0:01

So this is about as classic a case as you get.

0:04

If you're not familiar with this lesion, it might be a little bit harder.

0:08

It does have a differential diagnosis. But on this lesion,

0:14

as you see on the pre GAD T one wade scan is bright on the

0:19

pre GAD T one wade scan,

0:21

it's a lesion that is really centered on the petrus apex.

0:26

It's a lesion that is expanding the petre apex and it's a

0:31

lesion that usually displaces the carotid artery in the petre canal.

0:36

When you look, compare the pre gad to the post gadd,

0:40

you really don't see any contrast enhancement. Let's see what uh,

0:46

this'll drop or in my volume. Oh good. Okay.

0:49

So on the T two way scan we have this heterogeneous lesion

0:54

that has areas that are right as well as areas that are dark.

1:00

And uh,

1:00

again that is relatively typical of a cholesterol granuloma.

1:06

So cholesterol granuloma is a lesion that evolves

1:11

largely secondary to hemorrhage in the petri apex.

1:14

And then the foreign body reaction with cholesterol crystals.

1:18

And there's some debate about whether or not this,

1:21

whether the brightness is due to the hemorrhage or due to cholesterol

1:26

material.

1:27

Suffice it to say that usually comes out as a crank case oil type stuff and not

1:32

true blood, but it does have elements of met hemoglobin,

1:36

which is the blood product that is bright one t one way scan.

1:41

Again,

1:42

you often heterogeneous because you have a mixture of deoxyhemoglobin and

1:46

intracellular met hemoglobin as well as extracellular met hemoglobin within the

1:51

lesion. So this is a,

1:55

a relatively pathic monic.

1:57

There is a differential diagnosis and what we know about

2:02

the lesion is that it occurs in aerated petrus apex cells.

2:07

So if we go back in time three years this and we look at the

2:11

petrus apex,

2:12

we would see that there's air in the petru apex on the right side and that's

2:17

where, because of atmospheric processes,

2:19

you can have this weeping of hemorrhage that occurs and then the foreign body

2:24

reaction,

2:24

then more hemorrhage and then foreign body reaction and this thing expands.

2:28

It would not occur on the left side because this left

2:33

petri apex is fully fat and it's not aerated.

2:39

I mean we might look for some aerated cells here if we had a CT scan,

2:43

but at this level, you know, here's our clus, here's a petri apex,

2:48

it's a non aerated features apex.

2:51

So cholesterol granuloma cannot occur in that setting.

2:56

When you have aerated uh,

2:59

Petra air cells,

3:02

you could have a differential diagnosis of a mucus seal of

3:07

the petris apex.

3:10

How would we distinguish a mucus seal which looks like a sinus mucus seal

3:15

for example, uh,

3:17

a mucus seal of the features apex versus a cholesterol granuloma?

3:22

Well,

3:22

what I usually go for is that the mucus seal by and large

3:27

is homogeneous in its signal intensity and this pattern on the T two will

3:32

be very unusual for a mucus seal canker. It's unusual.

3:37

Most of our mucus seals are homogeneously the same signal intensity,

3:42

uh, because of the pro tenacious material.

3:45

So instead of hemorrhage and cholesterol material, uh,

3:49

and foreign body reaction,

3:50

we have hyper protein tenacious material which could be bright on a T

3:55

one and either dark or bright on a T two, but usually homogeneous.

4:00

The third thing that's in a differential diagnosis,

4:03

which I believe one or two of you uh mentioned, is a,

4:07

an aneurysm or a pseudo aneurysm of the internal cryo artery.

4:11

So it's always important to identify the internal

4:15

carotid artery.

4:17

It's usually displaced by the cholesterol granular or a

4:21

mucus seal and doesn't have any irregularity in its wall.

4:26

Is it worthwhile to do A C T A? Well,

4:29

probably the surgeon's gonna want a C T A anyway just to make sure he knows

4:34

exactly where the carotid artery is and in at our institution they do the

4:39

C T A with a three D mode with fiducials on.

4:43

So that way at the time of surgery they have surgical navigation.

4:47

It's nice because this is the bone lesion.

4:49

Things are not gonna move around what the brain does when you take out the tumor

4:53

and suddenly your three D navigation stinks because the anatomy's all

4:58

moved. But this is a bone lesion so it actually would be good.

5:02

So on the C T A you would be able to tell, um,

5:07

here you can see the carotid artery kind of draped over,

5:11

so we're seeing the vascular structure here

5:16

with the gadolinium within it. Um,

5:19

this is another opportunity to use cyst In this case we

5:24

did not, uh, have the cyst imaging, but you know,

5:28

usually you're able to see the artery on the sagittal scan as well.

5:34

And uh, you know, if this has an irregular border or is dilated,

5:39

then a pseudo aneurysm or,

5:42

or with wall thrombus is in the differential diagnosis.

5:45

But this looks like a pretty nice looking carotid flow

5:51

signal. We can look on the other side

5:55

and the carotids there.

5:57

So diffusion weight scan. So, uh,

6:01

what's the value of the diffusion weight scan?

6:03

The diffusion weight scan's gonna be tricky because it's hemorrhage,

6:06

so you know,

6:09

it's heterogeneous like this.

6:12

This is really not restricted diffusion when you have something that's bright on

6:16

the T one and bright on the T two, um, it's going trick you on the um,

6:20

diffusion weight scan.

6:22

So all betts are off on the D W I when you have hemorrhagic products.

6:26

So we often just sort of punt on that.

6:31

Um, epidermoids, so we were talking about diffusion weight scan,

6:35

but epidermoid sometimes you can have the quote unquote white epidermoid that's

6:40

an epidermoid that is bright on a T one weighted image because of the

6:45

protein content within the epidermoid that's in the differential diagnosis.

6:49

So although we say this is pathognomonic with the expansion of the bone

6:56

right on the pre gadd T one and heterogeneous on the

7:01

T two, we do have a differential diagnosis,

7:03

which I've gone through a mucus seal, a pseudo aneurysm of the carotid artery,

7:08

an epidermoid, uh,

7:10

maybe even a lipoma except a lipoma should be homogeneous on the tib.

7:15

So I will go to the article.

7:18

Unfortunately the article did not give a, uh,

7:22

example of a cholesterol granuloma despite the fact that that's a pretty

7:27

common lesion.

7:28

These result from chronic obstruction of air cells with accumulation of the

7:32

secretion producing expansion. Um,

7:35

they should say that this is hemorrhage and M r i shows high

7:40

T one, T two peripheral low single intensity, no enhancement, which is correct.

7:47

Let me just, um, also mention that you can have, uh,

7:51

petris a sitis.

7:53

How do we distinguish petrus a bositis from a cholesterol oma?

7:57

So typically petru a bositis is not bright line T one wave scan.

8:01

Typically petrus a bositis does not cause marked expansion of

8:06

the petrus apex. Petru a bositis,

8:09

the classic history is great Nigo syndrome where you have the eaa,

8:14

you have the fifth pineal nerve pain symptoms and you have a six nerve

8:19

palsy because it may involve the, um, DRES canal and,

8:23

and the sixth nerve. So, uh, that's another thing to consider.