Categorization and characterization of lesions of the orbital apex.

INTRODUCTION: The apex of the orbit is formed by the union of the lesser and greater wings of the sphenoid bone and acts as an osseous tunnel for numerous neurovascular structures entering the orbit from the cranial vault. Lesions of the orbital apex are clinically important as they can have an adverse effect on vision. A broad range of lesions can occur here, and our purpose is to organize the pathologic processes which occur in the orbital apex into logical imaging differentials, establish an organized approach to image analysis, and present examples of representative lesions. METHODS: We review the anatomy of the orbital apex and categorize and describe the pathologic entities that are encountered most frequently in this anatomically compact region and identify imaging patterns that can help to narrow the differential diagnosis. RESULTS: Categories of orbital apex lesions include neoplasms, inflammatory processes, infections, lesions causing extrinsic compression, and vascular lesions. This categorization provides an organized framework to facilitate a reasonable differential diagnosis. Computed tomography and magnetic resonance imaging are the modalities of choice to evaluate and characterize orbital apex lesions, and imaging examples utilizing these modalities will be presented. CONCLUSION: The orbital apex is a clinically important anatomical region and hosts diverse pathologic processes. An awareness of common imaging patterns can help to generate a focused differential diagnosis. A systematic categorical approach can be of help to radiologists attempting to accurately characterize lesions in this area.