CT-criteria of orbital hemangiomas and their importance in differential diagnosis of intraconal tumors

CT-Scans of 29 histologically proven cavernous hemangiomas were evaluated with respect to their location, shape, delineation from surrounding tissue, contrast-enhancement, and secondary changes of the bony orbit. Whenever a round or oval tumor, located in the outer upper muscle cone, sharply delineated from surrounding tissue, unattached to optic nerve and ocular muscles, spares a small triangular space in the orbital apex, it is in all probability a cavernous hemangioma. Evaluation of the tumors shape and its separation from surrounding tissues requires imaging in multiple sections in two planes oriented, if possible, at right angles. Changes in position of the optic nerve and eye muscles in different directions of gaze demonstrated by CT rule out significant tumor-attachments. The portion of the intraconal space least affected by optic nerve shifts and muscle contractions during eye movements, as demonstrated by CT, is the upper outer quadrant, the site preferred by the mobile tumor. Tumors which cannot be differentiated from cavernous hemangiomas by CT-criteria are rare usually benign. Reports of rare examples of well delineated or encapsulated malignant intraconal lesions indicate the possibility - however remote - of mistaking a malignant tumor for a cavernous hemangioma by CT. (orig.)