0:00

This next case is another patient who came in this time

0:04

with aphasia, and we have a CT, a CTA

0:09

and a CT perfusion study.

0:12

So let's look at the whole shebang, as we say, on this case.

0:16

So on this non-contrast CT scan, which is the first thing

0:20

that we're gonna be looking at, remember we look at the

0:22

thick sections to see where there's hemorrhage,

0:24

because if there's hemorrhage,

0:26

the ball game is over pretty much for thrombectomy

0:28

and thrombolysis therapy.

0:31

So looking at this case, we don't see anything hyperdense.

0:34

This is a little area of calcification that's

0:38

partial volume averaged,

0:40

but what we do see is an area of low density

0:45

along the perisylvian region

0:47

and in the frontal opercular region

0:49

of the left frontal lobe.

0:52

So now we're looking at imaging for stroke,

0:55

and what we're seeing is loss

0:57

of gray white matter differentiation

1:00

in the left frontal region, as well as in the

1:05

peri-insular region.

1:06

There is something called the insular ribbon sign that is

1:10

where there is low density to the normally bright

1:16

insular density of gray matter.

1:18

So on the right side, we have a slight hyper density

1:22

to the insula.

1:24

On the left side, we have loss of that hyperdense insula,

1:28

as well as a more focal area of low density with loss

1:33

of gray-white differentiation.

1:35

So we know the patient’s had a stroke.

1:37

It'll be unusual for this stroke to be within an hour or two,

1:41

because, in the acute setting,

1:43

often we do not see changes in the density of the brain

1:47

until we’re talking at the three to six

1:48

or more hours of age.

1:52

But in this case, we see the stroke initially.

1:57

So the next section of the study is going to be

2:01

the CTA with the CT perfusion.

2:05

What are we looking for? We’re looking

2:06

for an occluded blood vessel that might account

2:09

for this stroke, but we’re also looking

2:11

to see whether this is the only area

2:14

of the brain that is at risk for infarction,

2:18

or whether this is just the tip of the iceberg,

2:21

in which case, maybe there’s a lot more brain tissue

2:24

that is in danger of infarct that we could still save.

2:28

So let’s go to the CTA for the purposes of this review.

2:33

Again, I’m going to stick with the thick section images.

2:37

Normally, I would be more reliant on the thin section images,

2:40

but just for time considerations, we’re going

2:43

to look at the thick sections.

2:45

So here is our study.

2:48

I’m gonna window this so it’s a little bit better

2:50

for a CTA.

2:54

And we’re at the aorta,

2:55

and we know that it’s on the left side.

2:57

So let’s focus on

2:58

the origin of the left common carotid artery,

3:02

and we see it come off.

3:04

This is the cervical portion

3:05

of the left common carotid artery.

3:06

We're just following that blood vessel upwards.

3:10

We come to the carotid bifurcation, and it looks very clean.

3:13

Here is the external carotid artery

3:16

and the internal carotid artery.

3:18

They both look clean.

3:20

The left internal carotid artery courses superiorly

3:24

to the petrous portion.

3:25

Here we are in the petrous bone.

3:27

That portion of the blood vessel looks a little bit narrowed

3:32

compared to the right side.

3:34

Again, must confirm this on the high-resolution images.

3:38

I'm gonna magnify this so it is a little bit better seen.

3:42

So we're contrasting the width of the

3:48

left petrous internal carotid artery with the width of the right

3:52

petrous internal carotid artery, as well

3:53

as its irregular shape.

3:55

So there is some atherosclerotic change here

3:57

as we come into the cavernous internal carotid artery.

4:00

Again, we compare the caliber of the left versus the right.

4:05

It's a little bit narrowed compared to the right.

4:09

We come to the paraclinoid portion

4:13

of the left internal carotid artery.

4:15

That looks good. The M1 segment is open,

4:19

and the middle cerebral artery distal branches here

4:24

look like they’re open on the thick sections.

4:27

And there is that area of absence

4:32

of blood vessels here compared to the right side,

4:35

which may be the occluded pericallosal branch

4:39

of the middle cerebral artery on the left side.

4:44

Just looking quickly at the vertebral arteries,

4:47

they look pretty good coming up.

4:49

No areas of stenosis.

4:51

If we look on the right side,

4:53

and take it from the aorta

4:56

to the right common carotid artery,

4:59

and the carotid bifurcation looks good.

5:01

The right internal carotid artery petrous portion looks good,

5:05

certainly better than the left.

5:07

And the cavernous portion looks good,

5:10

even compared to the left.

