Angiographically occult and spontaneously thrombosed large brain arteriovenous malformation

Treatment for brain arteriovenous malformations (AVM) include combinations of surgery, radiosurgery and embolization. Very rarely, spontaneous obliteration may occur, especially among small lesions with single superficial vein drainage and prior bleeding. We report the case of a large symptomatic AVM, without history of hemorrhage or prior treatment, in which self-obliteration was noted at surgery. Although MRI suggested the presence of an AVM, no evidence of arterial anomaly was observed in the brain angiography. At surgery, a large cortical nidus with tortuous arterial vessels, resembling that of an AVM but without blood flow, was identified. Complete resection was easily performed without relevant bleeding. The histopathologic study confirmed the diagnosis of a thrombosed AVM. Despite the low probability of recanalization, surgical resection of a suspected spontaneously obliterated AVM may be warranted, in order to reach a definitive diagnosis and to avoid the risk of an eventual bleeding, especially among younger patients.