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Address reprint requests and correspondence: Stephen S. Newton, MD, Department of Otolaryngology—Head and Neck Surgery, Children′s Hospital of Colorado, Pediatric Otolaryngology, University of Colorado, 4125 Briargate Pkwy, Colorado Springs, Colorado 80920.
Department of Otolaryngology–Head and Neck Surgery, University of Colorado, Division of Pediatric Otolaryngology, Children's Hospital of Colorado, Colorado Springs, Colorado
Thyroglossal duct cysts are the most common congenital neck masses and represent the most likely cause of central neck masses in children. Surgical excision is recommended because of the risk of infection, sinus, or fistula formation, cosmetic concerns and possible site of cancer development. While major complications are rare, recurrence continues to be a concern for the surgeon and the patient or family. Walter Sistrunk made a great contribution to surgical resection technique by using embryological information to better understand the role that the central hyoid bone may play and introducing its partial resection to improve cure rates. Over the last few decades, an improved understanding of the anatomy has further refined surgical techniques and has led to even lower recurrence rates.
Thyroglossal duct cysts (TGDC) are the most common congenital neck masses and result from failure of the thyroglossal duct to obliterate following the descent of the thyroid from the base of the tongue. During this embryological process, the thyroid starts its descent from the foramen cecum, often ventral to the developing hyoid, continuing to its final position in the neck anterior to the trachea. However, the duct can be located posterior to the hyoid in up to 30% of cases and this has significant implications during surgical resection.
The proximity of TGDCs to the hyoid bone was initially recognized by Schlange in 1893. This discovery led to a refined surgical procedure by Sistrunk in 1920,
During the fourth embryonic week, the thyroid primordium develops as an endodermal mass at the foramen cecum. Over the next several weeks, thyroid develops and descends inferiorly in the neck, typically anterior to the developing hyoid bone and laryngeal cartilages. It ultimately lays to rest inferior to the cricoid cartilage.
A TGDC may present anywhere along the path of descent (Figure 1). Some groups have classified the cysts based on location: intralingual, suprahyoid or sub mental, thyrohyoid, and suprasternal.
Although we typically think of a cyst as a continuation of a single tract along this pathway, studies have shown that the remnant tracts are often more complex. These studies showed that a varying number of tracts distal to the hyoid bone may merge to a single duct at the cranial level of the hyoid bone and then may diverge again.
The ducts and cysts are true cysts with epithelial lining. There may be surrounding granulation tissue that likely represents a reactive process from seepage of TGDC contents into the surrounding tissue.
Histologically, there is some debate as to whether the tract actually runs through the hyoid bone or is in close apposition to the bone.
Presentation
The cyst typically presents as a midline neck mass near the hyoid bone, but may present anywhere along the tract of descent. They are typically nontender, soft, asymptomatic, and somewhat mobile. Because of its association with the hyoid, the mass may elevate with swallowing or extension of the tongue. If there has been chronic infection, the cyst may be adherent to the overlying skin or other surrounding tissue. Upper respiratory tract infections may cause the mass to enlarge. These infections may cause the cyst to develop a fistula tract. Those that present in the tongue are most often discovered incidentally but may present with dysphagia or signs or symptoms of airway obstruction.
Evaluation
The evaluation process always starts with a thorough history. Some questions to be asked include: Is the mass stable in size or fluctuating? Has there been drainage or infection? If there have been infections, how have these been treated? Are there any symptoms of dysphagia, globus sensation, cough, or airway obstruction? If so, are these symptoms persistent or only associated with mass enlargement? Are there any symptoms of hypothyroidism (fatigue, weakness, cold intolerance, weight gain, and hair loss)? Did the patient undergo any previous surgical procedures to treat the mass, either needle drainage, incision and drainage, or previous resection attempts?
A full head and neck examination should be performed with additional focus on the oral exam (evaluation of the tongue) and the neck. Depending on the patient׳s age, weight, anatomy, and compliance with the examination, one may be able to visualize the tongue posterior to the circumvallate papillae. During the neck examination, one should assess the nature of the mass and evaluate for normal thyroid tissue and any lymphadenopathy. If there is any concern for lingual mass (dysphagia, globus sensation, cough, or airway obstruction), a flexible laryngoscopy can be performed to evaluate for mass extension to the base of tongue.
