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Hello everyone, it's Sydney Levy here.

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Today we will talk about level 2 out

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of the lymph node levels of the neck.

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This is the upper internal

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jugular or deep cervical chain.

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It is divided into two sub

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levels, level 2A and level 2B.

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I would like to use pre-contrast

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T2 and T1 weighted imaging

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to demonstrate the boundaries for you and

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the landmarks that you need to look for

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in order to be able to distinguish them.

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So starting off with level 2A.

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The first thing to remember is that level 2A is

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situated posterior to level 1B and superior to level 3.

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So level 2A's boundaries are, anteriorly,

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the posterior border of the submandibular gland.

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We draw a plane here.

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These are the submandibular glands.

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Anything anterior to that plane is level 1B.

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Anything posterior to it is level 2A or level 2B.

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The next boundary is the posterior boundary.

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There are two landmarks to be aware of.

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The first one is the posterior

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border of the internal jugular vein.

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So firstly we'll draw the internal jugular vein.

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That's here.

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It's curving slightly at this level.

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And on the other side, it's here.

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So if we draw a plane posterior to the posterior

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margin of the internal jugular veins, we have

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level 2A in front and level 2B behind.

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The other landmark you need to be aware of is

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the posterior border of the sternocleidomastoid.

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So the sternocleidomastoid is this structure

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here, anything anterior to the posterior border

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of the sternocleidomastoid belongs within level two.

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Anything posterior to it or lateral

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to it belongs in level 5A.

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We'll come to that later in a subsequent vignette.

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For the purposes of this vignette, you need to remember

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that level 2A is anterior to the posterior margin

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of the internal jugular vein and anterior to the

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posterior margin of the sternocleidomastoid.

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The other boundaries you need to know

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are the superior and inferior boundaries.

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They're more straightforward.

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The superior margin is the base of the skull.

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The inferior margin is the inferior

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border of the hyoid, which is often easy

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to appreciate in the sagittal plane.

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This is the hyoid here.

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Anything superior to that

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belongs within level 2A or level 2B according

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to the other boundaries we discussed and

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anything inferior to the base of the skull as well.

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Now once you understand that,

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level 2B is quite straightforward.

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And once again, I will draw for you the posterior

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margin of the internal jugular vein as well as

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the posterior margin of the sternocleidomastoid.

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The key thing that distinguishes level 2A

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from level 2B is that for a lymph node to be

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considered level 2B, it must be posterior to

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the posterior margin of the internal jugular

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vein, but it must also have a fat plane.

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For example, there is already an abnormal

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lymph node here within level 2A, but that's

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easy because it's anterior to the posterior

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margin of the internal jugular vein.

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Where it gets a little more difficult is

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if you have a lymph node that is touching

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the posterior margin of the internal jugular vein, i.e.,

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This is still considered level 2A.

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For it to be a level 2B lymph node,

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there should be a fat plane in between.

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There has to be visible fat in between the lymph node

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and the posterior margin of the internal jugular vein.

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In every other respect, level

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2B has the same boundaries as level 2A.

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So i.e.,

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the base of the skull, the inferior border of the hyoid.

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So lastly, I will just draw in this

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particular axial plane, the two levels, so

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so you can see them in relation to one another.

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So level 2A, posterior margin of the submandibular

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gland, posterior border of the internal

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jugular vein, all of this is within level 2A.

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Level 2B, posterior to the internal jugular vein

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with a fat plane going back all the way here.

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Remembering that the posterior border of

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the sternocleidomastoid is an important

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boundary because anything lateral or posterior

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to that belongs within level 5, which we

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will discuss in a subsequent vignette.

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In our next vignette, we will discuss level 3.