Gamma Knife Radiosurgery For Large Arteriovenous Malformation -a New Staged Strategy Of Targeting Only The Nidus Of Feeder Side At Early Arterial PhaseHiroyuki Kenai1, Masanori Yamashita2, Hori Yuzo2, Akira Yamada2, Tomoshige Asano2, Yukihiro Wakabayashi2, Yayoi Kondo2, Hirofumi Nagatomi21Oita, Japan 2Nagatomi Neurosurgical Hospital, Oita, Japan Keywords: arteriovenous malformation, outcome, gamma knife, technique, vascular malformationInteractive ManuscriptAsk Questions of this Manuscript: What is the background behind your study?In the treatment of large AVM, it is necessary to consider the strategy by some treatment modalities combination. However, in some cases, we could not perform microsurgery or embolization practically. And basically, these cases have been considered out of indication. Then in such cases, some of the trials of staged methods of stereotactic radiosurgery have been reported, but there are no decided one accepted widely. What is the purpose of your study?Including such cases, as a treatment method of large AVM, we are now adopting the new staged strategy by using Gamma Knife (GK). Although it is just on the preliminary stage, we report and introduce this strategy here. Describe your patient group.We have treated 7cases by this strategy until now. Maximum diameter of every case was over 3cm. Describe what you did.In the first stage, we decided the target basically 6-8cc of the feeder side nidus at the early arterial phase through the angiography, then irradiated 21-22Gy at the margin. And about 1-2 years later, we considered the irradiation to the shrunk residual nidus. Describe your main findings.Only by the treatment of first stage, total nidus including the outside of irradiation field had shrunk definitely within about 1-2years. And we added the second stage, then after 1-2further years, complete obliteration was confirmed in two cases. In another 2cases, we had already obtained shrunk nidus, then performed second stage and under follow up now. In the other huge case after first stage, which had repeated hemorrhage and seizure attack, no hemorrhage has been observed after first stage and seizure is now controlled. Describe the main limitation of this study.This is a retrospective study. Describe your main conclusion. Still now, it is only in five cases including the cases still in progress that we have been able to confirm the results. Describe the importance of your findings and how they can be used by others.Although it is necessary that the accumulation of the cases and other results in the future, as a strategy of the GK for large AVM, the possibility that the definite nidus reduction can be obtained by identifying surely the nidus of feeder side and irradiation only this area was suggested. Yet, the additional stage in this strategy certainly increases the obliteration rate, but the necessity of these treatments should be examined further more. In the treatment of large AVM, it is necessary to consider the strategy by some treatment modalities combination. However, in some cases, we could not perform microsurgery or embolization practically. And basically, these cases have been considered out of indication. Then in such cases, some of the trials of staged methods of stereotactic radiosurgery have been reported, but there are no decided one accepted widely. Including such cases, as a treatment method of large AVM, we are now adopting the new staged strategy by using Gamma Knife (GK). Although it is just on the preliminary stage, we report and introduce this strategy here. We have treated 7cases by this strategy until now. Maximum diameter of every case was over 3cm. In the first stage, we decided the target basically 6-8cc of the feeder side nidus at the early arterial phase through the angiography, then irradiated 21-22Gy at the margin. And about 1-2 years later, we considered the irradiation to the shrunk residual nidus. Only by the treatment of first stage, total nidus including the outside of irradiation field had shrunk definitely within about 1-2years. And we added the second stage, then after 1-2further years, complete obliteration was confirmed in two cases. In another 2cases, we had already obtained shrunk nidus, then performed second stage and under follow up now. In the other huge case after first stage, which had repeated hemorrhage and seizure attack, no hemorrhage has been observed after first stage and seizure is now controlled. This is a retrospective study. Still now, it is only in five cases including the cases still in progress that we have been able to confirm the results. Although it is necessary that the accumulation of the cases and other results in the future, as a strategy of the GK for large AVM, the possibility that the definite nidus reduction can be obtained by identifying surely the nidus of feeder side and irradiation only this area was suggested. Yet, the additional stage in this strategy certainly increases the obliteration rate, but the necessity of these treatments should be examined further more. Project Roles:
H. Kenai (), M. Yamashita (), H. Yuzo (), A. Yamada (), T. Asano (), Y. Wakabayashi (), Y. Kondo (), H. Nagatomi ()
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