Initial imaging is limited to an ultrasound of the neck. The purpose of the ultrasound is to determine if normal thyroid tissue is present in the typical thyroid bed and to further delineate the mass.
If the ultrasound does not show normal thyroid tissue in the expected location, if the mass is consistent with ectopic thyroid, or if there is a primary tongue base mass, one should obtain thyroid function studies, thyroid scintigraphy, and magnetic resonance imagine. Computer tomography scans are usually avoided to reduce radiation exposure in children and are not necessary for the vast majority of cases.
Treatment options
While some have used sclerotherapy agents such as ethanol and OK-432,
the standard of care is surgical excision via a Sistrunk or modified-Sistrunk procedure. Patients who have active infections should be treated with antibiotics before undergoing surgical excision. The most common pathogens responsible for infected TGDC are Haemophilus influenzae, Staphylococcus aureus, and Staphylococcus epidermidis.
surgery is almost always recommended. With recent concern regarding the effects of general anesthesia on the developing brain, the age of the patient should be considered when determining the timing of surgery.
Details for surgical technique
The patient should undergo general anesthesia induction and oral intubation with the endotracheal tube secured laterally and with no tape extending below the level of the mandible. A single perioperative dose of antibiotics is usually administered. Typically, a first generation cephalosporin is given unless previous cultures from the cyst or fistula have demonstrated resistant organisms. The proposed incision line is drawn in a natural neck crease below the mass or as an ellipse around any skin or fistula that may need to be excised (Figure 2). The patient should then be placed in a modified Rose position, with use of a shoulder roll and adequate support for the head. Standard povidone-iodine skin preparation of the surgical region is performed. The patient is draped, exposing the neck from the mentum to the sternum. The proposed incision is then injected with 1% lidocaine with epinephrine or 0.5% lidocaine with epinephrine for small children.
Figure 2Planned anterior neck incision with ellipse around involved skin.
The incision is typically around 4 cm in length and carried down through the level of the platysma. If the cyst extends up to the skin or a fistula tract is present, then the incision must be wide enough around the area of concern so as not to enter the cyst. Inferiorly and superiorly based myocutaneous flaps are created. Superiorly, the flap should extend above the level of the hyoid to the submental triangle. Inferiorly, the flap should be raised inferior to the known TGDC contents to allow full exposure of the thyroid cartilage (Figure 3).
Figure 3A myocutaneous flap is being elevated superiorly above the level of the hyoid bone. Skin ellipse is in continuity with the cyst.
The strap muscles are divided at the median raphe from the hyoid down to the thyroid cartilage. As the strap muscles are bluntly dissected from their surrounding tissue, they are retracted laterally. If the cyst is adherent to the thyroid cartilage, then the cyst is retracted superiorly and dissected off the thyroid cartilage until the alae of the thyroid cartilage are exposed and the notch of the thyroid cartilage is identified (Figure 4). The soft tissue contents and cyst are then grasped and pulled upward as the dissection continues onto the thyrohyoid membrane. Because of the possible arborization of cystic tracts below the level of the hyoid, a 1-2 cm cuff of tissue around the area of concern should be dissected along with the cyst itself.
Any granulation tissue should also be resected en bloc.
Figure 4(A and B) Strap muscles are retracted laterally. The cyst and surrounding tissue is being excised off the thyroid cartilage. The goal is to carry this superiorly to expose the superior edge of the thyroid cartilage and the thyrohyoid membrane.
The dissection now continues along the surface of the thyrohyoid membrane towards the hyoid bone (Figure 5). This then continues into the posthyoid space as described by Maddalozzo et al.
This is performed using blunt dissection with a hemostat along the thyrohoid membrane under the hyoid bone. The anterior surface of the hyoid bone is cleared of soft tissue just medial to the attachment or tendon of the digastric muscle. To resect the middle portion of the hyoid bone, fibers of the sternohyoid and mylohyoid will likely need to be detached, typically performed with monopolar cautery (Figure 6).
Figure 5The cyst and duct are being elevated with a cuff of surrounding tissue off the thyrohyoid membrane. The posthyoid space is entered with blunt dissection to ensure the tract is not truncated with hyoid resection.
Figure 6Fibers of the sternohyoid and mylohoid have been detached from the hyoid bone to allow for exposure of the bone. The cuts of the hyoid have been made medial to the attachment of the digastric tendon and with sufficient length so as not to cut the duct.
