CT characteristics of orbital pseudotumors and other orbital inflammatory processes.

Orbital pseudotumor is a nonspecific inflammatory process of unknown etiology that may mimic a true orbital neoplasm, specifically lymphoma. It exhibits a highly variable clinical and radiographic presentation. Thirty-nine patients with a presumptive diagnosis of orbital inflammatory disease were examined with CT and evaluated with respect to 13 findings associated with inflammatory disease of the orbit. Pseudotumor was included as part of the differential diagnosis in 25 patients. Twenty-one cases received a final (clinical) diagnosis of pseudotumor. The remainder were comprised of a broad range of orbital inflammatory conditions. Key radiographic features required to entertain or exclude the diagnosis of pseudotumor included establishing the presence of an orbital mass, extraocular muscle enlargement, bony erosion, enhancement, and associated paranasal sinus disease.