Abstract W P416: Outcomes following Microsurgical Resection of Intracranial Arteriovenous Malformations previously treated with Stereotactic Radiosurgery

Abstract

INTRODUCTION: Large and complex intracranial AVMs can be challenging to treat and may require a multimodality strategy. The success rates of stereotactic radiosurgery alone for large and deep intracranial AVMs is only 25-50%. Many of these previously irradiated AVMs, with or without embolization may require additional treatment. This study hypothesizes that prior remote radiation therapy can aid microsurgical resection of lesions to achieve cure. METHODOLOGY: This retrospective study utilized the Stanford AVM database, to identify 92 patients treated with microsurgery after prior radiation between 1990-2014. A total of 84 patients with complete data were used for this study. RESULTS: Patients were 7 to 64 years old (mean 33), and underwent microsurgical resection 6 mos-11 yrs after radiosurgery. Sixty-nine patients (82%) underwent endovascular embolization prior to surgery. Initial AVM volumes were 0.6-117 cm3 (mean 21). Radiation doses were 4.6-45 GyE (mean 21.5). Seventy-three AVMs (87%) were located in eloquent or critical areas. Venous drainage was deep in 28, superficial in 32 or both in 20 lesions. Spetzler-Martin grades were I (4%), II (12%), III (31%), IV (39%) and V (14%). Prior to surgery, twenty-one patients (25%) experienced hemorrhage in a delayed fashion following radiation or embolization, while 14 (17%) developed radiation necrosis. At surgery AVMs were partially thrombosed, markedly less vascular, and more easily resected than if the patient had not received radiosurgery. Blood loss was minimal and the radiosurgery transformed difficult AVMs into easily resectable ones. Despite persistent angiographic AVM filling, much of the small-vessel component was obliterated by the radiosurgery. Complete AVM resection was achieved in 71 (85%) of cases. Five patients (6%) died of delayed re-bleeding from residual AVM following deliberate subtotal surgical resection. Over a mean follow-up of 24 months, clinical outcome was excellent in 33%, good in 48% and poor in 11%. CONCLUSIONS: Stereotactic radiosurgery several years prior to microsurgical resection is a useful adjunct for treating large and complex intracranial AVMs. Excellent or good clinical outcome can be achieved in most patients using this multimodal therapy.