OPTIC NEUROPATHY CAUSED BY AN ISOLATED MUCOCELE IN AN ONODI CELL

A rare case of retrobulbar optic neuropathy caused by an isolated muco cele in an Onodi cell is presented. A 63-year-old man suffering from l eft recurrent optic neuropathy had shown improved visual acuity with s teroid treatment at the age of 48 and 56 years. Impaired visual acuity and blurred vision in the left eye appeared again, and a marked infer ior decrease in the left visual field was noted. Although axial comput ed tomography (CT) showed no abnormal findings, magnetic resonance ima ging (MRI) revealed a small squamous-shaped lesion(17 x 17 x 7.3 mm) i n the left posterior ethmoidal air cell (Onodi cell) hanging over the left optic nerve. Endoscopic sinus surgery was performed. The optic ca nal was extruding into the Onodi cell cavity, and the superior bony wa ll of the canal was eroded by the mucocele. The isolated mucocele in t he Onodi cell seemed to be compressing the optic nerve downward and ca using retrobulbar optic neuropathy. An Onodi cell lesion, even if it w as isolated and small, would cause optic neuropathy. MRI and coronal C T scanning should be performed for the diagnosis and preoperative plan ning in a case of retrobulbar optic neuropathy.