0:00

We're focused on the MR appearance of meningiomas

0:03

as they relate to different pulsing sequences.

0:06

I'm going to start out with a sagittal,

0:08

garden variety T1-weighted image.

0:10

Here's our extra-axial mass in this 43-year-old

0:13

man with left-sided weakness.

0:16

It's compressing the corpus callosum downward, and it's

0:20

pretty iso-intense with the adjacent gray matter,

0:23

a little darker than the white matter, better,

0:25

but it's very sharply marginated,

0:27

so it doesn't infiltrate the surrounding tissues.

0:29

And it has this nice hypointense pseudocapsule around

0:33

it which consists of fibrous tissue and some dura.

0:36

Now, this is a meningioma.

0:37

It's a large falx meningioma.

0:39

So here's your axial T2,

0:41

and that demonstrates the typical feature of meningioma,

0:45

which is that it's iso-intense, rather bland-looking,

0:48

it's a little bit heterogeneous inside,

0:51

and sometimes you can see little areas of microcyst

0:53

formation. In this case, not so much.

0:56

By the way, uncommonly, you can get macrocyst formation.

0:59

Oh. CSF-like, which can be a little bit confusing.

1:02

This one pushes over the falx in the midline,

1:06

but it's typically very similar to brain parenchyma.

1:09

This one a little brighter than the adjacent cortex,

1:11

but pretty darn close. Then we move over to the FLAIR.

1:15

Typically on the FLAIR,

1:17

the meningioma is going to be hyperintense relative to

1:20

brain and even a little bit hyperintense

1:22

relative to the cortex. Not too much.

1:25

But note the vasogenic edema around the lesion.

1:29

Now, this vasogenic edema pretty calm, not so extreme,

1:33

but it can be really extreme.

1:34

And you and I have both seen young residents looking at

1:37

these cases when the edema is extreme and the swelling

1:40

of the brain and mass effect is profound.

1:42

People,

1:42

first thing they say is GBM (Glioblastoma multiforme).

1:45

And you certainly don't want to do that.

1:47

You want to get in the habit of identifying

1:49

that this thing is attached to the falx,

1:51

that you don't have brain parenchyma

1:53

along its deep margin.

1:54

So there is buckling of the white matter and gray matter

1:57

over top of the lesion, but not underneath.

2:00

There are displaced vessels.

2:02

Don't let the vasogenic edema, especially on the FLAIR,

2:05

dissuade you from the correct diagnosis.

2:08

Now, let's keep going, shall we?

2:10

Let's pull down our ADC map and our diffusion-weighted

2:15

image. So on the left is our diffusion image.

2:17

And there isn't really much diffusion restriction.

2:20

There's a little bit,

2:21

and the reason is it's a very firm lesion.

2:24

It's a desmoplastic lesion.

2:27

So you're going to see a little bit of diffusion

2:29

restriction, but not to the degree that you'll see with,

2:31

say,

2:32

a medulloblastoma where they're really

2:34

heavily diffusion restricted.

2:35

And these are also frequently desmoplastic lesions.

2:39

So some similar diffusion characteristics

2:41

to medulloblastoma, but not as profound.

2:44

And with the lesions that are more cystic or a little more

2:47

loose-looking, you may have no fusion restriction at all.

2:51

Here's the ADC map.

2:53

And notice that it's not black like you would expect

2:57

with really strong diffusion restriction.

3:00

We don't have a spec image here, a spectroscopy image,

3:03

but one characteristic of meningioma that I'll

3:05

bring to your attention is they get elevated.

3:07

Alanine, so if you're taking a neural specialty exam,

3:10

that's one you ought to be aware of,

3:12

whereas one of the look-alike schwannoma will

3:14

have elevation of Taurine and GABA.

3:16

So we'll set that aside, that's a little bit more advanced.

3:20

Then we'll move on to the next pulsing sequence,

3:23

which is the T1,

3:24

and I want to bring that up alongside the gradient echo.

3:28

So I got T1 and GRE.

3:30

Now, on the T1,

3:30

there are some little speckly bright areas,

3:33

but they're on the periphery,

3:34

so those are not areas of hemorrhage,

3:35

even though these can bleed very uncommonly.

3:38

These are areas of slow compressive flow in the adjacent

3:42

blood vessels that are draped over the lesion.

3:44

And you can see they're a bit darker on the gradient echo,

3:48

but I'm showing the gradient echo because of this twinkly

3:51

speckly irregular low signal intensity character of

3:56

somatomatous calcifications in meningioma. Now,

3:58

we know 20% of

3:59

them will have visual calcifications on CT macrocalcifications.

4:04

But it's really common when you section them to see some

4:06

microcalcifications in meningioma, and they're best seen on

4:10

GRE or susceptibility-weighted image such as SWAN

4:14

or blood-sensitive imaging. Then finally,

4:17

I go over to the coronal T2,

4:20

which shows the same characteristics

4:22

that we saw on the axial.

4:23

This is a very beautiful T2 that reemphasizes

4:26

the isointensity with the brain parenchyma,

4:29

the draped vessels around the lesion,

4:31

the buckling of the cortex and white

4:34

matter around the lesion.

4:35

There's no brain parenchyma on the

4:38

falx side of the lesion.

4:39

We have a beautiful CSF cleft of this large falx

4:43

meningioma pushing the ventricular system on down.

4:47

And for those of you that are observing very carefully,

4:49

yes, there is left-sided odontoid air cell disease.

4:53

Now, I want to turn to you in this next vignette and talk about

4:56

the vascular enhancement characteristics of meningioma.

4:59

So let's move on, shall we?

5:00

Sure.