0:01

Children with Down syndrome often present

0:04

with hearing loss. Overall,

0:07

conductive hearing loss is more common in Down

0:10

syndrome than sensorineural hearing loss.

0:12

And this is often because the children have external

0:15

auditory canal stenosis as well as a predilection

0:20

for chronic otitis media.

0:22

So that's the most common cause of hearing

0:25

loss in Down syndrome patients.

0:27

However, we published an article on Down syndrome

0:29

in those patients who presented predominantly

0:32

with sensorineural hearing loss.

0:34

And what we found were the following findings:

0:37

lateral semicircular canal hypoplasia with

0:41

a dysmorphic-looking vestibule,

0:43

a small central bone island of the

0:45

lateral semicircular canal,

0:48

higher incidence than in the baseline population

0:51

of superior semicircular canal dehiscence,

0:55

as well as examples of patients who have cochlear

0:58

aperture stenosis and internal

1:00

auditory canal stenosis.

1:01

So all of these are relatively common

1:06

inner ear anomalies that may be associated with Down

1:09

syndrome. And this is a patient with Down syndrome

1:13

to your right.

1:14

What do we see?

1:15

We see a very unusual-looking vestibule which is fused

1:19

into the lateral semicircular canal without a central

1:24

bone island to separate the vestibule

1:27

from the lateral semicircular canal.

1:29

So it all becomes this one fused portion. Here's

1:32

the posterior semicircular canal. In addition,

1:35

this patient shows a very nice example of a patient

1:39

who has cochlear aperture stenosis.

1:41

Normally, this bone would not be there, and it would be

1:45

a more widened communication between the internal

1:48

auditory canal and the cochlea.

1:50

So this patient has both lateral semicircular canal

1:53

hypoplasia and vestibular dysmorphism,

1:56

as well as cochlear aperture stenosis.

1:59

Here's a patient who has Down syndrome,

2:02

who has external auditory canal stenosis

2:04

and atresia on the left side.

2:06

And this was the source of the conductive hearing

2:09

loss that the patient had on the left side,

2:12

but on the right side

2:14

also had cochlear vestibular deformity...

2:17

I'm sorry, on the left side.

2:19

So here's the patient's external...

2:22

sorry,

2:23

inner ear structures on the MRI scan.

2:25

And again,

2:26

this is dilated vestibule, dilated anterior

2:31

turn of the lateral semicircular canal.

2:34

And these two limbs never communicated,

2:36

never

2:38

came together.

2:40

This vestibule fusing with the lateral semicircular

2:43

canal without an intervening bone island is one of the

2:47

abnormalities that are associated with Down syndrome.

2:51

The other thing in this patient was that the patient

2:53

had very tight-looking internal auditory canals.

2:58

So here we have the coronal scan, CT,

3:02

this is the internal auditory canal on the right

3:04

side and portion of it on the left side.

3:07

These are narrowed.

3:08

This would lead to an MRI scan to look for whether or

3:12

not the patient has cochlear nerve hypoplasia

3:15

or absence. And in point of fact,

3:17

this was the same patient in which the

3:21

internal auditory canal was narrowed.

3:23

And you can see that it looks like the nerves

3:25

are kind of fused together here.

3:27

You don't see them outlined by CSF.

3:30

That's because the IAC was narrowed in this individual,

3:33

and in point of fact, there was not a cochlear nerve.

3:36

So cochlear nerve deficiency may occur in isolation,

3:40

but it is one of the findings that

3:42

one can see with Down syndrome.

3:45

And this, obviously, as I said,

3:47

will affect whether or not this patient is a good

3:50

candidate for a cochlear nerve implant as opposed

3:54

to a brainstem implantation for hearing.

3:58

As I mentioned previously, and we saw cases of this,

4:01

the bony labyrinth of the cochlea,

4:03

the modiolus may look normal in some cases, and the

4:08

internal auditory canal may actually look normal.

4:10

And you might still have cochlear nerve deficiency.

4:13

So one does not necessarily lead to the other.

4:18

Cochlear nerve implantation requires the

4:21

presence of the cochlear nerve.

4:23

But you also want to look at whether or not the

4:28

cochlea is obliterated from fibrous occurrence.

4:32

Or sometimes you may have what's called labyrinthitis

4:36

ossificans, where the cochlea is completely filled

4:40

with bone and therefore you cannot insert

4:43

the cochlear nerve implant.

4:44

So when looking for patients who are

4:47

being considered for cochlear implantation,

4:49

we look to see whether there's an infection that

4:51

may lead to a delay in putting in the implant,

4:55

because you don't want to put it into an infected

4:58

ear and then draw the infection into the inner ear

5:02

structures in the cochlea, whether or not they have

5:04

otospongiosis, which we'll talk about shortly.

5:07

Facial nerve dehiscence,

5:08

cochlear dysplasia, and a large endolymphatic sac,

5:11

which can lead to a CSF leakage during the

5:14

implantation of the cochlea and to make sure that the

5:17

internal carotid artery and the jugular

5:19

bulb are in the normal position,

5:20

so that inserting the cochlear implant,

5:23

you don't hit a vascular structure.