Definition

Bell's palsy is an acute, unilateral facial nerve weakness or paralysis of rapid onset (less than 72 hours) and unknown cause.

Aetiology

Herpes simplex virus, varicella zoster virus, and autoimmunity may contribute to the development of Bell's palsy, but the significance of these factors remains unclear.

Prevalence

Bell's palsy affects 20–30 people per 100,000 each year.
It most common between 15 and 45 years of age.

Complications

Eye injury
Facial pain
Facial weakness
Dry mouth
Intolerance to loud noises
Abnormal facial muscle contraction during voluntary movements|
Psychological sequelae

Diagnosis

1. Exclude other causes of facial weakness or paralysis.

2. Rapid onset (less than 72 hours).

3. Facial muscle weakness (almost always unilateral) involving the upper and lower parts of the face.
   reduction in movement on the affected side
   drooping of the eyebrow and corner of the mouth
   loss of the nasolabial fold.

4. Ear and postauricular region pain on the affected side.

5. Difficulty chewing, dry mouth, and changes in taste.

6. Incomplete eye closure, dry eye, eye pain, or excessive tearing.

7. Numbness or tingling of the cheek and/or mouth.

8. Speech articulation problems, drooling.

9. Hyperacusis.

Differential diagnosis

• Stroke — forehead spared

• Brain tumour — possible history of cancer, mental state changes, gradual onset.

• Traumatic injury to the facial nerve (for example, basal skull fracture, or as a consequence of surgery)

• Facial nerve tumour, skin cancer, parotid tumours. Onset of symptoms is gradual. May be painful.

• Infectious causes:

  Herpes simplex — history of fever and malaise.
  Lyme disease — may cause bilateral symptoms. Associated with a history of tick exposure, rash (bullseye lesion in 70%), and arthralgia.
  Otitis media — otalgia, conductive hearing loss, gradual onset.
  Mastoiditis —mastoid region tender or swollen.
  Cholesteatoma — foul smelling otorrhoea and hearing loss
  Ramsay Hunt syndrome — pain followed by vesicular rash of VZV on the pinna, or in the ear canal or pharynx. Associated with sensorineural hearing loss.
  Encephalitis/meningitis — headache, neck stiffness.
  HIV — fever, malaise, CD4 count.
  Syphilis — other neurological and skin symptoms and signs.
  Glandular fever — malaise, few distinguishing characteristics.

• Diabetes — history of, or other symptoms and signs of diabetes.

• Multiple sclerosis — intermittent symptoms and additional neurological symptoms.

• Guillain-Barré — ascending paralysis, weakness of hands and feet, then trunk.

• Sarcoidosis — symptoms may be bilateral, elevated angiotensin-converting enzyme level

• Arteriovenous malformation.

Management

1. The person should be advised to keep the affected eye lubricated by using lubricating eye drops during the day and ointment at night. The eye should be taped closed at bedtime using microporous tape, if the ability to close the eye at night is impaired.

2. For people presenting within 72 hours of the onset of symptoms, prescription of prednisolone should be considered. Prednisolone 50 mg daily for 10 days.

3. Antiviral treatment alone is not recommended, but it may have a small benefit in combination with a corticosteroid; specialist advice is recommended if this is being considered.

Specialist referral

1. Features atypical of Bell's palsy require referral for exclusion of an alternative diagnosis.

2. Worsening of existing neurologic findings, or new neurologic findings.

3. Features suggestive of an upper motor neurone cause.

4. Features suggestive of cancer.

5. Systemic or severe local infection.

6. Trauma.

Referral to a facial nerve specialist should be arranged if there is doubt about the diagnosis or there is:

1. No improvement after 3 weeks of treatment.

2. Incomplete recovery 5 months after the onset of initial symptoms.

3. Any atypical features.

Referral to an ophthalmologist is needed if the person has eye symptoms (for example pain, irritation, or itch).

Referral for further support or counselling should be considered if there are emotional consequences of persistent facial paralysis or paresis.

Prognosis

Most people with Bell's palsy begin to recover, even without treatment, within 2–3 weeks.

Complete recovery usually occurs within 3–4 months

Over 90% with incomplete paralysis, and about 70% of people with complete paralysis, recover completely within 6 months, even without intervention

Moderate to severe long-term sequelae are experienced by 16%

Favourable prognostic factors:

• Signs of recovery within 2w.

• Younger age

• Initiate steroids within 72hr of onset of symptoms