Interventional neuroradiology had reached a point where it was not a real problem anymore to cure brain arteriovenous malformations thanks to advances in embolics, according to Laurent Spelle, professor, Interventional Neuroradiology, Paris Diderot University, Beaujon Medical Center, France. In a debate on Onyx vs. Glue, he told delegates at the European Society of Minimally Invasive Neurological Therapy congress (ESMINT) in Nice, France: “It is important to remember that it is not the material used which induces complications, but the doctor and his skills in carrying out the procedure and the actual disease itself, which we do not understand at all which can influence the complication rate.”
He also stated that it was time to lay the battle of Onyx vs. glue to rest. “We must quit focussing on Onyx vs. glue—each material has its own proper indications, and we should focus our efforts to better understanding how arteriovenous malformations behave. We must move forward to settle on the right indication for treatment. The first question is should we treat asymptomatic brain arteriovenous malformations, or even all arteriovenous malformations,” he said.
Spelle set out to defend Onyx embolization of arteriovenous malformations. “I do not think it should be a boxing fight between Onyx and glue as there are advantages and disadvantages to using each of these materials. The advantage with glue is that it is the best embolic material for use in intranidal aneurysm cases, where it is impossible to reach the nidus. This is because glue can be injected from some distance away. Another important, and maybe obvious fact is that glue ‘sticks’, so it can be extremely useful for direct fistula which can be done with an 80% concentration of glue. In such a case, you need a material that will polymerise rapidly and glue cannot be replaced by Onyx. The disadvantages of glue are that the cure rate could be less-efficient, and a smaller volume is injected. The latter raises important issues and might have a bearing on the lesser complication rates seen with glue, he said.
“Of course glue is more difficult to control because you have a shorter duration of injection. The maximum length of time is 15 minutes compared to Onyx where you have 35–45 minutes. With glue, when it starts to reflux along the microcatheter, it is finished,” Spelle said.
In his position defending Onyx in the debate, Spelle stated that “Reflex along the microcatheter for Onyx is part of the technique and if you do not understand that you cannot manage this material. Onyx gives you time to think, which is very difficult to understand for anyone who has never used this material. It is easier to use when compared to glue because you have time to think about what you should do, how you should proceed and even if you should proceed at all. It has a much better penetration of the nidus, and this leads to a larger volume of nidus that can be occluded using Onyx. It allows embolization and complete cure of even large brain AVMs and has a higher rate of occlusion.
Edoardo “Dodi” Boccardi, director, Interventional Neuroradiology, Ospedale Niguarda, Milan, Italy, had to defend glue against Onyx in the debate at ESMINT. He said “At Niguarda, we were very excited when Onyx arrived in our field because we thought that we could finally cure arteriovenous malformations by endovascular treatment. Why? Because we thought Onyx would penetrate much better in the nidus, it would allow much longer injection and we could fill the arteriovenous malformation with a lot of embolic material in the first session. So Onyx was seen as a real cure for this disease.
“However, we then began to see the disadvantages of the Onyx as well. The high radiopacity hides details such as vein occlusions. It is so black that once you start injecting you arrive at a point when you cannot see it anymore. There also used to be the issue of catheter entrapment, which could cause subarachnoid haemorrhages from having to pull it. There also used to be the issue of having to take the catheter away— but with the new catheter, this better. In the beginning, we saw some haemorrhages resulting from having to do this,” he said.
He also explained that injection of collaterals could be a problem with Onyx as also intravascular hyperpressure (rupture of vessels and extravascular accumulation of Onyx). “But the biggest problem with Onyx is that an increase in the number of intra and post-procedure haemorrhages what were not seen with before with glue,” he said.