Head and Neck Session 8 Flashcards
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?
corneal reflex
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?
superior rectus
levator palpebrae superioris
muscles supplied by ventral branch of oculomotor nerve proper?
medial rectus
inferior rectus
inferior oblique