0:00

So, moving on, we, uh, this is a nice

0:03

segue to the parapharyngeal space.

0:05

Representative image, uh, MRI, FASAT T2, and our, uh, obvious

0:10

question is, uh, which of the following

0:13

is not a content of the parapharyngeal space?

0:16

Fat, lymph nodes, uh, V3 branches of the

0:19

trigeminal nerve, or, uh, salivary tissue?

0:23

Uh, and as we're thinking of this,

0:25

we'll start discussing the case.

0:27

And again, similar to what

0:29

Dr. Guzman has said before, always location of

0:31

the epicenter of the mass and then from there

0:33

the differential diagnosis of the lesion.

0:36

So I'm looking at a lesion here

0:38

that is in the suprahyoid neck.

0:41

And it looks like it's predominantly situated

0:43

in the parapharyngeal space compared to the

0:45

other side where the fat is suppressed.

0:47

And it's not outside of a little bit of

0:49

mass effect on the medial pterygoid muscle.

0:51

It's not doing a whole lot of displacement.

0:52

So I know more likely than not that the space is

0:56

intact and it's most likely coming from the space.

0:59

It is very T2 hyperintense.

1:02

And on post-contrast sequence, it demonstrates

1:05

significant enhancement to bits and portions

1:09

of it while other parts are not enhancing.

1:12

Uh, and then my lead differential when I

1:13

see a lesion like this in the perpharyngeal

1:15

space is going to be either a, uh, salivary,

1:19

uh, gland or salivary tissue, uh, primary

1:22

lesion or a, uh, neurogenic lesion.

1:25

Just knowing which of

1:27

the two are the most common.

1:28

And then based on the imaging appearance and

1:31

the significant T2 hyperintensity.

1:33

I, you know, I would favor something like

1:36

a benign mixed cell tumor or pleomorphic

1:37

adenoma as the primary lesion with the

1:40

back of my mind thinking of something

1:42

like a schwannoma as the less likely consideration,

1:45

given the appearance on the sequences.

1:47

So moving forward, again,

1:49

think about the differential.

1:51

Let's talk a little bit about the anatomy,

1:53

contents, and boundaries.

1:55

And I know Dr.

1:55

Guzman talked about a little bit of

1:57

boundaries, so we'll skip that and

1:58

just talk predominantly about the contents.

2:01

The majority of the space is made of fat.

2:03

It does have, to a variable

2:06

degree, variable vessels from the

2:08

external carotid artery branches.

2:11

And then from the pterygoid venous

2:12

plexus, again, there's variability in how

2:15

much vessels, if any, are present based on the

2:17

variable anatomy, but typically more likely

2:19

than not there are branches of

2:22

V3 in particular supplying the tensor veli

2:24

palatini muscle and salivary tissue, and there's

2:27

always a debate if the primary is salivary.

2:32

Is it truly from a minor

2:34

salivary tissue in the periphery in

2:36

the space, or is it exophytic coming from

2:38

the deep lobe of the adjacent parotid?

2:41

And sometimes it is really hard to

2:43

say; sometimes it might be easy, as Dr.

2:45

Guzman said, based on the displacement of

2:46

the space or if there's residual space.

2:50

In terms of the lesions of the parapharyngeal space,

2:52

the majority of the lesions are benign, 75 to 85%.

2:56

Thank you.

2:57

It does not constitute much of the

2:59

primary head and neck tumors, as only 0.5%

3:01

of all primary head and

3:03

neck tumors arise in the parapharyngeal space.

3:05

The most common primary of the

3:07

parapharyngeal space is going to be salivary

3:09

gland, followed by neurogenic.

3:11

Of the salivary, the most common is benign

3:15

mixed cell tumor or pleomorphic adenoma.

3:18

And of the neurogenic,

3:19

paraganglioma, typically from vagal

3:22

nerve branches, followed by schwannoma.

3:24

And then, given that the majority of the

3:26

content is fat, there's

3:30

always a possibility of lipoma or

3:32

liposarcoma, and certainly infection spread

3:35

from adjacent spaces is another consideration.

3:39

So, when talking about differential, as

3:41

we spoke earlier, this is a paraganglioma.

