Session 4- Cranial nerves I-VI Flashcards
role of cranial nerves
supply tissues and structures of head and neck region including special sense organs
what is CN 1
olfactory special sense smell
absence or reduced sense of smell
anosmia
hyposmia
commonest cause of anosmia and other causes
upper resp tract infection
head/facial injury- impact
anterior cranial fossa tumours
what is cranial nerve 2
optic special sense vision
function of CN2
pupillary size and response to light
visual acuity - snellen chart and visual fields
opthalmoscopy
describe the visual pathway
retinal ganglion cells
axons from optic nerve
exits back of orbit via optic canal
fibrres cross and merge at optic chiasm
what communication is present to aid the visual reflexes
visual infor coming in from the optic nerve will have a communication into the brainstem from the optic tract and will help form part of the light reflex
function of optic nerve
carries sensory fibres from the one eye
optic chiasm
mixing of sensory fibres from right and left optic nerves
optic tract
carries sensory information from part of the right eye and part of the left eye
what is bilateral heminopia
pituitary tumours that compress teh optic chiasm cause bilateral visual symptoms
cranial nerve topography
2 2 4 4 2- brain-forebrain 2-midbrain 4-pons 4-medulla
cranial nerve 3
oculomotor- motor and parasympathetic
how do we determine if there any issues with cranial nerve 2
inspect the pupillary size and response to light
what are the target tissues of the cranial nerve
3 from the midbrain
extra occular muscles (4 out of 6)
levator palpebrae superiosis
sphincter pupillae- in iris surrounds pupil
how do we determine if there is something wrong with the third nerve
inspect the resting gaze could find -ptosis -abnormal positioning of eyes -pupil may or may not be dilated
what is teh main blood supply to the occulomotor nerve
vaso nervosum
what are the secondary back up blood supply to the oculomotor nerve
pial blood vessels
cranial nerve 4
trochlear - motor
where does CN 1 orginate
forebrain
CN 2 origination
extension of forebrain
where does cranial nerve 3 come from
midbrain
where does cranial nerve 4 orginate
midbrain
target muscle of CN4
superior oblique muscle
how do we determine if there is anything wrong with the 4th cranial nerve
inspect resting gaze and eye movements
how would pathology of CN4 present
abnormal eye position
head tilt
route of trochlear nerve
orginates from midbrain then travels through cavernous sinus then through superior orbital fissure into back of eye
CN VI
ABDUCENS
where does CN VI originate
pons
target of CN VI
lateral rectus - moves eye laterally
how do we determine if the abducens nerve is working
inspect resting gaze and eye movements
route of abducens nerve
travel from pons and has a steep upwards route to the cavernous sinus and travels through the superior orbital fissure
what is the consequence of the steep upwards route of the abducens nerve
makes it vulnerable when there is an increase in intracranial pressure it gets stretched
route of the first cranial nerve
travels from nasal cavity through holes in ethmoid bone to the temporal lobe
route of occulomotor nerve
travels from the midbrain in a spiral corkscrew way very closely to the tentorum cerebelli then through the cavernous sinus then enters the superior orbital fissure
what is the common route of the cranial nerves supplying the eye muscles
exit brainstem- at slightly different levels
pass through cavernous sinus
enter into the orbit via the superior orbital fissure
what are the cranial nerves that supply the eye muscles
occulomotor- 3rd
abducens- 6th
trochlear- 4th
cranial nerve 5
trigeminal - motor and general sensory
what does the 5th cranial nerve supply
branches have extensive distribution supplying skin of the face and scalp and deep structures of the face
how do you determine if there is damage to the trigeminal nerve
light touch to the Va Vb and Vc dermatomes
muscles of mastication
corneal reflex- SENSORY (motor is by facial nerve through orbicularis oculi)
route of the trigeminal nerve
the opthalmic and maxillary travel through the cavernous sinus however mandibular doesnt
opthalmic-> cavernous sinus -> superior orbital fissure
maxillary -> cavernous sinus -> foramen rotundum
Mandibular -> foramen ovale
what kind of nerve is CN I
special sense smell
sensory
what kind of nerve is cranial nerve 2
special sense vision
optic
what kind of nerve is the 3rd nerve
motor and parasympathetic
occulomotor
what kind of nerve of CN 4
motor
trochlear
what kind of nerve is the 6th nerve
motor abducens
what kind of nerve is CNV
motor and general sensory
trigeminal
