Thyroglossal duct cysts are remnants of the embryonic thyroglossal duct that may occur anywhere from the base of the tongue to the thyroid gland. The majority, however, are found at the level of the thyrohyoid membrane, under the deep cervical fascia. They are midline or just off the midline, and move up and down upon swallowing.
Infected thyroglossal duct cysts (above and right)
Occasionally, a sinus tract is present in the midline without a visible cyst. This midline sinus tract represents the remnant of the thyroglossal duct. It may open into the region of the hyoid or lower above the sternal notch.
Because the embryonic hyoid bone forms around the thyroglossal duct, it is important to remove the body of the hyoid along with the thyroglossal duct and follow it to the foramen caecum at the base of the tongue (Sistrunk procedure)
A radio-opaque dye is injected into the opening of the thyroglossal duct. The course of the thyroglossal duct from the lower neck, to the region of the hyoid.
This axial CT scan shows a thyroglossal duct cyst that is located slightly off the midline. For some obscure reason, thyroglossal duct cysts that are not exactly in the midline are usually on the left.
Methylene blue is injected to highlight the thyroglossal duct and make it easier to dissect.
Axial CT showing a thyroglossal duct cyst attached to the hyoid bone
The duct dyed with methylene blue is now readily visible. It is dissected under the skin via two incisions.