Bell's Palsy

What happens in Bell's palsy

The facial nerve (cranial nerve VII) leaves the brainstem and passes through a narrow bony canal in the skull before spreading across the face. It controls the muscles of facial expression, eye closing and blinking, and also carries taste from the front of the tongue, controls tears and saliva, and dampens loud sounds in the ear.

In Bell's palsy, the nerve swells inside its bony canal. The pressure and inflammation stop signals getting through, so the muscles on that side of the face weaken. Reactivation of herpes simplex virus is the leading suspected cause, but in most people no cause is proven.

Symptoms

Symptoms develop quickly, usually reaching their worst within 72 hours:

• drooping of one side of the face, including the corner of the mouth
• inability to close the eye fully, blink or wrinkle the forehead on that side
• drooling and difficulty keeping food or liquid in the mouth
• a dry eye, or a watery eye because tears do not drain properly
• pain behind or around the ear, sometimes a day or two before the weakness
• altered taste on the front of the tongue
• sensitivity to loud sounds on the affected side
• the face may feel numb or heavy, although sensation is actually normal

Bell's palsy vs stroke

Only a clinician can be sure. Treat any sudden facial droop as a possible stroke and get emergency help.

Causes and risk factors

Bell's palsy is diagnosed when no other cause of facial nerve palsy is found. Risk factors:

• pregnancy, especially the third trimester and the first week after birth
• diabetes
• a recent cold, flu or other upper respiratory infection
• obesity and high blood pressure
• age 15 to 60, though it can occur at any age

Other causes of facial nerve palsy that doctors consider:

• Ramsay Hunt syndrome: shingles of the facial nerve, with a painful blistering rash in the ear, hearing loss and vertigo
• Lyme disease: a common cause in tick areas, sometimes affecting both sides
• Ear infections and middle ear disease
• Tumors: of the parotid gland or acoustic neuroma, usually with slower onset
• Guillain-Barré syndrome and sarcoidosis: can affect both sides
• Injury such as a skull fracture

Diagnosis

Diagnosis is clinical. A doctor will examine the face, eyes, ears, mouth, neck and nervous system, and ask about rash, ear symptoms, tick exposure and other illnesses. Routine blood tests and scans are not needed for typical Bell's palsy. Tests are used when something is unusual:

• Lyme serology in tick-exposed areas
• MRI or CT for slow onset, recurrence, other neurological signs, or no improvement after 3 months
• Hearing tests
• Nerve conduction testing (electroneurography) in complete paralysis to predict recovery

Treatment

Steroids

Oral corticosteroids, such as prednisolone or prednisone, started within 72 hours of symptom onset, are recommended for people aged 16 and over. They reduce nerve swelling and significantly increase the chance of full recovery. Evidence in children is less clear, and decisions are made case by case.

Antivirals

Antiviral drugs alone do not help. Adding an antiviral such as valacyclovir to steroids may offer a small benefit in severe cases and is an option discussed with the patient.

Eye care

Protecting the eye is essential, because a dry eye that cannot close can be damaged:

• lubricating eye drops during the day, as often as needed
• lubricating ointment at night
• taping the eye closed at night or using a moisture chamber
• sunglasses or glasses outdoors to protect from wind and dust

Get urgent help for eye pain, redness or reduced vision.

Other measures

• Facial exercises and physical therapy guided by a specialist, particularly during recovery.
• Pain relief for ear pain: acetaminophen (paracetamol) or ibuprofen, following the label dose.
• For persistent weakness: Botox injections to balance the face, and facial plastic surgery or nerve procedures in selected people.

Recovery

• Most people notice improvement within 2 to 3 weeks.
• About 70 to 85% recover completely, usually within 3 to 6 months.
• Recovery is less complete in people with total paralysis, age over 60, diabetes, high blood pressure, severe pain, or no improvement by 3 weeks.

Possible long-term effects include:

• lasting weakness or asymmetry
• synkinesis: involuntary movements, such as the eye closing when you smile, caused by nerves regrowing to the wrong muscles
• crocodile tears: watering of the eye when eating
• muscle tightness on the affected side

Bell's palsy comes back in about 7 to 15% of people, sometimes on the other side. Recurrence on the same side warrants imaging.

Frequently asked questions

What causes Bell's palsy?

Bell's palsy is caused by inflammation and swelling of the facial nerve. The exact trigger is often unknown, but reactivation of a herpes virus is suspected. It is more common during pregnancy, in people with diabetes and after colds or flu. It is not caused by a stroke.

How long does Bell's palsy last?

Most people start improving within 2 to 3 weeks and recover completely within 3 to 6 months. Some take longer, and a minority are left with mild weakness or other long-term effects, especially if the paralysis was complete.

How can I tell if it is Bell's palsy or a stroke?

Bell's palsy usually affects the whole side of the face, including the forehead, and develops over hours. A stroke usually spares the forehead and often comes with arm or leg weakness, speech problems or confusion. Any sudden facial droop needs emergency assessment.

What is the best treatment for Bell's palsy?

Oral steroids started within 72 hours of symptoms give the best chance of full recovery in adults. Eye protection with drops, ointment and taping at night is essential. Adding an antiviral may be considered for severe cases.

Is Bell's palsy contagious?

No. Bell's palsy itself is not contagious. Although a virus may trigger the nerve inflammation, the condition is not passed from person to person.

Can Bell's palsy come back?

Yes, but it is uncommon. Bell's palsy recurs in about 7 to 15% of people, on the same or the opposite side. Repeated episodes on the same side should be investigated with an MRI to look for other causes.