Introduction: Endovascular embolization is an important modality in the treatment of cerebral arteriovenous malformations (AVMs). Onyx is an ethylene vinyl alcohol copolymer dissolved in dimethyl sulfoxide that is approved for use as an embolic agent for brain AVMs.
Case report: We describe a case of revascularization of an occluded vertebro-basilar artery during embolization of an AVM with Onyx, by using the Merci device.
Conclusion: Reflux embolization of patent vessels is a rare complication of using Onyx to treat AVMs. It can be successfully managed by retrieving the Onyx substance using mechanical retrieval devices like the Merci device.