The treatment goal for cerebral AVMs is mainly to prevent hemorrhage. Bleeding risks of cerebral AVMs depend on several factors such as size/location of the nidus, types of presentation, and angiographical cure does not necessarily mean no risk of hemorrhage. The treatment strategy based on Spetzler-Martin grading is proposed in several guidelines: Grade I, II, and III are a therapeutic target; Grade IV and V should be treated conservatively. According to AHA Scientific Statement, surgical extirpation should be conceded for Spetzler-Martin Grade I and II, and surgical extirpation with preoperative feeder embolization is often effective for Spetzler-Martin Grade III, but single surgical extirpation is not recommended for Spetzler-Martin Grade IV and V. Although low grade AVMs are reported to be amenable to extirpation with low morbidity, patient selection bias seems to reduce estimates of risk.
It is difficult to decide the treatment only by the Spetzler-Martin grading system because of degraded ability of AVM patients to communicate, and wide ranges of risk of hemorrhage and risk of extirpation in each patient. Treatments should be individualized using adequate pre-, and intra-operative assessment of risk.