Fungal Ball of the Sinus

A fungal ball (mycetoma) of the sinus is a non-invasive accumulation of dense fungal hyphae in a paranasal sinus, most often the maxillary sinus and then the sphenoid. It occurs in immunocompetent patients, and tissue is not invaded.

It makes up about 3% to 5% of surgically treated chronic rhinosinusitis. It affects mainly women over 50 years. Aspergillus fumigatus is the commonest cause. Risk factors include previous dental work with root canal filling material (zinc oxide), and ostial obstruction.

Pathophysiology.

Fungal spores enter a poorly ventilated sinus, and hyphae proliferate on the secretions without invading the mucosa. A grey brown, clay like or cheesy mass forms, with chronic mucosal inflammation.

Unilateral nasal blockage, discharge, facial pressure, foul smell and cacosmia. Many patients have no symptoms and the ball is found by chance on imaging.

Red flags.

• Visual loss, double vision or proptosis (sphenoid involvement or invasion).
• Severe headache.
• Immunosuppression or diabetes.
• Bone destruction on CT.

CT shows unilateral opacification of one sinus with focal hyperdense areas (calcification, metallic density) and thickened bone, without bone destruction. Magnetic resonance imaging shows a signal void on T2. Endoscopic sampling confirms fungal hyphae without tissue invasion on histology (Grocott stain), and culture identifies the species. Test for diabetes and immune deficiency.

Differential diagnosis.

• Chronic invasive fungal rhinosinusitis.
• Allergic fungal rhinosinusitis.
• Odontogenic sinusitis with foreign body.
• Inverted papilloma.
• Antrochoanal polyp.
• Sinonasal malignancy.

The treatment is endoscopic surgical removal of the fungal ball with widening of the sinus opening for drainage. Systemic antifungal drugs are not needed in immunocompetent patients. Recurrence is under 5%.

• Saline irrigation: 240 mL isotonic saline into each nostril twice daily for 4 to 8 weeks after surgery; monitor crusting; use boiled or sterile water.
• Mometasone nasal spray 50 micrograms for each spray (after surgery): 2 sprays into each nostril once daily for 4 to 8 weeks; maximum 200 micrograms daily in each nostril; monitor for epistaxis.

Add voriconazole in immunocompromised patients when tissue invasion is shown: 6 mg/kg IV every 12 hours for 2 doses, then 4 mg/kg IV every 12 hours or 200 mg orally twice daily, for at least 6 weeks; maximum 600 mg daily orally; monitor trough levels and liver tests; halve the maintenance dose in mild to moderate cirrhosis.

Monitoring. Endoscopy at 2 weeks, 6 weeks and 6 months after surgery.

Referral and escalation. ENT.