Case 20 - Retropharyngeal Space Collections
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Let's finish our discussion of retropharyngeal collections
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with this classic article written by one of my
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colleagues at Johns Hopkins, Jenny Hong.
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And the article was published in 2011 before she
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came to Hopkins, she was actually at Duke,
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and this is entitled Multiplanar CT and MRI of
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Collections in the Retropharyngeal space: Is it an abscess?
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And she refers to this four step procedure to determine
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whether or not you're dealing with an abscess, a lymph node,
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or just retropharyngeal edema. And she says,
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look at the distribution of the fluid,
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look at the configuration, whether it has mass effect,
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look at whether or not it has a thick enhancing wall,
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and look at ancillary findings.
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So retropharyngeal, by enlarged,
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doesn't have that much in the way of mass effect.
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It kind of fills the retropharyngeal
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space from side to side and
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does not show contrast enhancement, and
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may be secondary to adjacent infections.
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Contrast that with Suppurative
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Retropharyngeal lymph node,
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which you heard me use the term necrotizing lymphadenitis,
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is another term here. It's usually unilateral,
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doesn't cross the midline and more rounded,
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it may have an enhancing wall and look like an abscess
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but it's really just the wall of the lymph node.
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And usually, it's a secondary reactive
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lymph node to adjacent pharyngitis.
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The final entity is the retropharyngeal abscess.
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Remember, this is one that crosses the midline,
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goes from side to side.
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If it's unilateral,
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probably a lymph node. If it's going into the midline or
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crossing from side to side, more likely to be an abscess,
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has mass effect, has an enhancing wall, and again,
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may have the same thing,
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a tonsillitis or a pharyngitis as
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the initial ideology of that.
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What Jenny did not refer to in this article is a phlegmon.
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And that's sort of this transition
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zone between retropharyngeal edema
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and abscess. The phlegmon will have mass effect.
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It will expand the retropharyngeal space.
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It does look like a localized collection,
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and yet it does not have a peripheral enhancing wall, and
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it does not have such well-defined borders
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as you would see with a retropharyngeal abscess.
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The final thing I want to mention about the retropharyngeal
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space, is this concept of the danger space.
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So the danger space is a reflection of the fascia
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that also encloses the retropharyngeal space.
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And the difference being that the retropharyngeal space,
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as you see depicted in this diagram,
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extends to the T3, T4 level, down here.
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Whereas, the danger space is the space that's in purplish,
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dark purple, that actually expands and can extend to the
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inferiormost portion of the thoracic cavity,
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and even down to the diaphragm in its location.
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So these are reflections of, in general,
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what we call the Alar fascia, that separates and distinguish
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retropharyngeal space versus danger space.
David M Yousem, MD, MBA
Professor of Radiology, Vice Chairman and Associate Dean
Johns Hopkins University
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