Long-Term Follow-Up Results of Two-Stage Gamma Knife Radiosurgery with a ?3 Year Interval for >10 cc Arteriovenous Malformations

Keywords: arteriovenous malformation, radiosurgery, gamma knife, technique, outcome

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     Little information is available on staged gamma knife radiosurgery (GKRS) with an interval of >3 years for relatively large arteriovenous malformations (AVMs).
     We sought to determine outcomes after staged AVM radiosurgery.
     Among our 250 AVM patients treated with GKRS during a 16-year period (1988-2004), the courses of 31 (15 females, 16 males, mean age; 29 range; 10-63 years) were selected for study.
      The median nidus volume was 14.0 (maximum; 55.8) cc, respectively. In all 31 patients, relatively low doses (12-16 Gy at the lesion periphery) were intentionally employed for the first GKRS. The second GKRS was scheduled for at least 36 months later.
     Complete nidus obliteration was attained after the first GKRS in one patient. To date, 26 patients have undergone a second procedure with a post-GKRS mean interval of 41 (range 24 to 83) months, while two patients refused the second GKRS and no further treatment was not applicable because of severely morbid and death due to bleeding in one each. Among the 26 patients, three refused follow-up DSA, two died due to bleeding and follow-up DSA is awaited in one. The remaining 20 paients have undergone follow-up DSA. Complete nidus obliteration was confirmed in 13 (65.0%), remarkable shrinkage in the other seven (35.0%). In the two of the seven patients, a third GKRS achieved complete nidus obliteration. Therefore, the cumulative complete obliteration rate in this series was 76.2% (161+13+2/21 eligible patients). Seven patients (22.6%) experienced bleeding; six before and one after GKRS. Mild symptomatic GKRS-related complications occurred in two patients (6.5%).
     This was a retrospective review.
     Although a final conclusion awaits further studies and patient follow-up, these results suggest two-stage GKRS to have certain benefits even for relatively large AVMs.
     We encourage others to evaluate and report this concept.


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