0:00

I'd like to review the material that we've just gone

0:03

over in this course on the external auditory canal.

0:09

First off, infections are the most common pathology to affect

0:13

the external auditory canal. However,

0:14

most cases of external otitis

0:18

are not sent for imaging.

0:20

They are treated topically or with antibiotics

0:25

and rarely imaged.

0:27

The exception to that rule is the case of the diabetic

0:31

elderly patient who has malignant otitis externa.

0:36

In that situation,

0:37

not only do we use CT scanning for the bony portion

0:40

of the external auditory canal disease,

0:42

but we often employ MRI scans to demonstrate the extent

0:46

to the skull base and the potential infiltration

0:49

leading to osteomyelitis and cellulitis.

0:53

This is often required because the patient

0:56

presents with cranial nerve palsies.

0:59

With respect to the congenital lesions,

1:02

we talked about external auditory canal atresia as one

1:05

of the most common indications for CT of the external

1:10

auditory canal. External auditory canal atresia,

1:14

however, is often associated with middle ear disease and,

1:18

to a lesser extent, inner ear abnormalities,

1:21

so it does require complete evaluation

1:23

of the temporal bone.

1:25

We also talked about the checklist for patients who

1:28

are being evaluated preoperatively for external

1:30

auditory canal atresia correction.

1:33

And those include making sure you know where the blood

1:35

vessels are, carotid artery and jugular vein,

1:38

making sure you know where the facial nerve is and

1:41

predictably the fact that it may often be anteriorly

1:44

located in the temporal bone,

1:49

potentially in the way of the reconstruction.

1:52

And that we look at the middle ear ossicles.

1:55

It is also important to make sure that the inner ear

1:58

structures are normal because there's no value in

2:02

correcting the external canal atresia if the

2:05

patient either doesn't have a cochlear nerve or has

2:08

abnormalities of the cochlear or vestibule that are

2:11

primarily addressed with sensorineural hearing loss.

2:15

Finally, we talked about soft tissue masses

2:18

in the external auditory canal.

2:20

I mentioned that far and away what you're going to

2:22

see on routine imaging is ceruminous impaction,

2:26

particularly in those patients

2:27

who are totally asymptomatic.

2:29

So you'll see little soft tissue masses in the

2:31

external auditory canal and you'll

2:33

wonder what they are.

2:34

Hopefully, there'll be a little bit of lower density or

2:37

have a little rim of low density around the periphery

2:40

in that plug in the external auditory canal that

2:42

will identify it as a ceruminous impaction.

2:45

However, there are other soft tissue masses that occur in the

2:48

external auditory canal, and we talked about both the

2:50

congenital cholesteatomas using the term "epidermal

2:55

AIDS" as well as acquired cholesteatoma secondary

2:59

to chronic infections that can occur there.

3:01

However,

3:02

there are a lot of other relatively bizarre masses

3:05

which include neurofibromas or schwannomas,

3:08

polyps, ceruminomas which are tumors

3:12

of the ceruminous glands.

3:15

Finally, we talked about malignancies that affect

3:17

the external auditory canal.

3:19

Most of these are going to be cutaneous sources

3:22

of basal cell, squamous cell, or melanoma.

3:25

And rarely, you will have other lesions,

3:28

particularly in the pediatric population where you may

3:30

see a primary rhabdomyosarcoma of

3:33

the temporal bone potentially

3:36

originating in the external auditory

3:39

canal or, for that matter, lymphomas.

3:42

So with this overview of the external auditory canal, I think

3:45

that we can now move on to our next series, which will

3:48

deal with the middle ear cavity

3:50

and finally the inner ear.