1.
Vestibulocochlear Nerve
Presenter- Dr. Roopsingh
Unit head –Dr prbhat kanvariya
Department of medicine
SNMC JODHPUR

2.
• The eighth cranial nerve consists of two separate functional
components:
• the auditory (cochlear) nerve concerned with hearing and the
vestibular nerve concerned with equilibrium. The auditory nerve
receives information from the tonotopically organized cochlea, the
organ of hearing.
• The vestibular nerve derives its input from the saccular and
utricular macules (which sense linear acceleration) and the cristae
of the semicircular canals (which sense angular acceleration of the
head).

3.
Auditory pathway-

4.
Clinical examinationof cochlear system-
-Before testinghearing, otoscopicexamination should be done to ensure the
tympanic membrane is intact, and to exclude the presence of wax, pus, blood,
foreign bodies, and exudate.
- The mastoid region should be examined for swelling and tenderness.
1.Rinne test
2.Weber test
3.Schwabach test
4.Audiometry
5 Impedance audiometry
(a)tympanometry
(b)stapedial reflex
6.OAE
7.BERA

5.
Rinnes Test-
- The Rinne's test compares the patient's air and bone
conduction.
- The stem of the vibrating tuning fork is applied
against the mastoid process.
- When the patient no longer hears the vibration, the
fork is placed next to the ear (approximately 1 cm from
the external auditory meatus).
- In normal individuals, because air conduction is
better than bone conduction, the vibrations are
perceived in the ear after they are no longer perceived
at the mastoid.

6.
• The Rinne's test is said to be normal, or positive,when the tuning fork is
heard approximatelytwice as long by air conductionas by bone
conduction.
• In cases of conductiondeafness, bone conduction is better than air
conduction,and therefore the tuning fork cannot be heard when it is
placed next to the ear.
• Withsensorineuralhearing loss, both air and bone conduction are
diminishedto a similarextent, and air conductionremains greater than
bone conduction.

7.
The Weber's Test
- The purpose of the Weber's test is to help
differentiate a conductive from a sensorineural
hearing loss in a unilateral hearing loss.
- This test is conducted by placing a vibrating tuning
fork over the midline of the skull or forehead, over the
nasal bone, or over the anterior upper incisors.
- Normally, the vibrations are perceived equally in
both ears (no lateralization) because bone conduction
is equal bilaterally.

8.
Schwabach test-
• As in the Rinne's test, the tuning fork is held
against the mastoid process until the patient
is unable to perceive any sound.
• The examiner then places the tuning fork
over his or her own mastoid bone and
compares the bone conduction to that of the
patient.
• If the examiner hears the tuning fork after
the patient no longer hears it, a sensorineural
hearing loss is suspected.

9.
Audiometry
• An audiometer is an instrument by which sounds of varying
intensity and frequency are presented to a patient.
• There are many different audiologic techniques; those used most
commonly for neurologic purposes are pure tone and speech
audiometry.

10.
Impedance audiometry
• uses an electroacoustic device, which measures the impedance, or
compliance, of the conductive hearing mechanism, like measuring
the tightness of a drumhead.
• A very stiff drumhead has high impedance, or low compliance, and
reflects sound back to the source.
• Low impedance allows for greater transmission of sound through
the system and less reflection.

11.
The stapedius reflex, or acoustic reflex
measures the change in compliance in response to
loud sounds to assess the function of the stapedial
muscle.
• The reflex arc is via CN VIII, brainstem
interneurons, and CN VII.
• In the absence of severe hearing loss, an
abnormal stapedius reflex may suggest a lesion
of CN VII or VIII or the brainstem.

12.
Vestibular system

13.
•Clinical Examination of vestibular system
• 1 vestibulo ocular reflex
• 2 vestibulosi nal reflex

14.
Vestibulo-ocular reflexs
• The vestibulo-ocular reflex (VOR) serves to move the eyes at an
equal velocity but in the direction opposite the head movement.
. This keeps the eyes still in space and maintains visual fixation while
the head is in motion.
• There are several ways to examine the VOR including
• Doll's eye test
• Head thrust test
• Dynamic visual acuity
• Calorics.

