0:00

So, how do we differentiate metastases

0:03

with restricted diffusion versus

0:04

multiple embolic strokes?

0:07

So first of all, metastases that may have

0:09

restricted diffusion include those from

0:11

lung, breast, colon, testicular,

0:13

and renal cell carcinoma.

0:14

The pathophysiology is hypercellularity

0:17

or dense cell packing can also be from

0:20

liquefactive necrosis or hemorrhage.

0:22

Differentiating features from emboli.

0:24

Remember, when you have an acute embolus,

0:26

you don't have enhancement for five days to a week.

0:30

Metastases will enhance.

0:32

Acute emboli don't have surrounding edema.

0:35

Metastases tend to have extensive

0:37

surrounding edema and small acute

0:39

emboli cannot have hemorrhage,

0:41

whereas metastases may have hemorrhage,

0:44

especially melanoma and renal cell carcinoma.

0:47

One caveat is that septic emboli may have

0:51

all the features of metastases

0:53

such as early enhancement, edema,

0:56

and hemorrhage.

0:57

These are images of a 55-year-old with

1:01

lung carcinoma, who had a headache

1:05

and acute mental status changes.

1:09

These are the diffusion-weighted images on the top left.

1:12

And when we look at them,

1:14

we see multiple foci with restricted diffusion.

1:18

And then, the ADC maps are next to them

1:21

and you can see these areas with restricted diffusion

1:23

are bright on DWI and dark on ADC.

1:26

Here's another big focus in

1:28

the right frontal lobe.

1:29

And there's a big focus at the vertex.

1:33

And so, how do we know whether these are

1:36

metastatic disease or whether

1:39

these are multifocal emboli?

1:41

So, there are some clues here.

1:44

So, let's look at this big lesion in the

1:46

right frontal lobe.

1:48

We can see that it's got restricted diffusion,

1:50

but there's some enhancement there.

1:52

Now, you shouldn't see enhancement with an

1:54

acute embolus, that's not going to

1:55

happen for five to seven days.

1:58

Same, that's true with this lesion.

2:00

This one enhances as well.

2:05

How about this periatrial lesion?

2:07

That one also enhances and you'll notice that

2:09

has a little bit of rim enhancement.

2:11

Acute emboli shouldn't enhance and they shouldn't

2:14

have rim enhancement.

2:14

So, that's making me think that,

2:16

wow, these might be metastases.

2:18

There's another small one

2:20

in the right insular region,

2:23

and additional lesions as you can see.

2:25

Now here's another clue, this lesion at

2:27

the vertex has got rim enhancement.

2:29

It's got some restricted diffusion.

2:34

It's bright on DWI, dark on ADC.

2:36

But look at all this surrounding FLAIR hypertensive.

2:39

That's extensive vasogenic edema.

2:42

And that has facilitated diffusion

2:44

as you'd expect edema to have.

2:46

So, all of these things, enhancement,

2:49

surrounding vasogenic edema,

2:52

some actual rim enhancement,

2:55

are all suggesting metastatic disease.

2:57

Now, there's one more image that I'd like to

2:59

show you and that is the susceptibility

3:03

weighted image, and you can see this

3:05

lesion at the vertex has susceptibility

3:08

consistent with hemorrhage, and an acute

3:11

bland embolus wouldn't have

3:13

hemorrhage early on.

3:16

And here's another lesion in the

3:18

cerebellum that has hemorrhage.