Progressive spontaneous occlusion of a cerebellar AVM: pathogenetic hypothesis and review of literature.

Cerebral arteriovenous malformation (AVM) is a complex network of vascular channels consisting of arterial feeders, a nidus and enlarged venous drainage. AVMs usually increase in size with time, but may rarely obliterate; spontaneous angiographic regression occurs in less than 1.5% of cerebral AVMs. Several causes of spontaneous regression have been postulated such us hemodynamic alterations due to hemorrhage, hypercoagulability, atherosclerosis, and tromboembolism from associated aneurysms. In this report we describe a case of spontaneous, complete and asymptomatic occlusion of a left cerebellar hemispheric AVM; angiograms clearly demonstrate a progressive decrease in size of the AVM at follow-up. Thrombosis of the dominant-draining vein caused by turbulent blood flow seemed to be the main driver. Possible mechanisms leading to the occlusion are discussed and a review of the literature is reported.