The onodi cell is a posterior ethmoidal cell that is pneumatized laterally or superiorly to the sphenoid sinus with close proximity to the optic nerve. A mucocele, a benign, expansile, cyst-like lesion of the paranasal sinuses, may uncommonly involve the onodi cell causing compression of the optic nerve and nearby structures. In this paper, we report a rare case of onodi cell mucocele causing orbital apex syndrome, with prompt recovery after endoscopic removal. However, optic neuropathy did not improve and the patient remained blind.
Mucoceles arising from the sphenoid sinus or a posterior ethmoidal cell are uncommon and may result in compression of the optic nerve and adjacent structures, leading to orbital apex syndrome. Onodi cell is a posteriorly positioned ethmoid cell that pneumatizes laterally or above the sphenoid sinus, adjacent to the course of the optic nerve. Mucocele formation in such a cell may lead to compressive optic neuropathy and blindness, as in the case presented here.
A 53-year-old female presented with vision loss in her right eye that started one day earlier, accompanied by pain in eye movement. On examination, visual acuity was finger counting in her right eye and 20/20 in her left eye. There were also swelling and erythema of the right eyelids and a right relative afferent pupillary defect. The rest of the ophthalmic examination was normal. She was afebrile with no signs of active infection. CT demonstrated opacification of the ethmoidal and sphenoidal air cells parallel to the optic nerve (Figure
(a) Axial CT showing the mucocele of the right onodi cell. (b) + (c) Fluid attenuated inversion recovery (FLAIR) axial MR image (b) and T2 weighted sagittal MR image. (c) Demonstrating onodi mucocele with close proximity to the optic nerve.
A few hours later, the patient complained of binocular diplopia and paresthesias along the distribution of cranial nerves V1 and V2. In addition, eyelid swelling had worsened and visual acuity deteriorated to light perception only. An almost complete limitation of abduction and adduction in her right eye was noted (Figure
Clinical photograph showing right eye limitation of abduction and adduction.
There are only a few reports on onodi cell mucocele causing orbital apex syndrome [
Paranasal sinus mucoceles affect the optic nerve by either mechanical compression causing ischemic injury or by direct extension of the inflammatory process to the optic nerve [
Our patient demonstrated rapid visual loss. When inflammatory signs subsided and no recovery of the optic nerve function was noted, it was suspected that ischemia of the posterior optic nerve may have occurred. The finding of clear mucoid fluid also supports the diagnosis of ischemic injury to the optic nerve. However, considering the acute inflammatory signs, inflammation may also have a role in the presence of optic neuropathy.
Treatment of mucocele is based on prompt endoscopic surgical decompression and systemic steroids to reduce inflammation [
In conclusion, clinical signs of orbital apex syndrome in patients with a history of chronic sinusitis should raise the suspicion of mucocele arising from the posterior paranasal sinuses. An immediate orbital and sinuses imaging is required with early surgical intervention. With prompt treatment, vision and eye movements can be restored even though permanent visual loss may occur.
The authors declare that there is no conflict of interests regarding the publication of this paper.