We look at the causes, symptoms and treatment for Bell’s palsy, the onset of weakness of the muscles of one side of the face.
Medically reviewed by Dr Juliet McGrattan (MBChB) and words by Dr Michael Wareing
Bell’s palsy is a type of facial paralysis characterised by an inability to control the muscles on one side of the face. Symptoms can vary from mild to severe and often include muscle twitching and weakness, or total loss of the ability to move one (or rarely both) sides of the face.
We look at Bell’s palsy symptoms, causes, treatment, longterm prognosis and other facial weakness causes to look out for:
What is Bell’s palsy?
Bell’s palsy is the 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 causing inflammation 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. It can happen to anyone but is more likely in those who are diabetic or pregnant and less likely in children.
Bell’s palsy symptoms
Bell’s palsy symptoms include weakness of one side of the face, the onset of which is usually quite rapid – over a few hours to two days.
Some or all of the following symptoms may be present on the same side as the weakness:
- Facial drooping with an inability to smile or raise the eyebrow and forehead on one side.
- Difficulty properly closing the eye, this may make the eye dry or watery.
- A feeling of numbness of the face, although the sense of touch remains normal.
- Loss of taste on one side of the tongue.
- Loss of saliva production and increase in tear flow.
- Pain in the ear.
- Sometimes, increased hearing sensitivity.
There is no disturbance of balance in Bell’s palsy.
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.
It can be hard to chew food, to whistle and sometimes to pronounce certain words.
Bell’s Palsy treatment
How is Bell’s Palsy treated? It will resolve on its own however, there have been a number of clinical trials in the last 10 years on the treatment of Bell’s palsy. The evidence is strong that oral corticosteroids (usually prednisolone) are helpful in reducing the length of palsy and reducing the risk of less than complete recovery. They should ideally be given within 72 hours although some benefit can be obtained up to one week after onset.
Bell’s palsy is the sudden onset of weakness of the muscles of one side of the face.
Even though it is thought that the palsy may be due to a viral infection, there’s no clear evidence that taking antiviral medications will help.
If an eye is unable to fully close then it needs to be protected from scratches, dust and drying out. Eye drops may be given to keep the eye moist and an eye pad or tape should be considered to keep the eye closed, especially at night.
Can you prevent Bell’s palsy? At present we know of nothing that can be done to avoid Bell’s palsy.
Other causes of facial weakness
Aside from Bell’s Palsy there are a number of other potential causes of facial weakness:
Loss of power in one side of the face can be a symptom of a stroke. Strokes happen very abruptly where as Bell’s Palsy develops a little more slowly. There will be other features present, such as loss of power in a limb (inability to raise both arms above the head and keep them there), or slurred or confused speech, which point to the correct diagnosis.
⚠️ Concerned about stroke symptoms? If there is any doubt then a stroke should be assumed and you should dial 999 for an emergency ambulance.
- Ramsay-Hunt Syndrome
Ramsay-Hunt Syndrome is a viral infection with the chickenpox virus, herpes zoster, which is shingles of the facial nerve. There is usually significant pain and a rash in or around the ear. Other cranial nerves may be affected leading to hearing loss, balance disturbance and numbness.
- Skull fracture
Skull fractures involving the temporal bone that contains the middle ear can cause facial weakness. The facial nerve travels through this bone on its way to the facial muscles and so may be damaged, usually with significant trauma to the head.
- High neck injuries
High neck injuries can cause facial weakness, particularly a stab wound to the upper neck.
Tumours anywhere along the course of the facial nerve, which includes the base of skull, the ear and the parotid gland just in front of the ear. These will usually present with a gradual loss of weakness to distinguish them from Bell’s palsy.
- Middle ear disease
Middle ear disease, especially cholesteatoma, can cause facial weakness.
- Ear surgery
Damage to the facial nerve during ear surgery can cause facial weakness.
Bell’s palsy diagnosis
How does the doctor make a diagnosis? The diagnosis is made by excluding other possible causes. The history and examination are the most important aspect. The ears are examined to exclude evidence of significant ear disease such as cholesteatoma and to look for Ramsay-Hunt syndrome which occurs 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 an MRI scan of the head to exclude other diseases.
Bell’s palsy longterm prognosis
What’s the prognosis for people with Bell’s Palsy? About 70-75 per cent of people with Bell’s palsy recover spontaneously within three months. By 9 months about 85-95 per cent have completely recovered. However that still leaves 5-15 per cent of people with some residual weakness, varying from a mild asymmetry to no recovery of function.
About 70-75% of people with Bell’s palsy recover spontaneously within three months.
Physiotherapy may be offered to people with significant and slow to recover facial weakness. There are surgical options too for unresolved weakness causing facial deformity.
A complete palsy, especially one that show no signs of recovery at three weeks, is associated with a less good outcome. If the Bell’s Palsy is only ever partial then the prognosis is very good. Ramsay-Hunt Syndrome is associated with a worse outcome.