Bilateral Rhinogenous Optic Neuropathy Caused by the Regrowth of a Large Sphenoid Sinus Mucocele

A 59-year-old man, who had a history of left blind at 36 years old, suddenly lost right visual acuity. Magnetic resonance imaging revealed a large left sphenoid sinus cyst, which protruded intracranially. The cyst was fenestrated by endoscopic sinus surgery, but his right vision did not recover. Ten cases of bilateral rhinogenous optic neuropathy caused by mucocele have been reported, and the cause was sphenoid sinus in 9 cases. Postoperative visual acuity in these cases was poor, especially in slow progressive cases, because it was diagnosed as an unknown cause, and surgery was delayed. Rhinogenous optic neuropathy caused by mucocele should be differentiated from bilateral visual impairment of unknown cause. The authors highlight the importance of early diagnosis of sphenoid sinus mucocele and fully informing patients about the future risk of bilateral visual impairment, even if they are asymptomatic or have been treated.