vestibulocochlear nerve, sensory nerve, its origin and the course. its termination and the function it caries

1. VESTIBULOCOCHLEAR
NERVE
DR SANAYASEEN
ANATOMY DEPARTMENT
KIMS

2. INTRODUCTION
Components:
VESTIBULAR:concern
with position and
movement of head
balance
COCHLEAR: concern
with sound

3. COCHLEAR NERVE

4. INTRODUCTION
The cochlear nerve (also auditory or acoustic nerve) is
one of two parts of the vestibulocochlear nerve
 Is the sensory nerve that transfers auditory information
from the cochlea’s organ of Corti (auditory area of the inner
ear), to the brain

5. PATHWAY
Sound waves enter the
ear and hit the EAR
DRUM/ TYMPANIC
MEMBRANE, which inturn
vibrates the malleus ,
incus and stapes.
Stapes causes hit/
vibrates on cochlea
through oval window.

6. This
sends
vibration in
the fluid
present in
the basilar
membrane
causing
hair cells to
move.

7. The bipolar basilar
cells leaves the
membrane as
peripheral fibers and
enter into spiral
ganglion, containing
the cell body.
 cell processes leaves
and run in form of
bundle called cochlear
nerve. there are on
average 30,000 nerve
fibers within the cochlear
nerve

8. It runs through
INTERNAL
ACOUSTIC
MEATUS along with
vestibular nerve and
facial nerve.

11.  and it enters the brainstem at pontomedullary junction, reaches upper part
of medulla and synapse in the cochlear nuclei
 The three major components of the cochlear nuclear complex are:
the dorsal cochlear nucleus (DCN)
the anteroventral cochlear nucleus (AVCN)
the posteroventral cochlear nucleus (PVCN)

12. Each of the three cochlear nuclei are tonotopically organized.
The axons from the low-frequency region of the cochlea project to the
ventral portion of the dorsal cochlear nucleus and the ventrolateral
portions of the anteroventral cochlear nucleus.
The axons from the high-frequency region project to the dorsal portion of
the anteroventral cochlear nucleus and the uppermost dorsal portions of
the dorsal cochlear nucleus.
 The axons from the intermediate frequency region project to intermediate
targets, such that tonotopy is preserved between the cochlea and the
cochlear nuclei

15.  axons from DCN runs to contralateral
site as Dorsal acoustic strai and
synapse in nuclei of lateral lamniscus.
Axons from ACN (VPCN) goes to
opposite side as intermediate acoustic
strai and synapse as in lateral
lamniscus while other fibers goes to
inferior colliculus in mid brain
 axons from AVCN goes to same also
contralateral side as ventral acoustic
strai/ trapezoid body and synapse in
superior olivary nucleus. From here
fibers goes to inferior colliculus as
lateral lemniscus.
Nuclei of lateral lamniscus sends fibers
to opposite side of nucleus of lateral
lemniscus to ensure the recieving of
sound from both the side even if one
side is damaged.

16. Most fibers
goes to medial
geniculate body
as inferior
brachium and
from here to
primary
auditory cortex
(superior
temporal gyrus)
area no 41, 42.
Fibers from nucleus of lateral lemnisci ascends as lateral lemniscus and ends in
inferior colliculus .
Some fibers from inferior colliculus go down ward as TECTO-SPINAL TRACT
(auditory reflex).

18. VESTIBULAR NERVE

19. COURSE
It helps in maintaining two types
of equilibrium; static (macula,
utricle) and dynamic (semicircular
canal)
Fibers originate from macula,
utricle and semicircular canal and
move towards vestibular ganglion.

20. Then they enters skull
through the internal
acoustic meatus along
with its co fibers cochlear
nerve.
Passing through the
ponto medullary junction it
enters into brain stem and
ends by synapsing into
vestibular nuclei namely
superior, inferior, medial
and lateral located in the
floor of fourth ventricle.

21. Now the nerve takes 3 course. It goes
DOWNWARD, UPWARD AND BACKWARD
 downward fibers goes down as vestibulospinal tract from medial and lateral nuclei
and synapse at different level of spinal cord in ventral gray column. Fibers from
medial nuclei controls head and neck muscles and from lateral nucleus control
trunk and limbs. Fibers from Lower motor neuron goes to specific muscles to
maintain balance.
BACKWARD FIBERS: moves backward through inferior cerebellar peduncle and
enters into flocculonodular lobe also known as vestibulocerebellum or archi
cerebellum and participates mainly in balance and sptial orientation. These fibers
synaps in festigial nuclei.
UPWARD FIBERS: fibers moving upward follows two pathway

