Imaging of granulomatous and chronic invasive fungal sinusitis: comparison with allergic fungal sinusitis

Objective: To study the radiological features of chronic/granulomatous invasive fungal sinusitis (IFS) and identify differentiating characteristics, if any, from allergic fungal sinusitis (AFS).

Study design: Prospective radiological study.

Setting: Tertiary hospital in northern India.

Subjects and methods: Subjects were nonacute fungal sinusitis patients with orbital involvement presenting between January 1999 and December 2003. Seventeen IFS and 12 AFS patients with mean age 27 years (range 7-59 years) underwent computed tomographic scan (CT) and magnetic resonance imaging (MRI) of paranasal sinuses with contrast. These were operated within one month of doing the scans and had histologically confirmed fungal sinusitis. Outcome measures were characteristics of opacity produced by the diseased tissue on CT and MRI, side and number of sinuses involved, expansion of sinuses, areas of bone erosion, and extra-sinus extension.

Results: IFS showed homogenous opacity (isodense or hyperdense to muscle tissue) on CT and isointense and hypointense signal on T1- and T2-weighted MR images respectively. IFS showed involvement of one or two sinuses only, homogenous contrast enhancement, lack of expansion of sinuses, and bone erosion localized to the area of extra-sinus extension, and the extra-sinus component of the disease was more than the intra-sinus component. AFS showed heterogenous opacities with hyperattenuation areas on CT, isointense/hypointense to signal void on T1- and T2-weighted MR images. Expansion of sinuses, extensive bone erosion, lack of contrast enhancement, multiple sinus involvement, and major bulk of disease being intra-sinus rather than extra-sinus were other characteristics of AFS.

Conclusion: Radiological features of IFS are described that are different from AFS.