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We often talk about the jugular chain of lymph nodes

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when we're speaking of the carotid space.

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Truly, the lymph nodes are outside the carotid sheath.

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They don't occur within the carotid sheath.

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However, their close opposition to the carotid sheath may

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lead to infiltration of the carotid space structures.

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Let's just review Sam's work here from the American

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Journal of Radiology looking at the nomenclature

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of the lymph nodes for the purposes

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of the carotid sheath structures.

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We're really talking about the jugular chain

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of lymph nodes which include the two A,

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two B lymph nodes.

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These are defined by being above the hyoid bone

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and being entirely behind the jugular vein.

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Two B versus in front of or along the jugular vein,

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two A. For them to be two B lymph nodes,

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they must be entirely behind the jugular vein level.

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Three jugular lymph nodes are those that are between

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the hyoid bone and the cricoid cartilage.

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These may be in front of,

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beside or posterior to the jugular vein,

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but not posterior to the sternocleidomastoid

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muscle level.

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Four lymph nodes are those lymph nodes that are in

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the internal jugular chain that are below the

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cricoid cartilage and as you can see,

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go down to the clavicle.

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So these are the lower jugular lymph nodes.

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This is a patient who has breast cancer and as you

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can see, has supraclavicular lymphadenopathy,

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which is relatively large in size.

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In this case,

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one can see that the subclavian artery is encased

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with tumor on both sides of it and the left common

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carotid artery is being displaced

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by the nodal disease.

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So this is an example of encasement

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of the subclavian artery,

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not the internal carotid artery by the breast

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cancer supraclavicular lymphadenopathy.

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These are lymph nodes in the lower jugular chain.

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How about this example?

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This is a primary thymoma which shows displacement

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of the right internal carotid artery posteriorly

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and with some displacement of the carotid

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artery also by the tumor.

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And here you can see that the subclavian artery

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which is coming off the innominate artery is

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also displaced posteriorly by the tumor.

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there is not 270 degrees of involvement

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of the carotid artery.

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This is the MR also showing that the wall

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is involved approximately 180 degrees,

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but not along the posterior wall of the internal

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carotid artery by the thymoma.