Overview

Bell’s palsy is the most common cause of acute lower motor neurone (LMN) facial nerve palsy. It is idiopathic and presents unilaterally. It is a diagnosis of exclusion i.e. other causes must be ruled out first.

It is essential to differentiate between an upper motor neurone (UMN) and LMN lesions, as a UMN can be the presenting feature of a stroke.

Epidemiology

  • More common in pregnancy
  • More common in people with diabetes
  • There may be a familial component

Risk Factors

  • Pregnancy
  • Diabetes
  • Obesity
  • Hypertension
  • Immunodeficiency

Presentation

Patients have a rapid onset of symptoms (usually within <72 hours:

  • Unilateral lower motor neurone facial nerve palsy – the forehead is also affected
    • Upper motor neurone lesions spare the forehead and upper face and suggest a stroke
  • Ear and postauricular pain may precede the palsy
  • Dry eyes or excessive tearing
  • Altered taste
  • Hyperacusis

Differential Diagnoses

Ramsay Hunt syndrome (Herpes zoster oticus)

  • There is usually a vesicular rash around the ear
  • Auricular pain is usually the first feature
  • There may be vertigo/tinnitus

Stroke

  • There are signs of a UMN lesion – the upper face and forehead are spared 

Diagnosis

Diagnosis

  • Clinical diagnosis – none needed
  • As long as patients have an acute unilateral LMN facial nerve palsy with an otherwise normal physical examination

Referral

  • Urgent referral to relevant specialist if the patient has facial nerve palsy and any of:
    • Worsening/new neurological findings
    • Features suggesting a UMN lesion
    • Features suggesting cancer
    • Severe local/systemic infection
    • Trauma
  • Urgent referral to ENT if there is diagnostic doubt or:
    • There is no improvement after 3 weeks of treatment
    • Has atypical features
  • Urgent referral to ophthalmology if the patient has any eye symptoms

Management

All patients

  • 1st-line: oral prednisolone within 72 hours of onset + artificial tears/lubricants
  • Antiviral treatments are not recommended
  • Urgent referral to ENT if there is no improvement after 3 weeks

Monitoring and Patient Advice

Monitoring

  • Patients are usually followed up within 1-2 weeks to assess their response to treatment. If there is no improvement after 3 weeks, urgently refer to neurology.

Patient Advice

  • Patients should be reassured that the prognosis is good, and most patients fully recover within 3-4 months
  • Patients should keep the affected eye lubricated and keep their eyes closed using microporous tape at night if needed
  • If patients develop eye e.g. irritation/pain/vision changes, they should seek immediate medical advice

Complications and Prognosis

Complications

  • Ectropion
  • Facial pain and paraesthesia
  • Dry mouth
  • Hyperacusis
  • Synkinesis – abnormal facial muscle contraction during voluntary movement
  • Psychosocial complications e.g. depression

Prognosis

  • Most patients fully recover within 2-3 weeks
  • Patients improving within 2 weeks indicates a better prognosis
  • Younger patients are more likely to have better outcomes
  • Initiating corticosteroids within 72 hours improves prognosis

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