0:01

Let's evaluate this patient who has bilateral

0:04

congenital sensorineural hearing loss.

0:07

So as always,

0:08

I'm going to start with the external auditory canal

0:10

and make sure that there's no atresia of it.

0:13

There seems to be a bit of wax in this person's

0:17

external auditory canal, on the left side.

0:19

I'll next look at the middle ear ossicles, and we have

0:22

our normal ice cream and ice cream cone, and then the

0:25

parallel lines of the neck of the malleus

0:28

and long process of the incus.

0:30

And we see the incudostapedial joint, and we have

0:33

seen very nicely the footplate of the stapes here

0:36

on the right side, and on the left side,

0:40

similar anatomy with the footplate of the stapes

0:43

inserting in the oval window.

0:46

So the oval window looks good.

0:48

And then I move to the inner ear structures.

0:51

Having cleared the middle ear structures again,

0:54

what's our most common cause of congenital

0:56

sensorineural hearing loss?

0:57

It's enlarged vestibular aqueduct.

0:59

So as we look at our vestibular aqueduct,

1:02

we see this massive enlargement of the vestibular

1:05

aqueduct when we compare it to the lateral

1:08

semicircular canal caliber.

1:09

And we see that that's present actually bilaterally

1:13

with a very large vestibular

1:15

aqueduct on the left side,

1:17

which is three to four times larger than the caliber

1:20

of the lateral semicircular canal or

1:22

the posterior semicircular canal.

1:25

Having looked at that and identified it,

1:28

we want to make sure that we look for the other

1:30

potential findings that are associated

1:32

with an enlarged vestibular aqueduct,

1:34

and that is incomplete partitian type 2.

1:38

Now, the enlarged vestibular aqueduct can occur in

1:41

isolation and may be a source of congenital sensorineural

1:45

hearing loss in and of itself.

1:48

However, it does have that association with incomplete

1:51

development of the cochlea.

1:53

As we look at the cochlea on the left side,

1:55

we identify the round window and

1:58

the basal turn of the cochlea.

2:00

And then we come into this bulbous area which is

2:05

not separating into middle and apical turns.

2:09

And this is that Mondini malformation that is

2:14

associated with the endolymphatic sac enlargement

2:17

in incomplete partitian type 2.

2:20

On the contralateral side, the left hand side,

2:22

we have a similar finding.

2:24

We have a good basal turn,

2:25

we've got some development of the modiolus,

2:28

but at the middle and apical turns we really don't

2:31

have any of the bony separations of these turns.

2:34

And hence we can make the diagnosis

2:36

of incomplete partitian type 2.