Antrochoanal Polyp

An antrochoanal polyp is a benign, solitary, unilateral, non-allergic inflammatory polyp. It arises from the mucosa of the maxillary sinus (antrum), usually near the accessory ostium or the posterior wall. It extends through the sinus ostium (or accessory ostium) into the nasal cavity, and then posteriorly through the choana into the nasopharynx.

It accounts for 4 to 6 percent of all nasal polyps (about 33 percent of nasal polyps in children). It occurs predominantly in children and young adults (peak age 10 to 20 years), with a male preponderance (about 2:1).

It consists of a cystic part within the sinus and a stalk through the ostium. A solid, oedematous part lies in the nose, attached by the stalk to the antral mucosa.

The aetiology is uncertain. It may be due to a cystic dilation of a mucous retention cyst, allergy, infection (chronic inflammation), or an anatomical obstruction by the ostium.

Unlike ethmoidal polyps, it is not associated with asthma or cystic fibrosis, nor aspirin sensitivity. Unlike the latter, it is rarely recurrent when the sinus origin is cleared.

Histology: oedematous stroma with chronic inflammatory cells (neutrophils, with fewer eosinophils than ethmoidal polyps), covered by respiratory epithelium (pseudostratified ciliated) with focal squamous metaplasia.

• Unilateral progressive nasal obstruction (the commonest symptom, in over 90 percent), initially intermittent and then permanent, as the polyp enlarges.
• Mucoid rhinorrhoea, snoring, mouth breathing, hyponasal speech (rhinolalia clausa), postnasal drip, and, with a large polyp, a sensation of a lump in the throat and dysphagia.
• A sleep disordered breathing (obstructive sleep apnoea) in a child, and, occasionally, a polyp that is visible behind the soft palate, hanging into the oropharynx (seen on depressing the tongue).
• Epistaxis (rare), anosmia (rare, unlike ethmoidal polyps), facial pain or headache (uncommon), and serous otitis media (from Eustachian tube obstruction by the nasopharyngeal component).
• Anterior rhinoscopy: a smooth, grey, glistening, pearly, mobile, and insensitive mass in the middle meatus extending to the posterior choana, with a "pedunculated" appearance; nasal endoscopy shows the polyp emerging from the maxillary ostium and passing into the choana.

• Nasal endoscopy: smooth grey polyp emerging from the middle meatus, going backwards to the choana; flexible nasopharyngoscopy shows the posterior extension.
• CT of the paranasal sinuses (the key imaging) shows:
  • an opacified maxillary sinus (with a cystic dilation of the ostium and widening of the ostium or accessory ostium)
  • a polypoid mass with a soft tissue density extending through the ostium into the nasal cavity and choana (the "Funnel sign" or the "sinus-nasal-choanal" tract)
  • no bone destruction
  MRI shows a T2 hyperintense signal with peripheral enhancement and high water content, differentiating from tumour (a non-enhancing centre).
• Differential diagnosis: nasal polyposis (bilateral, multiple), inverted papilloma (unilateral, vascular and cerebriform surface), juvenile angiofibroma (adolescent males, bleeding, vascular), encephalocele (pulsatile, with a bony defect), mucocele, nasopharyngeal carcinoma, lymphoma, and other tumours; unilateral polyps in adults should be biopsied to exclude neoplasm.
• Histopathology of the excised lesion for confirmation.

Medical therapy does not resolve antrochoanal polyps, and surgery is the definitive treatment.

• Surgical removal under general anaesthesia: functional endoscopic sinus surgery (the standard).
  • The nasal part of the polyp is removed with a microdebrider or forceps and snare.
  • The maxillary sinus ostium is widened by middle meatal antrostomy (with uncinectomy).
  • The antral portion and stalk (the origin on the sinus wall) are removed completely, using angled endoscopes (30 and 70 degrees) or a combined approach with a canine fossa trephine. This allows the complete removal of the stalk and the antral part, to prevent recurrence.
  • The nasopharyngeal part can be delivered through the choana or the mouth.
  Complete excision, including the sinus component, results in a recurrence rate of about 5 percent. Simple nasal avulsion alone (without addressing the antral origin) has recurrence rates of 25 to 40 percent.
• Children: endoscopic surgery with the microdebrider; consider a canine fossa puncture for the antral component if the stalk cannot be accessed by endoscope; preserve the inferior turbinate and avoid excessive removal of mucosa.
• Pre-operative: CT, assessment of anaesthesia risks including obstructive sleep apnoea; perioperative antibiotics only in case of infection (amoxicillin clavulanate 625 mg three times a day, children 25 to 30 mg/kg of amoxicillin component per day in 2 to 3 divided doses, for 5 to 7 days).
• Postoperative: saline nasal irrigation (twice daily for 4 to 6 weeks), a topical nasal steroid spray (mometasone 2 sprays per nostril daily or fluticasone) for 4 to 8 weeks, endoscopic debridement at 1 and 4 to 6 weeks, and analgesia; avoid nose blowing for 1 week.
• Follow up: endoscopy at 3, 6 and 12 months (recurrence usually within 2 years), and imaging if recurrence is suspected.
• Complications: bleeding, orbital injury, adhesions and synechiae, ostial stenosis, infraorbital nerve injury (with Caldwell-Luc, so avoided in children because of tooth bud injury), and recurrence.
• Prognosis is excellent with complete removal, including the stalk and the sinus origin.