0:01

This was a young patient who had conductive

0:04

hearing loss and this was in the left ear.

0:07

So as we scroll up,

0:08

we'll just look at the anatomy on the right side.

0:10

So we have our nice looking head of the malleus

0:13

with the short process of the incus,

0:15

the ice cream and the ice cream cone.

0:17

We see the little muscle that is attaching from the

0:21

cochleariform process to the neck of the malleus

0:24

representing the tensor tympani muscle.

0:27

We have the parallel dot of the neck of the malleus

0:31

and the long process of the incus and then

0:33

the incudostapedial joint and the stape.

0:36

At the oval window, we have the round

0:40

window niche and the cochlea.

0:42

And then we have the sinus tympani pyramidal

0:44

eminence and facial nerve recess with

0:47

the facial nerve just behind it.

0:49

And the anatomy here is all looking really good.

0:54

Let's go to the symptomatic side.

0:56

I just want to point out here the endolymphatic sac,

0:59

which is this tiny little linear structure.

1:02

It should be smaller in size than the semicircular

1:05

canals and it is indeed in this patient.

1:09

Let's look at the endolymphatic sac on the right side.

1:13

So on the right side, we see erosion.

1:15

So this bone is irregular.

1:18

It's corresponding to the endolymphatic

1:20

sac region on the right side.

1:23

On the left side we see also that there is this

1:26

moth-eaten appearance to the bone that's just

1:30

posterior to the lateral semicircular and posterior

1:32

semicircular canal, and it is growing along the plane

1:37

of the petrous portion of the temporal bone

1:41

here. A little bit of opacification

1:43

of some mastoid air cells.

1:45

So this would be concerning in an adult,

1:49

potentially a metastasis.

1:51

It could represent an endolymphatic sac tumor.

1:55

So we know that MRI is useful with regard to

1:58

endolymphatic sac tumors because it has a

2:01

pathognomonic feature of bright signal intensity

2:04

on pre-gad T1. So let's look at that MRI scan.

2:08

So on the MRI study,

2:12

we want to pay attention to our T1-weighted

2:15

sequences. And in this situation,

2:18

we've got the sagittal T1-weighted scan and we

2:21

see a lesion that is affecting the temporal bone

2:25

which has speckled bright signal intensity that

2:29

is not present on the contralateral side.

2:31

So if I make an axial projection on this,

2:35

even though it's a thick section imaging,

2:39

you can see that there is indeed bright signal

2:42

intensity parallel to the plane of the petrous

2:46

portion of the left temporal bone.

2:48

Let's look at it on the post-contrast scans.

2:53

Here's our post-contrast scan.

2:55

We're at the sigmoid sinus junction with

2:58

the jugular bulb and jugular foramen.

3:01

And here we see a contrast-enhancing mass

3:06

which has irregular margination.

3:09

It has that sort of speckled appearance that we

3:12

typically see with endolymphatic sac tumors.

3:15

It's along the plane of the endolymphatic

3:18

sac vestibular aqueduct.

3:19

You can see that on the contralateral side,

3:21

there's nothing analogous to it.

3:23

And this was indeed a patient who

3:25

has an endolymphatic sac tumor.

3:27

Remember to look at the cerebellum because we want

3:31

to make sure there are no contrast-enhancing

3:33

lesions in the cerebellum,

3:35

which would suggest multiple hemangioblastomas

3:38

and in patient who may have von Hippel-Lindau disease.

3:41

So this was a nice example of a relatively subtle

3:45

left-sided endolymphatic sac tumor.