Bell's Palsy

Bell's palsy is a type of facial paralysis resulting from dysfunction in the cranial nerve VII (facial nerve), leading to an inability to control facial muscles on the affected side. It is named after Scottish surgeon Charles Bell, who first described the condition.

An individual with Bell's palsy on the right side, showing inability to raise the eyebrow and fully show teeth on the affected side.

Signs and Symptoms

Bell's palsy is characterised by a sudden onset of facial weakness or paralysis, usually affecting one side. Key symptoms include:

• Inability to move facial muscles on one side
• Drooping of the mouth and eyelid
• Loss of taste on the front two-thirds of the tongue
• Pain around the ear
• Hyperacusis (increased sensitivity to sound)

The condition typically develops rapidly, over 48 hours, and can cause significant facial asymmetry.

Causes and Risk Factors

The exact cause of Bell's palsy is unknown. However, it is believed to result from viral infections that cause inflammation and swelling of the facial nerve.

Potential triggers include:

• Diabetes
• Recent upper respiratory tract infection
• Pregnancy

Diagram showing the facial nerve (cranial nerve VII) pathways and connections.

Diagnosis

Diagnosis is primarily clinical, based on the patient's history and presentation. Bell's palsy is a diagnosis of exclusion, requiring the elimination of other causes of facial paralysis, such as:

• Brain tumour
• Stroke
• Ramsay Hunt syndrome type 2
• Lyme disease

No specific laboratory tests are required, but imaging studies may be performed to rule out other conditions.

Treatment

Corticosteroids

Corticosteroids, such as prednisone, are the mainstay of treatment and are most effective when started within 72 hours of symptom onset. They help reduce inflammation and improve recovery outcomes.

Antivirals

The use of antiviral medications in conjunction with corticosteroids is controversial. Some studies suggest a small additional benefit, while others do not support their routine use.

Eye Protection

Patients who cannot fully close their eyelids are at risk for corneal damage. Protective measures include:

• Lubricating eye drops
• Eye ointments
• Eyepatches or taping the eye shut during sleep

Physiotherapy

Physical therapy can help maintain muscle tone and stimulate the facial nerve, potentially aiding in recovery. Techniques include facial exercises and massage.

Surgery

Surgical intervention is rarely recommended and generally reserved for severe cases that do not improve with other treatments. Procedures such as facial nerve decompression are controversial and carry risks, including hearing loss.

Prognosis

Most individuals with Bell's palsy begin to recover within three weeks, and complete recovery occurs in about 70-85% of cases within six months. Factors associated with a poorer prognosis include older age, complete paralysis, and severe initial symptoms.

Complications can include:

• Persistent facial weakness
• Synkinesis (involuntary facial movements)
• Gustatolacrimal reflex (crocodile tears)

Epidemiology

Bell's palsy affects 1-4 per 10,000 people annually, with equal incidence in males and females. It is most common between the ages of 15 and 60.

Sir Charles Bell, the Scottish neurophysiologist after whom Bell's palsy is named.

Understanding Bell's palsy is very important for healthcare professionals, including dentists, as prompt recognition and appropriate management can significantly impact patient outcomes.

Self-assessment MCQs (single best answer)

Which cranial nerve is affected in Bell's palsy?

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What is the typical duration for symptoms of Bell's palsy to start improving?

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Which of the following is a common symptom of Bell's palsy?

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What is the most effective initial treatment for Bell's palsy within 72 hours of onset?

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Which of the following is NOT a differential diagnosis for Bell's palsy?

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Bell's palsy is often associated with which of the following viruses?

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What percentage of Bell's palsy patients typically achieve complete recovery?

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Which of the following is a common complication of Bell's palsy?

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What is the recommended eye protection method for Bell's palsy patients who cannot close their eyes completely?

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Which historical figure is Bell's palsy named after?

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