0:00

So we'll turn our attention to

0:02

the carotid space, uh, next.

0:04

Uh, and, uh, we'll start by showing

0:06

a representative image of your

0:07

lesion within the carotid space.

0:08

You can start thinking about it in, uh,

0:11

in the meantime, uh, the question is which, uh,

0:15

which of the following cranial nerves is not

0:17

considered part of the suprahyoid carotid

0:19

space: cranial nerve 7, 9, 10, 11, or 12.

0:25

So as I look at the carotid space, the way I like

0:27

to think about it is, and in general, on head and

0:30

neck lesions, is placing the lesion in a space and

0:33

then looking on MRI at the signal, vascularity,

0:37

and what it's doing to the surrounding structures.

0:39

So when I look at this image here, what I

0:41

see is, uh, a lesion situated in the carotid

0:44

space that is T2 hyperintense, and I'm seeing

0:48

that lesion displacing the, uh, internal

0:51

carotid artery anteriorly, and on T2, I do

0:54

see a lot of what looks like flow voids,

0:57

uh, or T2 hypointensity within the lesion.

1:02

So, I'm gonna, uh, ask you

1:04

a couple of questions here.

1:06

One is, what do you think is the

1:07

leading differential diagnosis?

1:09

To, to think of.

1:10

And, uh, number two, how many

1:11

lesions do you guys see on the MRI?

1:14

Uh, and then you, you can write that

1:15

in the chat if you, if you'd like to,

1:20

I can show you the PET right now.

1:23

Uh, and as you know, we're looking at the

1:25

PET, the one, the first question I want you to

1:27

think of is what radiotracer we're using here?

1:30

And how can they tell that?

1:31

And then, uh, obviously the other

1:33

question is how many lesions are present?

1:37

So one thing, you know, when I look at

1:39

radiotracers, and this is a DOTATATE or

1:42

somatostatin receptor, which is predominantly

1:45

used for neuroendocrine tumors, including

1:47

this entity here to differentiate between

1:49

it and another common entity in the

1:51

carotid space: normal physiological uptake.

1:54

And the reason why I can tell that is

1:57

very strong in the pituitary and a variable

1:59

degree of uptake in the carotid or salivary

2:02

tissues and the thyroid, which tend to be

2:04

generally moderate but can be intense.

2:06

And I see a very intense uptake in two areas.

2:09

And this is the, uh, uh, the

2:11

bilateral carotid spaces.

2:13

And this is the benefit of using, uh, the

2:15

DOTATATE PET, because the smaller lesions

2:17

sometimes can be challenging on MRI.

2:19

And as you see here, it might be hard to

2:22

see on the T2, and even when I, uh, look at

2:24

the post-contrast, the contralateral lesion

2:27

might be hard to pick up and can be easily missed.

2:29

So the PET gave us the benefit of, uh,

2:32

detecting those lesions in addition to allowing

2:35

us to differentiate between it and other

2:36

common entities, which we'll discuss shortly.

2:39

The other thing I, uh, always want to

2:41

discuss with the carotid space is location,

2:45

uh, can help us sometimes predict not

2:48

only the pathology, but potentially

2:50

which, uh, component of the carotid space.

2:53

So again, as I'm looking here, I can see

2:56

a significantly arterially enhancing

2:57

lesion, uh, with respect to the muscles.

3:00

And I see the internal carotid artery being

3:02

displaced anteriorly on the contralateral

3:05

side at the bifurcation of the carotid.

3:07

I see a lesion sitting and

3:09

uh, not quite splaying the internal and

3:11

external carotid arteries, but, uh, given

3:14

its size, it's sitting there at the

3:15

bifurcation and you can appreciate that

3:18

very nicely on the sagittal images.

3:22

With the bifurcation.

3:23

Okay, so turning our attention to the

3:27

discussion of the carotid space before we move on.

3:31

So it's always important to talk about

3:33

anatomy and boundaries when we're

3:34

coming up with a differential diagnosis.

3:36

So the carotid space itself is a cylindrical

3:39

space that extends from the jugular foramen to

3:41

the thoracic inlet, and it's divided superior

3:44

and inferior by the hyoid bone and today we're

3:46

turning our attention to the suprahyoid carotid.

3:49

Its contents are in the suprahyoid neck.

3:52

The crown jewel of it is the internal carotid

3:55

artery, uh, and it's located medially and slightly

3:58

more anterior to the internal jugular vein.

4:01

Uh, and those are the two prominent

4:03

vascular structures, and it contains four

4:05

cranial nerves in the suprahyoid neck.

4:08

Uh, there is variability of location of the

4:10

nerves based on anatomical cadaveric sections,

4:13

but this is the most common appearance.

4:15

Cranial nerve nine typically is anterior,

4:18

situated between the two vessels.

