A paranasal sinus fungal ball, a type of infections-sinus, is minimally invasive. The ball forms when fungus traps within the paranasal sinus. The trapped fungus grows, occupies most of the sinus and blocks the sinus drainage system. The ball may even affect the bone. This unilateral mass of fungus usually occurs only in one sinus. In rare cases, the ball may affect more than one sinus. Generally, the ball occurs in the maxillary sinus. The balls may rarely develop in the frontal and sphenoid sinuses. The balls are more commonly found in female patients in their mid-life.

The fungi found in the air cause the ball. The fungi may vary from geographic region to region. However, Aspergillus fumigatus is the most common cause of the fungus ball. Other species of Aspergillus and Scedosporium apiospermum also initiate the ball formation. Fungi may travel through the airway or odontogenic route to reach the sinus. The ball looks like an onion in the histology sections.

If sinuses are inadequately ventilated and exposed to the fungus, the ball may develop.

The ball, a common form of fungal sinusitis, is one of the principal causes of chronic unilateral infections-sinus.

The fungal ball comprises many fungal hyphae layers. Inflammation is very little within or around the ball. 

In many cases, there may be no symptoms at all. However, some patients with fungus ball may complain about strange facial fullness or may suffer from any other sinonasal tract disorder. 

Allergic symptoms are rare in patients with the ball. However, fetid smells, congestion, and pressure and pain in the face may appear. The expanding ball obstructs and worsens the symptoms.

The ball is an incidental finding in diagnosing different types of sinusitis. The following criteria may help in diagnosing the ball:

Radiological scans of the sinus display opacification with / without calcification.

Materials resembling to clay or mucopurulent cheesy are present in the sinus.

The sinus mucosa is separate from the dense ball.

Chronic inflammation is non-specific.

Allergic mucin and granuloma are absent.

There is no evidence of invasion of the bone, blood vessels or mucosa.

As the ball is mostly asymptomatic, radiography is necessary for diagnosis. Since the ball neither attaches nor invades the tissue / sinus cavity blood supply, medication does not help. This ball should be removed surgically. Moreover, sinus drainage and ventilation should be restored. No antifungal drugs are given, as the ball rarely reoccurs.