Anatomy
- Facial nerve arises at junction of pons and medulla
- Traverses the following structures
- Posterior cranial fossa
- Internal auditory meatus
- Temporal bone in the facial canal
- Stylomastoid foramen
- Parotid gland
- The terminal motor branches are:
- Temporal
- Zygomatic
- Buccal
- Marginal mandibular
- Cervical
Function
- Motor to the muscles of facial expression
- Parasympathetic secretomotor to the lacrimal gland
- via the greater petrosal nerve
- Parasympathetic secretomotor to the submandibular and sublingual salivary glands
- Taste to the anterior two-thirds of the tongue
- via the Chorda tympani and lingual nerve
- Somatic sensory to an area of skin around the external auditory meatus
- via fibres from the geniculate ganglion
Facial nerve palsy
- Lower motor neurone affects whole of one side of face
- Upper motor neurone spares the forehead
- Bell's palsy accounts for 40% of facial nerve palsies
- Idiopathic and usually self-limiting
- May result from viral infection
Causes
- Intracranial
- Brainstem lesions
- Cerebrovascular accident
- Multiple sclerosis
- Acoustic neuroma
- Cholesteatoma
- Intratemporal
- Otitis media
- Ramsay Hunt syndrome - herpes zoster oticus
- Trauma - temporal bone fracture
- Iatrogenic
- Infratemporal
- Parotid tumours
- Trauma
- Surgery
Management
- Protection of eye
- Tarsorrhaphy may be required if palsy persists
- Surgery
- Bell's palsy - steroids may be beneficial
- Ramsey Hunt syndrome - acyclovir
Bibliography
Baver C A, Cocker N J. Update on facial nerve disorders. Otolarngol Clin North Am
1996; 29: 445-454.
Friedman R A. The surgical management of Bell's palsy: a review. Am J Otol 2000;
21: 139-144.
Jackson C G, van Deersten P G. The facial nerve. Current trends in diagnosis, treatment and
rehabilitation. Med Clin North Am 1999; 83: 179-195. |