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What I'd like to do right now is to go over some

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basic CT anatomy with you by PowerPoint.

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And then we will look at a specific.

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Case and review the anatomy.

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So we're going to start from below.

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And we're going to start at the level.

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Of the cochlear aqueduct.

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What we see here is the cochlear aqueduct.

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In some cases.

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It kind of looks like a small.

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Internal auditory canal.

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But this anatomic structure is below the internal.

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Auditory canal, and as you can see.

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Is associated with the jugular vein here and the.

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Internal carotid artery canal in its petrous.

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Portion. So this is at the very lowest.

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Most portion of the inner ear structures.

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The cochlear aqueduct.

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This next section up is a section.

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Through the hypotympanum.

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But it shows very nicely the beginning.

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Of the round window.

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The hypotympanum is marked by the sinus tympani.

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As well as the pyramidal eminence and the facial.

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Nerve. And in the facial nerve recess.

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This area right here.

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Leading to the basal turn of the cochlea

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Basal turn of the cochlea.

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Is the round window.

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So we call this the round window niche.

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So we're about to enter the cochlea.

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The importance of the round window is that it is.

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Through the round window that the.

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Cochlear implants are inserted.

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That's their way of getting into the cochlea.

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And the various turns of the cochlea.

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This next slice allows us to see the basal.

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And middle turns of the cochlea.

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Here we have the base turn of the cochlea.

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And this is the middle turn.

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We may be getting a tiny bit of the apical turn.

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So the cochlea we say as.

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The basal, middle, and apical turns.

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And we have the entry into the basal.

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Turn through the round window.

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This image also is showing.

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Us the endolymphatic sac.

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Which is the soft tissue portion.

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Of the vestibular aqueduct.

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So the vestibular aqueduct we usually.

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Refer to as the bony part.

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And what is residing within the bony.

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Part is the endolymphatic sac.

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Also part of the inner ear structures.

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You're also starting to see some

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of the semicircular canals,

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including the posterior semicircular canal.

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And we're just getting a piece

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of the vestibule as well.

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Busy anatomy.

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Another section showing the similar anatomy.

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And in this section at least,

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we can see the entrance of the internal auditory

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canal leading to the cochlear.

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Basal turn and middle turn,

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as well as the vestibule,

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the endolymphatic sac,

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and portions of these semicircular canals.

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Our next slice up is through the mid portion of

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the internal auditory canal. So here is our IAC,

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the internal auditory canal.

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And we lead to the cochlea through an area

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of anatomy called the cochlear aperture.

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And this is a normal cochlear aperture,

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which, as you can see,

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is going to be around 2 mm in width.

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The density in the center of the cochlea

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is referred to as the modiolus.

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Some people will call it the modiolus,

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but modiolus is what we are using

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in the east coast at least.

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And you also see a very small canal coming off

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The posterior portion of the internal auditory canal.

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In this small canal is the singular canal,

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which transmits the singular nerve,

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which is a nerve that goes to the semicircular canals.

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We have the vestibule here,

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and if we look carefully at the vestibule,

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which is the entrance into the labyrinth,

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you can see the turns of the cochlea of the stapes.

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So this is the cochlea of the stapes.

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This is the posterior crus of the stapes,

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Kurora being the plural.

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And you have the capitulum of the stapes right here.

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So this is going to be our oval window.

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We talked about the round window leading

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into the basal turn of the cochlea.

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This is the oval window in which the stapes

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sits and inserts on the vestibule.

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Again,

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we have the endolymphatic or vestibular aqueduct.

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Let's continue. More superiorly. So,

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at this juncture,

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we're at the high portion of the internal auditory canal.

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And what we see here is the internal auditory canal.

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And we're cutting through portions of it.

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We're missing the more medial aspect.

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But what we're seeing is this nerve,

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which is going here.

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And this is our 7th cranial nerve,

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the facial nerve.

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And we talk about the labyrinthine

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portion of the facial nerve,

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the point where it makes its first genu.

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And right here is where the ganglion is.

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And the ganglion of the 7th cranial nerve

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is called the geniculate ganglion.

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And then it makes that bend back to the tympanic

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portion of the 7th cranial nerve,

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or horizontal portion, if you will.

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So this is the anatomy here.

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You can also see the nerve going here,

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which is going to the vestibule.

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So this is the vestibule of the labyrinth.

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And there's a nerve going to it.

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We're at the upper posterior portion

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of the internal auditory canal.

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So.

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Here is likely to be the canal for the superior

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vestibular nerve. So facial nerve,

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anterior and superior. Superior vestibular nerve,

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posterior and superior.

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And we're just catching into the lateral

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semicircular canal here.

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This is the remnant of the endolymphatic

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sac or vestibular aqueduct.

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I think we have one more slice to go through.

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So here we are seeing portions

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of the semicircular canals.

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We have the two quora of the superior

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semicircular canal,

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and we have a portion of the posterior

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semicircular canal.

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And we're just at the very top

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of the internal auditory now,

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just seeing a small portion of the geniculate

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ganglion, the ganglion of the 7th cranial nerve,

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the final slice. So there was one more.

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Slice is also through the superior

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semicircular canals.

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So portions of the superior semicircular

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canals cut in cross-section. Here's

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a little bit of the posterior semicircular canal.

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And this little small structure here is one of the

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semiacuate arteries that lead between the

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Qura of the superior semicircular canal.

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So this would be a diagram of the

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superior semicircular canal.

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There's a little vessel that courses between the

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arch of the superior semicircular canal.

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So that's the CT anatomy we wanted

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to go through in PowerPoint.

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And now we will look at it on an actual

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case with all of the slices available.