Complicated allergic fungal rhinosinusitis: diagnostic complexities and management strategies.

A man in his 60s presented with diplopia, headache and facial numbness. Examination demonstrated a unilateral right abducens nerve palsy which rapidly progressed to a bilateral abducens palsy, partial right third nerve palsy and bilateral facial numbness. Nasendoscopy and imaging findings suggested an erosive fungal lesion centred on the sphenoid sinus. He underwent aggressive clearance with functional endoscopic sinus surgery, which revealed pan-sinus allergic fungal disease with marked bony erosion of the sphenoid, exposing the dura and optic chiasm. Corticosteroids and systemic antifungals were commenced postoperatively. Histopathology demonstrated eosinophilic mucin and no invasive features. However, no fungal organism was identified. His diplopia persisted for 8 weeks, resolving fully by twelve weeks. This case highlights chronic allergic fungal sinusitis as an important differential in patients with ocular complications, the diagnostic challenges which require multimodal assessment and MDT involvement, and the role of aggressive surgical management and postoperative corticosteroid and antifungal therapies.