Abstract
INTRODUCTION Intermediate grade brain arteriovenous malformations (AVMs) are at the boundary of surgical resection, with great debate on appropriate management. METHODS All surgically treated supplemented Spetzler-Martin score (SM-score) intermediate grade (5, 6, and 7) AVMs from 2011 to 2018 from two centers were analyzed. A worsen neurological outcome was defined as an increase mRS on postoperative exam. A second analysis on SM-score 7 AVMs, combining patients from 2000–2011, was performed to determine subtypes with improved and/or unchanged neurological outcomes following resection. The SM-score 7 patients were separated into three groups based on nidus size (S1: <3 cm, S2:3-6 cm, S3: >6 cm) and age (A1:0-20 years, A2:20-40 years, A3: >40 years) followed by any combination of the combined supplemental grade: low risk (S1A1, S1A2, S2A1), intermediate risk (S2A2, S1A3, S3A1, and high risk (S3A3, S3A2, S2A3). RESULTS 246 patients were found to have an intermediate SM-score AVM, with 102 SM-score 5 (41%), 99 SM-Score 6 (40%), and 45 SM-Score 7 patients (18%). A significant difference for a worse mRS at follow-up was found between the groups, with 25 patients (25%) in the SM-score 5, 29 patients (29%) in the SM-score 6, and 26 patients (58%) in the SM-core 7 cohort (P < .001). In univariate analysis, a SM-score 7 was found to have a significantly increase odd of a worse mRS (P < .001, OR 3.7, 95% CI 1.9-7.3). A second analysis, combining all SM-Score 7 patients (N = 197) found a significant difference in patients with improved/unchanged neurological exams in the low (N = 17, 81%), intermediate (N = 43, 61%), and high-risk group (N = 54, 51%) following resection (P = .037) CONCLUSION SM-score 7 patients are at an increased risk for a worsen neurological outcome following surgery. However, low risk SM-score 7 patients (young and small nidus) have favorable outcomes following resection. Further studies on the natural history vs surgical resection of such lesions are warranted.