The 8th cranial nerve, also known as the vestibulocochlear nerve, carries sensory information about hearing and balance. It has two divisions - the cochlear nerve for hearing and the vestibular nerve for balance. The nerve exits the brainstem between the pons and medulla and crosses the posterior cranial fossa into the inner ear. Damage to the 8th cranial nerve can cause symptoms like hearing loss, vertigo, and loss of balance. Tests like the caloric test and Dix-Hallpike maneuver examine the vestibular component, while audiometry tests the cochlear component. Treatment may include rest, medications, exercises, or surgery to relieve severe symptoms.

1. TOPIC--8th cranial
nerve
SUBMITTED TO..
MA’AM DIDENKO
victoria
Sub.by…MOHD.ALI
GROUP 4th
Sem.7
PATOK- 1
5YEAR COURSE

2. NTRODUCTION
 8th cranial nerve
 consists of two divisions:
2 components:
 a) cochlear (hearing)
 b) vestibular (equilibrium)
 OBJECTIVES
 1) Anatomy and
 2) functions.
 3) Blood supply
 4)Clinical Significance
 5) Examination
 6) How to test
 7) Treatment

3. Vestibulocochlear nerve VIII
•ANATOMY
The vestibulocochlear nerve [VIII] carries SA fibers for hearing
and balance,
consists of two divisions:
1. A Vestibular component for balance.
2. A Vochlear component for hearing.
1.The vestibulocochlear nerve
attaches to the lateral surface of the brainstem,
between the pons and medulla,
 after emerging from the internal acoustic meatus and
crossing the posterior cranial fossa into the single nerve seen
in the posterior cranial fossa within the substance of the
petrous part of the temporal bone

4. ANATOMY

5. Vestibular nerves
 Vestibular nerves
 • The vestibular nerves, joined by the cochlear nerve,
form the vestibulcochlear nerve.
 • enter the pontomedullary junction near the lateral recess of
the fourth ventrlde.
 • Whereas the cochlear fiben spilt dorsllly to reach the
Cochlear nudei,
 the vestibular fibers split ventrally to terminate in
 • 1. Vestibular nuclei (superior , lateral , medial and
inferior )
 • 2. cerebellum (flocculonoclular lobe).
 The flocculonoclular lobe functions with the semicircular
canals to detect rapid changes In direction.
 • 3. Reticular formation.

6. Blood supply
 The blood supply to the cochlea and auditory
brainstem nuclei arises from the internal auditory
(labyrinthine) artery, usually a branch of the anterior
inferior cerebellar artery.
 The superior olivary complex and lateral lemniscus
are supplied by circumferential branches of the basilar
artery
 the inferior colliculus is vascularized by branches of
the superior cerebellar and quadrigeminal arteries
 whereas the medial geniculate bodies receive their
blood supply from the thalamogeniculate arteries.
 Branches of the middle cerebral artery supply the
primary auditory and associated cortices

7. FUNCTIONS--8th cranial nerve
 This is the nerve along which the sensory cells
(the hair cells) of the inner ear transmit information
to the brain.
 It consists of the cochlear nerve, carrying
information about hearing, and
 the vestibular nerve, carrying information
about balance.
 It emerges from the pontomedullary junction and
exits the inner skull via the internal acoustic
meatus (or internal auditory meatus) in
the temporal bone.
 The vestibulocochlear nerve carries axons of type
SSA (special somatic afferent)

9. Clinical Significance
Symptoms of damage
Patients may present with pain in or behind the ear preceding
or appearing with the development of facial weakness.
There is inability to close the eye or move the lower face and
mouth
 Damage to the vestibulocochlear nerve may cause the
following symptoms:
 hearing loss
 vertigo
 false sense of motion
 loss of equilibrium (in dark places)
 nystagmus is a condition of involuntary (or voluntary, in
some cases) eye movement
 motion sickness
 gaze-evoked tinnitus -is the perception of sound)

10. Examination
Method of testing:
 A) For cochlear component
 1) Rinne’stest
 2) Weber’s test
 3) Absolute bone conduction (ABC) test
 4) Schwabach test
 5) Audiometric test
 6) Evoked response
 B) For vestibular component
 • 1) Rotationaltest.
 • 2) Caloric test.
 • 3) Dix Hallpikemaneuver for nystagmus.
 • 4) Electronystagmography

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15. Treatment
 In the acute attack most patients require bed rest
 accompanied by an injection or suppository to
relieve
 the vomiting. In adults a prochlorperazine
suppository of 25 mg or an injection of 6.25–12.5
mg may
 be useful. Frequent attacks may be treated with a
 vestibular sedative such as cinnarizine or
betahistine, although there have been no proper
trials of

16. Treatment
 treatment in the acute phase. Most treatment regimens
now use a graded approach, starting with
 dietary changes with the elimination of caffeine and
 vestibular sedative. Vestibular rehabilitation exercises
may also be used. About 80% of patients
 respond to such measures but in those that do not,
 surgery may be employed – either endolymphatic sac
Surgery or ablative therapy to destroy the affected
labyrinth or its function.
 These procedures will produce deafness but can give
relief

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