0:01

What I'd like to do now is to talk

0:03

to you about the coronal anatomy.

0:06

These coronal images were derived from the thin

0:09

section axial scans by performing

0:11

multiplanar reconstructions.

0:13

The main anatomy that we're going to be looking at

0:15

in the inner ear is going to revolve around

0:17

the cochlea. And here is the cochlea here.

0:20

Remember, the cochlea has around two and a half

0:22

to two and three quarters turns: the basal,

0:26

middle, and apical turns. In addition,

0:29

the other anatomic structure that I want

0:30

to highlight here is the facial nerve.

0:33

So here is our internal auditory canal here.

0:37

The more medial soft tissue structure is the

0:40

7th cranial nerve labyrinthine portion.

0:43

And the more lateral one is going to be the

0:47

tympanic portion of the facial nerve.

0:50

So this is that on the axial plane,

0:54

we have the appearance here with

0:57

the geniculate ganglion here.

1:01

And this is the labyrinthine portion.

1:03

This is the tympanic portion.

1:04

And when you cut them in a coronal plane,

1:06

you're going to see them coming and going,

1:08

so to speak.

1:10

Here we have a section that's more closely

1:13

approximates through the actual internal auditory canal.

1:16

So this is our IAC (internal auditory canal).

1:20

And as you know,

1:21

we have a little bony spicule

1:23

called the crista falciformis.

1:25

And the crista falciformis separates the superior

1:28

portion of the internal auditory canal from the

1:30

inferior portion of the internal auditory canal.

1:33

In the superior portion,

1:34

we have the 7th cranial nerve anteriorly and

1:38

the superior vestibular nerve posteriorly.

1:41

And in the inferior portion anteriorly,

1:44

we have the cochlear nerve and the inferior

1:46

vestibular nerve, and they are separated

1:49

by the crista falciformis

1:51

and the superior-inferior plane and anterior-posterior,

1:53

you have something called Bill's Bar,

1:57

which can be found on 7th Street and Main

2:00

here in Cincinnati. Just joking.

2:02

Anyway,

2:03

the other anatomy that we want to look at in this

2:06

case is the vestibule and these semicircular canals.

2:09

So here is our vestibule.

2:11

This is going to be the oval window where we

2:14

would expect to see the stapes insert.

2:17

And you're just getting a little bit

2:19

of the lateral semicircular canal.

2:21

We would soon expect to see the superior

2:23

semicircular canal and in a more posterior plane,

2:26

the posterior semicircular canal.

2:28

So this is the vestibular system

2:30

that is being depicted here.

2:32

And we're just catching a tiny

2:34

portion of the cochlea.

2:36

This is an additional slice through the internal

2:40

auditory canal in the coronal plane.

2:42

And I think a little bit more convincing now here is the

2:47

crista falciformis, which is, as I said,

2:50

that anatomic bony structure that separates the

2:55

superior from the inferior portion in

2:58

the internal auditory canal

3:00

with the facial nerve and the superior vestibular

3:02

nerve above and the cochlear nerve and the inferior

3:06

vestibular nerve below. Here, I think,

3:09

more convincing is the superior semicircular

3:11

canal, the lateral semicircular canal,

3:13

and this is the connection to

3:15

the cochlea more inferiorly.

3:17

And I just want to point out that below the lateral

3:21

semicircular canal or horizontal semicircular canal,

3:24

one sees the tympanic portion of the facial nerve.

3:28

So it's that small soft tissue structure that is

3:33

present just below the lateral semicircular canal.

3:38

Right here.

3:39

Lateral semicircular canal here.

3:41

Facial nerve right below it.