Risk Factors Affecting Surgical Outcome of Large and Giant Arteriovenous Malformations

Abstract

The authors planned a retrospective analysis of the outcome of surgery for large and giant arteriovenous malformations (AVMs), and a clarification of the risk factors affecting the outcome.
Thirty-five cases having AVMs larger than 4 cm in diameter were subjected to the present study. Of this series, 74% had a favorable outcome, but in 26% the result was unfavorable.
The risk factors giving rise to unfavorable outcome were as follows. 1) Giant AVM larger than 6cm in diameter, 2) Poorly demarcated AVM, in other words, diffuse AVM, and 3) AVM fed by deep feeders, such as lenticulostriate artery, thalamoperforating artery, and anterior/posterior choroidal artery. Fifteen out of 17 operations on patients who had no risk factors resulted in a favorable outcome. However, only one out of 6 patients having all of the 3 risk factors had a favorable outcome. These differences were statistically significant (p<0.01).
Six out of 9 patients having severe morbidity and mortality suffered from intraoperative or postoperative intracranial hemorrhage. Massive postoperative hemorrhage, which accounted for most of the unfavorable outcome, was related to a small residual nidus. One half of the postoperative bleeding due to residual AVM occurred within 24 hours after surgery. Therefore, postoperative angiography and emergent excision of the residual nidus must be made immediately after surgery to improve the surgical outcome of large and giant AVMs.