Advance Access: Long-term Outcomes With Planned Multistage Reduced Dose Repeat Stereotactic Radiosurgery for Treatment of Inoperable High-Grade Arteriovenous Malformations: An Observational Retrospective Cohort Study

Cerebral arteriovenous malformations (AVMs) are rare clinical entities with an incidence of approximately 1.12 to 1.42 cases per 100 000 person-years.1 While relatively uncommon, AVMs can be a considerable source of neurological morbidity and mortality, predominantly due to the risk of intracranial hemorrhage (ICH). The overall annual hemorrhage rate is estimated to be approximately 2.2% to 4.5%, and several factors, including prior hemorrhage, deep AVM location, and exclusively deep venous drainage, have consistently been shown to modify the propensity for bleeding.2

In general, management options consist of microsurgical resection and stereotactic radiosurgery (SRS) used as monotherapies or in combination with endovascular embolization, as well as conservative management. A significant proportion of AVMs are inoperable, often due to an unacceptably high anticipated risk of surgical morbidity and mortality. To assist therapeutic decision-making, the Spetzler-Martin (S-M) grading system is used to estimate the risk of postsurgical complications based on maximum AVM nidus diameter (<3 cm = 0; 3-6 cm = 1; >6 cm = 2), pattern of venous drainage (superficial = 0; deep = 1), and eloquence of brain location (noneloquent = 0; eloquent = 1).3 The composite score corresponds to an S-M AVM grade ranging from I to V. AVMs that are large, with deep venous drainage and/or in eloquent locations, are generally considered to be high-grade AVMs. As such, SRS has been a commonly employed modality in the management of inoperable, high-grade AVMs, albeit with a unique yet equally challenging set of treatment considerations.

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