What happens when the vestibulocochlear nerve is damaged? – Human Anatomy | Kenhub

If you know anything about the vestibulocochlear
nerve, you’ll note that it’s a pretty important cranial nerve responsible namely
for the functions of hearing and balance. So, if we were to get injured, wouldn’t
we be in a rather undesirable predicament? Well, carry on watching as we’re going to
let you in on exactly what happens when the vestibulocochlear nerve gets damaged. First, let’s talk about the inner ear. You may at one time or another have had the
thought that the vestibulocochlear nerve must have been invented purely to confuse medical
students. But let’s break it down simply. Those who discovered the inner ear actually
visualized it as a compartment of two chambers.

One like a snail-shell which they called the
cochlea, the Greek word for snail, and you can see that just here – and let’s have
a little bit of fun and slip in an image of the snail to illustrate. The second chamber was named vestibule for
its similarity to a small foyer leading to the largest space of the cranial cavity. You can see the vestibulocochlear nerve highlighted
in green here on this image. As you might have already guessed, the vestibulocochlear
nerve has two components. The first is a vestibule chamber which holds
the vestibular nerve – and you can see it outlined in blue – and the cochlear chamber,
which holds the cochlear nerve – and you can see this here outlined in blue.

These two nerves unite as they’re about
to exit the inner ear and into the cranial cavity at the internal acoustic meatus, which
you can see – yup – circled in blue. If we move beyond it, we can see the vestibular
and cochlear nerves merging to become a single vestibulocochlear nerve, which is highlighted
in green. An important thing to note about the vestibulocochlear
nerve is that it is the eighth of twelve cranial nerves, and is abbreviated as CNVIII in Roman
numerals. So now that we’ve briefly looked at the
topographical and gross anatomy of the vestibulocochlear nerve, it’s time for a very important question. So, what exactly happens when it gets damaged? Conditions of the vestibular system and the
vestibular nerves can present as vertigo. Vertigo is a symptom describing the perception
of space rotating on its own. This condition can be experienced centrally
or peripherally.

Central vertigo is related to cerebellar and
brainstem lesions and is usually accompanied by vertical but sometimes horizontal or rotational
nystagmus. The nystagmus does not lessen when the patient
focuses their gaze and persists for a longer period than in peripheral vertigo. Peripheral vertigo then is due to a lesion
or condition of the vestibular system, and nerves may present with horizontal and rotational
nystagmus which does lessen or disappear when the patient focuses their gaze. Lesions of the cochlea or the cochlear nerve
can be the cause of sensorineural deafness – a condition where sound cannot be transmitted
from the inner ear to the central nervous system. Sensorineural deafness can be differentiated
from conductive deafness which arises due to a mechanical obstruction of sound waves
by using a tuning fork.

Should you place a tuning fork on the forehead
of the person with normal hearing, they’ll hear a similar sound volume in both ears. But a person with sensorineural deafness will
not hear any sound in their affected ear. Further still, a person with conductive deafness
will hear a higher volume in their affected ear. Wow, it doesn’t sound like a whole host
of fun, right? Balance and hearing, for which the vestibulocochlear
nerve is primarily responsible, are huge aspects of our day-to-day activity. If they’re impaired, life can really end
up going a little awry. The take-home message? Take good care, and if you’re worried that
you may have one of these conditions, see a doctor. And that’s all for today. If you’re looking to learn more about the
vestibulocochlear nerve in lots more detail, you can find the full video lowdown over on
our main website at kenhub.com. Here, you’ll also find a full atlas of the
structures relating to the vestibulocochlear nerve, in-depth articles, and fun quizzes
to test your knowledge. Let’s be honest.

It’s a total party over there, so let’s
go and join in, and we’ll see you on the next video. Thanks for watching!.

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