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The vestibulocochlear nerve, the eighth cranial nerve, transmits sound and equilibrium information from the inner ear to the brain.
It consists mostly of bipolar neurons.
It splits into two large divisions: the cochlear nerve and the vestibular nerve.
It goes to the pons, the middle portion of the brainstem called the pons.
From the base of the pons the 8th cranial nerve runs to the medulla oblongata.
This junction between the pons, medulla, and cerebellum that contains the 8th nerve is called the cerebellopontine angle.
Accompaning the vestibulocochlear nerve is the labyrinthine artery, which usually branches off from the anterior inferior cerebellar artery at the cerebellopontine angle, and then goes with the 8th nerve through the internal acoustic meatus to the internal ear.
The cochlear nerve starts at the spiral ganglia and travels away from the cochlea of the inner ear.
The organ of Corti conducts afferent transmission to the spiral ganglia.
The vestibular nerve travels from the vestibular system of the inner ear.
The vestibular ganglion houses the cell bodies of the bipolar neurons and extends processes to five sensory organs.
Hair cells of the cristae, three of the 5 sensory organs, located in the ampullae of the semicircular canals activate afferent receptors in response to rotational acceleration.
The vestibular neurons also process the maculae of the saccule and utricle.
Hair cells of the maculae in the utricle activate afferent receptors in response to linear acceleration.
The hair cells of the maculae in the saccule respond to vertically directed linear force.
The nerve consists of the cochlear nerve, which carries information about hearing, and the vestibular nerve, carrying information about balance.
Damage to the vestibulocochlear nerve may cause the following symptoms:
hearing loss
vertigo
false sense of motion
loss of equilibrium
nystagmus motion sickness
gaze-evoked tinnitus
Rinne’s test demonstrates conductive hearing loss when air conduction is greater than bone conduction, and is abnormal.
If Rinne’s test indicates bone conduction is greater than air conduction then the test is normal.
With hearing loss, if bone conduction is greater than air conduction and Weber’s test lateralizes to abnormal side then it is connductive hearing loss.
If air conduction is greater than bone conduction and Weber’s test lateralizes to normal side then it concludes sensorineural hearing loss.