Acute Visual Loss Caused by an Onodi Cell Mucocele

An Onodi cell is the most posterior ethmoidal cell that pneumatises laterally and superiorly to the sphenoid and is intimately proximal to the optic nerve. The optic nerve often runs so close to the small cavity of the Onodi cell that bulging of the optic canal into the wall may be observed. The incidence of Onodi cells is 7 to 14%. However, an isolated mucocele of an Onodi cell causing compressive optic neuropathy is rare and only a few patients with such a condition have been reported. We report a case of acute non light perception (NLP) visual loss caused by an isolated mucocele of an Onodi cell.