Allergic fungal sinusitis with extensive bone erosion of the clivus presenting with diplopia

Objective: We report a case of allergic fungal sinusitis causing bone erosion and diplopia. Case report: A 43-year-old man presented with a four-month history of increased nasal congestion and progressive diplopia. Clinical examination revealed bilateral nasal polyposis and a right lateral gaze deficit, consistent with a VIth cranial nerve palsy. Computed tomography of the paranasal sinuses demonstrated a large sellar mass with extensive bony erosion and both supra- and infra-sellar extension. An endoscopic approach to the sphenoid sinus, clivus and posterior cranial fossa with image guidance was performed, enabling surgical treatment involving nasal polypectomy, wide marsupialisation of the sphenoid sinus and removal of the extensive allergic fungal mucin. The patient awoke from anaesthesia with complete resolution of his diplopia. Conclusion: Otolaryngologists should be aware that approximately 20 per cent of patients with allergic fungal sinusitis demonstrate paranasal sinus expansion and bone erosion involving surrounding anatomical structures. Such patients may have clinical findings involving the orbit and cranial vault.