4th Branchial Cleft Sinus Anomaly Presenting as Recurrent Thyroid Abscess in A Child: A Case Report

Introduction

Fourth branchial anomalies characteristically present in close association with the thyroid gland, with a tract ascending to the pyriform sinus [1]. Clinical presentation includes recurrent anterior neck abscesses, thyroiditis and thyroid abscess. Diagnosis is based on imaging and direct laryngoscopy. Management options include endoscopic approaches, open transcervical approaches and a combination of both.

Discussion

Branchial cleft anomalies occur in 1 of 3 forms: cysts, sinuses, or fistulae. Cysts are epithelial-lined structures that do not have external openings that connect to the skin or pharynx. Sinus tracts connect either the skin or the pharynx to a blind pouch. Sinus tracts communicate either externally with skin as a visible punctum or internally with the pharynx or larynx, where the punctum opening will only be visible on endoscopy. Branchial cleft fistulae are true communications connecting the pharynx or larynx with the external skin [2]. Second branchial cleft anomalies are most common accounting for up to 90% of branchial anomalies with the remaining 10% are 1st, 3rd, 4th branchial anomalies of which fourth branchial anomalies are rarest [3].

A fourth branchial arch anomaly most commonly presents as a sinus tract that courses from the apex of the pyriform fossa to the upper lobe of the left thyroid. Fourth branchial arch anomalies are remnants of an embryological tract which arises from the pyriform sinus. The tract descends from the pyriform fossa along the tracheoesophageal groove, posterior to the internal and common carotid arteries [4]. Fourth branchial cleft fistula presents as recurrent neck abscesses, thyroiditis and thyroid abscess.

Diagnostic tests usually combine imaging tests and direct laryngoscopy. Direct laryngoscopy can be performed during an acute infection and if a sinus tract is identified it confirms the diagnosis. Direct laryngoscopy aids in identification of the sinus tract during neck exploration by insertion of various probes, catheters contrast fluids or by transillumination of the tract. Definitive treatment with cauterization of opening of the sinus tract can be done [5].

Although the sinus or fistula tract cannot be seen easily on imaging, the combination of an infected neck cyst with adjacent thyroid inflammation and inflammation of tissues along the expected tract is pathognomonic [1]. In patients presenting with acute suppurative thyroiditis or neck infection with thyroid gland involvement, the presence of T2 high signal behind the cricothyroid joint on MRI is highly suggestive of the diagnosis of congenital pyriform sinus fistula [6]. Contrast swallow studies can be useful after acute inflammation has subsided as contrast can pool in the pyriform fossa sinus and proximal tract. Barium swallow examination may however, fail to demonstrate the sinus tract, even after the Valsalva maneuver because they require a quiescence of inflammation of the tract for the entry of the barium contrast into the sinus [7]. Ingested contrast with CT can also aid the surgeon in complete removal by delineating the tract and its relationship to surrounding structures in the setting of prior infection and surgical manipulation [8].

Management options include complete surgical excision, a combined treatment involving external surgery with internal cauterization of the mucosal communication to eradicate the disease process [9], or solely endoscopic approaches.

Endoscopic options include electrocauterization of sinus opening, coblation treatment of the sinus opening [10], obliteration of the opening using fibrin glue [11], trichloroacetic acid cauterization [12].

These solely endoscopic approaches via direct laryngoscopy allow for management of the underlying pathology and at the same time reduce the risks associated with transcervical, open approaches. However, the endoscopic approaches do not address any persistent abnormality within the thyroid gland and may not fully treat the source if residual abnormality persists [13].

Hemithyroidectomy as well as partial resection of the ipsilateral posterior thyroid ala should be considered as usually as there is a history of suppurative thyroiditis or the tract is noted to run through the thyroid itself [1]. In the series reported by Sihag A, et al. [14] hemithyroidectomy was combined with complete sinus tract excision in only 36% of cases where the sinus tract was very closely adhered to the left thyroid lobe due to repeated suppurative thyroiditis in past. Hemithyroidectomy may not always be necessary if the sinus tract can be adequately exposed to thyroid lobe without damaging the recurrent laryngeal nerve. In the series by Arunachalam P, et al. [9], all the patients underwent combined electrocauterization of the internal opening with neck exploration and excision of anomalous tract. Cannulation of the tract under direct visualization with a small catheter aided complete and safe dissection. In one of their cases, the fibrous tract involved the thyroid lobe and hemithyroidectomy was done. As per Nicoucar K, et al. [5] complete excision of the entire fistula tract during a quiescent period, together with a partial thyroidectomy, appears to be the treatment of choice. However, they suggest that open surgery should be reserved for patients older than age 8 years to minimize complications. In children less than 8 years, they recommend medical management with endoscopic cauterization as an effective alternative strategy.

In our case we combined electrocauterization of the pyriform sinus opening, with hemithyroidectomy and excision of the tract. Intraoperative neuromonitoring and use of transillumination of tract through pyriform fossa using flexible fiberoptic scope aided in avoiding the complication of recurrent laryngeal nerve injury and aided complete excision with no recurrence at 1 year follow up. Histopathology demonstrated the tract coursing through the thyroid gland.

Conclusion

Fourth branchial arch anomalies should be suspected in children with recurrent anterior neck abscesses and thyroid abscesses. Imaging and direct laryngoscopy are used for diagnosis. A sinus opening in the pyriform fossa identified on direct laryngoscopy confirms the diagnosis. Management includes cauterization of the sinus opening and transcervical excision of the tract, with ipsilateral hemithyroidectomy. Intraoperative neuromonitoring and fiberoptic transillumination can be useful to prevent complications and recurrence.