Dural arteriovenous fistula involving the transverse sigmoid sinus presenting as chemosis. A case report.

Dural arteriovenous fistulas (DAVFs) not directly shunting into the cavernous sinus are a rare cause of chemosis. An unusual case of a transverse sigmoid sinus DAVF associated with chemosis related to high intravenous pressure is presented. A 39-year-old man presented with a two year history of left chemosis. Ocular examination disclosed left episcleral and retinal venous congestion, and optic disc paleness. Visual acuity and visual field were normal. Angiography revealed a DAVF supplied by a branch arising from the left postauricular artery, the left middle meningeal artery and the left occipital artery, which drained into the vein of Trolard into the superior sagittal sinus and the sphenoparietal sinus via the mild dilated vein of Labbé. Endovascular treatment was performed by transarterial embolization with Onyx-18, which resulted in occlusion of the fistula and complete clinical cure confirmed at discharge. Chemosis may be caused by an arteriovenous lesion remote from the optic organ as a result of rerouting venous drainage promoting the intracavernous pressure. Transarterial embolization of a DAVF may result in complete cure if advantageous arterial anatomy allows for flow control and occlusion of the fistulous connection with liquid nonadhesives.