Bell's Palsy: Sudden Facial Weakness and What to Do About It

• Bell's palsy causes sudden one-sided weakness affecting the eye, mouth, and cheek

• It is caused by inflammation of the facial nerve and affects around 20–30 per 100,000 people each year

• Steroids started within 72 hours significantly improve the chance of full recovery

• Most patients recover well with prompt treatment

Bell's palsy causes sudden one-sided facial weakness — affecting the eye, mouth, and cheek on the affected side. Early treatment with steroids within 72 hours significantly improves the chance of complete recovery.

Bell's palsy — sudden one-sided facial weakness caused by inflammation of the facial nerve — affects around 20 to 30 people per 100,000 each year and has a good prognosis when treated promptly. High-dose oral steroids started within 72 hours of onset significantly improve the rate of complete recovery, making same-day assessment essential for any patient with sudden facial weakness.

Waking up to find one side of your face not moving is one of the most frightening experiences a patient can describe. The eye won't close properly, the mouth droops, the face feels stiff and strange. For most patients, the immediate fear is that they are having a stroke. In the majority of cases, however, the cause is Bell's palsy — an inflammation of the facial nerve that, while alarming in its presentation, has a generally good prognosis with prompt treatment.

This article explains what Bell's palsy is, how it is distinguished from other causes of facial weakness, what treatment is needed, and what recovery looks like.

What Is Bell's Palsy?

Bell's palsy is a sudden-onset, one-sided weakness or paralysis of the muscles of facial expression, caused by inflammation and swelling of the facial nerve (the seventh cranial nerve). It is the most common cause of acute facial palsy, accounting for the majority of cases.

The condition is named after the Scottish surgeon Sir Charles Bell, who first described the anatomy of the facial nerve in the early nineteenth century.

Bell's palsy can affect anyone at any age, though it is most common between the ages of 15 and 60. It affects men and women equally. The annual incidence is approximately 20 to 30 cases per 100,000 people.

What Causes Bell's Palsy?

The exact cause is not always identified, but Bell's palsy is strongly associated with viral infection — most commonly reactivation of the herpes simplex virus (HSV-1), the same virus responsible for cold sores. Other viruses — including herpes zoster (which causes shingles), Epstein-Barr virus, and cytomegalovirus — have also been implicated.

The virus is thought to trigger inflammation of the facial nerve as it passes through a narrow bony canal (the Fallopian canal) in the skull. This inflammation causes swelling of the nerve within the confined space, leading to compression and disruption of nerve conduction — producing the characteristic facial weakness.

Certain factors are associated with an increased risk of Bell's palsy, including pregnancy (particularly the third trimester), diabetes, and immunosuppression.

Symptoms of Bell's Palsy

Symptoms typically develop over hours to a day or two and may include:

• Sudden weakness or complete paralysis of one side of the face

• Inability to close the eye on the affected side — this is one of the most important features, as it puts the cornea at risk

• Drooping of the corner of the mouth

• Drooling

• Loss of the nasolabial fold (the crease between the nose and mouth)

• Difficulty eating and drinking on the affected side

• Altered or absent taste on the front two-thirds of the tongue

• Sensitivity to sound (hyperacusis) on the affected side — due to involvement of the nerve to the stapedius muscle in the middle ear

• Pain behind the ear, often preceding the facial weakness by a day or two

• A sensation of numbness or heaviness in the face — though true sensory loss is not a feature of Bell's palsy

The onset is rapid — most patients notice full weakness within 24 to 48 hours. Weakness that develops more slowly over days to weeks suggests an alternative cause and warrants investigation.

Bell's Palsy Versus Stroke — How to Tell the Difference

This is the most important question when a patient presents with facial weakness, and it needs to be answered quickly.

The key distinguishing feature is forehead involvement:

• In Bell's palsy, the forehead muscles are affected — the patient cannot raise their eyebrow or wrinkle their forehead on the affected side.

• In a stroke or other central (brain) cause of facial weakness, the forehead is typically spared — the patient can raise their eyebrow normally, because the forehead receives motor input from both sides of the brain.

This distinction exists because the part of the brain controlling forehead movement receives signals from both cerebral hemispheres. A stroke affecting one hemisphere therefore does not fully paralyse forehead movement. The facial nucleus in the brainstem, and the facial nerve itself, do not have this bilateral input — so peripheral facial nerve damage (as in Bell's palsy) produces weakness of the entire face including the forehead.

Other features that suggest a central cause rather than Bell's palsy include:

• Limb weakness or sensory changes on the same side

• Difficulty speaking or understanding speech

• Visual disturbance

• Severe headache

• Gradual rather than sudden onset

Any patient with facial weakness and these associated features should be assessed as a potential stroke and managed accordingly — this is a medical emergency.

Ramsay Hunt Syndrome

Ramsay Hunt syndrome is an important variant that must be distinguished from Bell's palsy. It is caused by reactivation of the varicella-zoster virus (the chickenpox/shingles virus) in the geniculate ganglion of the facial nerve.

In addition to facial palsy, Ramsay Hunt syndrome is characterised by:

• A painful blistering rash in the ear canal, on the outer ear, or on the soft palate

• Severe ear pain

• Hearing loss and tinnitus

• Vertigo

Ramsay Hunt syndrome has a worse prognosis than Bell's palsy — a lower rate of complete recovery — and requires antiviral treatment with aciclovir or valaciclovir in addition to corticosteroids.

