0:00

So let's look at this patient who has basically

0:04

a normal temporal bone to review the anatomy.

0:07

And we'll cover both the external auditory

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canal as well as the middle ear cavity,

0:12

and then finally the inner ear structures.

0:15

So as you can see by the nomenclature

0:19

down below here,

0:20

we are scanning. Here's the initial slice at slice

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location 57.2, and the next one is at 57.8.

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So you can see these are 0.6

0:31

millimeter thick sections.

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It says 0.5 varies from zero six to zero four on

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the slice location because of some element of

0:40

obliquity. But these are very thin sections.

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And once you scan with just the axial plane,

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you can make multiplanar images in coronal,

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sagittal, radio, etc.

0:52

That allows us to really focus down on

0:55

the anatomy. So why don't we do that?

0:57

So we're going to scroll up from the

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inferior aspect.

1:00

We start out with the mastoid tip, and we are

1:05

continuing up, and we're going to start

1:08

with the external auditory canal.

1:09

So here we are at the level of the external

1:11

auditory canal. As you can see,

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We have the cartilaginous portion of the external.

1:16

Auditory canal as well as the bony portion.

1:19

Of the external auditory canal.

1:21

Now,

1:21

At this thin section,

1:23

Often you can see the tympanic membrane.

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Even in the normal patient.

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So let's see where it comes in.

1:30

So here you're basically seeing a portion.

1:34

Of the tympanic membrane right here.

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It's very fine and thin and normal.

1:40

And the portion of the malleus when its insertion.

1:44

In the tympanic membrane is called the umbo.

1:48

When we look at the middle ear oscillos.

1:51

We typically look at them with the initial image.

1:56

Of the ice cream and the ice cream cone.

2:00

This refers to the head of the malleus.

2:03

And the short process of the incus.

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We are in the middle ear cavity.

2:08

And there is a connection from the middle.

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Ear cavity into the mastoid antrum.

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And that is the aditus ad antrum.

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With that hourglass appearance of the narrow area.

2:22

Of connection between the aditus and the antrum.

2:28

The so-called aditus ad antrum.

2:32

As you look at the anatomy going from downward.

2:38

Here we come to a point where we see two parallel

2:42

Dots, and this is the neck of the malleus.

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Remember:

2:45

The malleus is always anterior to the incus.

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And this becomes the long process of the incus.

2:51

And we're going to follow the long process.

2:53

Of the incus to its communication.

2:56

We're just seeing here with the stapes.

2:59

So here we are.

3:00

Starting to see the posterior.

3:01

Crus of the stapes.

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And this is the anterior crus of the stapes.

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And the stapes inserting at the oval window.

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Communicating with the vestibule.

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So continuing downward.

3:14

We're seeing that joint of the long process of the incus.

3:19

Communicating with the capitulum of the stapes.

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And then a crus of the stapes.

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Posterior and anterior. Seen here,

3:30

You notice that there is a muscle coming

3:33

To the neck of the malleus.

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It's this soft tissue structure.

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And that muscle is the tensor tympani muscle.

3:40

And it hooks around a little bony process.

3:43

Called the cochleariform process.

3:46

So that's going from the cochleariform

3:48

Process to the neck of the malleus.

3:50

And that would be the tensor tympani muscle.

3:53

As we come to the state bees and the capitalum,

3:57

you see that there is a little bony hill.

4:00

Here, which has an indentation on either side.

4:05

This is the pyramidal eminence with the sinus

4:08

tympani medial to it and the facial nerve recess.

4:12

With the facial nerve behind it just lateral to

4:15

the pyramidal eminence, a tiny muscle which

4:18

is just being faintly visualized.

4:20

Here goes from the pyramidal

4:22

eminence to the stapes.

4:23

And that's the second muscle of the middle ear

4:26

cavity. And that's the stapedius muscle.

4:28

And it's infrequently seen.

4:30

So the other structures that we want to

4:33

emphasize here are the facial nerve.

4:37

So when we want to find the facial nerve, we look

4:40

at the internal auditory canal and we identify the

4:44

facial nerve coursing anteriorly in the fallopian

4:48

canal in its labyrinthine portion.

