Case: Thyroglossal Duct Cyst
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In looking at
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masses in the neck,
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we mentioned that thyroid lesions and lymph
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nodes were the most common in adults.
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I want to talk about the most common cystic lesion
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in the neck. It actually is not the branchial cleft cyst.
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The most common cystic lesion in the neck
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of an adult is the thyroglossal duct cyst.
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Let's look at thyroglossal duct cysts
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and where we expect to see them.
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Remember that the thyroglossal duct cysts arise from the foramen
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cecum at the tongue base and the duct will extend through
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the tongue base, around the hyoid bone and then down,
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leading to the normal thyroid location.
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And this is the root upon which the thyroid enlarged will
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descend from the foramen cecum to the normal
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position of the thyroid gland in the lower neck.
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Well, most of the thyroglossal duct cysts that we see
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are in the infrahyoid portion of the neck,
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and then the remainder are either in the tongue and tongue
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base or immediately associated with the hyoid bone itself.
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So when you look for the thyroglossal duct cyst,
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or if you're seeing a lesion in this location,
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you want to look in the midline,
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because 75% of thyroglossal duct cysts are in the
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midline and only 25% are off midline.
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And most of those that are off midline are also
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in the infrahyoid portion where 65% arise.
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So looking through this patient's neck,
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they were complaining about a mass
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in the midline near the hyoid bone.
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So here we are coming down through the mandible.
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We reach the hyoid bone,
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and we see that there's nothing in the tongue base
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or at the hyoid bone itself, but immediately
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below the hyoid bone, we come into this cystic mass,
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which is intimately associated with the strap muscles that are
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located between the hyoid bone and the thyroid cartilage.
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So the thyrohyoid musculature of the strap muscles.
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You notice that it's in the midline,
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embedded in the strap muscle.
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This is pathognomonic for a thyroglossal duct cyst.
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This doesn't occur in any other region to be embedded
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in the strap muscles in the midline.
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So we say this is clearly a thyroglossal duct cyst.
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When you see the thyroglossal duct cyst,
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you want to look for any enhancing or hyperdense
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tissue associated with the cyst,
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which may represent residual thyroid tissue within the cyst.
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The reason why this is important is because just like you
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can have incidental cancers in the thyroid gland,
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you can have incidental
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cancers in a thyroglossal cyst thyroid tissue that is present.
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So in this case, no enhancing tissue to be concerned about.
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The patient has normal thyroid gland down here and the cyst
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terminates at the junction of the thyroid notch, frankly.
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So it's really located between the hyoid
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bone and the thyroid notch.
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This is nicely demonstrated on the sagittal scan where you see
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a heart shaped appearance of this thyroglossal duct cyst.
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And it is often on either side of the hyoid bone,
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both the anterior and posterior margin of the hyoid bone,
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which is another characteristic feature
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of a thyroglossal duct cyst.
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This is treated surgically because of that potential for
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having thyroid tissue within it and the potential for having
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a cancer develop within a thyroglossal duct cyst.
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And so, they do what's called a sistrunk procedure.
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The sistrunk procedure takes out a portion of the tongue base
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in the midline where there may be tracking thyroglossal
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duct tissue and then takes out the cyst,
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leaving the thyroid gland intact.
David M Yousem, MD, MBA
Professor of Radiology, Vice Chairman and Associate Dean
Johns Hopkins University
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