Stereotactic Radiosurgery for Partially Resected Cerebral Arteriovenous Malformations

Incomplete microsurgical resection of cerebral arteriovenous malformations (AVM) occurs uncommonly. However, such patients harboring postoperative residual nidi remain exposed to the risk of AVM hemorrhage and are therefore reasonable candidates for further intervention. The goals of this retrospective case-control study are to analyze the radiosurgery outcomes for partially resected AVMs and determine the effect of prior resection on AVM radiosurgery outcomes.

We evaluated a prospective database of AVM patients treated with radiosurgery from 1989-2013. Previously resected AVMs with radiologic follow-up ≥2 years or nidus obliteration were selected for analysis and matched, in a 1:1 fashion and blinded to outcome, to previously unresected AVMs. Statistical analyses were performed to assess relationship between prior resection and AVM radiosurgery outcomes.

The matching process yielded 88 patients in each of the previously resected and unresected AVM cohorts. In the resected AVM cohort, the actuarial AVM obliteration rates at 3 and 5 years were 47% and 75%, respectively; the rates of radiologic and symptomatic radiation-induced changes (RICs) were 10% and 3%, respectively; and the annual postradiosurgery hemorrhage risk was 1.1%. The lack of prior AVM resection (P < 0.001) and superficial AVM location (P = 0.009) were independent predictors of radiologic RIC. The actuarial rates of obliteration (P = 0.849) and postradiosurgery hemorrhage (P = 0.548) were not significantly different between the resected and unresected AVM cohorts.

Radiosurgery affords a reasonable risk-to-benefit profile for incompletely resected AVMs. For those with a small-volume residual nidus after resection, radiosurgery should be considered an effective alternative to repeat resection.