Pneumosinus dilatans of the ethmoid sinus presenting with proptosis

No eye globe, conal or extra-conal pathology. The distended left ethmoid air cells compresses medial rectus muscle. No evidences of ethmoidal sinus disease. No abnormal enhancement of the extra-ocular muscles or enlargements. Note also hyperostosis of left floor of anterior cranial fossa. Pneumosinus dilatans usually involves frontal sinuses and involvement of ethmoid air cells are case reports.