0:01

In our discussions of patients,

0:02

with down syndrome,

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we open the door to the entity of

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cochlear aperture stenosis.

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Now, cochlear aperture stenosis occurs not just with

0:13

patients with down syndrome, and in point of fact,

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can occur as an isolated anomaly.

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The aperture to the cochlea is abnormal when it's

0:23

less than 1 mm or less than 1.5 mm in narrowing.

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And there have been, as I said,

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a number of different studies looking at

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how to measure the cochlear aperture,

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either oblique to the opening or

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in a true transaxial scan.

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The aperture stenosis may be more predictive of

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the absence of a cochlear nerve than

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internal auditory canal narrowing.

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When the internal auditory canal

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now is more narrow than 2.5 mm,

0:53

we would say that's the definition

0:55

of IAC narrowing.

0:59

And in many cases of patients who have congenital

1:02

sensorineural hearing loss,

1:03

they may have a normal cochlear aperture and have

1:07

it on the basis of other abnormalities.

1:11

Some of these abnormalities may be drug-induced.

1:14

This is a diagram of the different

1:18

types of cochlear hypoplasias,

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and we've seen several of these before.

1:23

So here is the cochlear hypoplasia type 1,

1:28

where one sees the absence of

1:30

development of the cochlea

1:32

and we just have this kind of cystic structure.

1:35

Here is where we see the communication into a

1:38

cochleo vestibulo cystic structure in our what's

1:42

called cochlear hypoplasia type 2,

1:44

but is common in the incomplete

1:47

partition type 1.

1:49

Here we have separation of the

1:51

cochlea from the vestibule,

1:53

but abnormal development of the cochlear

1:55

with only the basal turn really well seen

1:58

and a very rudimentary middle-term

2:02

in our cochlear hypoplasia type 3.

2:04

Our aperture stenoses may be either

2:08

stenotic or completely athretic,

2:10

and that is determined by the degree in which

2:14

there is that narrowing of the aperture less than 1 mm.

2:20

And then we have our corkscrew type of picture that we

2:23

may see within incomplete partition

2:25

type 1 or type 3.

2:27

Here is an example of a patient who had a normal

2:30

cochlear aperture on the left side,

2:32

and you can see this width.

2:34

And if you measure this, you could be over 1 mm,

2:37

as opposed to this patient who has this very

2:41

tight narrowing of the cochlear aperture,

2:43

less than 1 mm in a patient with cochlear aperture

2:47

stenosis on the right side and a normal aperture

2:50

on the left side. As I mentioned,

2:53

in association with the cochlear aperture stenosis,

2:55

you may see narrowing of the internal

2:58

auditory canal, less than 2.5 mm.

3:01

And these two findings would be highly predictive that

3:05

the patient does not have a normal cochlear

3:07

nerve going to the cochlea.

3:10

This is another example of this aperture stenosis

3:13

where you have just a bony block that is

3:16

preventing the nerve from actually

3:18

entering the cochlea.

3:20

And that again would be highly predictive of

3:22

absence of the cochlear nerve on MRI scanning.