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Editor,—Rhinogenic optic neuropathy is a clinical entity including rhinogenous optic neuritis and optic neuropathy caused by a paranasal cyst. The damage to the optic nerve seems to be caused mainly by cyst compression and inflammatory changes. Rhinogenic optic neuropathy secondary to paranasal lesions is not so rare, and paranasal sinus mucoceles with unilateral blindness have already been reported. Bilateral loss of light perception caused by rhinogenic optic neuropathy, however, has not been reported in the literature.
A 48 year old man complained of acute visual loss in both eyes. His corrected visual acuities were light perception in both eyes, and the light reflex was defective. No remarkable finding was observed on routine ophthalmic examination. Optic atrophy was not present, and intraocular pressures were normal. He had a history of surgery for sinusitis 28 years ago and had been complaining of headache for a year. A computed tomogram showed a large high density area in the sphenoid sinus (Fig 1). Sphenoidotomy was undertaken and the mucocele was opened (Fig 2). It was confirmed that a large sphenoid mucocele was pressing both the optic nerves. Treatment with systemic corticosteroids and antibiotic was initiated upon admission. Despite this treatment, his visual acuities deteriorated to no light perception both eyes, and they never recovered. No remarkable finding was observed in the electroretinogram, but flash visually evoked potential was non-recordable.
Sphenoid sinus mucocele is a rare entity that can occur alone or as a result of ethmoid sinusitis and polyposis. A myriad of presentations is possible because of the presence of important contiguous neurological and vascular structures.1
Clinically, sphenoid sinus mucocele can cause a wide variety of signs and symptoms including bilateral visual loss, depending upon which adjacent structures are affected by the expanding cyst. The prognosis of visual disturbance is thought to be dependent on visual acuity preoperatively and the time from onset of the disease to the operation.2 Recovery is quite difficult in patients who have severe preoperative disturbances such as no light perception. The prognosis is also poor in cases of sudden onset. In our case, the onset of visual disturbance was sudden, and preoperative visual acuity was only light perception in both eyes. Although the patient underwent surgery within 24 hours from the onset, the recovery was unsatisfactory.
Vascular distribution to the optic nerve in the optic canal is less than in other sites, so that the optic nerve is very susceptible to a decrease in vascular supply. In this case, compression from the mucocele was thought to have caused ischaemia and/or venous congestion of the optic nerve. The presence of a headache for a year suggests long standing chronic inflammation of the mucocele. So in this case, besides compression by the mucocele, inflammatory disorders seemed to have contributed to irreversible damage to the optic nerve.
Patients with a sphenoid sinus mucocele often experience only ophthalmic symptoms such as visual impairment, external ophthalmoplegia, and diplopia.3 Therefore, for early diagnosis and an improved prognosis, ophthalmologists must be alert to this as a possible cause of blindness.