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Dr. P here to talk about the 8th cranial nerve,

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the vestibulocochlear nerve,

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which transmits sound and equilibrium

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or balance information from the inner ear to the brain.

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My point today in this vignette is to show you some of

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the key components of the real origin of the

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hearing mechanism.

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And real means nuclei.

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Where are these nuclei located?

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They're located in the pons, laterally,

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kind of close to the middle.

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When we talk about from anterior to posterior,

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from here to here, right about in the middle,

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you can see the 7th and 8th nerves right there.

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That's the 8th nerve.

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And these nuclei are paired on each side.

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There is a ventral and a dorsal one.

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The fact that we have two paired nuclei on each side

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and some additional reasons explain why

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you don't often get central hearing loss

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with a brainstem lesion.

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Now, we've got a structure that courses from

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one side to the other.

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I think I'll make that kind of orangey yellow.

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And it's got a course that is slightly

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oblique from one side to the other.

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And I'd also like to draw the nuclei

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in the coronal projection too.

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So let's pair up our cochlear nuclei,

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which are located right at the bottom of the

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basis pontis right here on each side.

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And now let's draw our crossing structure,

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which is known as the trapezoid body

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or trapezoid pathway,

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comes over to the side.

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Not only does it have a slight anterior course,

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it also has a slight superior course.

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And then it connects with the superior olivary nucleus.

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And there is a lateral and a medial one.

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Now, from there,

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we've got a very important tract.

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And that tract is the lateral lemniscus,

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which is part of the auditory pathway.

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Let's give it its dew.

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I think green would be appropriate.

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And it's coming up this way.

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Now, I'm not going to scroll my coronal,

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but it's coming up in a rather dorsal position.

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And when it hits the top,

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what's it going to hit?

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The inferior colliculus.

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So, I'm going to draw

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the inferior colliculus as a round structure,

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and then I'm going to scroll to it in a second.

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I'm going to use dark green for that.

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And now, I'm going to take my colors away

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and I'm going to go right to the inferior colliculus.

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And you'll see it's right there.

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There's the inferior colliculus.

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So, the inferior colliculus is one of the way stations

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for the vestibulocochlear system.

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Then an arm of the inferior colliculus goes out to the side,

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to the medial geniculate nucleus then onto the transverse

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temporal gyrus of Heschl,

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and the planum of the temporal lobe.

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One more thing about the apparent origin

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of the 7th and 8th nerve complex.

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I want to scroll up a little bit because I showed

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you the lateral lemniscus heading north

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in the coronal projection.

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And I'm going to take a unique color,

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something we haven't used before.

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Let's try light blue.

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And our lateral lemniscus is coming up this way,

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from the superior olivary nucleus,

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which has medial and lateral components,

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it goes to the inferior colliculus

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before it goes out sideways

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to the medial geniculate nucleus.

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But where is the lateral lemniscus in the axial projection?

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It's located dorsolaterally, right about here.

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So, more posterior than the paired cochlear nuclei

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which are located somewhere mid-coronal from A to P.

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That's a pretty complicated explanation of the apparent

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origin of the vestibulocochlear system.

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Dr. P out.