23. DOWN WARD FIBERS
Some fibers (from medial nuclei) goes to contralateral side and synapse with 3rd,
4th and 6th cranial nerve nuclei. Now these fibers run as medial longitudinal
fasciculus.
They help in vestibulo occular reflex.
Other fibers from superior nucleus moves upward ipsilaterally without synapsing
ends up in VPMN of thalamus .
Post synaptic fibers moves through internal capsule and radiate as corona
radiata towards cortex:
post central gyrus
insular cortex
temporo parietal cortex

25. DISTURBANCE OFVESTIBULOCOCHLEAR
NERVE FUNCTION
 Causes vertigo and nystagmus.
 Vestibular function can be tested by Caloric test.
 If the ear is irrigated with a fluid having a temperature different than the body (either warmer or
cooler), a thermal gradient will be conduced across the small space of the middle ear. Like cold
water is put in the right ear. About 20 ml is injected over about 30 s.The cold water cools the
tympanic membrane, which cools the air in the middle ear, and finally the endolymph.This primarily
affects the horizontal semicircular canal because it is close to the middle ear space.
 Cooling somehow hyperpolarizes the hair cells, causing the eyes to drift slowly to the right as if the
head was moving to the left.When the eyes have moved as far to the side as they can go, there is a
quick resetting movement in the opposite direction.This cycle of slow and fast eye-movements is
called a nystagmus

26. irrigation of one ear with cold water produces a nystagmus away from
the irrigated ear, while warm water produces a nystagmus toward the
same ear.
The normal response in a caloric vestibular test is symmetric and
opposite responses in both ears.
Weakness of the caloric response (eyes not moving when warm or cold
water is flushed through one ear), or a spontaneous nystagmus
(constantly moving eyes, as if the head was spinning when it is stable),
indicates vestibular lesions.

27. MENIER’S DISEASE
 Meniere's disease is a disorder of the
inner ear that can lead to dizzy spells
(vertigo) and hearing loss.
 In most cases, Meniere's disease affects
only one ear.
 Meniere's disease can occur at any age,
but it usually starts between young and
middle-aged adulthood.

28. Sign an symptoms
 Recurring episodes of vertigo.You have a spinning sensation that starts and
stops spontaneously. Episodes of vertigo occur without warning and usually
last 20 minutes to several hours, but not more than 24 hours. Severe vertigo
can cause nausea.
 Hearing loss.
 Ringing in the ear (tinnitus).Tinnitus is the perception of a ringing, buzzing,
roaring, whistling or hissing sound in your ear.
 Feeling of fullness in the ear. People with Meniere's disease often feel
pressure in an affected ear (aural fullness).
 Loss of balance, headache
 After an episode, signs and symptoms improve and might disappear entirely
for a while. Over time, the frequency of episodes may lessen.

29.  Hearing test
 A hearing test, or audiometry, is used to determine if you’re experiencing
hearing loss. In this test, you’ll put on headphones and hear noises of a variety
of pitches and volumes.You’ll need to indicate when you can and cannot hear
a tone, so the technician can determine if you’re experiencing hearing loss.
 Your hearing will also be tested to determine if you can tell the difference
between similar sounds. In this portion of the test, you’ll hear words through
the headphones and repeat what you hear.The results of this test will tell your
doctor if you have a hearing problem in one or both ears. A problem in the
inner ear, or with the nerve in the ear, can cause hearing loss. An
electrocochleography (ECog) test is done to measure the electrical activity in
the inner ear. An auditory brainstem response (ABR) test checks the function
of the hearing nerves and the hearing center in the brain.These tests can tell
your doctor if the problem is caused by your inner ear or with your ear nerve.

30.  Balance tests
 Balance tests are performed to test the function of your inner ear. People who
have Meniere’s disease will have a reduced balance response in one of their
ears.The balance test most commonly used to test for Meniere’s disease is
electronystagmography (ENG).
 In this test, you’ll have electrodes placed around your eyes to detect eye
movement.This is done because the balance response in the inner ear causes
eye movements.
 During this test, both hot and cold water will be pushed into your ear.The
water causes your balance function to work.Your involuntary eye movements
will be tracked. Any abnormalities can indicate a problem with the inner ear.

31. VESTIBULAR REHABILITATION EXCERCISES

32. SUMMARY
NAME: vestibulocochlear nerve
TYPE OF NERVE : SENSORY
FUNCTIONAL COMPONENT : SSA
ORIGIN:VESTIBULAR NERVE: MACULA, UTRICLE, SEMICIRCULAR CANAL
COCHLEAR NERVE: ORGAN OF CORTI(COCHLEA)
FUNCTION: HEARING, BALANCE

33. THANK YOU...