CN VIII Flashcards
What is the name given to CN VIII?
Vestibulocochlear nerve
What kind of information is carried by CN VII?
special sensory only
How many nerves make up CN VIII and what are they?
2; vestibular and cochlear
Where does the vestibular nerve terminate?
vestibular nuclear complex
What are the 4 parts of the vestibular nuclear complex?
superior (bechterew), medial (schwalbe), lateral (deiter), and inferior
Which part of the vestibular nuclear complex gives rise to most of the fibers of the vestibulospinal tract?
lateral (deiter)
Where do fibers in the vestibular nerve originate?
cell bodies in the vestibular ganglion
Where is the vestibular ganglion?
internal acoustic meatus
T/F: the vestibular ganglion has 2 parts, inferior and superior.
true
Where does the cochlear nerve terminate?
in the two cochlear nuclei (anterior and posterior)
Where do the axons composing the cochlear nerve originate?
spinal ganglion
What kind of neurons make up the cochlear nerve?
bipolar neurons
Where are the cell bodies of the neurons that make up the cochlear nerve?
in the spiral ganglion of the cochlea
What is the route of peripheral processes of the cochlear nerve?
from spiral ganglion to spiral organ
What is the other name for the spiral organ?
organ of Corti
Where are the nuclei of termination for the cochlear nerve (cochlear nuclei) located?
in the posterior, superior MO, lateral to the vestibular nuclei
From the cochlear nuclei, axons cross to the other side of the brainstem and synapse in what nuclei?
trapezoid nuclei
What do axons from the trapezoid nucleus form?
lateral lemniscus
Where do fibers from the lateral lemniscus travel?
to medial geniculate body of thalamus (with a few fibers dropping off in the inferior colliculus)
What 3 inner ear structures are innervated by peripheral processes from the vestibular ganglion?
saccule, utricle, and semicircular canals
Where are the vestibular nuclei?
in the MO on the floor of the rhomboid fossa
Where do central processes from the vestibular ganglion convey info to?
vestibular nuclei
Where do most vestibular nerve fibers terminate?
in the medial vestibular nucleus (Schwalbe)
How do some fibers of the vestibular nerve travel directly to the cerebellum?
by way of the inferior cerebellar peduncle
Which direction does info in CN VIII travel?
from distal to proximal
Where is the apparent origin of CN VIII?
cerebellopontine angle
T/F: CN VIII has no branches to structures outside of the ear.
True
From its apparent origin, what fossa does CN VIII travel in to get to the internal acoustic meatus?
posterior cranial fossa
What other cranial nerve enters the internal acoustic meatus along with CN VIII
Facial (VII)
T/F: The cochlear nerve carries about 60,000 fibers.
False; 30-40k
After traversing the internal acoustic meatus inferior to the facial nerve, the cochlear nerve leaves the temporal bone to reach what structure?
spiral ganglion of the cochlea
How many fibers are carried by the vestibular nerve?
about 20k
Which branch of the vestibular nerve is bigger, the superior or the inferior branch?
superior branch is bigger
What does the inferior branch of the vestibular nerve supply?
saccule and posterior ampullary crest
what two nerves compose the inferior branch of the vestibular nerve?
saccular nerve and the posterior ampullary nerve
What is supplied by the superior branch of the vestibular nerve?
lateral and anterior semicircular canals
What two nerves form the superior branch of the vestibular nerve?
lateral and anterior ampullary nerves
What branch(es) supply the utricle?
a branch from the lateral ampullary nerve and a branch directly off the superior branch of the vestibular nerve
In addition to the semicircular canals and the utricle, what else is supplied by the superior branch of the vestibular nerve?
saccule
What is the name of the branch from the superior branch of the vestibular nerve which innervates the saccule?
Voit’s nerve
T/F: all of the nerve fibers that innervate the utricle ultimately come from the superior branch of the vestibular nerve.
True
What ganglion does the cochlear nerve travel to?
spiral ganglion
What ganglion does the vestibular nerve travel to?
vestibular ganglion
What clinical consideration of CN VIII can cause hearing problems and perhaps get large enough to increase pressure on the brain stem/cranium?
Acoustic neuroma
What is the other name for an acoustic neuroma?
vestibular schwanoma
What is tinnitus?
ringing in the ears
What disease mentioned in class can tinnitus be the 1st sign of?
Manier’s Disease
Other than ringing in the ears, what other symptoms are associated with tinnitis?
hearing deficits and vertigo
Are cochlear implants more or less common modernly?
more common
Patients with severe hearing loss, specifically sensorineural hearing loss with a functioning cochlear nerve, are candidates for what?
cochlear implants
Sit a patient in a swivel chair, hold the head stationary, and swivel the chair to identify a cervical spine issue (if this causes vertigo). What is this a test for?
vestibular disease
T/F: vestibular disease has a differential diagnosis from cervicogenic vertigo.
true
