The cyst is usually located at the midline of the neck. The duct extends upward from the cyst with varying numbers of branches and secretory glands. These ducts or branches merge into a single duct at the level of the hyoid bone.
Thyroglossal duct cysts result from the dilatation of a remnant at the site where the primitive thyroid descended from its origin at the base of the tongue to its permanent location, low in the neck. Failure of subsequent closure and obliteration of this tract predisposes to thyroglossal cyst formation.
Thyroglossal duct cysts most often present with a palpable (able to be felt) asymptomatic midline neck mass at or below the level of the hyoid bone. The neck mass moves with swallowing. Some patients will have neck or throat pain, or dysphagia (difficulty swallowing). The spectrum of clinical symptoms may be as varied.
Since the persistent duct or sinus can promote oral secretions, such cysts can become infected. Up to one half of thyroglossal cysts are not diagnosed until adult life. The tract may lie dormant for years or decades until some stimulus leads to cystic dilatation. Infection sometimes causes transient appearance of a mass or enlargement of the cyst, at times with periodic recurrences. Spontaneous drainage occurs in some instances.
Antibiotics are indicated if there is infection. Definitive surgical management requires excision not only of the cyst but also of the path's tract and branches. The intimate association of the tract with hyoid bone mandates simultaneous removal of the central portion of the hyoid bone to ensure complete removal of the tract (Sistrunk procedure). Recurrence is unlikely after such an operation except with skin involvement and intraoperative cyst rupture.
Before thyroglossal duct cysts are excised, it is important to demonstrate that normally functioning thyroid tissue is in its usual location. Thyroid scans and thyroid function studies are ordered preoperatively.