Cranial Nerve Tests Flashcards
what is the origin of CN I?
forebrain
where do CN I fibers synapse?
olfactory glomeruli in olfactory bub
where does CN I project?
olfactory cortex of the temporal lobe
what is the clinical relevance for CN I?
cribriform plate is weak spot of anterior cranial fossa trauma/fracture here can lead to ANOSMIA
what is the origin of CN II?
forebrain
what passes through the optic canal?
retinal ganglion cell axons
where does info from optic nerve go?
optic chiasm, optic tract, left geniculate nuc, optic radiations
where does the optic radiations project?
occipital lobe
how can issue with the optic nerve present?
transection or pathologic damage can lead to anopsia (unilateral blindness)
what is the function of CN III?
somatic innervation to several extraocular muscles, sup/med/inf rectus, inf oblique, levator palpabrae
what is the parasympathetic function of CN III?
intraocular muscles
pupillary constrictor, ciliary muscle
where does CN III originate?
midbrain
where does CN III exit the skull
SOF
where are CN III nuclei?
in midbrain (including Edinger Westphal which are parasympathetic nuc)
where does CN III project?
frontal eye field in frontal lobe
what clinical presentation occurs with CN III lesions?
CN III palsy
ptosis, mydriasis, globe position down and out
what are some possible causes of CN III lesion?
trauma, aneurism, herniation in brain
what does CN IV do?
somatic control of superior oblique
what is the action of superior oblique?
intorsion
depression
abduction
where does CN IV originate?
dorsal midbrain (only CN to emerge dorsal)
where does info from CN IV go?
trochlear nucleus in midbrain
where does CN IV project?
frontal lobe
how might a CN IV lesion present?
-left eye elevated and adducted due to unopposed superior and medial rectus
-right eve extorted due to unopposed action if inferior oblique, compensatory head tilt to better align eyes
where is ganglia of sensory parts of CN V?
trigeminal sensory ganglion
where is the ganglia for the motor aspect of CN V3?
motor nucleus in pons
what is the job of CN VI?
somatic efferent innervation to lateral rectus
what is the origin of CN VI?
pontomedullary junction
where does CN VI exit skull?
SoF
where is CN VI nucleus?
abducens nucleus in pons
where does CN VI project?
frontal lobe
how might a CN VI palsy present?
ask pt to look straight and eye moves toward midline
where does CN VII project?
frontal lobe precentral gyrus
how to treat bells palsy?
corticosteroids, usually self resolving, protect effected eye from drying out
what does CN VIII do?
auditory and vestibular
where does CN VIII originate?
pontomedullary junction
where does CN VII have its nucleus?
vestibular and cochlear in pons/medulla
where does CN VII project?
auditory: temporal
vestibular: parietal
what is the sensory function of glossopharyngeal nerve?
general: posterior tongue, oropharynx, middle ear, Eustachian tube
special: taste posterior 1/3 tongue
what is the motor innervation for CN IX?
autonomic: secretomotor to parotid gland
where does CN IX originate?
medulla
where does CN IX, X and XI exit skull?
internal jugular foramen
where is the nuclei for CN IX?
medulla
where does taste register for CN IX?
insular cortex
what detects trigger for gag reflex?
sensory receptors for CN IX
what is the sensory functions of CN X?
larynx and pharynx, visceral organs, special sense taste on eppigottis
what is the motor function of CN X?
larynx, pharynx, soft palate
where does CN X originate?
medulla (nuc here too)
where does CN X project?
motor: frontal lobe
sensory: insular cortex
what is special about the spinal part of spinal accessory nerve?
fibers ascend spinal cord and enter skull through foramen magnum
what does CN XII innervate?
genioglossus
hyoglossus
styloglossus
where does CN VII exit skull?
hypoglossal canal
lesions superior to the hypoglossal nucleus will cause:
contralateral tongue deviation
CBT to hypoglossal nucleus what happens?
decussates
CN XII to genioglossus is
ipsilateral
lesions inferior to the CN XII nucleus cause:
ipsilateral tongue deviation
what is hypoalgesia?
(low pain) should feel pain but do not
what is allodynia?
lowered pain threshold, feel pain where should not
what is consciousness dependent on?
interaction between intact cerebral hemispheres and the upper brain stem where activating mechanisms reside
how do you check CN I?
make sure nasal path is clear, check each side individually seeing if pt can smell different things
what is anosmia?
loss of smell
what can cause temporary loss of smell?
swelling or congestion
what can cause permanent loss of smell?
fractures to cribriform plate, olfactory groove or tumors
what four procedures is needed to examine the optic nerve?
-measurement of visual acuity
-test visual fields
-pupillary light reflex
-visualization of the fundus
what does the afferent and efferent for pupillary light reflex?
CN II (afferent)
CN III (motor)
what is pupillary light reflex?
light shone on one pupil, if both sensory and motor intact the other pupil will also constrict
what can be done to test CN III, IV and VI?
eyelid position, pupillary light reflex, accommodation, extraocular eye movement
what is accommodation?
allows eyes to focus on near objects, and then far by changing vergence, lens shape, and pupil size
what symptoms present with oculomotor nerve palsy?
ptosis- inactivation of lev palp
mydriasis- decreased tone to P constrictor
down and out gaze
what is anisocoria?
unequal size of the pupils
what does cocaine do to pupils?
dilates
what does opiates do to pupils?
makes smaller
what is the corneal reflex?
touch cornea and both eye should blink
what does an UMN lesion of CN VII cause?
contralateral lesion with forehead sparing
what does lMN lesion oc CN VII cause?
damage from the facial nuc or lower causes ipsilateral paralysis
how do you test for a CN X lesion?
listen for hoarseness in voice, look at back of throat if uvula is midline, gag reflex on both sides
how do you test hypoglossal nerve?
stick out tongue straight, left then right
DEVIATE TOWARDS PARAIZED OR WEAK SIDE
what is quantitative sensory testing?
offers incite on potential mechanisms contributing to individuals experience of pain
