0:01

I just want to remind the attendee, the student,

0:06

that it's very important that you look at the T1

0:10

weighted images of the carotid artery when

0:14

looking for a potential clot in the wall.

0:18

These will be highlighted if you perform T1

0:21

weighted with fat suppression. Here is an example.

0:25

A patient has a normal internal carotid

0:28

artery on the right side.

0:30

On the left side, you see a carotid artery with

0:33

decreased luminal diameter as well as a bright signal

0:38

intensity clot associated with the dissection.

0:44

This was a patient who presented

0:45

with Horner's syndrome.

0:48

Notice once again that the soft tissue that resides

0:52

just anterior to the carotid sheath represents the

0:56

musculature of the stylopharyngeus, styloglossus,

0:59

stylohyoid muscle, and/or the posterior

1:03

belly of the internal carotid artery.

1:06

This next case is an example of the carotid web.

1:12

So on this image, you can see the presence of a small

1:19

area of linear hypointensity within the lumen,

1:25

which is bright in signal intensity on this MRI scan.

1:31

And that same area is low in density on the CTA.

1:36

So this represents an example of a carotid web.

1:42

Now, initially, people thought that maybe carotid

1:45

webs were just a normal variant,

1:48

but it has been shown in recent literature that the carotid

1:51

webs do increase the rate at which

1:54

you may see a thrombus and/or stroke.

1:59

So this is from...

2:01

very recently, May 2021 in JAMA

2:05

Neurology showing examples of these small

2:09

carotid webs on multiple patients.

2:12

And out of these patients,

2:14

five out of 30 with a carotid web had a recurrent stroke

2:20

compared to a much smaller percentage that did not

2:24

have a carotid web who had previous strokes.

2:26

So the hazard ratio is around five for the

2:31

potential for an additional stroke,

2:33

if you've had a previous stroke and

2:35

you have a coexistent carotid web.

2:39

Let's talk a little bit more about

2:41

dissection and strokes.

2:44

Just because you have a carotid dissection does not

2:46

mean that you're going to progress to a stroke.

2:50

Fifty percent of patients with internal carotid artery

2:53

dissection presented with a stroke or TIA,

2:58

but with the dissection,

3:00

you may have asymptomatic dissection. In those

3:04

patients who are asymptomatic and present,

3:07

for example,

3:08

just as an incidental discovery

3:11

during a trauma workup,

3:12

the risk of stroke is only 1.25% over the baseline,

3:17

and that risk is usually in the first two weeks.

3:20

So what do we do with a patient who has a dissection

3:24

at Johns Hopkins that is incidentally found

3:27

after a motor vehicle collision or a fall?

3:29

So these patients are generally treated

3:32

with antiplatelet drugs,

3:34

Aspirin and Plavix, for the first two weeks

3:36

and then if they remain asymptomatic,

3:39

those antiplatelet drugs are tapered off.

3:42

So again,

3:44

the risk is predominantly in the short period of time

3:47

immediately after the incident that led

3:50

to the dissection. Remember, however,

3:53

that although we're talking about the carotid sheath,

3:55

the most common dissections in the neck are

3:57

actually involving the vertebral arteries,

3:59

and these are frequently associated with

4:01

cervical spine fractures. Now,

4:04

what about the patient who has a dissection and

4:09

is given the antiplatelet drugs

4:11

but proceeds on to a stroke?

4:14

In those patients who have had an episode of

4:18

stroke while on the antiplatelet drugs,

4:23

there are two choices that are contemplated.

4:26

One is to fully anticoagulate the patient

4:30

and give them coumadin, for example.

4:33

But the other option is to put in a stent to correct

4:38

the primary process, which is the dissection.

4:42

Here's a study from 2003.

4:45

The most common abnormality identified for dissection

4:48

is irregularity of the lumen, then tight stenosis,

4:53

what's called a "rat's tail" stenosis,

4:55

and then finally complete occlusion.

4:57

You see that this is almost one-third,

4:58

one-third. Minor irregularity of the lumen,

5:01

a marked narrowing on stenosis of the lumen, or a

5:05

complete occlusion. Of these, pseudoaneurysms

5:09

were seen in six patients.

5:10

So 5% of the patients who had dissection

5:14

and stroke developed a pseudoaneurysm.

5:17

And these dissections generally occur in the

5:21

extracranial internal carotid artery rather than the

5:24

intracranial internal carotid artery or extending

5:28

from extracranial into the intracranial space.