The authors present a case of a patient with the syndrome of paradoxical worsening of dural-sinus cavernous arteriovenous malformation which was a iatrogenic consequence of embolization of the basal branches of a dural shunt with Yvalon. It is presumed that the thrombogenous Yvalon reached the basal branches of the medial meningeal artery to the superior ophthalmic vein, where it caused complete thrombosis. The impaired ocular and orbital venous outflow caused a dramatic worsening of the ocular congestive symptoms: venous stasis retinopathy with dilated veins, flame-and dot-shaped hemorrhages and a secondary increase in intraocular pressure. The diagnosis of thrombosis of the entire superior ophthalmic vein was confirmed by color Doppler imaging. The mechanism is discussed. Although the ocular pathology is usually self-limiting following the establishment of collateral venous outflow channels, in view of the patient's serious congestive ocular symptoms argon laser photocoagulation and conservative antiglaucomatous local therapy were applied. Once orbital collateral venous drainage was established, the ocular symptoms improved. In the one-year follow-up there was no other complication.