DR Medhat MRCP

VI. Vestibule-cochlear nerve :
- This nerve is composed of 2 divisions :
A. Cochlear division :
o Fibers originating from the cochlea pass centrally from the inner ear through the
internal auditory canal where they are joined by the vestibular division then they
pass through the cerebello-pontine angle to enter the brain stem where they relay in
the cochlear nucleus (in the lower pons) from which new fibers arise; some ascend in
the lateral lemniscus of the same side,while the remaining fibers decussate in the
lateral lemniscus to reach & relay in the medial geniculate bodies (M.G.B) from
which the fibers pass to the auditory sensory area in temporal lobes where hearing is
bilaterally represented.
o Lesion of cochlear division Tinnitus : if irritative lesion.
Deafness : if destructive lesion.
B. Vestibular division :
o Fibers originating from semilunar canals, uricle & saccule in the inner ear join the
cochlear division in the internal auditory canal then they pass in cerebello-pontine
angle to enter the brain stem where they relay in vestibular nuclei the brain stem.
o New fibers take 3 pathways :
1. To archicerebellum : concerned with equilibrium.
2. To medial longitudinal bundle : concerned with synchronous movements of
the eye,head&neck.
3. To the cerebral cortex : concerned with perception of sense of vertigo.
o Lesion of vestibular division : Vertigo.
Ipsilateral incoordination.
Spontaneous nystagmus.
Sensory neural hearing loss :
- It`s caused by lesions in the cochlea or the auditory nerve or central connections.
- It may be unilateral or bilateral.
- The overall incidence is about 2 in 1000 children
Risk factors:
1) Neonatal ICU admission ,low birth weight ,