Teaching Case

A four-year-old child presented with a discharging sinus on the right side of neck since 13 months of age. The patient had undergone incision and drainage at the age of one year for a cervical abscess, following which a discharging sinus developed at the operative site.

On clinical examination, a pyriform-shaped scar with a superior overhanging skin flap and an opening was evident in the right para-midline anterior neck along the anterior border of the sternocleidomastoid muscle at the level of the superior border of thyroid cartilage (Figure 1). Clinical photograph after a bolus of water showing discharge from the external opening (Figure 2). Ultrasound examination shows an air-filled tract extending into the right lobe of the thyroid (Figure 3).

An esophagogram performed using barium sulphate suspension (anteroposterior and lateral views) showed a linear tract extending into the soft tissue of the neck on the right at the level of the C4 vertebral body (Figure 4).

Fluoroscopic sinogram performed using water-soluble iodinate contrast (Diatrizoate Meglumine and Diatrizoate Sodium solution) and a plastic cannula in the external opening of the fistula in the right lateral neck demonstrated the fistulous tract opening into the apex of the right pyriform sinus (Figures 5a, 5b and 5c).

Based on the clinical and imaging findings, the patient was diagnosed to have a right-sided pyriform sinus fistula.

Background

The third and fourth branchial pouches form the future pyriform sinus during foetal development. Failure of obliteration of the third and fourth pharyngeal pouches results in the formation of a pyriform sinus fistula (PSF) [1–3]. Pyriform sinus fistulas are rare and observed predominantly in the paediatric population. In most cases, the fistula is seen on the left side of the neck [4]. Complete fistulae are rare; the majority first appear as sinus tracts before developing into secondary iatrogenic fistulae [5].

Clinical Perspective

Typical clinical signs of PSF include severe suppurative thyroiditis and recurrent neck infections with abscess formation. In patients with PSF, a cutaneous opening at the neck is usually found. The opening could represent the remains of the developing fourth branchial pouch, or it could just be the result of an abscess cavity burst [4].

Imaging Perspective

Traditionally, esophagogram has been used to demonstrate the fistula. However, it may fail to demonstrate the fistula in the setting of acute inflammation.

On ultrasonography, gas in the vicinity of the left upper pole of the thyroid is thought to be pathognomonic of a pyriform sinus fistula. On CT, air density within the tract on the axial images inferior to the pyriform sinus can help to identify the sinus tract of the PSF. On the other hand, direct laryngoscopy can be used for acute episodes and frequently makes the fistulous orifice in the pyriform fossa visible [1]. Fistulograms and CT fistulograms help confirm the diagnosis and demonstrate the size, course and extent of the fistulous tract and its relationship with neighbouring neck structures. This information is crucial for surgical planning, ensuring that a complete removal of the sinus tract is performed, lowering the likelihood of recurrence.

Outcome

Surgical excision is the definitive treatment option. When infectious signs are present, antibiotics should be given prior to surgery [6]. However, surgical intervention carries a high risk of recurrent laryngeal nerve damage, particularly when recurrent abscesses have resulted in scarring and fibrosis. Other less invasive treatment options include chemocauterizaton (using 40% trichloroacetic acid (TCA)) and electrocauterization, but these are associated with higher recurrence rates [7].

Take Home Message

Even though right-sided lesions are uncommon, branchial cleft cysts and pyriform sinus fistulas need to be taken into account in the presence of a neonate or an infant with recurrent cervical abscesses on either side of the neck.