🎯 Pathology

• acute, unilateral paralysis of the lower motor neurons of the facial nerve (CN VII)

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💡 Causes

• idiopathic

• risk factors

  • viral illnesses such as herpes simplex virus, varicella-zoster virus and Epstein-Barr virus

  • pregnancy

  • median age of onset is 40 years

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🩺 Clinical features

• signs and symptoms are rapid and progressive, reaching a peak in severity after 72 hours

• motor symptoms

  • ipsilateral paralysis of facial muscles including the forehead

• sensory symptoms

  • hyperacusis (innervation to the stapedius muscle is impaired)

  • loss of taste from the anterior 2/3rds of the tongue

• autonomic symptoms

  • reduced lacrimation leading to dry eyes, increasing the risk of exposure keratopathy

  • reduced salivation (loss of parasympathetic supply to the sublingual and submandibular salivary glands)

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🕵️‍♂️ Investigations

• clinical diagnosis

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💆‍♂️ Management

• oral prednisolone within 72 hours of the onset of symptoms

  • consider the addition of antivirals if severe facial nerve palsy

• eye protection

  • lubricating eye drops such as artificial tears

  • wearing an eye patch while sleeping

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🧲 High-yield tips

• dry eyes can lead to exposure keratopathy which can lead to permanent vision loss

• most patients make a full recovery within 3-4 months

• if there is no sign of recovery within 3-4 months, imaging studies must be performed to exclude neoplastic disease