0:00

Welcome to MRI online.

0:02

Non-glial tumors.

0:03

We're talking about extra-axial lesions.

0:05

To start,

0:06

I'm Dr. Stephen Pomeranz, neuroradiologist.

0:08

A younger, better-looking, smarter version.

0:11

Sitting next to me, Ben Laser, also a neuroradiologist,

0:14

and we're starting out with this 76-year-old lady

0:17

who's got a known mass.

0:18

She could have

0:20

although that wasn't part of the history.

0:22

But we do have a lesion in the olfactory groove.

0:24

And being a little smarter and a little younger,

0:28

how would you evaluate this lesion at first glance?

0:31

So, when looking at a case like this,

0:32

the first thing that I tried to look at is,

0:35

where is the lesion located?

0:36

So the location of the lesion is paramount to finding

0:41

out or giving a good differential or a diagnosis.

0:44

So in this case, when you're looking at this lesion,

0:46

is this lesion intra-axial or extra-axial?

0:49

So there are several different signs that you can use to

0:53

help make you determine or help you determine

0:55

where this lesion is.

0:56

So, for example,

0:58

one of the...

0:59

one of the best lesions...

1:01

one of the best ways to determine

1:03

if this is intra-axial or extra-axial

1:04

is looking at the T2 image.

1:06

One thing that you see is you see a mass with

1:09

hyperintense T2 signal surrounding it.

1:11

So, one of the signs is called the CSF cleft sign.

1:14

And I think this lesion on the right panel

1:18

demonstrates that...

1:19

You think this is it?

1:20

This bright, brightish area.

1:21

So that would be the CSF cleft sign.

1:24

The other thing that you can see on this same image is

1:27

the cortex is actually buckled, so it's being pushed.

1:30

So that gives you high suspicion or tells you that this

1:33

lesion is extra-axial and not within the brain.

1:36

So, you're talking the cortex of the parenchyma,

1:38

not the cortex of the bone?

1:40

Yes, the parenchymal cortex.

1:42

Sure.

1:42

And, you know,

1:44

another thing that might be in this cleft,

1:45

besides this sort of rim of CSF,

1:48

sometimes you'll have a little vessels

1:49

they may wrap around the lesion.

1:51

Sometimes you'll be able to see a sort of

1:54

a fibrous rim and a thick area of dura,

1:57

which makes a dark interface with the adjacent cortex.

2:00

And classically,

2:01

the buckle sign was originally described with white matter

2:04

that buckles around the lesion, but doesn't come 360 degrees

2:08

around the lesion.

2:09

So when you have cortical buckling,

2:10

you also have white matter buckling.

2:12

But you're right.

2:13

The first thing that any resident radiologist fellow

2:17

should do is decide,

2:18

is this intra or extra-axial?

2:19

And clearly this one is extra-axial.

2:22

No doubt about it.

2:24

So, we've got an extra-axial mass.

2:26

Where would you put it?

2:27

So, it's sitting actually on the floor of the anterior cranial fossa.

2:31

It's right in the olfactory groove.

2:33

So this would be considered an olfactory groove process or lesion.

2:37

Right.

2:38

And then as you go back,

2:39

you run into structures like the anterior clinoids in front

2:42

of the pituitary and the planum sphenoidale

2:45

and limbus sphenoidalis,

2:46

and then the olfactory groove.

2:47

That's kind of the transition in here.

2:49

And I'm not so much interested in you learning that anatomy,

2:52

but it is an olfactory groove mass.

2:54

It's extra-axial, and it has to be a meningioma, right?

2:56

Mm-hmm.

2:57

So, let's just briefly talk about,

2:59

in the next section,

3:01

the MR appearance of meningiomas.

3:04

Now that we've established that this cleft sign is a sign

3:08

of an extra-axial lesion.

3:09

Let's move on, shall we?