0:01

So this patient presented with numbness but also

0:09

clinical symptoms that were

0:11

involving the fifth nerve.

0:13

So the initial clinical suspicion in this

0:16

particular case was a schwannoma,

0:18

but not involving the left cerebellopontine angle,

0:21

but involving the left trigeminal nerve.

0:25

So what we're going to do is take our image

0:28

analysis, if you will, to the next level.

0:31

And how do we analyze this particular case in

0:35

order to come up with the proper diagnosis?

0:37

So clinically,

0:38

the patient was felt to have

0:39

a fifth nerve schwannoma.

0:41

So on the top left corner here is a non-contrast T

0:44

one-weighted image. And if you look very closely,

0:47

we can see this lenticular-shaped mass that's

0:50

involved in the left cerebellopontine angle.

0:52

And what I'd like to do is I'd like to draw a line

0:55

down the middle and compare one side to

0:57

the other side. Because remember,

0:59

the head and neck tends to be a relatively symmetric

1:01

structure. So when we look at the uninvolved side,

1:04

we can see the internal auditory canal here.

1:07

We can see the porous Acousticus here,

1:08

and we can see the cerebellopontine angle.

1:11

We also very closely and carefully can see this

1:14

adjacent CSS. Now, on the patient's left-hand side,

1:17

we can see this large mass here involving

1:20

the left cerebellopontine angle.

1:22

So we know that there's something there.

1:24

When we look at the contrast-enhanced study,

1:26

what we see is this mass is homogeneously enhancing.

1:29

But what are the things that we talked about that we

1:32

need to think about in order to make the proper

1:35

diagnosis and separate a vestibular schwannoma

1:39

from a meningioma? Well, first of all,

1:41

number one is an intraaxial or extraaxial.

1:43

It's extraaxial. Number two,

1:45

what's the relationship of the mass with the dura?

1:48

And here we can see that this mass has an obtuse

1:51

angle with the dura. So this is our dural tail.

1:53

So number two, there's a dural tail.

1:56

Number three, here's our internal auditory canal.

1:59

Is there a substantial component of this mass

2:02

extending into the internal auditory canal?

2:05

And the answer is no.

2:06

Maybe there's a little smidgen here,

2:09

but the majority of this is involving

2:11

the left cerebellopontine angle.

2:13

So now this tells us that we're probably

2:15

dealing with the meningioma.

2:17

When we look at the T2-weighted sequence,

2:19

this is the heavily T2-weighted sequence,

2:21

and we can see that the signal

2:23

is isointense to the brain.

2:25

So now we're really sure that we're dealing

2:27

with the meningioma. But remember,

2:30

the clinical symptoms were along the fifth nerve.

2:33

So we've already cleared the 7th-8th nerve

2:35

complex on the left-hand side.

2:37

But how do we explain the patient's symptoms?

2:41

Because I remember talking to the ENT surgeon,

2:43

they were quite sure that this was a trigeminal

2:45

schwannoma. Well, the reason is the following.

2:48

It's the normal spread pattern of

2:50

this particular meningioma.

2:53

If we draw our line down the middle, pair

2:55

one side to the other side,

2:56

especially when we do it on the

2:58

contrast-enhanced study.

3:00

What we see here is this densely homogeneously

3:03

enhancing mass that is just lateral to the carotid

3:06

artery. And on the uninvolved side,

3:09

we can see the carotid artery here.

3:11

And this area right here,

3:12

just lateral to the carotid artery in

3:14

the cavernous sinuses Meckel's Cave.

3:16

We can see that this mass is extending

3:18

anteriorly in Meckel's Cave.

3:20

When we look at the coronal T1

3:22

weighted image with contrast,

3:24

we draw a line down the middle compared to the

3:26

involved side with the uninvolved side.

3:29

The normal anatomy is that we see this little

3:31

circumferential enhancement right here.

3:34

This enhancement is the venous plexus that indicates

3:37

where the fifth nerve ganglion is.

3:39

And surrounding this is low signal, and that

3:42

is the CSF that defines Meckel's Cave.

3:45

In this particular case,

3:46

this tumor extended anteriorly,

3:49

extended along the fifth nerve and involved Meckel's

3:52

Cave. And just to confirm the diagnosis,

3:55

this is the coronal heavily T2-weighted images.

3:58

And when you do your imaging sequence just right,

4:01

remember the end goal of imaging is to see the

4:04

anatomy. You have to see that anatomy.

4:07

And when we look at the normal side,

4:09

we can see these little dots right here.

4:11

And these little dots are the small little

4:14

neurofibrils of the fifth nerve.

4:16

So this is the normal neural anatomy of the fifth

4:20

nerve in Meckel's Cave. And on the involved side,

4:23

you cannot see those small little dots.

4:26

And this is because the meningioma has completely

4:30

involved Meckel's Cave. So in summary,

4:33

this is a meningioma involving

4:35

the cerebellopontine angle.

4:37

But instead of presenting with

4:38

dizziness and hearing loss,

4:40

this meningioma extended anteriorly

4:43

into Meckel's Cave.

4:44

And this patient presented with symptoms

4:47

involving the fifth nerve.