RESUMO
BACKGROUND: Brain arteriovenous malformation (BAVM) is a life-threatening vascular congenital malformation due to the risk of intracerebral hemorrhage. The formation of a spontaneous cyst within a BAVM, without history of hemorrhage or gamma knife surgery, is rare and has an unknown pathophysiology. We suggest a novel theory of spontaneous cystic BAVM formation, subsequently treated with endovascular embolization followed by surgery with a favorable long-term outcome. METHODS: Review of the literature using PUBMED database and comparison between clinical presentation, diagnostic imaging studies, and treatment options. RESULTS: The high flow causing a shear stress over the drainage vein may be responsible for venous ectasia and thus incrementing hydrostatic intranidal pressure causing a serous effusion that develops into a pseudocyst. We hypothesize that hemodynamic factors may be responsible for both origin and growth of such cystic lesions. CONCLUSIONS: Endovascular treatment allowed us to achieve cyst volume reduction by managing its unique flow characteristics. To our knowledge, this is the first case report of combined treatment with endovascular and surgical approach of a cystic BAVM.