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Head and Neck Imaging

Fungal sinusitis

inflammation in the paranasal sinuses due to fungal disease, most commonly Aspergillus (see aspergillosis head and neck). Fungal sinusitis is classified in four clinicopathological categories:

  • Noninvasive mycotic colonization, with formation of a mycetoma or fungus ball. Such a mycetoma is semisolid and typically shows high attenuation on CT, low signal intensity on T2- and intermediate to low signal intensity on T1-weighted MR sequences (Fig.1).

  • Chronic invasive sinusitis occurs in otherwise normal hosts as an endemic disease in Sudan and Saudi Arabia. It may occur in other areas of the world in (moderately) immunocompromised hosts. The distinction between the noninvasive and invasive type is not clear-cut; it may be that the invasive form follows the noninvasive type in some patients. Bone destruction is commonly seen in this type.

  • Fulminant fungal sinusitis, seen in immunocompromised hosts. Such an aggressive fungal infection may cause extensive destruction of the skull base, with cavernous sinus thrombosis, blood vessel invasion and rapid intracranial spread of disease. Various fungal species may cause such a fulminant course, such as candidiasis, aspergillosis, histoplasmosis and mucormycosis.

  • Allergic fungal sinusitis is a benign sinus disease related to a hypersensitivity reaction to fungal antigens. Allergic fungal sinusitis should be suspected in any atopic patient with refractory sinus disease. The radiologial findings can be quite distinctive, showing central sinus high attenuation on CT and low signal on T2-weighted MR images, corresponding to areas of thick inspissated allergic mucin (Fig.2). Diagnosis requires histopathological examination, demonstrating allergic mucin. Hyphae can be demonstrated on special fungal stains or confirmed by a positive fungal culture.

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    Fig.1

    Coronal T2-weighted (a) and axial gadolinium-enhanced T1-weighted (b) spin-echo image. A mass with low (a, arrows) to intermediate (b, arrow) signal intensity is seen in the left frontoethmoid cells, showing no enhancement. Mycetoma, with surrounding inflammation. There is minimal orbital involvement.
    Fungal sinusitis, Fig.1 (a)
    Fungal sinusitis, Fig.1 (b)
    Fungal sinusitis, Fig.2 (a)
    Fungal sinusitis, Fig.2 (b)