15.
• Oculocephalic Reflex (Doll's
Eye Test)
• The oculocephalic response is primarily
useful in the evaluation of comatose
patients.
• Turning the head in one direction causes
the eyes to turn in the opposite direction.
• This response indicates that the
pathways connecting the vestibular
nuclei in the medulla to the extraocular
nuclei in the pons and midbrain are
functioning and that the brainstem is
intact.

16.
Head Thrust
• The head thrust test is done
in an awake patient.
• Abrupt, rapid movements
are made in each direction
while the patient attempts to
maintain fixation straight
ahead, as on the examiner's
nose.
• Normally the VOR will
maintain fixation and the
eyes will hold on target.

17.
• When the VOR is impaired, the compensatory eye movement
velocity is less than the head movement velocity; the eyes lag
behind the head movement and a corrective “catch-up” saccade
must be made to resume fixation in the eccentric position.

18.
Dynamic Visual Acuity
• The ability of the VOR to maintain ocular fixation
means that a patient can read even while shaking the
head to and fro.
• The dynamic visual acuity test is performed by
obtaining a baseline acuity, and then determining the
acuity during rapid head shaking.
• Degradation by more than three lines on the Snellen
chart suggests impaired vestibular function.

19.
Caloric Tests
• Cold calorics in a comatose patient with an intact brainstem causes
tonic deviation of the eyes toward the side of irrigation as the
normally active labyrinth pushes the eyes toward the hypoactive,
irrigated labyrinth.
• In an awake patient, cold calorics cause nystagmus with the fast
component away from the irrigated side because the cerebral
cortex produces a compensatory saccade that jerks in the direction
opposite the tonic deviation.

20.
• Nystagmus is seen only when the cortex is functioning normally.
• Warm water irrigation has opposite effects.
• Bilateral simultaneous cold calorics induce tonic downgaze, warm
calorics upgaze.

21.
Vestibulospinal Reflexes
Past pointing is a deviation of the extremities caused by either cerebellar
or vestibular disease.
- With acute vestibular imbalance, the normal labyrinth will push the limb
toward the abnormal side, and the patient will miss the target.
- The past pointing will always be to the same side of the target and will
occur with either limb.

22.
• With a cerebellar hemispheric lesion, the ipsilateral limbs have
ataxia and incoordination; past pointing occurs only with the
involved arm and may be to the side of the lesion or erratically to
either side of the target
• In vestibulopathy, after a period of compensation the past pointing
disappears and may even begin to occur in the opposite direction.

23.
• In rombergs test, in unilateral vestibulopathy if balance is lost with
eyes closed the patient will tend to fall toward the side of the lesion,
as the normal vestibular system pushes him over.
• If the patient has spontaneous nystagmus due to a vestibular
lesion, the fall will be in the direction of the slow phase.
• The patient, eyes closed, marches in place for one minute.
• A normal individual will continue to face in the same direction, but a
patient with acute vestibulopathy will slowly pivot toward the
lesion.

24.
• In the star walking test, the patient, eyes closed,
takes several steps forward then several steps
backward, over and over.
• A normal individual will begin and end oriented
approximately along the same line.
• A patient with acute vestibulopathy will drift
toward the involved side walking forward, and
continue to drift during the backward phase.
• The resulting path traces out a multipointed star
pattern.

25.
Vertigo-
Vertigo is the sensation of environmental motion (spinning,whirling
lateropulsion ,tilt).

26.
• The provocative positioning maneuver (Dix-Hallpike
maneuvers) (patient is briskly moved from the seated position
to a position where the head is hanging 45 degrees below the
horizontal and rotated 45 degrees to one side)allows for a
differentiation between a peripheral or a central origin for
positional vertigo.

27.
Thank you