The hyoid bone is then grasped with an Allis clamp or hook and then cut medial to the digastric tendon; ensuring there is sufficient hyoid around the tract site to be included in the specimen (Figure 6). The cut can be performed with monopolar cautery in very young children or with heavy scissors or small rongeurs in older children and adults. Remaining medial to the digastric tendon attachment should allow one to protect the superior laryngeal nerve. Once the hyoid cuts have been made, dissection should continue upward at a 45° angle into the lingual musculature. This is an area where the cyst tract can again arborize widely, so a healthy core of muscle should be taken (Figure 7). Unless there is obvious extension to lingual mucosa, mucosa does not need to be resected.
Figure 7The hyoid and cyst are retracted superiorly. A large cuff of muscle is being taken, extending at a 45° angle into the base of tongue.
Hemostasis is obtained using bipolar cautery. The wound site is irrigated to allow saline to fill the surgical site, and Valsalva maneuver is then performed by the anesthesiologist. Bubbling may alert the surgeon to any site of mucosal violation. Any defect in the tongue musculature is closed using a horizontal mattress stitch with 3-0 Vicryl suture. The cut edges of the sternohyoid muscles are reapproximated to the cut edges of the myohyoid muscle. To decrease dead space, the strap muscles may be sutured across the median raphe. A rubber band drain is placed under the strap muscle and allowed to course out of the lateral extent of the incision (Figure 8). The platysma is then closed, followed by deep skin closure with 4-0 Vicryl. The skin is then closed using a running subcuticular closure with 5-0 Monocryl. This decreases the need for the patient to return for suture removal (which may be difficult in young children) and still results in an excellent cosmetic result. The skin site is reinforced using steri-strips. The drain is secured with Monocryl sutures, leaving a large skin loop to make for easy cutting and removal. Burn netting is placed over the neck with fluffed Kerlix dressing to catch drainage.
Figure 8The wound has been closed in a layered fashion. The rubber band drain can be seen extending out of the lateral extent of the incision.
The patient should be admitted for overnight observation and placed on pulse-oximetry. As long as the mucosa was not violated, the patient is allowed to eat and drink following the procedure. The next day, the drain is removed as long as there is no subcutaneous fluid collection and drainage is minimal. Fluffed Kerlix dressing is reapplied. After discharge, the patient is allowed to shower or bathe in 48 hours, with no strenuous activity for 1 week. Follow-up should occur in 1 week.
Complications
The surgical recurrence rate varies from less than 1%-20% depending on the study and technique used. A systemic review performed by Gioacchini et al
showed that the most common complication was wound infections, affecting around 4% of patients. The other complications, in descending frequency, were seroma, hematoma, hypothyroidism, and salivary fistula. The review did not address scar formation, but this has to be considered, especially in patients with more pigmentation and history of hypertrophic scar formation.
The author typically places a drain because of concern for possible seroma or hematoma formation with resultant airway compression. A study by Hong
followed 30 consecutive pediatric patients that did not undergo drain placement. None of these patients developed complications related to hematoma or seroma formation. However, there is still limited data to suggest whether this practice is safe for all patients regardless of the extent of surgery or whether there was previous infection. Treatment of either a seroma or hematoma may be conservative observation or wound exploration, depending on the size and symptoms.
To reduce the risk of hypothyroidism following surgery, the author obtains a preoperative ultrasound to evaluate for normal thyroid tissue. If there are abnormalities on the ultrasound or there is a tongue base mass, a thyroid uptake study is ordered. The overall incidence of ectopic thyroid tissue has been estimated as 1:100,000-1:300,000, with 90% occurring in the tongue base and 10% in the anterior neck.
In general, postoperative thyroid studies are not supported by the literature.
Salivary fistulas are rare complications. The author recommends performing a Valsalva maneuver at the end of the case to look for possible mucosal defects. The technique of tongue muscle closure likely reduces the risk of fistula formation by decreasing dead space and creating a barrier of healthy tissue if there is an unrecognized mucosal defect.
Disclosure
The author reports no proprietary or commercial interest in any product mentioned or concept discussed in this article.
Acknowledgments
Special thanks to Dr. Allison Dobbie and Dr. Steve Hamilton for their review of this article and insightful recommendations.
References
Ellis P.D.
van Nostrand A.W.
The applied anatomy of thyroglossal tract remnants.
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