Facial Nerve Palsy

Original article by Tom Leach | Last updated on 16/5/2014
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Palsy of the facial nerve (VII), aka Bell's Palsy, named after Charles Bell (19th Century Scottish Surgeon).
 

Epidemiology and Aetiology

  • Incidence: 30 per 100 000 per year
  • Accounts for 80% of cases facial nerve paralysis.
  • Thought to be viral induced
  • The most common ‘mononeuropathy’
  • Can occur at any age, including children. Most common age group 20-50.
  • Equal incidence for both sexes
  • Slightly increased incidence during pregnancy (45 per 100 000), and in diabetes
  • Most cases resolve within 2-3 months
  • 1% of cases are bilateral resulting in total paralysis of the face

 

Signs and Symptoms

  • Rapid onset unilateral facial nerve weakness.
  • Generalised weakness of affected side. Patient unable to show teeth, crew up eye and raise eyebrows on affected side
  • In some cases may not be able to fully close eye-lid. In these cases, patients may require lubricatin eye drops and might tape close their eye overnight to stop the cornea drying out. Refer to ophthalmology for assessment if patient cannot fully close eye. If the palsy does not fully resolve after 6 months, patients should be referred to Plastics for consideration for reconstruction to allow full closing of eye.
  • Severe cases may also present with notable loss of taste sensation (classically anterior 2/3 of tongue), intolerance of high-pitched noises, mild dysarthria.
  • Lower Motor Neuron Signs (LMN)
  • Can be distinguished from an UMN lesion (e.g. a stroke) by testing if the forehead is affected
    • Forehead normal – UMN lesion – due to bilateral innervation of the forehead
    • Forehead affected – LMN lesion

 

Diagnosis

  • Usually clinical, based on the signs above
  • House-Brackman scale is occasionally used to describe the degree of paralysis. (Scale 1-6. ! is normal, 6 is total paralysis).

 

Treatment and Prognosis

  • About 75% of cases will totally resolve
  • Most cases start to resolve within a three weeks (85% of those who will recover), and complete recovery is seen in the remainder in 3-6 months.
  • Steroids – Prednisolone is the mainstay of treatment. Most effect if given within 72 hours of onset. 14% greater probability of recovery over no steroids if given within this time frame.
    • No evidence effective after 72 hours
    • No evidence effective in children under 16
  • Anti-virals – Aciclovir often given as it is thought many cases of Bell’s Palsy are due to herpes simplex or zoster infection. No evidence as to whether they are any more useful than steroids alone.  
  • Poor Prognostic Indicators:

 

Differentials

  • Rule out stroke, particularly in older patients
  • Guillain-Barre syndrome (usually bilateral)
  • Lyme disease