2020 Volume 48 Issue 2 Pages 116-121
The Spetzler-Martin grade (SMG) system is widely used to assess the treatment risk for arteriovenous malformations (AVMs). However, SMG II or III AVMs include diverse phenotypes, such as “large superficial” and “small deep” ones. Thus, it is worth analyzing the detailed treatment outcomes for each subtype. Among 724 consecutive patients who had AVM and were treated with stereotactic radiosurgery (SRS), 490 patients (238 with SMG II and 252 with SMG III AVMs) were included in the study. Upon classifying SMG II AVMs into S2, S1V1, and S1E1 and SMG III AVMs into S3, S2V1, S2E1, and S1V1E1, we analyzed the detailed treatment outcomes for each subtype. Significant neurological events (SNEs) were defined as any neurological events that caused > 1-point decrease in the modified Rankin Scale. The 5-year cumulative obliteration rates for SMG II and III AVMs were 88% and 77%, respectively. Among the subtypes, the rate was highest in S1E1 (91%) and lowest in S2E1 (66%). S2E1 demonstrated the highest, albeit well-acceptable, hemorrhage rate during the latency period (3.0%/year). The 12-year cumulative SNE rates were 1.6% and 6.0% in SMG II and III, respectively. Among the subtypes, the rate was highest in S2E1 (8.8%) and lowest in S2 (0%). The 12-year disease-specific mortality rates were 0.4% in SMG II and 2.2% in SMG III. Therefore, the outcomes of SRS for SMG II or III AVMs were different among the subtypes. S2E1 was associated with the lowest obliteration rate, which might be responsible for the highest hemorrhage rate, and, thus, the highest SNE rate. However, the outcomes seemed better than the estimated course of untreated cases and compatible with that of cases treated with direct surgery. SRS is an optimal therapeutic option for SMG II or III AVMs.
