Lingual thyroglossal duct cyst treated by intraoral marsupialisation

Abstract

The authors report a rare case of lingual thyroglossal duct cyst (TGDC) which is being treated by non-conventional technique of intraoral marsupialisation and the authors also review the embryology of TGDC and its diagnosis. The patient was operated upon by intraoral route and the cyst was marsupialised. There is no recurrence in the past 2-year follow-up. This approach avoids unnecessary scar and postoperative morbidity associated with opening neck planes and removing the central hyoid as indicated in conventional technique.

Background

A thyroglossal duct cyst (TGDC) is defined as a collection in the thyroglossal duct remnant presenting as a midline swelling anywhere along its path from the foramen caecum to the pyramidal lobe of the thyroid gland.¹ The lesion rarely occurs at the base of the tongue, and the patient may present with difficulty in swallowing and breathing. Previous surgeons advocated formal Sistrunk procedure (cervical approach) for lingual TGDC,² but this is associated with high morbidity and neck scarring. Good success rate with lower morbidity can be achieved with marsupialisation of lingual TGDC.^{3 4} We describe a case of lingual TGDC which was managed by marsupialisation via direct approach through the mouth and is without recurrence for 2 years. It also avoids the complications of tongue and mandible splitting or cervical approach. The present report also reviews the embryology of TGDC development.

Case presentation

A 4-year-old girl presented to our outpatient department with progressive difficulty in swallowing food for 3 months. On examination of the oropharynx a smooth, spherical swelling was seen at the midline base of tongue (figure 1). On palpation, swelling was roughly 3×3×3 cm and cystic.

Figure 1.

Clinical photograph showing smooth, spherical swelling at midline base of tongue.

Investigations

Ultrasonography of the neck confirmed thyroid at its usual location. Contrast-enhanced computed tomogram (CECT) of the pharynx revealed a well-circumscribed cystic swelling at the midline base of tongue with no enhancement and low intensity (figure 2). The swelling was mildly constricting the common passage for food and air (figure 3).

Figure 2.

Axial section of contrast-enhanced computed tomogram showing spherical, cystic with low-intensity, thin-walled, midline swelling over base of tongue.

Figure 3.

Sagittal reformatted image of contrast-enhanced computed tomogram showing swelling arising from base of tongue minimally compromising the air and food passage.

Treatment

The patient was taken up for surgery under general anaesthesia. Fibreoptic nasotracheal intubation was done while tongue was kept pulled out to avoid accidental bursting of cyst and to provide field free for surgery. Cyst was opened at the level of tongue mucosa and the external wall removed completely. The base of the lesion was further inspected for any extension of the duct, and none was found. The edges of the cyst were electrocauterised. Postoperative period was uneventful and feeding was started orally the next day. The specimen sent for histopathology revealed capsular wall composed of columnar epithelium (luminal side) with mucous glands in the submucosa and non-keratinising squamous epithelium outside, that is, consistent with TGDC.

Outcome and follow-up

The patient has been under close follow-up for the past 2 years and there has been no recurrence.

Discussion

The normal migration of embryonic thyroid tissue from the foramen caecum to its mature position in the anterior neck results in the creation of the thyroglossal duct. The lumen of the duct is usually obliterated by the 9th or 10th gestational week forming thyroglossal tract. Any part of the thyroglossal tract may persist into adult life. The commonest finding is persistence of the lowest part of the tract as the pyramidal lobe of the thyroid gland. Less frequently, the tract may fail to descend into the neck from the base of the tongue so that it persists as lingual thyroid.⁵ However, the most common clinical condition resulting from persisting tract remnants is the thyroglossal cyst. The endothelial elements of the ductal lining produce mucus, leading to development of a cyst. Such cyst may arise anywhere along the duct, mostly from distal part, presenting as a midline, anterior cervical mass in children. Eighty-five per cent are found infrahyoid, 8% are found above the hyoid, 5% are found in the suprasternal region of the neck and only 1–2% is found at the base of the tongue.⁶

In a series of 300 TGDC, only two (0.67%) were in the region of the foramen caecum⁷, that is, located at the junction of the anterior two-thirds and the posterior one-third of the tongue in the midline. The low incidence of lingual TGDC is because the duct initially atrophies from the oral side, from where the thyroid descent first begins. The low incidence of lingual TGDC is responsible for poor knowledge about the management of such cases.

