Anatomy

1. Facial nucleus + superficial salivatory nucleus + nucleus solitarius [pontine]
2. Enter internal acoustic meatus [petrous bone]
3. Br greater superficial petrosal nerve > lacrimal glands and palatine glands
4. Br chorda tympani > taste to anterior 2/3 tongue
5. Exits through stylomastoid foramen
6. 5 terminal branches: temporal, zygomatic, buccal, mandibular, cervical

Branches:

1. Motor
   • N. stapedius
   • posterior digastricus
   • 5 divisions - to muscles of facial expression
2. Secretomotor
   • via greater petrosal nerve to lacrimal, nasal and palatine glands
3. Taste
   • via chorda tympani to anterior 2/3 or tongue
4. Sensory
   • uncommon sensory component of facial nerve carrying cutaneous impulses from the anterior wall of the external auditory meatus (nervus intermedius or pars intermedia of Wrisberg)

Causes of facial nerve palsy

1. Intracranial
   • Vascular: CVA
   • Tumour: acoustic neuroma
   • Infection - meningitis
2. Intratemporal
   • Infection - otitis, herpes zoster
   • Idiopathic - bell's palsy
   • Trauma - surgical, accidental (basal skull fracture)
   • Tumour - paragalnglioma, SCC
3. Extratemporal
   • Parotid gland malignancy
   • Surgical
   • Accidental lacerations

Approach

• Think surgical causes

1. Inspect
   • General - loss of facial expression
   • Eyelids - on blinking, the affected side closes after the normal eyelid (Bell's sign)
   • Eyes - widened palpebral fissure
   • Nasolabial fold - flatter on affected side
   • Mouth - affected side droops and moves less when talking
2. Test muscles involved systematically
   • Occipitofrontalis - raise eyebrows
   • Orbicularis oculi: close eye as tightly as you can
   • Orbicularis oris: show me your teeth
   • Buccinator: puff out your cheeks
3. Look for obvious cause
   • Look for scar over parotid - iatrogenic facial nerve palsy
   • Look for parotid gland enlargement
   • Look in the external auditory meatus for HZV (Ramsay-Hunt syndrome)

Completion

1. Take history to determine duration and effects of condition on patient
2. Examine for taste with salt/sweet solutions (chorda tympani)
3. Test patient hearing (hyperacusis can result from involvement of the nerve to stapedius muscle, efferent branch of facial nerve)