A thyroglossal cyst or thyroglossal duct cyst is a fibrous cyst that forms from a persistent thyroglossal duct. Thyroglossal cysts can be defined as an irregular neck mass or a lump which develops from cells and tissues left over after the formation of the thyroid gland during developmental stages.

Thyroglossal cysts are the most common cause of midline neck masses and are generally located caudal to (below) the hyoid bone. These neck masses can occur anywhere along the path of the thyroglossal duct, from the base of the tongue to the suprasternal notch. Other common causes of midline neck masses include lymphadenopathy, dermoid cysts, and various tooth development anomalies.

Complications

Infection

An infected thyroglossal duct cyst can occur when it is left untreated for a certain amount of time or simply when a thyroglossal duct cyst hasn't been suspected. The degree of infection can be examined as major rim enhancement has occurred, located inferior to the hyoid bone. Soft tissue swelling occurs, along with airway obstruction and trouble swallowing, due to the rapid enlargement of the cyst.

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File:Infected site.jpg|Post surgery infection on a Thyroglossal Cyst, reaction from stitches

File:Post stitches infection.jpg|Post removal of stitches from surgery on a Thyroglossal Cyst infection

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Thyroglossal fistula

A thyroglossal duct cyst may rupture unexpectedly, resulting in a draining sinus known as a thyroglossal fistula.

Thyroglossal duct cyst carcinoma

thumb|Thyroglossal cyst with papillary excrescences (magnified at right), where microscopy showed [[papillary thyroid cancer]]

Rarely (in less than 1% of cases), cancer may be present in a thyroglossal duct cyst. These tumors are generally papillary thyroid carcinomas,

Causes

Thyroglossal duct cysts are a birth defect. During embryonic development, the thyroid gland is being formed, beginning at the base of the tongue and moving towards the neck canal, known as the thyroglossal duct. Once the thyroid reaches its final position in the neck, the duct normally disappears. In some individuals, portions of the duct remain behind, leaving small pockets, known as cysts. During a person's life, these cyst pockets can fill with fluids and mucus, enlarging when infected, presenting the thyroglossal cyst.

Thyroid scans and thyroid function studies are often ordered preoperatively; this is important to demonstrate that normally functioning thyroid tissue is in its usual area. An ultrasound of the neck is both inexpensive and effective; CT scans or magnetic resonance imaging are also useful, but not routinely indicated. Cystectomy is an inadequate approach.

Sistrunk procedure

The Sistrunk procedure, first described in 1920, is the surgical resection of the central portion of the hyoid bone along with a wide core of tissue from the midline area between the hyoid and foramen cecum. It involves excision not only of the cyst but also of the path's tract and branches, and removal of the central portion of the hyoid bone is indicated to ensure complete removal of the tract. The original papers by Walter Sistrunk (the "classic" procedure described in 1920, and the "modified" procedure described in 1928) are available on-line with a modern commentary.

In general, the procedure consists of three steps:

  1. incision
  2. resection of cyst and hyoid bone
  3. drainage and closure

There are several versions of the Sistrunk procedure, including:

  • "classic": excision of the center of the hyoid bone along with a thyroglossal duct cyst, removal of one-eighth inch diameter core of tongue muscle superior to the hyoid at a 45-degree angle up to the foramen cecum to include mucosa, removal of one-quarter inch of the center of the hyoid bone, closure of the cut ends of the hyoid bone, and placement of a drain.

The procedure is relatively safe. In a study of 35 pediatric patients, Maddalozzo et al. found no major complications, but did observe minor complications (6 patients presented with seroma and 4 patients with local wound infections). A more recent paper analyzed 24 research studies on different treatment complications of thyroglossal cyst, and reported a total minor complications rate of 6% for the Sistrunk operation (classical or modified) and simple cystectomy treatment modalities. The Sistrunk procedure also showed better outcomes concerning the rate of overall recurrence, i.e. has the lowest rate of recurrence.

Epidemiology

  1. 90% of cases are presented in children before the age of 10
  2. 70% of neck anomalies are from thyroglossal cysts
  3. Thyroglossal duct carcinoma occurs in approximately 1 to 2% of thyroglossal cyst cases.

See also

  • Cutaneous columnar cyst
  • Branchial cleft cyst
  • Cystic hygroma
  • Preauricular sinus and cyst
  • Ranula

References

Further reading

  • http://www.doctoronline.nhs.uk/masterwebsite1Asp/targetpages/testandprocedures/surgery/thyroglo.asp