Cholesterol granulomas of the middle ear cavities: MR imaging.

Symptomatic cholesterol granuloma developed in the middle ear cavities in three cases. At computed tomography (CT) after the administration of contrast material, the granulomas appeared as nonspecific, nonenhanced soft-tissue masses with variable bone erosion. These features are indistinguishable from those of other similar clinical entities, especially cholesteatoma, paraganglioma, and endaural brain hernia. At magnetic resonance (MR) imaging, cholesterol granulomas had a more characteristic appearance. In two cases, the granulomas were depicted as areas of high signal intensity with both T1- and T2-weighted sequences. In the third case, an expansile mastoid cholesterol cyst exhibited medium signal intensity on T1-weighted images, with only a small hyperintense area and a hypointense area located in the cystic wall. Correlations between CT, MR, and microscopic findings show that MR imaging is far superior to CT in tumoral characterization, which is crucial for planning surgical approaches. MR imaging has limitations, however, particularly its inability to depict subtle bone abnormalities.