Flashcards in Head and Neck Session 8 Deck (38):
Overview of fibres carried by CN III- oculomotor nerve>
somatic fibres to extrocular muscles- medial rectus, superior rectus, inferior rectus, inferior oblique, autonomic fibres to pupil of eye- sphincter pupillae and ciliary muscles- accomodation of lens, and autonomic fibres to eyelid- levator palpebrae superioris
how is trigeminal nerve assessed?
testing sensory division
testing motor division
which nerves must be funcitoning for corneal reflex?
trigmeinal- sensory limb, opthalmic division and facial- motor limb- orbicularis oculi
when testing motor component of trigeminal nerve- muscles of mastication, what will unilateral wkness causes when patient bites down or clenches their teeth?
jaw deviates towards side of lesion
3 fissures of cranial base that trigeminal nerve branches emerge through?
superior orbital fissure= opthalmic
foramen rotundum= maxillary
foramen ovale= mandibular
how is taste conveyed from anterior 2/3 of tongue?
via facial nerve fibres which joint with chorda tympani
how to distinguish between stroke and bell's palsy?
bell's= all muscles of facial expression impaired
stroke= forehead sparing= occipitofrontalis and orbicularis oculi, due to their bilateral innervation
what is the anatomical oculomotor nerve proper?
pure somatic efferent nerve to all extraocular muscles apart from sup oblique and lateral rectus, and to levator palpebrae superioris
what happens with a complete palsy of oculomotor nerve proper?
present with down and out position of eye due to paralysis of all extraocular muscles aside from sup oblique which moves eye down, and lateral rectus which moves eye out
drooping (ptosis) of upper eyelid due to LPS paralysis
why might patient with oculomotor nerve palsy present with a dilated pupil?
loss of PNS innervation to sphincter pupillae, and unopposed action of dilator pupillae innervated by intact sympathetic fibres.
PNS fibres actually hitch hike onto nerve, so likely to be damaged if nerve damaged, but actually originate from Edinger-Westphal nucleus whereas oculomotor nerve proper from oculomotor nucleus
origin of oculomotor nerve proper?
oculomotor nucleus in midbrain
oculomotor nerve site of exit from cranium?
superior orbital fissure
2 branches of extracranial portion of oculomotor nerve proper
dorsal and ventral
muscles supplied by dorsal branch of oculomotor nerve proper?
levator palpebrae superioris
muscles supplied by ventral branch of oculomotor nerve proper?
why is the presentation of a patient with a dilated pupil, in addition to a down and out eye and ptosis more worrying than if pupil wasn't dilated?
more likely that damage to oculomotor nerve is result of compression by an aneurysm of tumour
within which artery might an aneurysm occur to cause a complete palsy of the oculomotor nerve?
posterior communicating artery
what might be the cause of damage to the autonomic nerve fibres from the Edinger-Westphal nucleus, but sparing anatomical oculomotor nerve, causing a dilated pupil and loss of accomodation reflex?
bacterial or viral infection
presentation of a patient with damage only to PNS portion of oculomotor nerve?
dilated pupil- sphincter pupillae
loss of accomodation reflex- ciliary muscles
normal oculomotion- MR, SR, IR and IO intact
normal palpebral fissure- LPS intact
what is the usual cause of damage to only the somatic portion of the oculomotor nerve?
poor blood supply e.g. diabetes or increased BP
why are PNS fibres of oculomotor nerve susceptible to compression by an anuerysm of tumour?
fibres are relatively superficial
when does bilateral damage of facial nerve occur?
SE of certain medications e.g. anti-psychotics
when is the facial nerve at risk of damage?
nerve inflammation within facial canal
surgical procedures of infratemporal fossa
what nucleus do special sensory fibres for taste of facial nerve terminate in?
nucleus solitarius in medulla
what fibres does the chorda tympani, part of facial nerve, transmit?
special sensory to join lingual nerve to convey taste
pre-synaptic PNS fibres to submandibular ganaglion to supply SM and SL glands
how does the greater petrosal nerve, given off in the facial canal, contribute to PNS innervation?
carries pre-ganglionic fibres to pterygopalatine ganglion
where does facial nerve proper originate?
facial motor nucleus in pons
PNS fibres of facial nerve come from which nucleus?
general sensory fibres of facial nerve are from which ganglion?
what is innervation provided to by somatic sensory fibres of facial nerve?
small area of skin of concha of auricle
why would a parotid tumour cause a facial nerve motor palsy?
congestion would occur within tight parotid sheath which doesn't allow expansion if increased pressure and so the nerve would be compressed
3 PNS ganglia assoc with trigeminal nerve?
otic ganglion- glossopharyngeal, via auriculotemoral
submandibular ganglion- facial, via lingual
pterygopalatine ganglion- facial, via maxillary branch of trigeminal
the maxillary branch of the trigeminal is associated with which PNS ganglion?
pterygopalatine, to lacrimal, nasal and palate glands
occipitofrontalis and the superior part of orbicularis oculi are supplied by which branch of facial nerve?
which branch of facial nerve supplies inferior part of orbicularis oculi?
which branch of facial nerve supplies buccinator, orbicularis oris and zygomaticus?
which branch of facial nerve supplies mentalis?