Spetzler-Martin Grade III arteriovenous malformations: Surgical results and a modification of the grading scale

Abstract

OBJECTIVE: To analyze surgical results for the highly variable Spetzler-Martin Grade III arteriovenous malformations (AVMs), to demonstrate that outcomes vary among the different types of Grade III lesions, and to introduce a simple modification of the grading scale that might improve its usefulness for these AVMs. METHODS: In a consecutive series of 174 brain AVMs resected from 174 patients during a period of 4.8 years, 76 AVMs (45.2%) were Grade III. There were 35 small AVMs (S1V1E1) (46.1%), 14 medium/deep AVMs (S2V1E0) (18.4%), and 2 7 medium/ eloquent AVMs (S2V0E1) (35.5%). No large Grade III AVM (S3V0E0) was treated. RESULTS: Complete AVM resection was accomplished for 74 patients (surgical obliteration rate, 97.4%). Three patients (3.9%) experienced permanent, treatment-associated, neurological morbidity, and three patients died (surgical mortality rate, 3.9%). Good outcomes (Rankin scale scores of ≤2) were observed for 59 patients (78.7%). Surgical risks (new deficit or death), according to the Grade III type, were 2.9% for small AVMs (S1V1E1), 7.1% for medium/deep AVMs (S2V1E0), and 14.8% for medium/eloquent AVMs (S2V0E1). CONCLUSION: Grade III AVMs are a heterogeneous group, with each type possessing different surgical risks, and the Spetzler-Martin grading scale should be modified accordingly. Grade III- AVMs (S1V1E1) have a surgical risk similar to that of low-grade AVMs and can be safely treated with microsurgical resection. Grade III+ AVMs (S2V0E1) have a surgical risk similar to that of high-grade AVMs and are best managed conservatively. Grade III AVMs (S2V1E0) have intermediate surgical risks and require judicious selection for surgery. Grade III* AVMs (S3V0E0) are either exceedingly rare, with a surgical risk that is unclear, or theoretical lesions with no clinical relevance.