INTRODUCTION: The CyberKnife, a frameless, robotic, stereotactic device, has been developed to radiosurgically treat arteriovenous malformations (AVMs). While most AVMs are obliterated within two-to-three years, a subset remain recalcitrant; long-term data on these difficult to treat AVMs are limited in the neurosurgical literature.MATERIALS AND METHODS: A retrospective analysis of all patients who underwent CyberKnife treatment for intracranial AVMs at a single U.S. institution between 2002 and 2012, whose AVMs had failed to obliterate within 48?months or longer from the treatment start date, were eligible for inclusion.RESULTS: Eleven patients (9 AVMs; 7 males, 2 females) were followed for an average of 85.2?months (range 56.2-119.4). The median lesion size was 3.5?cm (range: 2.8-8.0?cm) and median Spetzler-Martin grade was 3 (range: 2-5). All AVMs were treated with one radiation dose (median prescribed dose was 18.0?Gy; median Dmax: 23.7?Gy). Six (66.7%) were obliterated in a median time of 84?months (range: 52-94?months), while 3 (33.3%) remained active after a median of 90.8?months (range 69.7-119.4). Transient, post-radiosurgery adverse radiation effects occurred in 5 (55.6%) cases. One (11.1%) patient had an acute hemorrhage from the AVM after radiosurgery. Four (44.4%) patients underwent repeat radiosurgery and/or embolization. Three of these lesions eventually obliterated, while 1 did not.CONCLUSION: The median time to obliteration was 84?months. Two-thirds of AVMs which persisted for over 4?years following initial radiosurgery treatment eventually obliterated. Transient post-radiosurgery adverse effects were common; delayed hemorrhages were rare in our case series.
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