When the Problem Became the Solution.

We present a unique case where a young man developed subtle cavernous sinus thrombosis (CST) due to underlying hypercoagulable state. He also had coexisting frontal lobe brain dural arteriovenous fistula (bdAVF). After CST developed, venous drainage from the optic nerve was redirected into the frontal lobe which was already under high venous pressure because of preexisting bdAVF. This caused backflow of venous blood into the optic nerve causing massive persistent optic nerve head swelling. Presumed acute venous hypertension event within bdAVF caused frontal mass effect presenting as seizure leading to thrombosis of bdAVF.