0:00

I'd like to take this case to review.

0:03

The CT anatomy with you,

0:06

just as we did with the PowerPoint.

0:08

So we are starting here at the lower portion of

0:11

the temporal bone, and we can identify some of the

0:15

anatomic structures. Already here, for example,

0:18

is our cochlear aqueduct, and we are also seeing

0:23

the round window as it is the entranceway

0:29

to the basal turn of the cochlea.

0:32

I want to point out that these slices

0:36

are labeled as 0.4 millimeter thick,

0:38

but as I scroll through them,

0:40

you see that they're scrolling at 0.2 mm thick.

0:43

So these are very thin slices going

0:46

through the temporal bone,

0:47

so that way we can have such great coronal and

0:49

sagittal and multiplanar reconstructions.

0:52

As we go up more superiorly,

0:55

we come to the structures of the hypotympanum,

0:58

those being the sinus tympani,

1:01

the pyramidal eminence,

1:03

and the facial nerve recess with

1:04

the facial nerve behind.

1:06

So this is the descending intramastoid

1:09

portion of the facial nerve here.

1:13

This is our round window leading to

1:15

the basal turn of the cochlea.

1:17

And we're just getting through the top of the.

1:20

Cochlear aqueduct as we go further superiorly.

1:24

So let's continue to scroll.

1:26

Above and as we go higher,

1:29

We're starting to lose our cochlear aqueduct and

1:32

Come into the middle turn of the cochlea.

1:36

So here we have our basal turn of

1:37

The cochlea and the middle turn.

1:40

And there's going to be a little nub in here,

1:43

Which is going to be our apical turn.

1:46

And we will see that shortly.

1:49

As we continue further superiorly,

1:52

We come to this section.

1:55

This section shows our vestibular aqueduct.

1:59

It shows the internal architecture of the cochlea,

2:03

Which is the modiolus,

2:05

The internal skeleton of the cochlea.

2:08

And we are at the level of the middle turn

2:12

And coming into the apical turn.

2:14

So let me just scroll one more time to

2:16

See how we go from the basal turn.

2:19

So here's our basal turn.

2:21

Below we come to the middle turn

2:24

And then this little portion,

2:27

Anterolaterally being the apical turn,

2:30

With the modiolus being the skeleton, if you will,

2:33

Of the cochlea. On the vestibular side,

2:37

We come to the Vestibular aqueduct here.

2:41

We have the vestibule here.

2:44

And remember,

2:45

the vestibule is going to have the oval window.

2:49

Associated with the stapes situated, as it were,

2:53

on the oval window. So let's find the stapes.

2:57

You're just making out a portion of the...

3:00

Stapes here. These are the core of the stapes.

3:02

They're very poorly seen. And again,

3:04

there's a lot of...

3:06

noise because of the thin section.

3:08

But we can see that the incus comes down right here.

3:12

And this is our incudostapedial joint.

3:15

And these are the core of the stapes

3:17

coming to the oval window.

3:19

Now,

3:19

the reason why this is not as well seen is because

3:22

the patient actually has pathology.

3:24

And that pathology is pretty subtle.

3:27

In this section,

3:28

this little area of demineralized bone is what

3:33

is known as otospongiosis or otosclerosis,

3:38

and it causes fixation of the stapes in the

3:43

oval window. So here's our oval window,

3:45

here's our otospongiosis, this is our cochlea.

3:49

This area just in front of the oval window

3:53

is the Fissula antefenestram,

3:57

and this is the classic location for fenestral,

4:02

otosclerosis or spongiosis.

4:05

But let's get back to anatomy.

4:08

So here is a better section through the vestibule.

4:11

Here's our vestibule.

4:13

And from this, we would expect to start

4:15

to see the semicircular canals.

4:17

We do see the vestibular aqueduct

4:19

or endolymphatic sac here.

4:21

Here is one portion of the semicircular system and

4:25

we'll see which semicircular canal

4:28

this represents in just a moment.

4:30

Here is our lateral semicircular canal,

4:33

or horizontal semicircular canal.

4:36

We still have a portion of the semicircular

4:38

canal here, as you can see.

4:40

This is going to be a portion of the

4:42

posterior semicircular canal.

4:45

And this is our superior semicircular canal.

4:49

That is

4:51

going to meet at the top here.

4:53

So the arch top is right here.

4:56

And then these are the two crura of

4:58

the superior semicircular canal.

5:01

And then this is the posterior semicircular canal.

5:04

And then the horizontal or lateral semicircular

5:07

canal connecting to the vestibule.

5:09

Let's just point out the facial nerve.

5:12

Here you have the internal auditory canal.

5:14

This is the labyrinthine portion of the facial

5:17

nerve coming to the geniculate ganglion.

5:21

Here's our vestibule, lateral semicircular canal,

5:24

vestibular aqueduct,

5:25

and a portion of the posterior semicircular canal.

5:29

But let's follow the facial nerve for a moment.

5:34

And as we follow it,

5:35

you can see that there comes the horizontal or

5:39

tympanic portion of the facial nerve right through

5:41

here. So this is the geniculate ganglion,

5:44

the junction of the

5:47

labyrinthine portion of the facial nerve.

5:49

Genius ganglion.

5:51

And then the horizontal or tympanic

5:53

portion of the facial nerve.

5:55

So that's our anatomy in the axial

5:57

plane for the inner ear.