Tumours of the Skull Base and Paranasal Sinuses by Ziv Gil & Dan M. Fliss

Author:Ziv Gil & Dan M. Fliss
Language: eng
Format: epub
Publisher: Springer India, New Delhi

Osseous Lesions

Fibrous dysplasia (Fig. 5.4) is a well-vascularized mixture of unorganized bone and fibrous tissue that replaces bone and causes medullary widening, leaving a thin rim of cortical bone. The most commonly involved bones are the ethmoid, sphenoid, frontal and temporal bones. Invasion of the paranasal and neurovascular foramina is rare but possible. Diagnosis is usually confirmed with a CT scan. The lesion is characterized by a heterogeneous ‘ground glass’ appearance [26]. 3D-CT reconstructions might aid surgical planning. MRI is non-specific and shows marked post-contrast enhancement [27]. Osteomas that usually originate from the frontal and ethmoid sinuses are homogeneous bone lesions with varying heterogeneous signal intensities on CT and MRI, ranging from sclerotic bone to less ossified osteoma [3]. The radiological diagnosis rests on CT and isotope bone scans. An osteoma (Fig. 5.5) appears as a radio-opaque lesion with a nidus, which has a radiolucent centre surrounded by dense sclerosis. This may sometimes be mistaken for osteomyelitis. MRI may not be diagnostic because the appearance of an osteoma depends on the amount of calcification within the nidus, the size of the fibrovascular zone, whether there is reactive sclerosis, and the amount of oedema in the bone.

Fig. 5.4Fibrous dysplasia. (a, b) Coronal and axial post-contrast T1-W MRI, respectively, showing right supra-orbital low-intensity mass with characteristic ‘ground-glass’ appearance. Inhomogeneous areas might represent fibrous tissue, cyst formation or haemorrhage

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