CHAPTER 1
INTRODUCTION
Thyroglossal Duct Cyst
The median cervical cyst is a remnant of the thyro- glossus duct, which runs from the pyramidal lobe of the thyroid gland to the foramen caecum in the dor- sal part of the tongue. Embryologically, the thyroid diverticulum develops in a caudal direction from the foramen caecum after formation of the tongue. The thyroid gland descends to the neck in the same peri- od of gestation as the hyoid bone develops from the second branchial arch. The thyroglossal duct may pass in front, behind or through the body of the hyoid bone in the middle of the neck, and islands of thyroid tissue may be found scattered along the tract.
At no time during embryogenesis does the thyroglos- sal duct contact the body surface; the original cysts thus never open to the skin. A fistula can only devel- op secondarily, e.g., following spontaneous perfora- tion or surgical incision of an infected cyst.
Thyroglossal cysts are the most common tumours of the anterior cervical region. They are usually lo- cated in the midline at the level of or somewhat be- low the hyoid bone. Due to the connection with the foramen caecum of the tongue, the lesion typically moves upwards with swallowing like the thyroid gland, and, different from the latter, also with tongue protrusion. In contrast, dermoid cysts or lymph nodes do not change their position with either act.
Ultrasound examination may be helpful, in the first instance to ascertain the presence of a normally situ- ated normally sized thyroid gland as well as to con- firm the cystic nature of the mass under considera- tion. In cases of a suppurative infection, incision and drainage in combination with antibiotics is the ap- propriate treatment followed by excision once the acute inflammation has settled.
Michael E. Höllwarth
Michael E. Höllwarth 4
1
Following induction of general anaesthesia with en- dotracheal intubation, the neck is hyperextended by placing a sandbag or towel roll beneath the shoul- ders. A horizontal skin incision is made over the cyst.
In case of a fistula, the cutaneous orifice is circum- cised in a horizontally oriented elliptical fashion.
Subcutaneous tissue, platysma and cervical fascia are divided exposing the capsule of the cyst. In cases with previous history of inflammation, these layers may be fibrosed and lack a clear demarcation against each other as well as against the cyst wall. The cyst is carefully separated from the surrounding tissue by blunt and sharp dissection.
Figure 1.1
The duct is attached to the cyst running in a cephalad direction between the sternohyoid muscles to the body of the hyoid bone. It is usually not possible to recognize whether the duct perforates the hyoid body or passes across its anterior or posterior sur- face. The central part of the hyoid bone is freed from the muscles attached to its upper and lower margin.
The thyrohyoid membrane is carefully dissected off the posterior aspect with scissors.
Figure 1.2
The exposed hyoid bone is then stabilized with strong Kocher forceps on one side, clearly lateral to the median line, and the central segment is excised with strong Mayo scissors.
Figure 1.3
If the duct is extending beyond on the posterior as- pect of the hyoid bone, it is followed cephalad and divided close to the base of the tongue with a 5/0 ab- sorbable transfixation ligature. If the floor of the mouth is entered accidentally, the mucosa of the tongue is closed with interrupted plain absorbable sutures. Often, however, no duct structures are found behind the hyoid bone, in which case some of the midline connective tissue is excised in the cranial di- rection to make sure that no duct epithelium is left behind.
The lateral segments of the hyoid bone are left separated, but the anterior neck muscles are approx- imated in the midline with absorbable 4/0 sutures.
Platysma and subcutaneous fat are closed with ab- sorbable 5/0 sutures, and the skin is closed either with interrupted subcuticular absorbable 6/0 stitch- es or with a continuous subcuticular nonabsorbable 4/0 suture, which can be removed 3–4 days later. A drain is usually not necessary, except in cases requir- ing extensive dissection as may occur after a previ- ously infected cyst or a recurrent cyst.
Figure 1.4
Chapter 1 Thyroglossal Duct Cyst 5
Figure 1.1 Figure 1.2
Figure 1.3 Figure 1.4
Michael E. Höllwarth 6
CONCLUSION 1
Complete excision of the thyroglossal cyst consists of removal of the cyst, the entire tract and the midpor- tion of the hyoid bone through which the tract pass- es. If this principle is followed, recurrence is extreme- ly unlikely. While the procedure is easily performed
in native tissue, dissection is much more difficult in a previously infected cyst. Therefore, postponement of the surgical procedure is not to be recommended once the diagnosis has been made.
SELECTED BIBLIOGRAPHY
Horisawa M, Niiomi N, Ito T (1991) Anatomical reconstruction of the thyroglossal duct. J Pediatr Surg 26 : 766–769 Smith CD (1998) Cysts and sinuses of the neck. In: O’Neill JA,
Rowe MI, Grosfeld JL, Fonkalsrud EW, Coran AG (eds) Pe- diatric surgery. Mosby, St Louis, pp 757–772
Telander RL, Deane S (1977) Thyroglossal and branchial cleft cysts and sinuses. Surg Clin North Am 57 : 779–791 Waldhausen JHT, Tapper D (2000) Head and neck sinuses and
masses. In: Ashcraft KW (ed) Pediatric surgery. WB Saunders, Philadelphia, pp 987–999
