0:00

I'd like to take this case of a patient who

0:04

presented with a painful left ear to review the

0:08

external anatomy quickly before

0:10

we look at the pathology.

0:12

So we're going to ignore the opacification

0:13

of the middle ear cavity.

0:16

Here we have our external auditory canal on the

0:19

right side, and we have the cartilaginous as

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well as the bony portion.

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And as I said,

0:24

usually we do not see soft tissue along the walls

0:28

of the external auditory canal

0:30

bony portion.

0:31

We come medially from the external auditory

0:35

canal and hit the tympanic membrane.

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And the most anterior of the ossicles

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is going to be the malleus.

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The malleus inserts on the tympanic membrane.

0:45

And that insertion site of the malleus on the

0:47

tympanic membrane is called the umbo, U-M-B-O.

0:52

This patient shows a nice example

0:54

of the nice sharp scutum,

0:58

which is the little bone spur upon which you

1:00

see the tympanic membrane inserting.

1:03

And the airspace between the malleus and the

1:07

scutum is going to be our Prussak's space,

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which is a part of the epitympanic space in the

1:13

superior portion of the middle ear cavity.

1:17

When we move further posteriorly,

1:19

we come to the second ossicle, which is the incus.

1:23

And usually you see a little bit of a right-hand

1:26

turn as the incus articulates with the stapes.

1:31

And the stapes is seen here,

1:33

extending to the oval window where you have the

1:37

vestibule with the multiple semicircular

1:40

canals associated with it.

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So we're seeing a portion of the stapes and the

1:44

incudostapedial joint on these sections.

1:48

Remember that the roof of the middle ear

1:52

cavity is called the tegmen tympani.

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And when we look at the semicircular canals,

1:58

we can identify the superior semicircular canal,

2:01

the lateral semicircular canal,

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and one that's going to be going posteriorly,

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the posterior semicircular canal.

2:07

Here we have the cochlea with some of its turns.

2:11

What's interesting is the vascular structure,

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which is just below the cochlea,

2:17

is the carotid artery.

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So you notice that the carotid artery is coming up

2:22

here and then making a turn to go into the cavernous

2:26

and petrous portion of the internal carotid artery.

2:30

And as it makes this turn,

2:31

it's fascinating to me that more people don't have

2:33

tinnitus because you have the pulsation of the

2:36

carotid artery just below the cochlea as it bangs

2:40

against the bone there and then makes that turn

2:43

into the petrous and then cavernous portion.

2:46

So pulsatile tinnitus. Why not?

2:49

In any case,

2:50

I want to just show again the internal auditory

2:52

canal with the crista falciformis,

2:54

which is that little bony spicula that separates

2:56

the superior nerves from the inferior nerves.

3:00

The superior nerves being the facial nerve

3:02

anteriorly and the superior vestibular nerve

3:04

posteriorly as we see here in this example.

3:07

We're coming anteriorly and we come to the

3:11

labyrinthine portion of the facial

3:13

nerve on the coronal scan,

3:15

the tympanic portion of the facial nerve on the

3:19

coronal scan, and they join together right

3:22

here at the geniculate ganglion,

3:25

the 7th cranial nerve ganglion.

3:29

Jugular vein is down here, and we have

3:32

the hypoglossal canal over here.

3:34

So a quick review of the coronal anatomy.

3:36

Let's look at the pathology.

3:38

So here we are on the external auditory canal and

3:40

curiously we have this rounded mass which is

3:44

present within the external auditory canal.

3:47

And we also note this thickening of the superior

3:51

wall of the external auditory canal.

3:53

We compare that to the contralateral side.

3:54

It's thickened all the way along this superior wall.

3:58

So this is indeed external otitis,

4:01

external canal infection which is associated

4:06

with middle ear cavity infection as well.

4:09

So you see the opacification of the

4:11

middle ear bilaterally, actually.

4:13

And we want to look and see whether the mastoid

4:16

air cells are opacified. They are indeed.

4:19

So the term we would use would

4:22

be otomastoiditis referring to oto,

4:25

the middle ear cavity, and mastoid referring to

4:28

the mastoid air cells as the infection

4:31

of otomastoiditis.

4:33

So this patient has external otitis associated

4:36

with bilateral otomastoiditis,

4:39

otitis media, and mastoiditis.

4:41

And we have this curiosity here of the soft tissue

4:45

mass which is present within the external

4:48

auditory canal. You don't see that on the contralateral side.

4:50

So what should you ask yourself?

4:52

What should you ask the clinician?

4:54

Simple question. Is it white or is it red?

4:57

If it's white, we're going with an epidermoid.

5:00

If it's red, it may be a hemangioma or venous

5:03

vascular malformation or any of the red

5:05

masses in the external auditory canal.