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Dr. Laser,

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This is a 43-year-old man with left

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sided weakness and numbness.

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This is a Sagittal 3D T1 image with contrast,

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and we've got a pretty large mass in the brain.

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What's your first impression of the mass?

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So, the first impression of the mass is that it avidly enhances.

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And then looking at the contours of the mass,

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the structures are rounded.

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You can see that the gray matter,

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which is the dark signal,

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the white matter in this case would be the more lighter

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gray signal contours around the lesion.

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So the first thought to myself is avidly enhances,

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and you have the brain Frankmas,

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actually contouring around the lesion.

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And there's no infiltration whatsoever.

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It's very sharply marginated.

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So even though it's kind of hard to tell.

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And at first glance,

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it looks like you might have white and gray

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matter all the way around the lesion,

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it's highly unusual to have a lesion

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this big that's so well marginated.

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So the fact that it's not infiltrating anything at least

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makes you suspicious that it really is outside

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of the brain in an extra-axial space,

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which you've emphasized repeatedly how important

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it is to document what space the lesion is in.

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So let's call up some other views of the lesion.

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Perhaps the coronal projection might be helpful.

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And I'll bring down the coronal T2.

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I'll give you a Coronal T1 with contrast,

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and I'll bring down an axial non-contrast

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component of the image.

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And now what do you think of the location of a lesion?

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Is it intra-axial or is it extra-axial?

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So now, looking at the lesion,

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you can confidently say that this lesion is extra-axial.

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Why?

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Because of all the different signs that we've talked

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about. For example, the cleft sign, the CSF cleft sign,

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which he's demonstrating right now.

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You have the Cortical buckling and the Cortical

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and white matter buckling sign.

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Right.

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It goes all the way around there,

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but it doesn't circumscribe it.

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Right. It only goes on the outside edge,

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not on the inside edge.

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Correct.

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And you can tell that this lesion is actually

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insinuating itself along the Falx.

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So that also is another sign that tells you that this

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is an extra-axial lesion. Vessels are displaced,

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cortex is displaced. You have CSF surrounding the lesion,

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all determined that this is an extra-axial lesion.

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Yeah. Here are a few displaced vessels.

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Here's some more CSF.

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There's a little vasogenic edema around the lesion.

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And does that preclude the diagnosis of an extra

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axial mass? Not at all.

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A lot of the times,

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these meningiomas can cause really severe vasogenic

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edema and reaction inside the brain.

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Parenchyma, sometimes it can cause none.

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It all depends on the type of tumor,

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and the amount of edema can be very profound.

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There are a few theories on that.

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Some people have postulated there's

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microthrombosis of small veins.

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Some people have suggested that there's micro

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ischemic change from compression.

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There are a number of theories on it,

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but the fact that you have moderate and even marked edema

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does not preclude the diagnosis of meningioma.

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Correct. You've got a nice little dural tail right here,

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which is also part of the diagnosis.

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The signal inside is a little bit twinkly,

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a little bit speckly, if you will.

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And that's okay. That doesn't bother me at all.

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Microcystic change very common in these lesions.

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Lipoid degeneration, not so much common.

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Hemorrhage occurs rare to uncommon, but it does occur,

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even though these are very hard, rock-hard, firm lesions.

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You can also see macrocysts inside the lesion.

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And as we stated, microcysts, but also microcalcifications.

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These calcs are noted histologically as psammoma bodies,

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and they can be little speckly areas of hypo and density.

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Not seen so much in this case,

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but that would be another MR.

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Appearance of meningioma. How about the signal?

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How about the signal on T1 without contrast and T2?

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So on T1,

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you notice right away that the lesion looks exactly

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like the brain parenchyma, the gray matter.

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It's iso-intense to the gray matter.

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On T2, the center of the lesion is heterogeneous,

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but the majority of the lesion is also hyper-intense

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or iso-intense to the gray matter.

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This one is an equilibrium phase MRI.

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But if we did a dynamic MRI with very early, say,

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10 seconds apart dynamic imaging,

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how would the lesion enhance?

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You're married, by the way.

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How would it enhance?

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So they call this the mother-in-law lesion.

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It's very early enhancement,

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so it'd be extremely early arterial phase enhancement.

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It comes early and it stays late.

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So even on delayed imaging,

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the lesion will be extremely enhanced and then they're

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very dense. So that's the typical mother-in-law lesion.

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They arrive early, they stay late, and they're very dense.

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I never heard the very dense part,

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but I certainly wouldn't use that on my own

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mother-in-law for fear of reprisal.

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But that's a very good summary of

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what meningiomas look like.

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Let's take a look at some of the other projections

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before we log out here together.

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Look at the axial contrast-enhanced image.

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You see a little bit of the dural enhancement.

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I'll blow it up a little bit so you have a nice view

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of the C plus T1 and the C minus T1.

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This one's a little unusual in that it's

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actually crossing the Falx now.

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It's not invading the brain on the other side,

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it's still extra-axial, pushing over to the other side.

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So this doesn't violate in any way the white

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matter buckle sign or the buckle sign.

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Here's the white matter buckled around the lesion.

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And then, just to summarize,

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you've got a lot of the other signs of meningioma.

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In this case, you've got the CSF clef sign,

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you've got the displaced vessel sign,

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you've got attachment to the Falx cerebri or to the dura.

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You've got a lesion that is iso-

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intense with the gray matter.

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It's a little bit heterogeneous and it is clearly an extra-

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axial lesion. This a giant convexity falx meningioma.

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Let's move on, shall we?