Sudden Unilateral Visual Loss Due to an Onodi Cell Mucocele.

In a patient whose sudden vision loss is suspected on the side of a previously operated sphenoid or ethmoid sinus, an ischemic insult to the optic nerve may occur due to a compressing mucocele, especially when there is bony dehiscence of the orbital apex. We report a case of a 41-year-old healthy male patient who had a history of previous sinus surgery, and visited the emergency department for an abrupt left ocular pain following visual loss of the affected eye. The patient's left eye's best corrected visual acuity (BCVA) was hand motions with a reduced light reflex. A sphenoethmoidal sinus cell (Onodi cell) mucocele with bone dehiscence in the left orbital apex was seen on computed tomography. Upon suspicion of compressive ischemic optic neuropathy, urgent endoscopy-assisted endonasal marsupialization of the Onodi cell mucocele with high-dose pulse intravenous dexamethasone was performed. The pathology showed an inflamed nasal mucosa, confirming a mucocele. On the second postoperative day, his BCVA slightly improved in counting fingers at 30 cm. However, even though the nasalized Onodi cell remained intact, his eyesight did not show further improvement. The optic nerve may be directly insulted when a mucocele in the Onodi cell takes place, especially when there is bony dehiscence in the orbital apex. Despite accelerated surgical marsupialization and high-dose steroids, the chance of visual recovery remains very low, as demonstrated in our case.