Brain AVM Embolization with Onyx(R): Analysis of Treatment in 34 Patients

The endovascular approach to arteriovenous malformations (AVM) using different embolizing agents is a well-established treatment option. This report assesses the results of our experience using a non "glueing" embolic material available for several years, commercially known as Onyx(R). We used Onyx to treat 34 consecutive patients in the last four years. All patients were treated in the same department by the same neuroradiological team, with a strictly repetitive technical strategy and procedural protocol. All our patients presented AVMs with Spetzler Grade 3 or more, because in our Institution Grade 1 or 2 AVMs are directly treated by surgical approach. We adopt a multidisciplinary treatment approach (embolization, surgery, radiotherapy) by which embolization is construed as work in progress offering definitive treatment of AVMs without severe risks. Embolization is mainly undertaken as the first step before surgery, to reduce flow and size of the AVM by a "targeted" technique. In addition to reducing lesion size, endovascular treatment aims to seal off AVM areas anatomically or haemodynamically complex for surgical treatment. Occasionally, the reduction in size allows a radiosurgical approach. Embolization seldom results in a definitive cure of AVMs. At the end of multimodal approach, we obtained the complete and definitive cure of AVM in 21/34 patients (two complete obliteration with interventional technique, 19 in combination with surgery); to these were added 5/34 patients who received radiosurgical therapy. No major complications arose during endovascular treatment. One patient had transitory (36 hour) impaired right arm pronation. The CT scan disclosed an asymptomatic mild SAH in the left sylvian fissure but no ischaemic areas. One patient still in treatment died from fatal rebleeding (the clinical onset had been with haemorrhage two weeks before the session) 12 days after the embolization. Excellent or good clinical outcome was obtained in 23/26 patients who completed the therapeutic protocol. Outcome was conditioned by focal symptoms present on admission in three patients due to haemorrhagic onset, but only one patient presented a severe disability on discharge. In our view, the main problem of Onyx is that the apparently easier approach will probably lead to a wider diffusion of these procedures. AVMs are extremely difficult and dangerous to treat: this is not affected by the quality of the embolizing agents used and must be kept in mind at all times.