Facial Nerve

Question 1

Where do the roots of the facial nerve leave the cranial area

Answer 1

via the internal acoustic meatus

Question 2

what do the roots of the facial nerve join to form

Answer 2

geniculate ganglion

Question 3

what does the greater petrosal nerve do

Answer 3

secretomotor function for lacrimal submandibular + sublingual glands

some palatine taste fibres

Question 4

what does the corda tympani innervate

Answer 4

medial portion of tympanic membrane and anterior 2/3 of tongue

Question 5

where does the facial nerve exit the skull

Answer 5

stylomastoid foramen

Question 6

what are all the branches of CN7

Answer 6

Main trunk with 5 muscular innervations - temporal, zygomatic, buccal, mandibular, cervical

Greater petrosal nerve 
Stapedius nn
Corda tympani 
Posterior auricular 
Ganglion auricular
Cutaneous branches (pinna, EAM, tympanic Membrane, sensory innervation)

Question 7

what does the stapedius muscle do

Answer 7

prevents excessive movement of stapes due to loud noise

Question 8

what does the posterior auricular nerve do

Answer 8

motor innervation to ear and occipital belly of occipito frontalis

Question 9

what does the ganglion branch of the facial nerve do

Answer 9

Joins lesser petrosal nerve and auriculotemporal nerve (branch of CNV3)

secretomotor innervation to parotid

Question 10

what is bells palsy

Answer 10

idiopathic CN7 LMN palsy

diagnosis of exclusion

Question 11

what causes the majority of bells palsy

Answer 11

80% of cases are a viral infection - swelling inside the bony canal thought to be responsible

Question 12

whats the presentation of bells palsy

Answer 12

sudden onset full one-sided (including eyebrow) facial palsy - often preceded by an URTI

Question 13

what is the diagnostic criteria for bells palsy

Answer 13

sudden onset
no CNS pathology
no ear pathology

Question 14

whats the treatment for bells palsy

Answer 14

<48 hours from onset = high dose oral steroids

otherwise supportive management

Question 15

what is the prognosis of facial palsy

Answer 15

most usually resolve completely but some patients have residual facial weakness

Question 16

what causes a poor prognosis for facial palsy

Answer 16

increased age
associated pain
complete palsy
increased latency of onset

Question 17

where does the facial nerve separate into upper and lower branches and then eventually into the 5 terminal branches

Answer 17

parotid gland

Question 18

what causes facial paralysis from parotid disease + what is a typical characteristic

Answer 18

pleomorphic adenoma in parotid, may cause total palsy but they’re usually small so there tends to be specific branch palsy

Question 19

what are signs and symptoms of a skull base pathology

Answer 19

Battles sign - bruising of mastoid process 
Raccoons eyes - bruising around eyes 
CSF rhinorrhoea 
cranial nerve palsy 
bleeding from nose/ear
haemotympanum  
sudden hearing loss
nyastagmus

Question 20

where would a skull base pathology affect the facial nerve, and what other nerves could potentially be affected

Answer 20

around the cerebellopontine angle, CN9/10/11/12

Question 21

where are skull base fractures most commonly

Answer 21

70% of all transverse skull base # are in the anterior fossa, 5% in the middle, 20 at middle central base, %% in posterior

Question 22

what kind of fractures are seen in skull base fractures most commonly

Answer 22

80% are longitudinal

10-20% are transverse

Question 23

what type of skull base fracture is more likely to give CN7 palsy

Answer 23

transverse

Question 24

whats the investigation for a suspected skull base fracture

Answer 24

full cranial nerve exam - nystagmus/webers test shows otological damage

urgent CT

Question 25

whats a labyrinthine concussion

Answer 25

less severe trauma causing tinnitus/vertigo/Hearing loss/BPPV

majority (75%) resolve in 2 years

Question 26

if someone presents with facial nerve paralysis what is important to differentiate

Answer 26

if it is UMN or LMN (UMN = forehead sparing)

Question 27

why are upper motor neurone facial palsys forehead sparing

Answer 27

forehead muscles receive contralateral motor innervation

Question 28

what are the causes of UMN facial nerve palsy

Answer 28

motor cortex/pons lesion
TIA
Stroke

Question 29

what are the causes of LMN facial nerve palsy

Answer 29

Ramsay-hunt syndrome
Middle ear damage
Bells palsy

Question 30

what is ramsay hunt syndrome

Answer 30

Herpes Zosters virus infection causing vesicular rash on ear drum/pinna/canal causing facial pain and weakness with vertigo and deafness

Question 31

how do you treat ramsay-hunt syndrome

Answer 31

eye care - drops, eye patch at night, ointment
oral steroids (80mg OD 2 weeks (taper down)
aciclovir
facial sling - physio for face muscles

Question 32

what is the supportive management for any facial nerve palsy

Answer 32

artificial tear drops + eye drops - CN7 closes eyelids to prevent ulceration

treat underlying cause

Question 33

what other symptoms point to a facial nerve palsy

Answer 33

drooling
hyperacusis (increased sensitivity to sound)
otological symptoms

Question 34

what is the house-brackman scale

Answer 34

scale for facial nerve palsy

1 normal
2 slight weakness on close inspection
3 obvious weakness not disfiguring
4 severe decrease in movement, incomplete eye closure
5 asymmetry @ rest motion barely perceptible
6 asymmetry @ rest no motion

Question 35

what do you need to exclude in a facial nerve palsy in children

Answer 35

Mobius syndrome
hemifacial microsomia 
forceps injury
chicken pox (HZV) 
acute otitis media

Question 36

what is mobius syndrome

Answer 36

bilateral CN6/7/8 with uni or bilat 12 palsy

due to congenital underdevelopment

Question 37

what is hemifacial microsomia

Answer 37

unilateral Cn7 palsy
microtia (small ear)
hemifacial hypoplasia

Question 38

what do you need to exclude in a facial nerve palsy in adults

Answer 38

trauma/iatrogenic causes
parotid tumour/lymphoma 
inflammation 
middle ear surgery/infection 
mastoiditis
Herpex zoster infection 
other rumours (bone tumour at skull bases -rare) 
petrosal bone tumours/trauma
intracranial tumours
strokes
MS

Question 39

whats the prognosis for Ramsey hunt syndrome

Answer 39

poorer than bells palsy