Intradiploic epidermoid cysts of the bony orbit.

Epidermoid cysts originating within the diploic space of the bony orbit are rare. The authors retrospectively studied four patients with an intradiploic epidermoid cyst of the orbital bones to investigate the clinical and the computed tomographic (CT) findings. The clinical presentation was dependent on the location of the slowly expanding epidermoid cyst. The sphenoid bone was involved in three patients and the frontal bone in one patient. Proptosis caused by intraorbital extension of the mass was the most common presenting sign. The findings on high-resolution CT scans appeared to be specific for intradiploic epidermoid cysts. The typical sclerotic margin, which is diagnostic of intradiploic epidermoid cysts, can be demonstrated by CT scans with a bone window setting.