mouth with drooling of saliva
• Distorted smile and frown
• Inability to close the eye completely
• Flat and expressionless features (e.g. loss of creases in forehead)

Ear problems:

• Fullness or pain behind the ear (common)
• Distortion of hearing, particularly loud sounds (known as hyperacusis)

Taste problems:

• Unusual taste
• Decreased taste

Tear problems (rare):

• Decreased tear production
• Recent cold or influenza

Signs:

• One-sided weakness of the upper and lower face (with sensation generally preserved).
• Pooling/overflow of tears (because of reduced blinking) - if tear production has not been affected.
• No evidence of other causes of the condition (e.g. ear infections, trauma, tumours, Lyme disease).

What will my doctor do?

Your doctor should be able to make a diagnosis of Bell's palsy by finding out all the details of your symptoms and by carefully examining you to exclude other less common causes of facial nerve paralysis. There are no particular blood tests that will confirm Bell's palsy (although your doctor may wish to test for diabetes or thyroid problems). Further tests, such as x-rays or MRI scans, are only required if there is little recovery from the condition; they are not necessary when Bell's palsy is first suspected.

See below for the treatment options your doctor is likely to use.

How is it treated?

Prescription drugs

Up until recently, there were two main treatment options for Bell's palsy: either no treatment (as most patients fully recover anyway) or the use of the steroid prednisone. Prednisone is used because of its anti-inflammatory effects and because it may reduce any associated pain. There is much debate as to whether it actually aids full recovery, although there is some evidence that it is beneficial if started within 24 hours of onset. If used, prednisone is usually prescribed for around 10 days, with the dose tapering over the last few days.

The new evidence that Herpes simplex I is implicated in Bell's palsy has prompted the use of the antiviral agent acyclovir (Zovirax). It is taken orally 5 times a day, for 10 days. This is an option that should be discussed with your doctor.

In the past, surgery was used to treat Bell's palsy (by 'decompressing' the nerve as it passes out of the skull). However, it was not particularly successful and is no longer recommended.

Eye and mouth care

It is important that the affected eye is protected during an episode of Bell's palsy. The inability to blink, and/or reduction in tears makes the eye more susceptible to injuries such as foreign bodies or corneal abrasions. Artificial tears should be used during the day to prevent these complications, and the eyelid should either be lightly taped shut at night or covered with an eye patch.

The teeth should be regularly brushed and dental floss used, to ensure good mouth hygiene.

Am I going to recover?

Bell's palsy develops rapidly, with symptoms 'peaking' within 48 hours of their onset in many patients, and maximal by 5 days overall. Patients often mistakenly believe they have had a stroke, because of the facial paralysis. In the majority of cases (60-80%), the condition gradually disappears completely within weeks to months. In some there may be slight residual paralysis that is barely noticeable to others. Unfortunately, some people are left with complications of the condition, which include:

• Obvious residual paralysis (e.g. asymmetrical smile, drooling of liquids, inability to close eye, abnormal blinking, tear pooling)
• Dry eye
• Affected taste
• Distorted nerve functions (e.g. tear production with eating, blinking when opening mouth).

In 7-10% of people, Bell's palsy will recur.

Hyperacusis (distorted hearing) and associated diseases such as diabetes are associated with a poor outcome. Factors that increase the likelihood of better outcome include:

• Young age
• Incomplete paralysis at outset
• Recovery of taste within 1 week
• Early recovery (within 10-21 days).
• The use of facial massage, neuromuscular retraining (e.g. using a mirror to practise the use of facial muscles), acupressure or acupuncture may help enhance the recovery process.