0:01

This is an MRI of the brain

0:02

in a 17-year-old with sensorineural hearing loss,

0:04

and as we look through the images on this

0:08

axial T2-weighted image, we see a lesion

0:12

in the right cerebral pontine angle cistern.

0:14

It's relatively hyperintense

0:16

on T2-weighted imaging.

0:18

If we go to the Fiesta imaging, which is a

0:22

balanced steady-state free procession technique,

0:24

which goes by names such as CIS on other

0:27

vendors, we see this lesion, not only facing

0:32

the cerebral pontine angle cistern, pushing on the

0:36

lateral aspect of the right middle cerebellar

0:37

peduncle, it is within the internal auditory

0:42

canal, and it expands the porous acousticus.

0:46

The porous acousticus is the opening of the

0:48

internal auditory canal, and it's much wider.

0:51

If we compare to the contralateral side.

0:54

This is a normal appearance of the porous

0:56

acousticus and a normal caliber of the

0:59

internal auditory canal post-contrast imaging.

1:05

shows us this lesion enhances.

1:07

There's fairly homogeneous enhancement.

1:10

There's slight heterogeneity.

1:13

It's a very circumscribed lesion.

1:16

And as I mentioned, it expands the internal

1:19

auditory canal and the porous acousticus.

1:23

The expansion of the porous acousticus

1:27

and internal auditory canal is strongly

1:30

suggestive that this lesion originated

1:33

within the internal auditory canal.

1:35

A lesion that begins in the cerebellar

1:36

pontine angle cistern is less likely

1:39

to expand the internal auditory canal.

1:43

The most likely entity for this on

1:46

imaging is a vestibular schwannoma.

1:49

That is a schwannoma of the vestibular nerve.

1:52

Now, clinically, people often refer

1:55

to these as acoustic neuromas.

1:57

Why is that?

1:58

Because they present with hearing loss,

2:03

oftentimes, and that hearing loss is not due

2:06

to this lesion being within the cochlear nerve,

2:09

but it is actually a secondary effect of mass

2:13

effect from the lesion on the cochlear nerve.

2:15

As evidenced by just the filling and

2:18

expansion of the internal auditory canal,

2:20

we can surmise that there's going to

2:22

be mass effect on the cochlear nerve.

2:25

So, this is an isolated right

2:28

side vestibular schwannoma.

2:30

It shows all the characteristic

2:32

features of a vestibular schwannoma.

2:35

One additional thing of interest, if

2:37

we look at FLAIR imaging, it would

2:40

compare to the T2-weighted image.

2:42

If we look on the left side, we can

2:44

see the hyperintense signal of the

2:47

endolymph and perilymph within the

2:49

cochlea and the vestibule on the left.

2:52

And there's predominant suppression

2:56

of that signal on FLAIR imaging.

2:58

In the right cochlea, we see absence

3:01

of FLAIR suppression of signal,

3:03

suggestive of proteinaceous fluid.

3:05

Same within the membranous labyrinth.

3:08

So, because the vestibule and cochlea

3:10

have proteinaceous fluid in it, that

3:12

is a sign oftentimes that there is

3:16

a lesion originating from one of the

3:18

nerves extending into the inner ear.

3:20

In particular, in this

3:21

case, the vestibular nerve.

3:24

As opposed to a cerebral pontine angle

3:26

meningioma, which is less likely to extend

3:29

into the porous acousticus, less likely

3:31

to expand the internal auditory canal,

3:33

and less likely to result in proteinaceous

3:36

fluid within the membranous labyrinth.

3:40

So, this is an isolated vestibular schwannoma.

3:44

If this patient has bilateral vestibular

3:46

schwannomas at some point down the

3:48

road, that would be, meet the diagnostic

3:51

criteria of neurofibromatosis type 2.

3:54

If this patient had a first-degree

3:56

relative with known neurofibromatosis

3:59

type 2, a single vestibular schwannoma

4:01

would reach the imaging criteria for

4:04

diagnosis of neurofibromatosis type 2.

4:08

A few imaging features to be aware of.

4:13

So looking at this balanced steady

4:14

state free procession imaging, where

4:16

the lesion is predominantly hypointense and CSF is hyperintense.

4:18

This is pre-contrast.

4:21

People often refer to this as a heavily T2-

4:23

weighted image, which tells part of the story.

4:25

But this is a post-contrast version of the same

4:34

image, we can see that the lesion enhances.

4:37

Just as it does on T1-weighted imaging,

4:40

that is because these balanced steady-state

4:41

free procession images have a T1 component.

4:45

That is something that can be used to

4:47

our advantage when evaluating lesions,

4:49

and it gives a very high-resolution

4:51

evaluation of some of the components.

4:54

So while people refer to them as heavily T2-

4:57

weighted images, they have a T1 component.

5:00

And so don't forget that there can be

5:03

a benefit to performing these images.

5:06

Pre-contrast and post-contrast.