The most common signs and symptoms of lingual TGDC in infants are due to upper airway obstruction and include intermittent or continuous stridor, laboured respiration with accessory muscle use, chest wall retraction and dyspnoea. In older children, lingual TGDC could lead to difficulty in swallowing and respiration depending upon volume of the cyst. In our case, the patient's main complaint was difficulty in swallowing solid food. Particularly, large cysts on the base of tongue may cause severe airway obstruction by a mass effect on the hypopharynx and by displacing the epiglottis. An unusual presentation of lingual TGDC is breath holding–like spells and life-threatening airway obstruction causing negative pressure pulmonary oedema and respiratory failure in an infant.⁸

Complications of untreated lingual TGDC are acute infection, abscess formation⁹ and airway obstruction. In English medical literature, six cases have been reported, where infants had died due to airway obstruction by lingual TGDC.¹⁰ All died suddenly in the bed or cot while sleeping without any significant symptoms and signs. Cause of death was due to airway obstruction by lingual TGDC, confirmed by postmortem examination.

The differential diagnosis⁶ includes cystic swellings like vallecular mucous cyst and lingual dermoid cyst; physiological swellings like lingual thyroid and hypertrophied lingual tonsil; benign tumours like adenoma, fibroma, haemangioma and lipoma and malignant tumours such as squamous cell carcinoma and lymphoma.

The diagnosis is confirmed by laryngoscopy and CECT of the region.¹¹ The laryngoscopy shows a pink, cystic, round, smooth-walled, midline, non-pedunculated mass over foramen caecum. The CECT confirms the above finding and shows the mass to be non-enhancing on contrast with low intensity and constricting the air passage.¹¹ Ultrasound neck or sometimes scintigraphy may be asked for, to confirm the presence of normal thyroid.⁵ This avoids excision of only thyroid tissue present in cases of lingual thyroid. Ultrasound neck was done in our case to confirm the same.

Aspiration of the cyst alone, or inadequate dissection, is associated with fairly rapid refilling of lingual TGDC.⁴ Cyst puncture can ameliorate the symptoms of the patients, while surgical removal is the method of radical cure. Modified Sistrunk procedure, that is, a combined intraoral and cervical approach has been reported to be successful, but is associated with high morbidity and scar. Similarly, cyst excision by midline tongue-splitting incision, by lateral pharyngotomy, transhyoid approach or by mandibulotomy leads to high morbidity which is unwarranted for this benign lesion. Urao³ described three children with a lingual TGDC in whom marsupialisation of the cyst was performed without excision. It had good success rate with lower morbidity and no recurrence after 2–5 years follow-up. We hereby confirm the same after successfully managing our case with the similar technique. Weldon⁸ used CO₂ laser for marsupialisation of the cyst.

Poor incidence of recurrence after marsupialisation is because of two reasons. First, the duct above the hyoid bone spreads into many ductuli as it approaches the foramen caecum.¹² Thus, the lack of lingual TGDC extension into the neck is attributable to atrophy of the distal portion of this duct, above the hyoid bone. Second, any additional ductuli could freely drain into the oral cavity after marsupialisation, which would prevent recurrence. This further supports our simple and effective technique of management of lingual TGDC.

Learning points.

• ▶Lingual TGDC is an uncommon variant of TGDC.
• ▶It is usually being managed by Sistrunk's operation.
• ▶Marsupialisation of cyst via intraoral route is suggested.