Fungal Rhinosinusitis

Fungal rhinosinusitis is a form of sinusitis that has recently been heralded as the underlying cause of all chronic rhinosinusitis. Although this theory has raised a lot of controversies, fungal rhinosinusitis remains high on the differential of any patient presenting with rhinosinusitis. Classically, fungal rhinosinusitis has been divided into two major categories, invasive and noninvasive, based on histopathologic evidence of fungal elements penetrating host tissue specifically the sinus mucosa, the submucosa, blood vessels or bone.

Within each category, several subdivisions are described. Noninvasive fungal sinusitis encompasses sinus fungal ball (SFB) and allergic fungal rhinosinusitis. Invasive fungal rhinosinusitis encompasses acute fulminant invasive fungal sinusitis (AFIFS) and chronic invasive fungal sinusitis (CIFS).

Noninvasive Fungal Rhinosinusitis:

Saprophytic Fungal Infestation (SFI):
It is the visible growth of fungus on mucus crusts within the sinonasal cavity. Patients usually have nonspecific complaints, and microcrusts are identified and removed during routine nasal endoscopy. No further studies are warranted and treatment is limited to daily nasal saline irrigation with weekly endoscopic examinations until the condition resolves completely.

Sinus Fungus Ball (SFB):
Usually referred to as “mycetoma”. It is a dense tangle of fungal elements sequestered within a paranasal sinus. Aspergillus is the most commonly isolated organism. Symptoms are usually unilateral and attributable to a mass effect within a confined sinus cavity. Mycetoma is usually confined to a single sinus (up to 94% of cases), with the maxillary sinus being most commonly involved (up to 85%). Nasal endoscopy shows mucosal inflammation. CT scan demonstrates radiodensities within the opacified sinus or bony sclerosis. Treatment is usually surgical and provides both diagnosis and cure (96%). Topical or systemic antifungal therapies are not recommended.

Allergic Fungal Rhinosinusitis (AFRS):
The exposure of the atopic host to an innocuous fungal species leads to the production of massive amounts of IgE resulting in mucosal inflammation, sinus ostial narrowing and obstruction, and the production of thick allergic mucin. This cycle is self-perpetuating and is known as the“AFRS cycle”. The end result is damage to the involved sinus

through pressure atrophy, bone remodeling and the continuous release of inflammatory mediators. Patients present with symptoms similar to chronic rhinosinustis with production of thick semisolid discharge. Successful management of AFRS requires a combination of both medical and surgical therapy. Surgery identifies a thick nasal discharge resembling peanut butter or grease (Figure 1-3). The goal of surgery is drainage with restoration of sinus aeration and mucociliary clearance. Medical management includes preoperative antibiotics and steroids to help reduce intraoperative bleeding to be continued postoperatively. Fungal immunotherapy specifically targeting IgE affords improvement in long term disease control.

 

Invasive Fungal Rhinosinusitis:

 

Acute fulminant invasive fungal sinusitis (AFIFS):

This form of sinusitis is characterized by a time course less than 4 weeks, has prominent vascular and neural invasion, and is nearly completely limited to immunocompromised patients (diabetics, patients with malignancies, immunosuppressed patients). Mucor and Aspergillus are the most frequently isolated pathogens. The presentation does not differ from acute bacterial rhinosinusitis. A thorough cranial nerve examination should be done for fear of spread along neural sheathes. On nasal endoscopy the earliest and most reliable manifestation of fungal angioinvasion is mucosal pallor. The finding of a necrotic eschar is a sign of advanced disease. CT scan is the best initial imaging modality to identify bony erosion or extrasinus extension. If orbital or intracranial extension is noted, MRI is needed to determine the extent of invasion. Diagnosis is established by biopsies of the nasal mucosa. Treatment requires a combination of both medical and surgical therapy. Reversing the underlying etiology of the immunosuppression results in the best outcome. Wide surgical debridement of all necrotic tissue until actively bleeding margins are reached is necessary. Systemic antifungal therapy should be started immediately. Cavernous sinus thrombosis and invasion of the CNS are common and carry a mortality rate of 50-80%.

 

Chronic Invasive Fungal Sinusitis (CIFS):

Unlike acute fulminant invasive fungal sinusitis, this form of fungal sinusitis is characterized by a time course of more than 4 weeks, is caused by Aspergillus in more than 80% of cases and occurs equally in immunocompetent and immunocompromised patients. The presentation is that of a rhinosinusitis that is refractory to conventional therapy. This often results in delay in diagnosis until facial deformity or visual or neurological symptoms develop. Diagnosis is similar to AFIFS. Treatment consists of both systemic antifungal therapy and surgical debridement.

 

 

 

 

 

 

 

 

 

Figure 1: Axial CT scan and MRI showing complete opacification of the left sphenoid sinus suggestive of fungal sinusitis.

 

 

 

 

 

 

 

 

 

Figure 2: Coronal CT scan and MRI showing complete opacification of the left sphenoid sinus suggestive of fungal sinusitis.

 

 

 

 

 

 

 

 

 

 

Figure 3: Intaoperative finding of allergic mucin in the sphenoid sinus showing its “peanut butter” consistency.