Risk factors for thyroglossal duct remnants after Sistrunk procedure in a pediatric population☆

1. Introduction 

Thyroglossal duct cyst (TDC) is one of the most common causes of anterior neck swelling close to the midline in children [1]. The successful management of this cyst requires an understanding of the embryogenesis of the thyroid gland and of the histopathology of the lesion. The thyroid anlage appears in the 2.0–2.5 mm embryo as a middle structure and projects downward from the floor of the pharynx at a point that corresponds to the foramen caecum in the adult. During the course of development, the thyroid descends along the midline to its position in the anterior neck, forming a tract that is known as the thyroglossal duct (TD). The thyroid gland develops at the distal end of the TD. Normally, the TD is obliterated. However, if remnants of the connecting band of tissue between the thyroid and the tongue persist, they may give rise to cysts, or fistulas later in life. The hyoid bone, arising from the second branchial arch, grows forward after the descent of the thyroid, and divides the tract into infrahyoid and suprahyoid portions. Rotation of the hyoid during its development results in the TD being draws posteriorly and cranially at the inferior margin of the bone. Eventual fusion of the anlagen in the midline may result in entrapment of the TD by the hyoid bone. Thyroglossal remnants remain a frequent complication in the treatment of TDC [2], [3], [4], [5], [6]. Since Schlange in 1893, several procedures have been described, with Sistrunk surgical technique being the most widely used, in order to decrease the risk of relapses [7]. In spite of this surgical progress, recurrence of operated TDC still represents a challenge even for skilled surgeon. The aim of this study was to identify factors significantly related to recurrence after surgery.

2. Materials and methods 

A retrospective chart review of all cases of anterior neck swelling surgically treated in our department during a 14-year period, from September 1985 to June 2000, was performed. Seventy-four cases were collected. The diagnosis of TDC was confirmed histologically in 57 patients, other cases being mostly dermoid cysts. All the children were postoperatively seen at 8 days, 1 and 3 months after surgery.

The following parameters were studied:

3. Results 

A total of 57 operated TDC were collected.

3.6. Risk factors (see Table 1) 

Table 1 summarizes the risk factors.

Table 1. Risk factors and recurrence RATE

	Risk factors		Recurrence rate	P
	Age	<1 year	6/12 (50%)
		1<age<2	7/21 (33.33%)
		>2 years	2/24 (8.3%)	<0.05
	No. infection before surgery	>2 infections	8/16 (50%)	<0.05
		<2 infections	3/25 (12%)
	Surgery	Sistrunk first (41/57)	5/41 (12%)	<0.05
		Preliminary procedure (16/57)	5/16 (31.25%)
	Histology	Monocystic (26/57)	1/26 (3.8%)	<0.01
		Pluricystic (18/57)	8/18 (47%)

4. Discussion 

Our study reviews TDC with particular emphasis on risk factors for recurrences. Analysis of parameters found essentially four risk factors: number of infection of the cyst before surgery, number of surgical procedure, histopathologic findings and age. Only the two first factors were correlated.

TDC is the most common congenital neck mass and the second most common of all childhood cervical masses [2]. A major problem in the surgical treatment of this cyst is the high frequency of recurrence (6–10%) which remains a treatment challenge even when operation is performed by a skilled surgeon [3], [6], [8], [9]. Recurrent cysts could be explained by the remaining duct epithelium after inadequate excision [1], [3], [4], [5], [6]. Another cause is the presence of multiple diverticuli connected to the tract. These diverticuli were clearly described by Hoffman and Schuster [3]. Some are shown on Fig. 1, Fig. 2.

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Fig. 1. Photomicrographs of a thyroglossal duct with many tracts (H-E, original magnification ×40). Note the position of the hyoid bone (HB), infra hyoid muscles (M), and thyroglossal duct (TD).

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Fig. 2. Photomicrographs (H-E, original magnification ×250) Enlargement of Fig. 1 showing the presence of many accessory tracts of the thyroglossal duct (white arrows) around the main duct (TD).

While observation of small TDC has been advised by some, most advocate early surgical removal to avoid subsequent infection [8], [9], [10]. While the presence of de novo carcinoma in TDC is unusual (less than 1% incidence), the possibility exists and is therefore a consideration when advising the patient on surgical removal [11], [12], [13], [14], [15].

There has been a significant decrease in the recurrence rate of TDC (less than 5% in most series) since Sistrunk [7] advocated resection of the midportion of the hyoid bone and a wide cuff of tissue around the proximal tract [5]. The morbidity is minimal and postoperative complications are generally minor. The Sistrunk procedure adds little time to local excision and should be employed in any mass that may possibly represent a TDC. The consequences of an inadequate excision far outweigh the additional time required for a Sistrunk procedure [16], [17].

More than two episodes of infected cyst were also associated with significant recurrence rate. Ducic and Flageole found similar results [7], [8]. In contrast, the series of Burgues Prades revealed no difference [10]. An existing infection, which obliterates the tract and anatomical landmarks can be another cause of recurrence. In these cases, total excision of duct-epithelium become technically difficult [18], [19], [20]. Pollock and Stevenson [18] stated that 55% of all patients with draining fistulae had a recurrence.

According to Brown [21] and Ward [22] the recurrence rate increases after operations on infected tissues and at a younger age. In our study, children less than 2 years revealed high and significant incidence of recurrences (50 vs. 9.5%).

TDC which received preliminary operation were found to be at greater risk of recurrences (40% in our series vs. 30% in Hoffman's series). This difference appeared to be significant. Residual tracts are hard to localize when the anatomical landmarks have been removed.

Sometimes, when a branched TDC occurs, residual tracts can be left behind while only the main tract is removed. Multicystic findings on histology were significantly noticed in patients with recurrent TDC. Ducic and others published same results [8], [11], [12]. All recurrences were managed successfully by further, wider excision. Histologic review demonstrated variability in patterns of drainage of the tract into the oropharynx, with accessory tracts and alveolar outpouchings off the main duct being present in 7.8% of specimens. This study demonstrates that the greatest opportunity for curative resection is at initial presentation, and that previous inadequate or unsuccessful excision is a major risk factor for further recurrence. The variability in microscopic anatomy of thyroglossal duct remnants can account for recurrent disease after lesser procedures, and underscores the importance of wide dissection above the hyoid bone. The tract position in relation to the hyoid bone is not always easy to determine [23]. The Sistrunk procedure with a wide excision of the hyoid bone remains a gold standard for this surgery as recently shown [24], [25] since it carries low rate of complications and overall recurrence.

5. Conclusion 

Optimal conditions to lower the risk for TDC remnants, concern children over 2 years who received for the first time Sistrunk procedure, without previous infection and whose histopathologic confirmation showed no multiple extensions.