A persistent thyroglossal duct is a usually benign medical condition in which the thyroglossal duct, a structure usually only found during embryonic development, fails to atrophy. The duct persists as a midline structure forming an open connection between the back of the tongue and the thyroid gland. This opening can lead to fluid accumulation and infection, which necessitate the removal of the duct. Signs and symptoms
Studies done on cadavers claim persistent thyroglossal ducts can be completely asymptomatic and found in 7% of the human adult population. However, the continued presence of the duct can often lead to complications due to infections and fluid buildup. The glands in the mucosa of the duct will continue their secretions until the fluid forms a cyst or exit the duct via the opening in the foramen cecum. Local infections, such as colds, tonsillitis, or inflammation of the lymph nodes in the area can also lead to the accumulation of fluid within the duct. Even if the cyst forms as secondary to another infection and improved after antibiotics, it will often reoccur and require treatment. Three-fourths of abnormalities within a persistent thyroglossal duct involve the formation of a cyst. If a persistent thyroglossal duct becomes fluid filled it will form a thyroglossal duct cyst, which accounts for 70% of congenital neck masses and is the most likely diagnosis if the mass is along the midline of the neck. These cysts are often diagnosed in children under the age of ten and have no particular gender prevalence.
The cysts are normally asymptomatic at this age and are noticed because of the swelling that will move if the patient swallows. Over 80% of these cysts are located at or below the hyoid bone.Very rarely, the persistent duct can become cancerous, called thyroglossal duct carcinoma. In the case of thyroglossal duct carcinoma, the cancerous cells are ectopic thyroid tissue that has been deposited along the thyroglossal duct and will present as a papillary carcinoma. However, the cells are less likely to metastasize in the cyst, than if they were present in the actual thyroid gland.The other fourth of abnormalities presents as draining abscess. This is from an infection that will rupture through the skin to allow for adequate drainage of the infected area. Anatomy
The tongue develops after the thyroid primordium so the foramen cecum becomes buried at the base of the tongue. The thyroglossal duct then continues through the neck and lies anterior to the laryngeal cartilage. The duct then passes anteriorly to the developing hyoid bone; however, as the bone continues to grow it can continue to grow posteriorly, become anterior, or even grow to surround the duct. The duct is found very close to the medial line of the neck. The duct continues in front of the thyrohyoid membrane, sternothyroid muscle, and sternohyoid muscle, before terminating in the inferior segment of the neck at the thyroid.Failures of duct removal surgeries have proven that the suprahyoid region of the duct can have many microscopic branches that connect to the base of the tongue.