Embolization of cerebral arteriovenous malformations with cellulose acetate polymer: Histological study of the resected specimens

To test the usefulness of a cellulose acetate polymer(CAP) solution for brain arteriovenous malformations (AVMs), we analyzed the clinical and histological results of patients with AVMs embolized using CAP solution. We reviewed the cases of six patients with cerebral AVMs treated by embolization prior to surgical resection. We used two types of CAP solutions, CAP-M and CAP-L, which are mixtures of 250 mg of solid CAP and 1800 or 2250 mg of bismuth trioxide dissolved in 5.5 or 7.0 ml of dimethyl sulfoxide, respectively. All patients underwent surgical resection 1 to 37 days after the embolization procedure. Resected specimens were fixed in formalin and stained for light microscopic examination. Eighteen feeding vessels were embolized. The reduction rate of the nidus volume was between 20% and nearly 100%. Mild ischemic deficits occurred in one patients but there were no hemorrhagic complications related to the embolization procedures. All AVMs were completely resected by surgery. Direct inspection at surgery revealed that there was no apparent swelling or hematomas in the normal brain areas adjacent to the nidus, and the AVMs were soft enough to be easily retracted. The histological examinations disclosed no or mild inflammatory reactions within two weeks after embolization. The internal elastic lamina was preserved in every case. Recanalization of embolized vessels was not observed until 37 days after embolization. CAP solution is a safe and useful embolic agent for brain AVMs. Further study is needed to resolve the issue of recanalization.