Embolization of cerebral arteriovenous malformations with silk: histopathologic changes and hemorrhagic complications.

PURPOSE To evaluate the safety of silk as an embolic agent for preoperative embolization of cerebral arteriovenous malformations (AVMs) by assessing the histopathologic changes and hemorrhagic complications associated with its use. METHODS Histopathologic specimens, medical records, and radiologic records of 73 patients with AVMs embolized with silk (alone or in combination with other agents) were reviewed retrospectively. Forty-eight histologic specimens obtained at surgery were analyzed for inflammatory responses and compared with the time interval between embolization and surgery. Postembolization angiograms were assessed for vasculitis and CT scans were reviewed for evidence of hemorrhage after embolization. RESULTS There was no angiographic evidence of vasculitis. Histologic evidence of vasculitis was absent or mild in 92% of cases and histologic evidence of perivascular inflammation was absent or mild in 73% of cases. The frequency of histologic changes associated with vasculitis, perivascular inflammation, and vessel necrosis varied with the time interval between embolization and AVM resection. Intracranial hemorrhage, as a direct complication of silk use, occurred in one patient. Another patient had subarachnoid hemorrhage 24 hours after embolization, caused by rupture of a posteroinferior cerebellar artery aneurysm. Intraventricular high-density material appeared on routine postembolization CT scans in two other patients who had intraventricular AVM extension. This high-density material was thought to be contrast extravasation from intrinsically leaky AVM nidus vessels and not frank hemorrhage. CONCLUSION Embolization of AVMs with silk does not result in marked inflammation or increased hemorrhagic complications as compared with other agents.