The Source for Neurovascular News and Education

August 11, 2020


Onyx embolization achieves a high occlusion rate, but stroke and death risks are higher than with medical management.


Onyx ethylene vinyl alcohol therapy, with or without radiosurgery, can produce a high rate of occlusion among patients with unruptured brain arteriovenous malformations (AVMs). Rates of stroke and mortality remain a problem, however. These are the main findings of a retrospective analysis from a single center in Belgium published online November 7, 2017, ahead of print in Stroke.


Onyx or other types of ethylene vinyl alcohols have been used worldwide for the treatment of brain AVMs since about 2000, senior author Luc Defreyne, MD (Ghent University Hospital, Belgium), told Neurovascular Exchange in an email. “It is an alternative for cyanoacrylate glue, which is still an important embolic agent for brain AVM,” he added.


Recent trials, however, including ARUBA and SIVMS, have demonstrated rates of stroke or death that are higher than those found with medical management alone. This has called into question whether Onyx or similar therapies should be used routinely for unruptured brain AVMs.


The investigators retrospectively reviewed outcomes of 61 patients with unruptured brain AVMs who were treated using Onyx and who met the inclusion criteria for the ARUBA trial. Their mean age was 38 years, and the median period of observation was 60 months. Patients were treated by embolization alone (41.0%), embolization and radiosurgery (57.4%), or embolization and excision (1.6%).


Among the 57 patients with completed treatment, occlusion was achieved in 44. Most patients had no clinical impairment at the end of follow-up, but rates of stroke or death remained high.


Outcomes of Onyx for Unruptured Brain AVMs




Modified Rankin Scale (mRS) Score 0-2


Stroke or Death Related to Unruptured Brain AVMs or Intervention


Treatment-Related Mortality




Is it an improvement on conservative management?

“We found that primary Onyx embolization works, on its own or in combination with radiosurgery, to achieve a high percentage of AVM occlusion,” said Defreyne. “Although the complication rate was lower and the mRS score better [than in the ARUBA study], we were not able to improve the outcome of interventional treatment in a way that we could challenge the nonintervention group of the ARUBA trial up to the end of our follow-up.” It still remains unclear, he said, if the risk associated with embolization or radiosurgery can be diminished enough to make it a superior option to conservative therapy in the long term.


As a result, he concluded that “primary Onyx embolization is a valuable strategy for treatment of incidental brain AVM, but a significant morbidity (and even mortality) has to be taken into account. The informed consent should include this [information], especially that mortality remains a real risk. We have stringent selection criteria for [treatment of] unruptured brain AVM and only treat when patients have and understand all the information on success rates and complications risks.”


Defreyne acknowledged that the study had no comparison group, noting that the number of patients with unruptured AVMs who were treated conservatively at their hospital was low.





Singfer U, Hemelsoet D, Vanlangenhove P, et al. Unruptured brain arteriovenous malformations: primary ONYX embolization in ARUBA (A Randomized Trial of Unruptured Brain Arteriovenous Malformations)-eligible patients. Stroke. 2017;Epub ahead of print.



Defreyne reports no relevant conflicts of interest.