Teaching NeuroImages: Isolated sphenoiditis An uncommon cause of abducens nerve palsy

A 35-year-old woman presented with a headache lasting 2 weeks and complained of recent diplopia. Neurologic examination showed limited left eye abduction. Initial brain CT scan was considered normal (figure, A). Brain MRI showed left sphenoiditis (figure, B). The patient was treated with amoxicillin/clavulanic acid and corticosteroids with rapid symptom improvement which deferred endoscopy that could provide a bacteriologic diagnosis.