Epidemiological aspects

The thyroglossal duct cyst (TDC) is the most common congenital cervical malformation [1,2,3]. Over a period of 10 years, Chrysostomos K. et al. reported an incidence of 55.9% of cystic neck masses. The other lesions were dermoid cyst (23.7%), branchial abnormalities (5.1%), lymphadenopathy (6.7%), cutaneous hemangioma (1.7%) and formations of unknown causes (6.7%) [4]. Our patient was a young adult female. In the study by Wenhao R. et al, TDC was more common in adults (56%) than in children (44%), and males were predominant in both groups [6]. However, Chrysostomos et al. reported this cyst in 33 children, with an average age of 6 years, during the same period [4]. Other authors have also reported this male predominance in their studies populations and the most clinical cases have been in male patients [7,8,9,10].

Diagnostic aspects

Clinically, our patient presented with isolated, anterior, cervical median and sub-hyoid swelling which, on physical examination, was characteristic of its ascending tongue traction. Uncomplicated cervical swelling is the most reported clinical sign in the literature [2,7,10,11]. Moreover, in the study of Ali I et al, it represented 75% of the signs, the others being represented by fistulized swelling in 3 cases (15%) and an isolated cervical fistula in 2 cases [7]. Uncomplicated neck mass was also the most common sign in most series [4,11,12,13,14,15]. The sub-hyoid localization of the cyst is the most frequent, as in the study of Sujatha et al, where it was 85.7% of cases [8]. A Serbian team reported in a meta-analysis, the sub-hyoid localization in 65% of cases, followed by the supra-hyoid (20%) and the juxta-hyoid (15%) localizations [16]. The other locations are rarer [17,18,19,20,21]. The clinic is sufficient to make a diagnosis of TDC, but cannot accurately assess the risk of malignancy. On imaging, ultrasound is the first-line exam [6,13,10,22]. It most often shows a cystic lesion, in the form of a midline, anechoic formation. However, it is characterized by a significant variability of signs [13]. It has very good diagnostic reliability, as it can differentiate it from cervical dermoid cyst with clear precision, as reported by the study by the team of Choi HI et al, in South Korea [10]. However, it can be the cause of false positives of 5%. In addition, it is less efficient than computed tomography and magnetic resonance imaging, particularly for intralaryngeal cysts [9,17,18,23]. In an american study published in 2016, ultrasound was used in only 40.1% of cases, while computed tomography was used in 55.9% of cases [11].

Therapeutic aspects

Treatment of TDC is surgical [5,15]. This surgery is performed mainly by the Sistrunk technique [5,14, 24]. The latter has three stages. The first step is an horizontal incision of 5 cm, midway between the upper edge of the thyroid cartilage and the hyoid bone. A possible fistula is removed through a wedge-shaped incision. Dissection is performed with fine Metzenbaum scissors and is continued by opening the linea alba, allowing dissection inferior to the isthmus of the thyroid. The second step is a resection of the cyst and of the hyoid bone, with resection of the prelaryngeal adipose connective tissue. The maneuver described by Sistrunk may be useful during dissection. It consists of introducing the left index finger (for a right-handed surgeon) with the tip of the finger pointing downward on the foramen cecum to guide the dissection. The dissection is performed flush with the lingual mucosa. The thyroglossal duct is then ligated before being cut. The last step is drainage and closure [5,24]. We performed in our patient a modified Sistrunk procedure with a lower incision, but 8 cm wide. The excision is done without capsular breakage. This is a safe technique, but it must be done with great care, because cases of papillary carcinoma on TDC have been reported, even though it could be an underlying thyroid cancer [8,25]. The postoperative follow-up was simple in our patient and the pathological examination of the surgical specimen confirmed the diagnosis of TDC, without signs of malignancy. The postoperative consequences are usually simple after excision, and the drain is often removed within 48 hours. However, we can have some complications like odynophagia and respiratory disorders caused by compressive hematoma [24,25]. In the long term, we can have a recurrence, after an intervention according to the Sistrunk technique, with a rate between 1.5% and 10% [9,26,27,28,29]. With a three-years follow-up, our patient had no recurrence.