3:44

The reason why I think it's paraganglioma, and

3:46

you can see the contralateral fat, predominantly

3:48

fat and small vessels in the space, is that

3:51

it is significantly enhancing, and I can

3:54

see increased vascularity along its margins.

3:57

So I would favor paraganglioma.

3:59

Schwannomas, you know, have a variable

4:02

signal, but typically they're T2 hyperintense

4:05

and they demonstrate a degree of enhancement.

4:07

They are usually on CT

4:10

hypointense to the muscle.

4:11

So when I'm looking at a lesion like this, I

4:14

am thinking it's not going to be paraganglioma

4:16

because it's not significantly enhancing

4:17

on CT, and then on T2 the typical appearance

4:21

of a benign mixed cell tumor is more bright or

4:24

more T2 hyperintense.

4:27

So I'm thinking it's

4:28

probably not going to be, and I would

4:29

lead with schwannoma in this instance.

4:32

And then, you know, every now and then

4:34

you'll see one of these lesions here.

4:36

This is the parapharyngeal space on the left.

4:39

And you can see the right

4:40

again, predominantly fat.

4:41

And you can see that this lesion, there is

4:43

expansion of the parapharyngeal space.

4:46

And there is fat content

4:48

and heterogeneous tissue inside of it.

4:50

So, you know, this would be,

4:52

you know, a fat, fat lesion.

4:54

And certainly if you have an MRI, you can

4:55

confirm it with the fat-sat sequences.

4:58

And I would, you know, given that I do see soft

5:00

tissue, I would favor that this would be a little

5:02

bit more aggressive than lipoma, possibly a

5:04

liposarcoma, which was the case in this case.

5:08

And then this is another case,

5:09

you know, more common in pediatrics, but you

5:11

tend to occasionally see it in adults.

5:13

This actual case I read last week is a

5:16

patient 30 years old that came in with,

5:19

you know, difficulty breathing and swallowing.

5:21

And you can see a T2, uh, hyperintense mass.

5:25

The mass is situated in the peripheral

5:27

space, but it does extend to the pharyngeal,

5:30

uh, walls and compresses the pharyngeal,

5:32

uh, uh, the nasopharyngeal airway.

5:35

At the same time, you know, it is at the

5:36

margin of the deep lobe of the parotid.

5:38

But notice it's not, you know, uh, doing a lot

5:40

of mass displacement; it's, you know, kind of

5:43

trans-spatial and embedding into the spaces.

5:45

So if you look a little bit closer,

5:47

there's also another component in

5:49

the retroauricular space.

5:51

So when I was reading this with one of our

5:53

fellows, the thought

5:54

process was, could this be a, uh, pre,

5:57

you know, again, with the differential,

5:59

could this be a, uh, a schwannoma, or could this

6:02

be a benign mixed cell tumor, or could this

6:04

be a pleomorphic adenoma, or could

6:07

this be, uh, something like a paraganglioma?

6:10

And then this is the DOTATATE PET, and there's

6:12

no increased signal, but if you look closely,

6:13

you can see some calcifications in the retro

6:16

auricular component or separate lesion.

6:19

And we thought that this is a low-flow

6:20

vascular lesion, which ended up being the case.

6:23

Now, these are more common in younger

6:25

patients in the parapharyngeal space, but you do

6:27

see them every now and then in adults.

6:29

So going back to our audience question

6:31

to recap, uh, you know, the,

6:34

the space, which of the following is

6:36

not a content of the parapharyngeal space?

6:42

And then the majority of, uh, if you got it

6:44

right, yes, remember, you know, there are

6:47

typically V3 branches in particular, uh, the

6:51

uh, you know, branches, uh, supplying the

6:53

tensor veli palatini, and then hence

6:55

why you will have neurogenic

6:58

tumors like, uh, paragangliomas and schwannomas.

7:01

And then the other thing when it comes

7:03

to, uh, salivary tissue, again, you know,

7:05

they're, you know, potentially debatable.

7:07

Is the salivary or the most common

7:09

tumor being the benign mixed cell tumor?

7:11

Is it arising actually from the

7:13

parapharyngeal space or the deep lobe?

7:15

And there is definitely peripheral, uh,

7:18

uh, parapharyngeal space, minor salivary gland.

7:21

Typically there's no lymph nodes in the space.