0:00

So this is an example of a real-world

0:03

application of imaging in the brachial plexus.

0:05

So this was a patient with known papillary

0:07

thyroid carcinoma that ends up having

0:10

metastasis to the base of the left neck.

0:12

So the surgeons know that there is a mass,

0:15

they know that there is a metastasis,

0:17

and they know that this mass right here

0:20

is due to papillary thyroid carcinoma.

0:23

What they want to know is what is the

0:25

relationship to the brachial plexus because

0:27

anytime that they see a mass involved in the

0:29

base of the left neck, and they're considering

0:31

doing a radical neck dissection, what they don't

0:34

want to do is that they don't want to have the

0:36

mass in close proximity to the brachial plexus.

0:39

Because if they take the margin of the

0:41

mass, and what they don't want to do is

0:43

potentially injure that brachial plexus

0:46

when they're taking an oncologic margin.

0:49

So, in this particular case, we see the

0:51

mass involving the base of the left neck.

0:54

This is our subclavian artery right here,

0:56

and remember, right above the subclavian

0:58

artery are going to be the cords of the

1:00

brachial plexus, which I just outlined.

1:02

So you can very nicely see.

1:04

The cords of the brachial plexus

1:05

adjacent to the subclavian artery.

1:07

Now, when we look at the middle

1:09

image, we can see this metastasis here

1:11

involving the base of the left neck.

1:14

Now, a couple things to point out on this.

1:16

What I'm going to do is I'm going to draw

1:17

my line down the middle, and I'm going to

1:18

compare the right side to the left side.

1:21

Here's our anterior scaling on the

1:23

right side, here's our posterior

1:24

scaling, and here's our brachial plexus

1:26

between the plane of those two muscles.

1:29

Now here we see this mass, and I have

1:31

shown a few cases of schwannomas

1:33

involving the supraclavicular plexus.

1:36

How do we know that this is a

1:37

lymph node and not a schwannoma?

1:40

Well, the way we know that is, notice how this

1:42

mass is not extending between the plane of

1:46

the anterior and the middle of the scalene.

1:47

In fact, it's narrowing this anterior component.

1:50

So, this tells us the mass is anterior

1:54

to the anterior scalene muscle.

1:55

So this is a classic level 4 lymph node.

1:59

Now, if you look at this lymph node, there

2:01

is a suggestion of extracapsular penetration.

2:04

Again, extracapsular penetration

2:06

is now a pathologic diagnosis and

2:09

it can be suggested radiologically.

2:11

So if you do say there's extracapsular

2:12

penetration, just make sure you say that it

2:15

needs to be correlated with clinical evidence.

2:17

But notice how the D portion of

2:19

this mass is abutting the anterior

2:21

margin of the anterior scalene.

2:23

So that's important to say.

2:25

You can say that there's radiological

2:27

evidence of extracapsular penetration and

2:29

it's abutting the anterior scalene muscle.

2:32

And if we look really closely, here is the

2:35

brachial plexus extending to the plane of

2:37

the anterior and the middle scalene muscle.

2:39

But look how close this mass is

2:43

to the brachial plexus as it's

2:45

exiting the anterior scalene muscle.

2:48

It's just a few millimeters away from it.

2:50

So that is really important

2:52

information for the surgeons.

2:54

And then when we look at the sagittal

2:56

images, we can see this mass right here.

2:58

Here's our subclavian artery, and

3:00

we know the cords are going to

3:01

be right adjacent to that mass.

3:04

So, the real value in this case was not to

3:08

give a differential diagnosis for this mass.

3:12

We know that it's a metastatic lymph node.

3:14

The surgeons know that it's a metastatic

3:16

lymph node from papillary thyroid cancer.

3:18

But what's most important in this case

3:20

is to talk about how this mass likely

3:23

has extracapsular penetration, how it's

3:25

abutting the anterior scalene muscle,

3:28

and how it's in very close proximity

3:30

to the exiting brachial plexus as

3:33

it's leaving the plane between the

3:35

anterior and the middle scalene muscle.

3:37

That's the information the surgeon

3:39

needs in order to make a treatment

3:41

decision and the imaging that's

3:43

provided on these imaging studies.