A school of red herring.

A 66-year-old man with chronic kidney disease presented with painless unilateral vision loss and bilateral optic disk swelling. Vision loss progressed in the affected eye and developed in the fellow eye. Evaluation for infectious, neoplastic, ischemic, and inflammatory disorders was unrevealing. High-dose corticosteroids appeared to stabilize his vision temporarily. Eventually he was diagnosed with papilledema in the setting of transverse venous sinus stenosis and dural arteriovenous fistula. His papilledema resolved, and his vision improved following stenting of the venous sinus stenosis and embolization of the fistula.