Imaging Findings

Both CT and MR findings of fungus ball are conditioned by the high content of heavy metals (iron and manganese) and calcium within fungal hyphae. As a result, CT density of the fungus ball is spontaneously hyperdense; microcalcifications can be observed, scattered within the lesion (Fig. 6.18). Though extremely specific, these signs lack sensitivity (Dhong et al. 2000). The MR pattern may often be misleading: actually, the paramagnetic properties of iron and manganese combined with the low number of freely moving protons provoke both T1 and T2 shortening. Consequently, on both sequences, MR demonstrates

Fungus Ball Maxillary Sinus

Fig. 6.18a,b. Fungus ball. Plain CT, coronal (a) and axial (b) plane. In (a) both sphenoid sinuses are completely filled by spontaneously hyperdense material. Focal areas of pressure demineralization are depicted at the roof of sinuses (arrows). In (b) some scattered calcifications are demonstrated within the fungus ball

Fig. 6.18a,b. Fungus ball. Plain CT, coronal (a) and axial (b) plane. In (a) both sphenoid sinuses are completely filled by spontaneously hyperdense material. Focal areas of pressure demineralization are depicted at the roof of sinuses (arrows). In (b) some scattered calcifications are demonstrated within the fungus ball a hypointense lesion bordered by hyperintense (T2) and enhancing (T1, after contrast administration) mucosa (Rao et al. 2001). In some cases, T1 and T2 shortening may be so marked to result in a signal void, making discrimination between fungus ball and intrasinusal air nearly impossible (Fig. 6.19).

In eosinophilic fungal rhinosinusitis, the CT density and MR paramagnetic characteristics of fungal material, as well as progressive dehydration of eo-

Fungus Ball

Fig. 6.19a,b. Fungus ball. Axial SE T2 (a), sagittal Gd-DTPA SE T1 (b). Retained fungal hyphae exhibit on both pulse sequences marked hypointensity, resembling an empty sinus. The non-invasive nature of this form of fungal infection is heralded by the complete preservation of the mucosa, detectable as a thin and continuous hyperintense and enhancing layer

Fig. 6.19a,b. Fungus ball. Axial SE T2 (a), sagittal Gd-DTPA SE T1 (b). Retained fungal hyphae exhibit on both pulse sequences marked hypointensity, resembling an empty sinus. The non-invasive nature of this form of fungal infection is heralded by the complete preservation of the mucosa, detectable as a thin and continuous hyperintense and enhancing layer sinophilic mucin, produce signal patterns similar to fungus ball (Fig. 6.20). The differentiation is based on localization of the disease - isolated and unilateral in 94% of fungus balls, diffuse and scattered in 95% of eosinophilic fungal rhinosinusitis - and association with nasal polyposis, which is more common in eo-sinophilic fungal rhinosinusitis (Dhong et al. 2000).

Bone changes in both fungus balls and eosino-philic fungal rhinosinusitis follow the same model exhibited by chronic rhinosinusitis and nasal pol-yposis. Mechanical pressure and osteoclastic activ

Nasal Polyps

Fig. 6.20a,b. Nasal polyposis, eosinophilic fungal rhinosinusitis. Ethmoid, nasal fossae, and maxillary sinuses are completely filled by polypoid material exhibiting scattered areas of spontaneous hyperdensity. Extensive bone remodeling and dehiscence at the level of the medial orbital walls, both pushed laterally (arrowheads). Focal areas of demineralization are also observed at the roof of the frontal sinuses (arrows)

Fig. 6.20a,b. Nasal polyposis, eosinophilic fungal rhinosinusitis. Ethmoid, nasal fossae, and maxillary sinuses are completely filled by polypoid material exhibiting scattered areas of spontaneous hyperdensity. Extensive bone remodeling and dehiscence at the level of the medial orbital walls, both pushed laterally (arrowheads). Focal areas of demineralization are also observed at the roof of the frontal sinuses (arrows)

ity result in bone demineralization, whereas sclerotic thickening is observed in the case of prevalent osteo-blastic activity. Sinus expansion and bone thinning are more commonly observed in eosinophilic fungal rhinosinusitis (93% vs 3.6%) (Mukherji et al. 1998; Ferguson 2000), whereas sclerosis of sinusal walls is more typical in fungus balls.

Invasive mycoses may manifest in two main forms, namely acute fulminant and chronic, the discrimination between the two being based on the clinical course. A rare invasive form involving immunocom-

petent patients has been reported in Southeast Asia and Africa, referred to as granulomatous or "indolent" fungal rhinosinusitis. Its CT and MR appearance is not yet clearly defined. Imaging findings of acute fulminant fungal rhinosinusitis basically consist of aggressive destruction of bony sinusal walls and invasion of adjacent soft tissues. At MR, abnormal changes of the sinusal investing mucosa (effacement of the hyperintense - T2 - and of the enhancing mucosal layer) are the direct demonstration of the invasive nature of the infection (Fig. 6.21). Intrasinusal hyperdensities are far less common than in noninva-sive forms. Spread to the pterygopalatine fossa, orbit, anterior and/or middle cranial fossa is a particularly severe complication (Saleh and Bridger 1997). CT and MR appearance of chronic invasive fungal rhino-sinusitis does not significantly differ from the acute fulminant form: intracranial and intraorbital infiltration is almost always observed, usually with inhomo-

geneous enhancing tissue invading the orbital apex or the cavernous sinus (Chan et al. 2000; Rumboldt and Castillo 2002) (Fig. 6.22). The differential diagnosis between these two entities is mainly based on the celerity and severity of the clinical course.

Reducing Blood Pressure Naturally

Reducing Blood Pressure Naturally

Do You Suffer From High Blood Pressure? Do You Feel Like This Silent Killer Might Be Stalking You? Have you been diagnosed or pre-hypertension and hypertension? Then JOIN THE CROWD Nearly 1 in 3 adults in the United States suffer from High Blood Pressure and only 1 in 3 adults are actually aware that they have it.

Get My Free Ebook


Post a comment