Fungal ball within Onodi cell mucocele causing visual loss.

The Onodi cell is a pneumatized posterior ethmoid cell located laterally and superiorly to the sphenoid sinus and closely related to the optic nerve. A mucocele is a benign, expansile, cystlike lesion of the paranasal sinuses that is filled with mucoid secretion. Therefore, optic neuropathy caused by an infected mucocele in an Onodi cell is uncommon. Furthermore, fungal infection superimposed on an Onodi cell mucocele is extremely rare and has not been reported previously. Here, we describe the first case of fungal ball within Onodi cell mucocele causing visual loss, which was completely removed via transnasal endoscopic approach.