Facial nerve

Question 1

function of facial nn

• sensory or motor or both(1)
• functions(4)

Answer 1

• both - mainly motor. receives some sensory information also
• main function is motor to mm of face
• some fibres secretory motor to sunmandibular gland
• some fibres sensory from anterior part of tongue
• -*some fibres motor to stapedius mm

Question 2

facial nn course

1) nucleus situated where(1)
2) emerges from brainstem where(1)
3) enters what meatus with what other nn(1)
4) travels through what bone(1)
5) emerges where (1)
6) first genu(1)
7) second genu(1)
8) exits skull to facial mms through what foramen(1)

Answer 2

• nucleus in pons
• emerges from brainstem at cerebellar pontine angle
• enters internal auditory meatus with cn 8
• travels through petrous part of temporal bone
• emerges on medial side of middle ear
• here turns posteriorly (making its first genu)
• then turns inferiorly (making its second genu) through mastoid bone
• exits the skull at stylomastoid foramen to supply facial mms

Question 3

facial nn palsy

-examination

>inspection(1)

>tests mms of face(5)

>how to differentiat between umn and lmn facial weakness (1)

• nb umn is not facial nn palsy as facial nn is a lmn*
• ask in hx (2)

-alongside facial nn examination what examination should you do in facial weakness(1)

>important to examine what what could indicate bell’s palsy(1)

Answer 3

• assymetry - no forehead wrinkles , drooped nasolabial folds , drooped angles of the mouth
• “raise your eye brows” note asymmetry
• “scrunch up your eyes & don’t let me open them” – assess power
• “blow out your cheeks & don’t let me deflate them” – assess power
• “can you do a big smile for me?” – note asymmetry
• “can you attempt to whistle for me?” – note asymmetry
• umn palsy caused by damage to nn fibres above level of facial nn nucleus (ie motor cortex or pons). umn spares forehead (received innervation from contralateral motor cortex as well) whereas lmn does not
• history
• Any hearing changes. supplies stapedius. paralysis results in hyperacusis
• Any taste changes anterior 2/3 of the tongue

-should do full ENT examination as tumour of structure associated with course of facial nn can cause it to dysfunction

>important to check external auditory meatus for zoster lesions possibly indicating bell’s palsy

Question 4

bell’s palsy

• -most common cause of facial nn palsy*
• pathophysiology of bell’s palsy (2)
• pc(1) hpc - micro timing(1) usual pmh(1)
• mx if pt presents in first 48 hours(1)
• course(1)

Answer 4

• probably virla infection of facian nn. dysfunction is cause by swelling of nn within its small bony canal
• pc - facial mm weakness. sudden onset. usually hx of urti
• high dose oral steroids
• usually resolves completely. may be residual facial weakness

Question 5

tumours affecting facial nn

• -should do full ENT examination as tumour of structure associated with course of facial nn can cause it to dysfunction*
• what tumours can involve facial nn(7)

Answer 5

• parotid gland tumours - involvement of facial nn usually suggests malignancy
• -*external and middle ear - malignancy lesions - scc, bcc
• cerebellar pontine angle - acoustic neuroma, glumous tumours
• petrous bone - cysts, secondary carcinomas