4:20

Cranial nerve twelve is typically medial

4:22

posterior to the carotid, and ten and eleven are

4:25

more posterior with a variable location.

4:28

And then along the posterior sheath, there is

4:30

the sympathetic trunk, and anteriorly, there

4:34

is the ansa cervicalis, which forms

4:36

from C1, C2, and C3 nerves, and supplies

4:39

the infrahyoid muscles.

4:43

So based on the internal contents, you know,

4:46

hence the differential for lesions can be formed,

4:49

uh, with respect to the space.

4:52

So the, so the margins anteriorly, anterior

4:55

to the carotid, uh, there is the masticator

4:58

and parapharyngeal space; medially, there

5:01

is the retropharyngeal space that

5:04

Dr. Guzman discussed laterally.

5:05

There's a parapharyngeal space, which we'll discuss

5:07

subsequently, and posteriorly there is

5:09

the paravertebral muscles, uh, and

5:12

their, uh, their components.

5:14

So speaking about the differential diagnosis,

5:18

uh, this lesion is, uh, a paraganglioma and, uh,

5:21

talking a little bit about paragangliomas of the

5:23

head and neck, they're typically rare entities

5:25

of tumors in the head and neck and constitute

5:28

a little bit more than 0.5%.

5:30

Now, unlike a lot of other areas in the

5:32

body, they're predominantly parasympathetic.

5:34

'Cause as you know, paragangliomas can

5:36

be sympathetic and parasympathetic.

5:37

The sympathetic typically secrete the

5:39

catecholamines; the parasympathetic typically

5:41

do not, and these typically do not secrete.

5:45

The most common of them is the carotid body tumor,

5:47

which constitutes about 60 percent, and 25 percent of the

5:50

cases, such as this case, can be multicentric

5:53

and the majority of the time if they are, they're

5:55

typically related to a syndrome or familial.

5:59

One important thing to understand when

6:00

it comes to syndromes is the succinate

6:04

dehydrogenase mutation is at the center of

6:05

the majority of these syndromes, and there are

6:07

a multitude of genes that contribute to it.

6:09

And there are a multitude of paraganglioma

6:11

syndromes associated with this, the

6:13

case that I showed you right now

6:15

is a, uh, paraganglioma, uh,

6:18

syndrome, familial syndrome 1.

6:20

And then one in three, for example, have

6:22

a high propensity to be present

6:24

with paragangliomas in the neck.

6:25

Another syndrome that is associated with it is

6:28

Carney's triad, where you have just tumors, uh,

6:31

lung chondromas, and you have paragangliomas.

6:34

And in fact, you know, I've

6:35

seen one in the last couple of weeks.

6:37

MEN type 2, NF1, and von Hippel-Lindau are other things.

6:39

163 00:06:42,010 --> 00:06:43,829 So when you see multiple paragangliomas

6:44

of the head and neck, those are

6:45

things you want to think of.

6:46

In terms of imaging, again, as I, you

6:48

know, going back to the anatomy, location

6:51

can help you predict which nerve it is.

6:53

So the carotid body tumor is the one that

6:57

splays the ECA and ICA and sits in between

7:00

them, as I showed you in that image.

7:02

The glomus tympanicum tumor, uh, tumors

7:06

are, you know, situated at the cochlear promontory,

7:08

and we're not talking about them today. At

7:10

the skull base, they arise from cranial nerve nine.

7:13

And then the jugular tympanicum or jugular in

7:16

the jugular vein arise from cranial nerve ten.

7:18

And glomus vagali are the ones that most

7:21

commonly are located between the jugular

7:23

foramen and the suprahyoid neck.

7:25

They have a propensity to be located

7:27

at the lateral mass of C1 because the majority of

7:31

them arise from the ganglion nodosum at that level.

7:34

And the case I showed you is one of those.

7:36

Uh, and then given their location, when

7:38

you think about it, cranial nerve ten, where

7:40

it's located, as we talk about it here,

7:43

that location is going to push the vessel

7:46

because it sits behind the internal carotid

7:48

artery, is going to push it anteriorly.

7:50

So that's one clue for you to determine

7:52

the origin or which nerve is the

7:55

responsible for a paraganglioma.

7:58

And lastly, especially in familial cases,

8:00

you can have laryngeal paragangliomas that

8:02

arise from the laryngeal paraganglia and

8:04

they're typically located in the visceral space.

8:06

Similar to other paragangliomas,

8:08

they're arterially enhancing and they

8:10

do not look like a mucosal lesion.

8:12

They're typically submucosal and, you know,

8:14

so they're, they're, you're looking at them,

8:16

and it doesn't look like a carcinoma.

8:17

So see an arterially enhancing

8:19

lesion in the larynx

8:21

that is not related to the mucosa.

8:23

One of the things to think about is definitely

8:26

paragangliomas and syndromic paragangliomas.