4:50

And then we have the geniculate ganglion and then we

4:54

have the first genu of the facial nerve where

4:56

it's turning from going anteriorly to

5:00

posterior laterally. And that's the first genu.

5:02

And this portion of the facial nerve,

5:04

which we're seeing, is the tympanic portion

5:07

of the facial nerve which, as you can see,

5:09

runs along the medial border.

5:10

of the middle ear cavity.

5:13

So this is the facial nerve tympanic or horizontal.

5:16

portion. And if we follow it,

5:18

it will turn downward just here at the.

5:21

facial nerve recess. Remember,

5:23

we had the pyramidal eminence, sinus tympani.

5:25

facial nerve recess with the.

5:27

facial nerve just here.

5:28

And then the facial nerve ultimately leaves.

5:32

at the stylomastoid foramen and down below.

5:35

So one other important anatomical structure to.

5:41

emphasize is the carotid artery which.

5:45

as we scroll up, we see the carotid canal.

5:48

So this is the canal.

5:50

and you can see that it has a bony wall which.

5:53

separates it from the middle ear cavity.

5:55

And then the carotid comes downward.

5:58

to enter the petrous portion.

6:01

So the carotid is one of the vascular structures.

6:04

The other of the vascular structures.

6:06

is the jugular vein.

6:09

which we will discuss later when we.

6:13

talk about jugular dehiscence.

6:16

So that's the main anatomical structures on the axial.

6:19

scan. We do have an anterior epitympanic recess.

6:22

which is this little bubble far anterior here.

6:25

Sometimes you can have inflammatory disease.

6:27

which gets constrained by some of the septations.

6:30

and remains in the anterior epitympanic recess.

6:34

So what I'm going to do now is I'm going to make a.

6:36

coronal reconstruction of the axial studies.

6:40

As you can see,

6:41

they're excellent quality because.

6:43

of the thin section imaging.

6:45

And as we go towards the external canal.

6:49

we'll start with that. So once again.

6:50

we're at the external auditory canal showing the.

6:52

cartilaginous portion and the bony portion.

6:55

And we come to the middle ear cavity here.

6:58

And again.

7:00

Faintly seen.

7:01

you can make out the tympanic membrane.

7:05

This is the pars flaccida of the tympanic membrane.

7:08

and this is the pars tensa of the tympanic.

7:10

membrane. So medial to the tympanic membrane.

7:12

obviously, is the middle ear cavity.

7:14

Most people have heard of the little drum spur.

7:17

which is the scutum. Again.

7:19

the tympanic membrane attaches to the scutum.

7:21

the space between the middle ear ossicles.

7:24

and the the scutum is Prussak's space.

7:28

And this is one of the locations.

7:30

where cholesteatomas may arise.

7:33

And then we have the epitympanic

7:36

space above the ossicles.

7:38

And it is confined by the roof of the temporal

7:42

bone, the so-called Tegmen tympani.

7:44

So the roof of the tympanic portion of the

7:47

temporal bone, making up that structure.

7:50

So as we go anteriorly, we find the ossicle,

7:55

which is the furthest anterior,

7:57

which is the malleus, and it attaches to

8:00

the tympanic membrane, as said previously.

8:02

This can be seen on otoscopy as the little indentation

8:06

there, the umbo. So this is our malleus.

8:09

And then we come to the next ossicle here,

8:11

which is going to be the incus,

8:13

which is posterior to the malleus.

8:16

And then the incus, as you can see here,

8:19

has a little articular process which makes a

8:22

little bit of a right turn in the

8:23

coronal plane with the stapes.

8:26

And then the stapes goes into the oval window

8:29

here. Here is your lateral semicircular canal,

8:32

your superior semicircular canal, your vestibule,

8:35

your horizontal portion of the facial nerve.

8:38

And the facial nerve comes here.

8:41

This is the labyrinthine portion of the facial

8:43

nerve and the tympanic portion of the facial nerve.

8:46

And they come together at the geniculate ganglion.

8:48

So I think that's a good review

8:50

of the anatomy initially.

8:51

And then we will go over the anatomy with each of

8:55

the pathological cases as well so that everyone's

8:57

comfortable with temporal bone anatomy.

9:00

Focusing on the middle ear cavity.