High grade AVMの治療 : われわれの反省と新たな試み(<特集>High grade AVMの治療)

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Stereotactic radiosurgery(SRS) is widely accepted as the optimum treatment strategy for small arteriovenous malformations(AVMs) of less than 3 cm diameter. However, the treatment of large and high grade AVMs classified as Grades III, IV, and V by the Spetzler-Martin system remains controversial, partly because SRS is not so effective, so many technologies have been developed to assist surgical removal of the nidus. Furthermore, the treatment may be influenced by individual variations caused by the complexity of the drainer-nidus-drainer system and the effects on the natural history of pedicle aneurysms, and deep or superficial, and eloquent or non-eloquent location. We have employed 2 different treatment strategies: intravascular embolization with liquid material to decrease AVM size followed by SRS during 1998-2000; and intravascular embolization to control feeders followed by nidus resection since 2001. Here we analyze the outcomes for patients treated by these protocols. Seven patients were treated by intravascular embolization: 2 patients received only intravascular embolization and 5 patients received intravascular embolization followed by CyberKnife irradiation in 4 patients and gamma knife followed by CyberKnife irradiation because of the poor initial response in 1 patient. One of the 2 patients treated by intravascular embolization had modified Rankin Scale(mRS) of 5, and the other patient died of bleeding from the AVM. Only 2 of the 5 patients treated by intravascular embolization followed by irradiation had complete obliteration of the nidus. Furthermore, the patient who received SRS twice later suffered from radiation necrosis. Nine patients were treated by intravascular embolization followed by surgery. The feeders far from the operative field were also embolized to decrease arteriovenous shunting and intraoperative bleeding, and to shorten the operative time, and the nidus was removed within 1 week to avoid newly formed fragile feeders. The hematoma wall adjacent to the nidus was fully utilized as a part of the dissection plane in patients with bleeding episodes. At the end of the operation, intraoperative angiography was performed to confirm complete resection of the nidus. Pre- and post-operative CBF studies were essential to predict NPPB, and this complication was never experienced in this series. The nidus of all 9 patients was completely removed, but 1 patient developed postoperative cerebellar ataxia. Embolic complication caused by intravascular embolization was observed in only one of the 16 patients in the entire study period. The present study suggests that large and high grade AVMs should not be treated by intravascular embolization to decrease the AVM size followed by SRS. Recently, recanalization of embolized nidus that was located out of the SRS irradiation field has been reported. Therefore, the low obliteration rate of our first strategy may have resulted from the presence of viable but angiographically occult nidus. In contrast, the second strategy achieved a high success rate. This study is limited by the small number of patients and large bias introduced by referral and the fact the patients with bleeding, but the findings indicate that intravascular embolization followed by surgery may be the optimum treatment for large and high grade AVMs. A new grading system for AVMs is needed to assess surgical feasibility based on the character of feeders, history of bleeding, and AVM location.
日本脳卒中の外科学会の論文
2007-07-31

High grade AVMの治療 : われわれの反省と新たな試み(<特集>High grade AVMの治療)

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