Facial Nerve Flashcards
Where do the roots of the facial nerve leave the cranial area
via the internal acoustic meatus
what do the roots of the facial nerve join to form
geniculate ganglion
what does the greater petrosal nerve do
secretomotor function for lacrimal submandibular + sublingual glands
some palatine taste fibres
what does the corda tympani innervate
medial portion of tympanic membrane and anterior 2/3 of tongue
where does the facial nerve exit the skull
stylomastoid foramen
what are all the branches of CN7
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)
what does the stapedius muscle do
prevents excessive movement of stapes due to loud noise
what does the posterior auricular nerve do
motor innervation to ear and occipital belly of occipito frontalis
what does the ganglion branch of the facial nerve do
Joins lesser petrosal nerve and auriculotemporal nerve (branch of CNV3)
secretomotor innervation to parotid
what is bells palsy
idiopathic CN7 LMN palsy
diagnosis of exclusion
what causes the majority of bells palsy
80% of cases are a viral infection - swelling inside the bony canal thought to be responsible
whats the presentation of bells palsy
sudden onset full one-sided (including eyebrow) facial palsy - often preceded by an URTI
what is the diagnostic criteria for bells palsy
sudden onset
no CNS pathology
no ear pathology
whats the treatment for bells palsy
<48 hours from onset = high dose oral steroids
otherwise supportive management
what is the prognosis of facial palsy
most usually resolve completely but some patients have residual facial weakness
what causes a poor prognosis for facial palsy
increased age
associated pain
complete palsy
increased latency of onset
where does the facial nerve separate into upper and lower branches and then eventually into the 5 terminal branches
parotid gland
what causes facial paralysis from parotid disease + what is a typical characteristic
pleomorphic adenoma in parotid, may cause total palsy but they’re usually small so there tends to be specific branch palsy
what are signs and symptoms of a skull base pathology
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
where would a skull base pathology affect the facial nerve, and what other nerves could potentially be affected
around the cerebellopontine angle, CN9/10/11/12
where are skull base fractures most commonly
70% of all transverse skull base # are in the anterior fossa, 5% in the middle, 20 at middle central base, %% in posterior
what kind of fractures are seen in skull base fractures most commonly
80% are longitudinal
10-20% are transverse
what type of skull base fracture is more likely to give CN7 palsy
transverse
whats the investigation for a suspected skull base fracture
full cranial nerve exam - nystagmus/webers test shows otological damage
urgent CT
