Seventh Nerve Palsies

Loss of innervation to the orbicularis oculi can lead to blinding exposure keratopathy

Anatomy nuggets

• Nuclei in the lower pons below the level of the fourth ventricle

  • Motor nucleus
  • Parasympathetic superior salivatory and lacrimal nucleus
  • Sensory nucleus (tractus solitarius)

• Motor neurones pass over the cerebellopontine angle into the internal auditory canal

  • Traverse the petrous temporal bone
  • Exit behind the stylomastoid process through the stylomastoid foreman
  • Terminate in temporal (supplying frontalis and orbital orbicularis oculi), zygomatic (supplying pretarsal orbicularis), buccal, mandibular and cervical branches

• Chorda tympani: salivary glands and anterior two-thirds of tongue

• Greater superficial petrosal nerve: lacrimal gland

Aetiology

• Bell’s palsy (idiopathic): diagnosis of exclusion

  • M=F, average age of 40
  • Associated with diabetes and pregnancy
  • Typically starts to recover spontaneously by 3 weeks
  • Oral prednisolone within 72 hours of onset increased recovery rate
  • Antivirals made no difference to recovery
  • Long-term surgical options: nerve repair/substitution, muscle transposition

• Ramsay-Hunt syndrome (VZV)

• Cerebellopontine angle lesions

• Trauma

• Otitis

• Neurofibroma (NF-2)

• Parotid gland pathology

• Congenital eg. Moebius’ syndrome

• Guillain-Barre syndrome

• Lyme disease

• Sarcoidosis

• Meningitis

Clinical features

• Facial weakness/asymmetry

• Lagophthalmos

• Lower lid ectropion

• Corneal exposure

• Isolated vs complex:

  • Check corneal sensation, tear film (lacrimal), lid closure
  • Associated CN palsy: Vn cerebellopontine angle; VIn pons; VIIIn cerebellopontine angle

• Upper vs lower motor neurone

Aberrant regeneration

• Synkinesis develops between salivation and lacrimation fibres

  • Tearing when eating (Crocodile tears)

• Synkinesis between orbicularis oculi and oris fibres

  • Eyelid closure on eating (reverse Marcus Gunn jaw winking)

Tests

• ENT or neurological referral for all new-onset facial nerve palsies
• Neuroimaging if recurrent

Ocular management

• Regular lubricants
• Lid taping
• Tarsorrhaphy
• Gold weight insertion