Assessment and Investigation

Most cases of Bell's palsy are diagnosed clinically on the basis of history and examination. Investigation is directed at excluding other causes.

Examination includes assessment of all branches of the facial nerve, documentation of the degree of weakness using a grading scale (most commonly the House-Brackmann scale), assessment of eye closure, and examination of the ear canal for herpetic vesicles.

Blood tests may include fasting glucose (to exclude undiagnosed diabetes) and, where Lyme disease is a consideration, serology.

Imaging — MRI of the brain and facial nerve — is not routinely required in straightforward Bell's palsy but is indicated when:

• The presentation is atypical

• There are features suggesting a central cause

• Recovery is not occurring as expected

• A structural cause such as a parotid tumour is suspected

Audiometry is arranged where hearing change accompanies the facial palsy, to assess for cochlear involvement.

Treatment of Bell's Palsy

Corticosteroids

Oral prednisolone is the most important treatment for Bell's palsy and should be started as soon as possible — ideally within 72 hours of symptom onset. Evidence from randomised controlled trials clearly shows that early steroid treatment significantly improves the rate and completeness of recovery. A typical course is prednisolone 50mg daily for ten days.

Antiviral Medication

The addition of antiviral medication (aciclovir or valaciclovir) to steroids is recommended by most guidelines, particularly in moderate to severe cases, though the evidence for antivirals alone is less strong than for steroids. For Ramsay Hunt syndrome, antivirals are essential and should be started promptly.

Eye Care — Critical

The inability to close the eye is the most urgent complication of Bell's palsy. The cornea is at risk of drying out, ulceration, and permanent damage if not protected. Eye care must begin immediately:

• Artificial tear drops — used frequently during the day (every one to two hours if needed)

• Lubricating eye ointment — applied at night before sleep

• Taping the eye closed at night — to ensure the cornea is protected during sleep

• Moisture chamber goggles — in severe cases during the day

Patients should be reviewed promptly if there is any eye discomfort, redness, or visual change. Ophthalmological assessment is arranged if there is any concern about corneal involvement.

Physiotherapy

Facial physiotherapy — specific exercises to maintain muscle tone, prevent abnormal patterns of recovery (synkinesis), and support nerve regeneration — is an important adjunct to medical treatment, particularly in patients with severe or complete palsy. It is usually started once some recovery of movement is beginning.

Prognosis and Recovery

The prognosis for Bell's palsy is generally good, particularly with prompt treatment:

• Around 70 to 80% of patients achieve complete or near-complete recovery

• Recovery typically begins within two to three weeks of onset

• Most recovery occurs within three to six months

• Patients with severe or complete initial paralysis have a longer and sometimes less complete recovery

Factors associated with a poorer prognosis include:

• Complete paralysis at onset (versus partial weakness)

• Older age

• Diabetes

• Hypertension

• Delayed treatment

Complications of Incomplete Recovery

In some patients — particularly those with severe initial paralysis — recovery is incomplete and complications may develop:

Synkinesis — abnormal co-contraction of facial muscles, such as the eye closing when the patient smiles, or the cheek moving when the eye blinks. This occurs when regenerating nerve fibres connect to incorrect muscle targets. It can be treated with targeted botulinum toxin injections and physiotherapy.

Crocodile tears — paradoxical lacrimation (tearing) when eating, caused by misdirected regeneration of autonomic fibres. Managed with botulinum toxin or lubricating drops.

Persistent weakness — in cases of incomplete recovery, surgical options including facial reanimation procedures may be considered in specialist centres.

Frequently Asked Questions

How quickly should I seek treatment for facial palsy?

Immediately. Early treatment with steroids — ideally within 72 hours of onset — significantly improves the likelihood of complete recovery. Do not wait to see if it improves on its own. Contact your GP or attend an emergency department the same day symptoms appear.

Will my face recover completely?

For most patients — particularly those treated promptly — yes. Around 70 to 80% of patients achieve complete or near-complete recovery. Patients with complete paralysis at onset have a somewhat lower rate of full recovery, but the majority still recover well.

Is Bell's palsy related to stress?

Stress and fatigue may lower immune function and increase the likelihood of viral reactivation, which is thought to trigger Bell's palsy. However, stress alone does not cause Bell's palsy, and many patients have no identifiable precipitant.

Can Bell's palsy recur?

Yes, though recurrence is uncommon — occurring in around 7 to 10% of patients. Recurrent palsy on the same side, or bilateral palsy, warrants more thorough investigation to exclude other causes.

Should I see an ENT or a neurologist for Bell's palsy?

Both are appropriate. ENT surgeons have particular expertise in the anatomy and pathology of the facial nerve, and manage the ear symptoms, eye care, and any surgical considerations. Neurologists assess for central causes and manage associated neurological conditions. In Singapore, ENT is often the first specialist point of contact for facial palsy.

Book an Assessment

If you or someone you know has developed sudden facial weakness, prompt assessment is essential. Dr Vyas Prasad assesses and manages facial palsy and Bell's palsy at Absolute ENT, Camden Medical Centre, 1 Orchard Boulevard, #09-08, Singapore.

Contact the clinic by WhatsApp on +65 8060 8079 or by email at camden.mmc@gmail.com.