Fungal Sinusitis Workup

Updated: Jan 19, 2022
  • Author: Hassan H Ramadan, MD, MSc, FACS, FARS; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Laboratory Studies

Elevated total fungus-specific IgE concentrations are often found in patients with allergic fungal sinusitis. This is less common in patients with sinus mycetoma.

Using enzyme-linked immunosorbent assays, one study examined the sinonasal tissue and secretions in patients with chronic rhinosinusitis for the presence of mycotoxins (ie, aflatoxin, deoxynivalenol, zearalenone, ochratoxin, and fumonisin) to determine their possible role, if any, in chronic rhinosinusitis. No mycotoxins were found, except ochratoxin in 4 of 18 samples. The clinical significance of these results has not been determined. [11]

A study by Payne et al of 41 patients with acute invasive fungal rhinosinusitis reported that predictive variables for the disease include an absolute neutrophil count below 500/μL (sensitivity of 78%), abnormalities of the septal mucosa (specificity of 97%), and necrosis and mucosal abnormalities of the middle turbinate (specificities of 97% and 88%, respectively). [12]


Imaging Studies

CT scanning of the paranasal sinuses in the coronal views is essential in the evaluation of patients in whom fungal sinusitis is suspected. [5, 6]  Middlebrooks et al devised a seven-variable, CT scan–based diagnostic model for acute invasive fungal rhinosinusitis. They reported that an abnormality associated with one of the model’s variables—which consist of periantral fat, bone dehiscence, orbital invasion, septal ulceration, the pterygopalatine fossa, the nasolacrimal duct, and the lacrimal sac—has a positive predictive value of 87%, a negative predictive value of 95%, a sensitivity of 95%, and a specificity of 86%, while the involvement of two variables gives the model a specificity of 100% and a positive predictive value of 100%. [13]

While intralesional hyperdensity on CT scan can be used in the detection of a maxillary sinus fungus ball, zinc deprivation can lead to the absence of this finding. However, a retrospective study by Cha et al indicated that other CT-scan characteristics can be used to help identify such lesions, including a “fuzzy appearance and maxillary sinus full haziness with mass effect.” [14]

Magnetic resonance imaging (MRI) with enhancement may be helpful in assessing patients with allergic fungal sinusitis and in patients in whom invasive fungal sinusitis is suspected. [6]  MRI may show low signal intensity, suggesting a fungal process versus a solid mass in allergic fungal sinusitis. It is also helpful in evaluating CNS spread in invasive fungal sinusitis.

A study by Kim et al indicated that T1-weighted images (T1WI) in MRI can be used in combination with T2WI to identify the presence of fungus balls in the paranasal sinuses. The investigators state that fungus balls “can be suggested by the presence of the hyper-signal intensity portions in the fungal mass on T1WI in conjunction with dark-signal lesions surrounded by high-signal, hypertrophic mucosal walls in paranasal sinuses on T2WI.” [15]


Histologic Findings

In allergic fungal sinusitis, allergic mucin contains intact and degenerated eosinophils, Charcot-Leyden crystals, cellular debris, and sparse hyphae. The sinus mucosa has mixed cellular infiltrate of eosinophils, plasma cells, and lymphocytes. The mucus membrane is not invaded by fungi.

No allergic mucin is present in sinus mycetoma. However, the sinus contains dense material that consists of hyphae separate from but adjacent to the mucosa. The sinus mucosa is not invaded.

Histopathologic studies in acute invasive fungal sinusitis reveal hyphal invasion of the mucosa, submucosa, and blood vessels, including the carotid arteries and cavernous sinuses; vasculitis with thrombosis; hemorrhage; and tissue infarction.

Necrosis of the mucosa, submucosa, and blood vessels, with low-grade inflammation, is observed in chronic invasive fungal sinusitis.

Granuloma with multinucleated giant cells with pressure necrosis and erosion is observed in granulomatous invasive fungal sinusitis.

A retrospective study by Melancon and Clinger indicated that in the diagnosis of acute invasive fungal sinusitis, frozen section biopsies have a positive predictive value of 100%, a sensitivity of 87.5%, and a specificity of 100% and are therefore important in the early diagnosis of this disease. [16]