Facial Nerve Palsy
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Introduction

Facial nerve (cranial nerve VII) palsy typically refers to Bell’s palsy. which is by far the most common cause of facial nerve palsy – accounting for about 80% of cases. About 12% of cases are caused by Ramsay-Hunt Syndrome – which is a facial nerve palsy caused by shingles of the facial nerve.

Unless otherwise stated, this article refer’s to Bell’s palsy. Bell’s Palsy is named after Charles Bell (19th Century Scottish Surgeon).

A useful distinguishing feature (and common exam question!) to differentiate facial nerve palsy from stroke is that in facial nerve palsy the forehead is also affected, but in stroke, the forehead is usually unaffected, even when the rest of that side of the face is affected.

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
Patient demonstrating right sided Bell's Palsy
Patient demonstrating right sided Bell’s Palsy. This file is taken from wikimedia commons and is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

Diagnosis

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

 

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.
  • Poor Prognostic Indicators:
  • Long term effects
    • Aberrant regeneration of the facial nerve can lead to some long-term consequences, such as excessive sweating on the affected side of the face and excessive tear production (“crocodile tears”). These symptoms are often induced by eating.

Treatment

  • 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
    • Give 1mg/Kg up to a maximum of 75mg a day, in the morning for 5 days
  • Anti-virals – Aciclovir often given as it is thought many cases of Bell’s Palsy are due to herpes simplex or zoster infection. A single kid quality study showed there was slight benefit when compared to steroids alone.
  • Eye care
    • Reduced eye closing can lead to dry eye and corneal damage
    • Ensure that if the eye cannot close properly precautions are taken – such as toping the eye closed or patching with eye closed, +/- the use of artificial tears
    • In severe cases, consider ophthalmology review

 

Differentials

  • Rule out stroke, particularly in older patients
  • Ramsay-Hunt Syndrome
    • Usually with vesicular shingles rash weather in the ear, on the affected side of the face, or in the affected side of the mouth
    • Sense of taste in the affected side of the mouth may also be reduced
    • May also have reduced hearing, tinnitus or dizziness if the vestibulocochlear nerve is also affected
    • History of previous chicken-pox / shingles
    • Flu-like prodromal symptoms for 3-7 days before the rash
    • Just like in Bell’s palsy, the forehead will also be affected
  • Guillain-Barre syndrome (usually bilateral)
  • Lyme disease

References

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Dr Tom Leach

Dr Tom Leach MBChB DCH EMCert(ACEM) FRACGP currently works as a GP and an Emergency Department CMO in Australia. He is also a Clinical Associate Lecturer at the Australian National University, and is studying for a Masters of Sports Medicine at the University of Queensland. After graduating from his medical degree at the University of Manchester in 2011, Tom completed his Foundation Training at Bolton Royal Hospital, before moving to Australia in 2013. He started almostadoctor whilst a third year medical student in 2009. Read full bio

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