Seventh (Facial) Nerve Palsy

Relevant physical signs

• Lower motor neurone or upper motor neurone
  • UMN injury causes contralateral facial weakness with sparing of the frontalis muscle
  • LMN injury causes ipsilateral facial weakness affecting all the muscles of facial expression
• Bilateral or unilateral
  • Most causes of facial palsy are unilateral
  • <5% are bilateral
• Hyperacusis: lesions proximal to the geniculate ganglion cause hyperacusis as stapedius is paralysed
• Muscles of facial expression
  • Frontalis: “raise your eyebrows”
    • Spared in UMN lesions
  • Orbicularis oculi: “close your eyes as tight as you can, don’t let me open them”
    • Bell’s phenomenon: ipsilateral upward gaze and inability to close the eye
  • Buccinator: “puff out your cheeks, don’t let me push the air out”
  • Orbicularis ori: “show me all your teeth”
    • General inspection: facial droop due to weakness of orbicularis ori
• Corneal reflex:
  • Touching cotton wool to affected side: contralateral blink (afferent V preserved)
  • Paralysis of blink reflex on the affected side only
• Localize the lesion
  • Parotid scars (previous surgery)
  • Hearing loss, ipsilateral loss of facial sensation (cerebellopontine angle)
  • Ipsilateral abducens palsy, contralateral hemiparesis, jaw jerk (medial pons)
  • Otoscopy (Ramsay-Hunt syndrome)
  • Mastoiditis (base of skull)
  • UMN weakness with weakness of the limbs (MCA stroke)
• Complete my examination by doing:
  • Otoscopy
  • Formal audiometry
  • Examining the upper and lower limbs

Differential diagnosis

• Unilateral facial nerve palsy
  • Upper motor neurone
    • Stroke
    • Space-occupying lesion
    • Demyelination
  • Lower motor neurone
    • Pontine stroke
    • Cerebellopontine angle tumour
      • Meningioma
      • Acoustic neuroma
    • Cholesteatoma
    • Parotid tumour
    • Mastoiditis
    • Osteomyelitis of the skull base
    • Infections
      • Ramsay Hunt syndrome (herpes simplex virus)
      • Lyme disease
      • Meningitis – bacterial, tuberculous
      • Syphilis
    • Inflammatory
      • Sarcoidosis
      • Wegner’s granulomatosis
      • Polyarteritis nodosa
      • Sjogren’s syndrome
    • Bell’s palsy
• Bilateral
  • Sarcoidosis
  • Lyme disease
  • Miller-Fisher syndrome
  • Poliomyelitis
  • HIV infection

Investigations

• Upper motor neurone
  • Computed tomography scan of the brain for stroke
  • Consider MRI/MRA if CT brain negative
  • Transcranial Doppler and ultrasound carotid Doppler to look for stenosis
  • Echocardiogram to look for intracardiac thrombus
  • ECG / Holter to look for paroxysmal atrial fibrillation
• Lower motor neurone
  • Magnetic resonance imaging to look for pontine pathology
  • MRI can also detect tumours at the CPA
  • Consider Lyme serology

Management

• Multidisciplinary
  • Patient education
  • ENT referral for formal audiometry
• Bell’s palsy
  • Moderate palsy, acute onset: trial of corticosteroids
  • Severe: consider antivirals
  • Based on evidence from two recent, prospective randomized controlled trials
• Ramsay-Hunt syndrome
  • Intravenous acyclovir
  • Oral prednisolone
• Lyme disease
  • Doxycycline
• Space-occupying lesion
  • Consider surgical removal

Summary

Sir, this patient has an isolated, lower motor neurone facial nerve palsy on the right side. There are no other cranial nerve abnormalities. Specifically, there is no impairment of abduction or clinical hearing loss to suggest a pontine lesion or a cerebellopontine angle lesion. There were no scars to suggest previous parotid or base of skull surgery, and general inspection of the external auditory meatus did not demonstrate any vesicles to suggest a Ramsay-Hunt syndrome. On screening the upper limbs, there were no obvious long tract signs.

In summary, this patient has an isolated right lower motor neurone facial nerve palsy. The most likely cause is Bell’s palsy.