0:00

We're going to take a walk through

0:02

the coronal anatomy now.

0:04

And these are coronal multiplanar reconstructions

0:07

from the axial CT data.

0:10

On this coronal image,

0:12

we're seeing the turns of the cochlea here.

0:16

And just below the cochlea,

0:18

we see the internal carotid artery.

0:22

And this always fascinates me why more

0:24

people don't have pulsatile tinnitus,

0:26

because you can see the proximity of the pulsating

0:30

internal auditory canal with respect to the cochlea,

0:34

just a millimeter or less above it.

0:39

So let's continue to scroll the anatomy here.

0:43

And we're coming into the internal

0:46

carotid artery here.

0:48

And you can see this is the petrous portion of

0:51

the internal carotid artery.

0:56

Our next section that we're going to stop in is

0:58

here. This is through the internal auditory canal.

1:01

So here again is our IAC.

1:04

We have the tiny little bony spicule of the

1:06

crista falciformis that we saw on the PowerPoint,

1:10

separating the superior portion and the inferior

1:12

portion of the internal auditory canal.

1:15

And at this juncture,

1:16

we're seeing the entrance into the vestibular

1:20

system as well as the cochlear system.

1:23

And that makes sense because inferiorly is going

1:25

to be where the cochlear nerve resides.

1:27

And superiorly,

1:29

we have the facial nerve and the superior vestibular

1:32

nerve in the internal auditory canal.

1:35

So let's continue to scroll a little bit further.

1:37

And here we come to the vestibule with the lateral

1:41

semicircular canal and the oval window.

1:44

We're going to look for the stapes inserting

1:46

into the oval window on the vestibule.

1:50

And here you can see faintly that portion

1:54

of the middle ear ossicles, the stapes.

1:58

You're seeing portions of these semicircular canals.

2:02

So let's point that out.

2:04

This is the superior semicircular canal.

2:07

Cut in portions of it, the more anterior portion.

2:12

Here you have the lateral semicircular canal.

2:14

And remember that just below the lateral

2:17

semicircular canal is the tympanic portion

2:19

of the facial nerve, cranial nerve VII.

2:23

This is the incus with its articulation

2:28

with the stapes.

2:29

And the stapes is going to

2:31

insert on the oval window.

2:34

As we continue further ahead,

2:38

we come into the semicircular canals where we have

2:43

the more posterior portion of

2:44

the semicircular canal.

2:45

So this is one of the turns of the superior

2:51

semicircular canal. We're now posterior.

2:53

And here we're coming into one of the posterior

2:56

semicircular canals. So this is the posterior

3:00

limb of the superior semicircular canal.

3:04

And this is the portion of the posterior

3:07

semicircular canal, seen in cross section,

3:10

coming to the vestibule. Finally,

3:14

I do want to point out once again the anatomy of the

3:18

facial nerve coming from the

3:20

internal auditory canal.

3:21

So if we go back to the internal auditory canal,

3:24

what we see is from the superior portion of the

3:27

internal auditory canal, above the crista falciformis,

3:30

you have the labyrinthine portion of the facial

3:33

nerve and the horizontal or tympanic portion

3:37

of the facial nerve. And as we scroll,

3:40

we can see them come together anteriorly

3:46

to the geniculate ganglion.

3:48

So, this is the geniculate ganglion.

3:52

Right here is our geniculate ganglion of

3:55

the facial nerve. And as we scroll,

4:00

we can see that the portion that goes to the

4:03

internal auditory canal is going

4:04

to be the labyrinthine portion.

4:06

And the portion that goes under the lateral

4:10

semicircular canal is going to be the tympanic

4:13

portion. Now, if we continue following this,

4:16

you will see it turn inferiorly at the

4:20

second genu of the facial nerve.

4:23

So, this is the descending intramastoid

4:28

portion of the facial nerve.

4:33

And here is where it makes that turn from going in

4:37

the tympanic portion and then going downward.

4:40

The intramastoid portion is what we refer to

4:42

as the second genu of the facial nerve,

4:45

the first genu being at the geniculate ganglion.

4:47

So let me just point that out one more time.

4:49

Here is the descending portion of the facial nerve,

4:53

coming out here at the stylomastoid foramen.

4:56

But watch it because it's going to

4:58

make this right-angle turn here

5:04

as the tympanic or horizontal portion

5:07

before it turns downward.

5:09

So, that's the anatomy of the facial

5:12

nerve in the coronal plane.