5:12

So at this juncture, we're gonna go

5:14

and look at our coronal MIPs.

5:17

Here we see the anterior cerebral arteries,

5:20

two vessels looking good.

5:22

Here is our A1 segment

5:24

of our right middle cerebral M1 segment,

5:26

of the right middle cerebral, A1 segment

5:29

of the right anterior cerebral artery,

5:32

small area of narrowing.

5:34

Here on the left side,

5:37

the A1 segment also shows

5:40

some narrowing distally.

5:43

We'll have to confirm that on the axial M.

5:45

Here's our M1 segment, which looks good.

5:49

And here are our middle cerebral artery branches.

5:53

Let's look on the axial MIP (Maximum Intensity

5:57

Projection) reconstruction.

5:58

And we note that in that area where we saw the infarction,

6:02

it looks like we have a paucity of blood vessels compared

6:06

to the contralateral MIP image.

6:09

So there probably is indeed.

6:12

Let's magnify this so we can convince you of that.

6:18

So right here, we have a vessel,

6:22

which looks like there is narrowing of the vessel

6:25

and possibly a luminal thrombus.

6:28

Here, you can tell it's different in density

6:32

than the more distal portion

6:33

and then the neighboring vessel.

6:35

And when we compare it to the contralateral side, again,

6:38

a lot of times this is not symmetrical,

6:40

but there is something wrong with this blood vessel,

6:43

and it kind of fits where there is the area of infarction.

6:47

So we have a thrombus in one of the Sylvian branches

6:51

of the left middle cerebral artery,

6:53

which is demonstrated here.

6:57

Maybe we can see that on our sagittal images.

7:02

Again, we see this vessel that comes up,

7:04

and it looks like it kind of peters out,

7:07

not showing the distal branches,

7:10

and it's less dense than some of the neighboring vessels.

7:14

So that's likely to be the area

7:17

where the thrombus has lodged.

7:20

The purpose of this study really is not to go over the CTA,

7:23

as much as to show you the CT perfusion.

7:27

So this is the CT perfusion analysis package.

7:31

Most institutions have adopted the

7:34

RAPID analysis package.

7:37

This is a CT perfusion package, which allows you

7:41

to have cerebral blood flow, cerebral blood volume,

7:46

Tmax, and time-to-drain images.

7:49

In this case, what we're seeing here

7:53

is the cerebral blood flow image,

7:58

and we see that there is an area of diminished

8:03

perfusion in cerebral blood flow.

8:07

The lower numbers are gonna be more purple.

8:10

The reddish-yellowish are gonna be the highest values.

8:14

So this is an area of diminished perfusion,

8:16

which is more focal in the left frontal region,

8:16

which is more focal in the left frontal region

8:20

where there was that low density on the CT scan.

8:23

This is cerebral blood volume.

8:26

It too is showing a similar area going out to the cortex,

8:26

It too is showing a similar area going out to the cortex

8:30

where there is diminished cerebral blood volume, indicative

8:34

of an area of infarction.

8:37

The more important thing is the Tmax images.

8:40

The Tmax images are gonna show you what part of the

8:45

brain tissue is at risk for

8:49

potential infarction.

8:51

So although there was that area of existing

8:54

infarction, the Tmax image will show you

8:57

that there is tissue at risk above

9:00

and beyond the area of existing infarction.

9:04

That means that there may be value in trying

9:09

for thrombolysis or thrombectomy.

9:11

If there is a matched deficit of perfusion,

9:16

ischemic tissue, and infarction,

9:18

then there is likely no benefit for going out

9:22

and trying to do a thrombectomy,

9:24

because the tissue

9:26

that is infarcted is the only tissue at risk.

9:28

It's already been infarcted. You're not gonna get

9:30

that tissue back.

9:32

There are other parameters, including the mean transit time

9:36

and the time to drain,

9:36

and the time to drain

9:38

that are calculated in perfusion imaging.

9:41

But for the purposes of analysis by neurology

9:45

and stroke teams, they look at cerebral blood flow,

9:49

less than 30% change, as well as

9:53

Tmax greater than six seconds.

9:56

And you can identify the perfusion

10:01

versus infarction mismatch.

10:04

So this is a nice data set, which identifies that

10:09

there is a blood vessel, a distal middle

10:12

cerebral artery blood vessel, that has a clot within it.

10:15

There is an infarction,

10:17

but there is additional tissue that may be salvageable

10:22

with either thrombolysis or a thrombectomy.

10:25

So we have the non-contrast CT, the CTA,

10:29

and finally, the CT perfusion series.