Onodi Cell Mucocele Causing Unilateral Visual Loss: A Case Study

Aim: Onodi cells (sphenoethmoidal cells) are anatomical variants of the posterior most ethmoid air cells which pneumatise superiorly or laterally to the sphenoid sinus. They can be intimately related to the optic nerve and so thorough pre-operative evaluation of the anatomy is essential to avoid potentially devastating complications. Although usually asymptomatic, rarely they can be complicated by sinus disease causing optic neuropathy. Methods: The authors report a rare such case of an Onodi cell mucocoele and its ensuing complications and surgical challenge. Results: An otherwise fit and well 62 year old woman presented elsewhere with sudden, painless right sided visual loss. Pre-operative CT and MRI scanning demonstrated a mucocoele abutting the optic nerve. She was taken to theatre on 2 occasions with unsuccessful drainage of the mucocoele, which was further complicated by an intra-operative CSF leak. This was repaired immediately. A second opinion was sought from our tertiary unit and after the patient’s vision deteriorated and further imaging demonstrated persistence of the mucocoele. A third procedure was carried out under image guidance to successfully drain the mucocoele, which was infected. Regrettably, there was no improvement to the patient’s vision. Conclusions: Mucocoeles within Onodi cells remain a rare cause of painless visual loss. A thorough systematic pre-operative evaluation of the anatomy must be carried out to identify anatomical variants. The authors advocate early intervention with the aid of image guidance.