CLINICAL ARTICLE J Neurosurg 127:1105–1116, 2017 ABBREVIATIONS AVM = arteriovenous malformation; bAVM = brain AVM; CTA = CT angiography; DSA = digital subtraction angiography; GKRS = Gamma Knife radiosur- gery; MRA = MR angiography; mRS = modified Rankin Scale; RCT = randomized controlled trial; VRAS = Virginia Radiosurgery AVM Scale. SUBMITTED May 17, 2016. ACCEPTED August 3, 2016. INCLUDE WHEN CITING Published online December 23, 2016; DOI: 10.3171/2016.8.JNS161275. Microsurgery for Spetzler-Ponce Class A and B arteriovenous malformations utilizing an outcome score adopted from Gamma Knife radiosurgery: a prospective cohort study Michael K. Morgan, MD, 1 Markus K. Hermann Wiedmann, MD, 1 Marcus A. Stoodley, PhD, 1 and Gillian Z. Heller, PhD 2 Departments of 1 Clinical Medicine and 2 Statistics, Macquarie University, Sydney, New South Wales, Australia OBJECTIVE The purpose of this study was to adapt and apply the extended defnition of favorable outcome established for Gamma Knife radiosurgery (GKRS) to surgery for brain arteriovenous malformations (bAVMs). The aim was to derive both an error around the point estimate and a model incorporating angioarchitectural features in order to facilitate com- parison among different treatments. METHODS A prospective microsurgical cohort was analyzed. This cohort included patients undergoing embolization who did not proceed to microsurgery and patients denied surgery because of perceived risk of treatment. Data on bAVM residual and recurrence during long-term follow-up as well as complications of surgery and preoperative embolization were analyzed. Patients with Spetzler-Ponce Class C bAVMs were excluded because of extreme selection bias. First, patients with a favorable outcome were identifed for both Class A and Class B lesions. Patients were considered to have a favorable outcome if they were free of bAVM recurrence or residual at last follow-up, with no complication of surgery or preoperative embolization, and a modifed Rankin Scale score of more than 1 at 12 months after treatment. Patients who were denied surgery because of perceived risk, but would otherwise have been candidates for surgery, were included as not having a favorable outcome. Second, the authors analyzed favorable outcome from microsurgery by means of regression analysis, using as predictors characteristics previously identifed to be associated with complications. Third, they created a prediction model of favorable outcome for microsurgery dependent upon angioarchitectural variables de- rived from the regression analysis. RESULTS From a cohort of 675 patients who were either treated or denied surgery because of perceived risk of sur- gery, 562 had Spetzler-Ponce Class A or B bAVMs and were included in the analysis. Logistic regression for favorable outcome found decreasing maximum diameter (continuous, OR 0.62, 95% CI 0.51–0.76), the absence of eloquent loca- tion (OR 0.23, 95% CI 0.12–0.43), and the absence of deep venous drainage (OR 0.19, 95% CI 0.10–0.36) to be signif- cant predictors of favorable outcome. These variables are in agreement with previous analyses of microsurgery leading to complications, and the fndings support the use of favorable outcome for microsurgery. The model developed for angioarchitectural features predicts a range of favorable outcome at 8 years following microsurgery for Class A bAVMs to be 88%–99%. The same model for Class B bAVMs predicts a range of favorable outcome of 62%–90%. CONCLUSIONS Favorable outcome, derived from GKRS, can be successfully used for microsurgical cohort series to assist in treatment recommendations. A favorable outcome can be achieved by microsurgery in at least 90% of cases at 8 years following microsurgery for patients with bAVMs smaller than 2.5 cm in maximum diameter and, in the absence of either deep venous drainage or eloquent location, patients with Spetzler-Ponce Class A bAVMs of all diameters. For patients with Class B bAVMs, this rate of favorable outcome can only be approached for lesions with a maximum diam- eter just above 6 cm or smaller and without deep venous drainage or eloquent location. https://thejns.org/doi/abs/10.3171/2016.8.JNS161275 KEY WORDS brain; arteriovenous malformation; vascular disorders; surgery; stereotactic radiosurgery; cohort study ©AANS, 2017 J Neurosurg Volume 127 • November 2017 1105 Unauthenticated | Downloaded 02/21/22 12:20 PM UTC