Orbital subperiosteal hematoma, cholesterol granuloma, and infection. Evaluation with MR imaging and CT.

Orbital subperiosteal space, a potential space, is an important entity due to its unique anatomy and susceptibility to various pathologic processes. CT scan and MR imaging are important tools in the diagnosis of orbital subperiosteal hematomas, cholesterol granulomas, and infections. MR imaging has emerged as the modality of choice in the evaluation of hematomas and infections of this space due to its multiplanar capability and various imaging sequences giving better information. High-resolution CT scan offers good differentiation in most of these cases. Osseous changes in a cholesterol granuloma is better seen in CT scan, although MR imaging offers better differentiation from epidermoid or dermoid cysts and other subperiosteal process, as well as lacrimal fossa lesions. Subperiosteal abscesses are best evaluated using MR imaging.