Bell’s palsy (facial paralysis)

Bell’s palsy, sometimes also called Bell’s paralysis or idiopathic facial palsy/paralysis, refers to paralysis of the facial muscles, usually on one side of the face only. It occurs as a result of damage to the facial nerve (nervus facialis). The paralysis is particularly likely to affect the muscles used in facial expression – for example, the muscles used in frowning, wrinkling up the nose or raising the eyebrows.

The facial nerve divides into many branches. As well as the facial muscles, it also controls the tear glands and salivary glands and plays a role in our sense of taste. In the ear, it also affects how loudly sounds are perceived.

As a result, damage to the facial nerve can cause extensive limitations. People with Bell’s palsy often experience difficulties when speaking and a limited ability or complete inability to show their feelings with facial expressions. This can be psychologically stressful.

In most cases, it is not known why Bell’s palsy occurs. When this happens, doctors may describe the facial paralysis as “idiopathic”, which means “of unknown cause”.

The facial paralysis occurs suddenly, usually within the space of a few hours. The paralysis may be mild or severe. Frequently, only one side of the face is paralyzed (unilateral paralysis).

These are typical signs of Bell’s palsy:

• The facial muscles slacken and the face feels stiff or as though it is being pulled to one side.
• The eyebrow droops.
• The cheek feels numb or tingles.
• Pain is felt in the ear.
• The sense of taste is impaired.

In severe cases, people may also lose the ability to close their eyelid or the corner of their mouth. Other possible symptoms include sensitivity to noise, a dry mouth and dryness in the eye.

The paralysis sometimes also causes difficulties with eating and drinking.

In up to 75 percent of cases, the cause of the Bell’s palsy remains unknown (idiopathic facial paralysis).

In the remaining 25 percent of cases, a cause for the unilateral facial paralysis can be identified, for example:

• facial fractures or injuries
• damage to other nerves
• tumors, for example in the cerebellum (at the back of the brain) or parotid gland (salivary gland in front of the ear)
• viral infections, e.g. with the varicella zoster virus, which causes shingles (herpes zoster)
• bacterial infections, such as a middle ear infection

The nerve may also become damaged during a surgical procedure.

In children, facial paralysis may also be caused by injuries sustained during a forceps delivery, for example, or by congenital diseases or deformities.

Every year, around 40 in every 100,000 people develop facial paralysis. Most of these are aged between 15 and 45.

In many cases, Bell’s palsy clears up by itself. In 85 percent of cases, there is a full or partial recovery within a few weeks. Another 10 percent of cases will recover partially or fully within 3 to 6 months.

After one year, 71 percent of adults with idiopathic facial paralysis will have made a full recovery. The equivalent figure for children is 95 percent.

In a severe case of Bell’s palsy, for example, following an infection with the varicella zoster virus, long-term effects may remain – such as impaired movement of the facial muscles or a lack of control over tear production.

If the eyelid cannot be closed when the facial paralysis develops, the cornea (outer protective layer of the eye) may become dried out.

The doctor will first determine the degree to which the facial paralysis has progressed. For this purpose, the patient will be asked to move their face in various ways, e.g.:

• open and close the eyes
• raise the eyebrows
• frown
• move the mouth

The doctor will examine the ear to detect or exclude a middle ear infection. The mouth is also checked for swelling.

Possible diseases, such as Lyme disease, can be detected by testing a sample of blood or cerebrospinal fluid (liquor).

Further tests will be conducted if the symptoms are unclear. By stimulating the nerves with weak electrical currents, they can determine how well the nerves and muscles are working. Imaging techniques, such as a computed tomography (CT) or magnetic resonance imaging (MRI) scan may also be used.

If the facial paralysis is a symptom of another condition, it is useful to begin by discussing its treatment with the doctor. If the patient has an infection, anti-bacterial or anti-viral medication is available.

Symptoms also disappear without treatment in most people with idiopathic facial paralysis – where the reason for the paralysis remains unknown. Treatment for around one week with glucocorticoids such as prednisolone improves the outlook to some extent. One of the effects of this drug is to reduce inflammation.

In severe cases, the facial paralysis may be permanent. One type of treatment that can be tried in this case is transcutaneous nerve stimulation. This involves the doctor using electrodes to stimulate the affected nerves and muscles. Following this treatment, some people with Bell’s palsy are once again able to use at least some of their muscles for facial expression. Sometimes, it is possible to restore some of the nerve and muscle functions by means of a surgical procedure.

If someone with Bell’s palsy is unable to close their eyelid, artificial tears and eye ointments can prevent the cornea from drying out. A bandage can also be worn at night to ensure adequate protection.

If someone has Bell’s palsy for a long time or permanently, it is important for them to learn how to cope effectively with it on a daily basis.

Training courses with professional instructors can teach them how to protect the eye in everyday life or how to eat and drink independently.

There are also special exercises and facial massages that can train the facial muscles to make facial impressions and improve speech. Support is provided by trained therapists.