Bell's palsy

Bell's palsy is the sudden weakness of the muscles on one side of the face caused by inflammation of the facial nerve. People wake up with a lopsided face, unable to smile or close an eye, and drinks run out of the corner of the mouth. Almost everyone thinks of a stroke first, and that instinct is right: until a doctor has proved otherwise, a face that has suddenly dropped is treated as an emergency. Bell's palsy itself is not life-threatening, in most people it settles within a few months, and treatment started in time noticeably improves the outcome. But there is little room to think it over: the medicines work best in the first three days.

What it looks like

The weakness comes on quickly, over hours or a day, rarely across two or three days, and almost always on one side only.

• the corner of the mouth droops, the smile is crooked, drinks leak out on that side and food gets trapped in the cheek;
• the eye does not close fully and rolls upwards when you try to squeeze it shut;
• the eyebrow will not lift and the forehead creases have vanished on that side;
• the eye is dry and gritty at times and watery at others, especially while eating;
• taste on the front of the tongue fades or turns strange;
• sounds seem uncomfortably loud on the affected side;
• a day or two before the weakness there is often an ache behind the ear or around the jaw.

The weakness may be partial, so that the face simply responds poorly, or complete, with one half of the face entirely still. How fast and how fully things recover depends largely on that difference.

The first thing to rule out

Call the emergency services straight away if, alongside the drooping face, there is weakness or numbness in an arm or a leg, slurred speech, trouble finding words, sudden loss of vision, severe dizziness with vomiting, or confusion. That is how a stroke presents, and here it is a matter of minutes.

There is one sign doctors use to tell the two apart, though it is no substitute for being examined. In Bell's palsy the forehead is affected too: the eyebrow will not rise and the eye will not shut. In a stroke the forehead usually still works, so the person can wrinkle it, while the lower half of the face does not obey. Relying on this yourself is not safe: there are exceptions and the cost of being wrong is far too high. Even if nothing but the face is troubling you, see a doctor the same day.

What else pulls a face out of shape

Bell's palsy is the commonest cause, but the diagnosis is only made once nothing else has been found. The following should raise suspicion.

• Shingles of the ear. Severe ear pain, blisters on the outer ear, in the ear canal or on the palate, hearing loss, vertigo. This form recovers less well and needs different treatment, which is why the ear is always examined.
• Lyme disease from a tick bite. Especially if it happened in summer, if there was a bite or a spreading red patch on the skin, and also if the face has dropped on both sides or the patient is a child. Antibiotics are what is needed here, not steroids.
• Ear disease. Discharge, long-standing pain, hearing loss after an ear infection.
• A tumour. The key clue is that the weakness builds up not within a day but over weeks and months, or that a lump can be felt beside the ear or under the jaw. A gradual onset is never Bell's palsy.
• A head injury, or previous surgery on the ear or the parotid gland.
• Facial weakness on both sides, together with weakness in the legs and arms, points to rare but serious conditions that need urgent assessment.

Pregnancy and diabetes deserve a separate mention: with both of them Bell's palsy is more common, and treatment is adjusted accordingly.

Why the nerve stops working

The facial nerve reaches the muscles of the face through a narrow bony canal inside the skull. If the nerve swells it has nowhere to expand: it is squeezed inside its own canal and the signal to the muscles stops getting through. The swelling is most likely caused by the reawakening of the herpes virus, which lives in the nerve ganglia of most adults. Bell's palsy cannot be caught and cannot be passed on. Cold weather, a draught and an open car window are the popular explanation, but there is no convincing evidence that they are to blame.

What the doctor does

There is no specific test for Bell's palsy. The doctor asks you to raise your eyebrows, screw your eyes shut, puff out your cheeks and bare your teeth, checks the strength of your arms and legs, your speech, eye movements and hearing, looks into the ear and at the eardrum, and feels the parotid area and the neck. If the picture is typical and everything else is normal, the assessment ends there. Blood tests are used when Lyme disease is suspected and to check the blood sugar, measured in mmol/L. Scans are needed if the onset was gradual, if more than one nerve is affected, if there is a lump near the ear, or if movement has not returned after three or four months.

A handful of days to decide

• Steroid tablets in a short course are the only treatment with proven benefit. They should be started as early as possible, ideally within the first seventy-two hours of the weakness appearing; after that the effect drops off sharply. That is precisely why waiting a week to see whether it clears up on its own is the wrong move.
• Antiviral medicines are added to the steroids in severe cases and always when shingles is found.
• Eye care is not cosmetic but sight-saving; it is set out separately below.
• Work with a rehabilitation therapist means gentle exercises and retraining of facial movement when recovery is slow. Stretching and kneading the face with force is unwise: it encourages abnormal linked movements to develop.

If you take medication for diabetes, have a stomach ulcer or high blood pressure, tell the doctor before the steroids are started, because the plan will need adjusting.

How to protect the eye

An eye that will not close is the one genuine danger in Bell's palsy. The cornea is left unprotected, dries out and can ulcerate, and that does threaten sight. What to do: artificial tears frequently during the day, up to several times an hour; a thick gel or ointment at night; the eyelid gently taped or covered while asleep; and glasses during the day to keep out wind and dust. See a doctor immediately if the eye becomes red or painful, if there is a gritty feeling, or if vision blurs.

How long recovery takes

In most people the first improvement shows after two or three weeks, and the face returns fully to normal within three to six months. When the weakness is partial, the chances of complete recovery are very high. If no movement at all has appeared after three or four months, the diagnosis is reviewed.

Some people are left with traces: slight asymmetry, the corner of the mouth pulling when the eyes close or the eye closing during a smile, watering while eating, oversensitivity to loud noise, altered taste. Rehabilitation therapists work on these, and in selected cases injections and surgery help. Bell's palsy rarely recurs; if it does, particularly on the same side, the assessment is repeated in more detail. And one thing that is discussed less often: a lopsided face is hard to carry. If it has ruined your sleep, taken away any wish to see people, or left a persistent anxiety, say so to your doctor, because it is part of the illness and not a weakness of character.

Online consultation

In an online consultation the doctor judges, from your answers and from how the face moves, whether this looks like Bell's palsy or whether urgent face-to-face care is needed, explains whether you are still inside the window for starting treatment, goes through how to protect the eye properly, and tells you which signs to expect over the coming weeks and when to come back.

This material is for information only and does not replace medical advice.