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Written by Dr Robert Mills, consultant ENT specialist
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What is Bell's palsy?
Bell's palsy is the sudden onset of weakness of the
muscles of one side of the face, for which no other cause can be
found.
It is due to a loss of function in the nerve that supplies the
facial muscles (the facial nerve). The cause is unknown, but there is some
reason to believe that a viral infection of the nerve is
responsible.
Bell's palsy is common, affecting approximately 23 per
100,000 people per year, or 1 in 60 to 70 people in a lifetime.
What are the symptoms?
Weakness of one side of the face, the onset of which is usually
quite rapid - over a few hours.
Some or all of the following symptoms may also be present on the
same side as the weakness:
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pain in the ear.
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a feeling of numbness of the face, although the sense of touch
remains normal.
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loss of taste on the front part of the tongue.
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loss of saliva production and increase in tear
flow.
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sometimes, increased hearing sensitivity.
There is no disturbance of balance in Bell's palsy. Because
of the weakness or paralysis of the facial muscles the person will usually have
difficulty in closing the eye properly on the affected side. The muscles on the
unaffected side of the face tend to pull the mouth over to that side, causing
the person to drool and often giving the initial visual impression that the
abnormal side of the face is the one with the movement.
What can be done to avoid Bell's palsy?
At present we know of nothing that can be done to avoid
Bell's palsy.
How does the doctor make a diagnosis?
The diagnosis is made by excluding other possible causes. The
ears are examined to exclude evidence of significant ear disease and the mouth
to look for evidence of viral infection in the form of blisters. The latter is
called Ramsay-Hunt syndrome and is due to infection of the facial nerve with
the
chickenpox virus,
herpes zoster. In this disease the facial weakness is associated with deafness
and dizziness.
It may be necessary to test the hearing and occasionally to
carry out a scan of the head to exclude other diseases.
What other causes of facial weakness are there?
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Skull fractures involving the temporal bone - the bone that
contains the middle ear. The facial nerve travels through this bone on its way
to the facial muscles and so may be damaged.
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Neck injuries, particularly a stab wound to the
neck.
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Tumours in the upper part of the neck.
-
Damage to the facial nerve during ear surgery.
Loss of power in one side of the face can be a symptom of a
stroke but there will
be other features present, such as loss of power in a limb, which point to the
correct diagnosis.
Good advice
Head trauma can be minimised by wearing appropriate head
protection during sport and when riding a motorbike.
How is it treated?
About 80 per cent of people with Bell's palsy recover
spontaneously within three months. Although
steroids are still
quite commonly prescribed for patients seen soon after the onset of facial
power loss, the evidence supporting their use is weak.
The antiviral agent
aciclovir (eg Zovirax) has also
been used in Bell's palsy but there is insufficient information available
to recommend it.
Facial weakness interferes with the ability to close the eyelid
normally. 'Artificial tears' (eye drops) may therefore be required to
protect the eye.
In long-standing cases, eye closure may be improved by
narrowing the space between the eyelids (tarsorrophy) or placing a gold weight
in the upper lid.
Plastic surgery techniques can also be used to improve drooping
of the lower part of the face in permanent facial weakness.
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References
Clinical evidence 2000; 4: 706-709 (BMJ Publishing
Group).
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Last updated 01.08.2005
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