0:01

As I mentioned,

0:02

the enlarged vestibular aqueduct syndrome, or EVAS,

0:08

on CT, is analogous to the enlarged endolymphatic

0:12

sac. You actually see the sac on the MRI scan,

0:15

and this is the most frequent finding in general

0:18

sensorineural hearing loss. Now,

0:20

we've seen examples in the incomplete

0:22

partition type two,

0:24

where it is so associated with abnormal

0:26

malformation of the cochlea. However,

0:29

it may be an isolated finding,

0:32

and it is an abnormality,

0:33

which is typically bilateral, we say,

0:35

in 90% of cases and occurs in

0:39

females more so than males.

0:41

So isolated endolymphatic sac enlargement is an

0:46

anomaly that may be associated with congenital

0:49

sensorineural hearing loss,

0:50

but it also may be seen in conjunction with abnormal

0:53

development of the cochlea in our incomplete

0:56

partition type 2. Here's a CT scan,

0:59

bilateral involvement with enlargement

1:02

of the vestibular aqueduct.

1:04

Here is what we might see on MRI scan.

1:07

On the MRI scan in this individual,

1:10

you see that there is a high signal intensity

1:13

abnormality on our T2 CISS image,

1:17

and this represents the enlarged vestibular

1:20

aqueduct, or endolymphatic sac.

1:22

So we're actually seeing the sac.

1:23

Again, the aqueduct we usually refer to in the CT,

1:27

whereas in MR we're seeing the sac,

1:29

the endolymphatic sac. And these are dilated.

1:32

How do we know they're dilated?

1:33

They're larger in caliber than the semicircular

1:35

canals when we compare to them.

Enlarged Endolymphatic Sac

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