Multimodality treatment for large and critically located arteriovenous malformations.

To define the current status of the multimodality treatment for large and critically located arteriovenous malformations (AVMs), we have made a retrospective review of 54 consecutive patients with Spetzler-Martin grade IV and V AVMs. The size of nidus is larger than 3 cm in diameter in all cases. Initially, all but one were treated by nidus embolization with the aim of size reduction. Only one patient had complete nidus occlusion by embolization alone. In 52 patients, the obliteration rate of nidus volume averaged 60% after embolization. Ten patients underwent complete surgical resection of AVMs following embolization with no postoperative neurological deterioration. Thirty-one patients underwent stereotactic radiosurgery following embolization. At the time of this analysis, 30 patients underwent follow-up angiography 2-3 years after radiosurgery. The results of radiosurgery correlated well with the preradiosurgical AVM volume. Of 16 patients with small residual AVMs (< 10 cm3, a mean volume of 4.7 cm3), nine (56%) had complete obliteration, and six (38%) had near-total or subtotal obliteration by 3 years after radiosurgery. In contrast, of 14 patients with large residual AVMs (> or = 10 cm3, a mean volume of 17.9 cm3), only two (14%) had complete obliteration, and eight (57%) had near-total or subtotal obliteration. Repeat radiosurgery was performed for the patients with remaining AVMs at 3-year follow-up review. This study indicates that a certain number of large and critically located AVMs can be safely treated by either microsurgery or radiosurgery following a significant volume reduction by nidus embolization. The present data also suggest the need and possible role of repeat radiosurgery in improving complete obliteration rate of large difficult AVMs, since many of those AVMs have significantly responded to initial radiosurgery.