Treatment of AVM: Endovascular Methods

Treatment of AVM: Endovascular Methods（1）

AVM的治疗：血管内介入方法

Emmanuel Houdart, Marc Antoine Labeyrie, Stéphanie Lenck, and Jean Pierre Saint-Maurice

1  Summary

In this chapter we review the technical aspects, the indications, and the results of endovascular treatment of intracranial arteriovenous malformation (AVM). From an endovascular perspective, AVM is a hemodynamic vascular area connecting the high-pressure arterial system with the low-pressure venous system by means of arteriovenous shunts. The low-pressure venous system exerts suction on the arterial system and if the arteries supplying the shunts are occluded in a proximal manner, arterial anastomoses develop from adjacent arteries and resupply the shunts. This supports the distinction between proximal embolization that occludes arteries and preserves shunts and distal (or curative) embolization where embolic agent is pushed up to the draining vein. The standard technique of embolization uses the transarterial approach that consists in superselective catheterization of the arterial feeders and injection of embolic agents through microcatheters. Two types of liquid embolic agents are used at Lariboisière: cyanoacrylate (Glubran) and EVOH Copolymer-DMSO  solvent (Onyx). Glubran is used through perforating and small cortical arteries while Onyx is used through large cortical arteries. Proximal arterial occlusion makes sense only in pre-surgical embolization. On the other hand, when embolization is the sole treatment or when it is performed to reduce the size of an AVM before radiosurgery, the embolic agent must be pushed up to the first centimeter of the draining vein. This venous occlusion carries on a risk of rupture of the shunts if all the arterial feeders going to the shunts have not been first occluded. By transarterial approach, the success of the procedure (defined as an angiographic cure with unchanged neurological examination) depends on several factors that participate to our personal score: perforating arteries (yes = 1, no = 0), en passage arteries (yes = 1, no = 0), watershed area supply (yes = 1, no = 0), size >3 cm (yes = 1, no = 0). A high score is predictive of a poor result. Recently, transvenous embolization has been developed with the help of Onyx. This technique has not been assessed in large series and its hazard is still unknown. We restrict transvenous embolization to small AVM located in very functional area, fed by small arteries with difficult access and drained by an accessible vein. Main risk of any types of embolization is the hemorrhage that occurs when part of the shunts remains patent. The key point concerning the indications of treatment is related to unruptured AVM. Two recent prospective studies using control groups (with patients left untreated) have questioned the  benefit of  treatment of unruptured AVM. Currently, unruptured AVM are left untreated in their vast majority. Ruptured AVM have a higher risk to bleed than unruptured ones and indications of treatment are larger in such cases. However, when the neurological risk linked to the occlusion of the totality of the arteriovenous shunts is high, we restrict our treatment to the part of the AVM that has been recognized as responsible of the bleeding. Endovascular treatment of AVM is the intervention that requires the longest training in interventional neuroradiology.

1  总结

本章我们回顾颅内动静脉畸形的技术方面，适应症，和血管内治疗的结果。从血管内介入的观点，AVM是血流动力学血管病变区域，通过动静脉瘘单元联系高压的动脉系统和低压的静脉系统。低压的静脉系统抽吸动脉系统，如果供应瘘的动脉在近端阻断，临近动脉重新建立动脉吻合并再次供应瘘。这点支持动脉近端栓塞而保留瘘和远端（或治愈性）栓塞其栓塞剂注入静脉两种治疗体系的区别。栓塞的标准技巧采取经动脉入路，包括供血动脉的微导管超选和经微导管栓塞剂的注射。两种液态栓塞剂在 Lariboisière医院可被采用: cyanoacrylate (Glubran) and EVOH Copolymer-DMSO  solvent(Onyx). Glubran被用于穿支动脉和细小皮层动脉而Onyx被用于大的皮层动脉。近端动脉栓塞仅在开颅术前辅助栓塞有意义。另一方面，当栓塞是AVM唯一治疗选择或当栓塞是为了放疗前减少血流量时，栓塞剂必须注射到引流静脉的最初的1cm距离。如果所有的供应瘘的供血动脉未首先闭塞，这种静脉阻塞方式会带来瘘破裂的风险。通过动脉入路，过程的成功取决于以下参与我们分级系统的几个因素：穿支动脉（有=1，无=0），过路动脉（有=1，无=0），分水岭区域供血（有=1，无=0），尺寸>3cm (有=1，无=0）。分数越高，意味着预后越差。最近，随着Onyx的帮助，经静脉入路栓塞不断发展。这一技巧还没得到大样本病例评估，其潜在危害还未知。我们限定静脉入路适用于功能区的小AVM，细小的动脉很难超选而引流静脉容易导管到达。任何一种栓塞方式的主要风险是出血，发生在部分瘘单元保持不闭。涉及治疗的适用症的关键点是未破裂的AVM。最近两个前瞻性对照研究（左侧未治疗）质疑了未破裂AVM的治疗收益。当前，未破裂AVM大多数选择未治疗，破裂AVM比未破裂AVM有较高的出血风险，选择治疗的适应症在此组更高。然而当考虑动静脉瘘全部闭塞相关的神经功能缺失风险较高，我们限定实施AVM的部分治疗，处理明确的出血责任部分。AVM的血管内治疗是需要介入神经放射培训时间最长的干预措施。