0:00

This patient presented with fullness

0:03

in the right side of the neck.

0:05

So, as you can see, we have a lesion,

0:07

which is relatively large in size,

0:10

that is extending from the skull base,

0:13

down into the neck to the region of the carotid bifurcation.

0:17

So once again,

0:18

we're in a situation here where we want to try to

0:21

distinguish between the various paragangliomas and

0:25

schwannomas that this could be

0:27

involving the carotid space.

0:29

How do we know it's a carotid space lesion?

0:31

You notice that the prestyloid parapharyngeal

0:34

space fat is being displaced anteriorly.

0:37

Here's the normal parapharyngeal fat,

0:40

it's being displaced anteriorly,

0:42

that identifies it as a carotid space lesion,

0:46

and it's going to the skull base.

0:47

So if we look at the jugular foramen on the left side

0:51

and compare it to the jugular foramen on the

0:52

right side, here's the jugular vein,

0:54

this lesion is not involving the jugular foramen.

0:57

Hence, I would say it's unlikely to

1:00

represent a glomus jugulare.

1:02

When we look at the positioning of the jugular

1:07

vein coming out of the jugular foramen,

1:10

we see that it is displaced laterally and posteriorly

1:15

compared to the normal jugular vein on the left side.

1:18

The internal carotid artery is being

1:20

displaced anteriorly and medially.

1:24

So this is in a position where we're more likely to

1:27

suggest that this represents a vagus schwannoma.

1:31

Why is it not a glomus vagale tumor?

1:34

Well, it is not that hypervascular.

1:37

It's not showing all that much enhancement.

1:40

And those tumors generally displace both the internal

1:44

carotid artery and the jugular vein anteriorly.

1:47

The posterior-lateral displacement of

1:49

the jugular vein implies a vagus schwannoma.

1:53

Why is this not a carotid body tumor?

1:58

So if we go down to the carotid bifurcation,

2:01

here's the common carotid artery,

2:04

we see that the external carotid artery is lateral,

2:07

the internal carotid artery is medial

2:11

and being displaced anteriorly.

2:13

Remember that carotid body tumors should push

2:16

that internal carotid artery posteriorly,

2:19

not anteromedially.

2:21

Hence, we would say that this is unlikely

2:23

to represent a carotid body tumor.

2:26

Note that despite the large size of the tumor,

2:29

we do not see vocal cord paralysis in this individual

2:34

and we don't see any pharyngeal abnormalities.

2:37

Remember that the vagus nerve has some motor component

2:40

to the pharyngeal musculature and sometimes you will

2:45

see uvula deviation in cases of vagus lesions

2:49

that are affecting the upper vagal fibers.

2:53

So, in conclusion,

2:56

the anterior medial displacement of the carotid artery,

2:59

the posterior medial displacement of the jugular vein.

3:02

The relative absence of an avidly enhancing tumor

3:06

argues in favor of this being a vagus schwannoma.

3:10

How do we know it wasn't a sympathetic

3:12

nervous system plexus schwannoma?

3:15

Sympathetic nervous system plexus schwannomas occur in

3:18

the posterior aspect of the carotid sheath

3:21

and are more likely to push the jugular vein anteriorly

3:25

rather than posterolaterally, like a vagus schwannoma.