8:28

In fact, I've seen one last week.

8:30

So very quickly, in terms of imaging on

8:33

ultrasound, this is ultrasound they did a

8:34

couple of days ago for a different patient.

8:37

They tend to be hypoechoic.

8:39

Again, they have a very intimate relationship with the

8:42

vessels given their location in the carotid space,

8:45

and they are very vascular, such as this case. This

8:49

is the ultrasound, and this is the companion CT.

8:52

You can see the internal and

8:53

external carotid arteries.

8:54

You can see a lesion displaying

8:56

them and being significantly vascular.

8:59

And this is its appearance on sagittal images.

9:02

On MRI, they're typically T2 hyper

9:04

intense, with flow voids on T2.

9:06

And then on T1, you can have hyperintensity,

9:09

which is reflective of, you know, slow flow

9:11

within the vessels or turbulent flow.

9:14

And it's, uh, two things that I want to

9:16

emphasize: one, the significance of not

9:21

doing a biopsy on these, uh, because we perform

9:23

biopsies, so not doing a biopsy and being

9:26

mindful of thinking about that differential

9:28

and angiogram for treatment planning.

9:30

The most common differential would be a nerve

9:32

sheet tumor, and they're typically given,

9:35

as they're arising from, you know, the nerves,

9:38

they tend to displace the

9:41

vessels anteriorly or medially, the carotid.

9:44

And then additional lesions always because

9:46

of the vessels, the vascular, and there's a

9:48

whole gamut of it that's hard for us to go

9:50

through, which includes dissection, boses,

9:54

aneurysms, pseudoaneurysms, carotid blowout, FFD,

9:55

vasculitis, and then carotidynia or facial

9:58

syndrome or typic syndrome, multiple names for it.

10:01

And then always remember lymph nodes,

10:03

whether it's infection, mass, or

10:05

lymphoma. A couple of common lesions

10:07

I wanted to talk very quickly about

10:09

is a carotid space schwannoma.

10:12

And, uh, things that, uh, you know, typical

10:14

appearance of schwannoma is, you know,

10:16

typically T2 hyperintense, but different

10:18

appearance based on the content.

10:20

And as you can see here, it's

10:21

displacing the carotid laterally.

10:23

Uh, and then on, uh, DOTATATE PET, it doesn't

10:26

demonstrate increased uptake, and that's one

10:27

way you can differentiate if you're not sure

10:29

between, uh, schwannomas and paragangliomas.

10:32

Other thing I want to talk about very

10:34

quickly before we, uh, wrap up the

10:36

carotid space is carotid blowout.

10:39

Because, you know, in my practice,

10:41

I do see quite a decent amount of these.

10:42

So I want to touch base with it because

10:44

I know not a lot of people see it much.

10:46

Carotid blowout is a potential risk for

10:49

treatment of head and neck cancer seen

10:51

in about three to 5 percent of patients

10:53

that have, you know, surgery and up to 10

10:55

percent with people that have radiation.

10:57

And then the, uh, what happens is it's

11:02

there's an effect on the vessel that increases

11:04

the risk of the vessel to bleed, and it's

11:07

classified as threatened where we see abnormal

11:10

imaging of the vessel whether it's,

11:11

you know, changing caliber, pseudoaneurysm,

11:14

uh, or, you know, stenosis, uh, or it can be

11:18

imminent or, you know, uh, active where you see

11:21

active bleeding or blush on your arterial phase.

11:24

Things that increase the risk of it are

11:26

location of tumor with respect to the

11:27

vessel if it's encasing the vessel, uh,

11:30

narrowing, changing caliber, pseudoaneurysm.

11:32

Uh, or, you know, obviously active bleeding and

11:34

one big thing that seems to be more sensitive

11:37

is necrotic tissue extending toward the vessel.

11:40

This is a patient that had neck cancer

11:42

that was treated with, uh, radiation and surgery.

11:46

And you can see the necrotic tissue and

11:48

ulceration from radiation and some of the ECA

11:50

branches. You can see here the caliber of the vessel.

11:53

So I'm going caudal to cranial.

11:55

There's significant narrowing

11:56

of two vessels, two branches.

11:58

This is a dot here.

11:59

And then that increases its caliber.

12:01

And then it's, you know, that's

12:03

the normal caliber of the vessel.

12:04

As you can see that change, changing

12:06

caliber, this patient came in with, uh,

12:08

uh, active bleeding at the time, uh, and

12:11

had to have, uh, a, uh, stent placement.

12:14

So that's, uh, pretty much, you know, the carotid

12:17

space and some of its differential diagnosis.

12:19

And then going back to the audience question.

12:22

Yep.

12:23

Perfectly, uh, correct.

12:25

Seems like everyone, you know,

12:26

was on board on that.