What are the procedural risks of a cerebral Arteriovenous Malformation (AVM) embolization using Onyx (ethylene-vinyl alcohol copolymer)?

From the Guidelines

Brain AVM embolization with Onyx carries significant procedural risks, including stroke, intracranial hemorrhage, and neurological deficits, with reported morbidity rates ranging from 2% to 5% 1. The most serious risks associated with this procedure include:

• Stroke, which can occur due to inadvertent embolization of normal brain vessels or occlusion of draining veins leading to hemorrhage
• Intracranial hemorrhage, occurring in approximately 2-5% of procedures when blood vessels rupture during catheter navigation or from pressure changes after embolization
• Neurological deficits, which may develop, either temporary or permanent, depending on the AVM's location and affected brain regions Other potential risks and complications of the procedure include:
• Seizures, which can occur in 2-6% of patients during or after the procedure, particularly with AVMs near eloquent cortex
• Catheter-related complications, such as vessel perforation, dissection, or catheter entrapment within the solidified Onyx material
• Allergic reactions to contrast media or Onyx itself, although these are possible but uncommon
• Radiation exposure from prolonged fluoroscopy, presenting long-term concerns, especially for young patients requiring multiple procedures
• Incomplete AVM obliteration, which often necessitates additional treatments, as a single embolization typically achieves only partial occlusion
• Pulmonary embolism, which can rarely occur if Onyx enters the venous system and travels to the lungs These risks must be carefully considered and balanced against the natural history risk of untreated AVMs, which carry a 2-4% annual hemorrhage risk, as reported in the management guidelines for intracranial arteriovenous malformations 1.

From the Research

Procedural Risks of Cerebral Arteriovenous Malformation (AVM) Embolization using Onyx

The procedural risks of cerebral AVM embolization using Onyx include:

• Bleeding complications:
  • Occurred in 8.4% of procedures 2
  • Related to the use of the microcatheter/guidewire in some cases and to the use of the embolization material in others 2
  • Higher amounts of Onyx injected per session increase the bleeding risk 2
  • Periprocedural bleeding complications can be severe and devastating, with a significant impact on patient prognosis 3
• Ischemic complications:
  • Can occur due to long-fluoroscopy and long-procedure times, embolisate reflux across a considerable extent of the vessel, catheter entrapment, extravasation of Onyx from the arterial lumen, catheter transgression through the arterial wall, and venous occlusion preceding arterial feeder shutdown 4
• Permanent disability and mortality:
  • Permanent disability rate was 6.5% and mortality rate was 2.2% in one study 2
  • Morbidity was 4.6% and mortality was 2.3% in another study 5
• Other complications:
  • Catheter entrapment and extravasation of Onyx from the arterial lumen can occur 4
  • Venous occlusion preceding arterial feeder shutdown can also occur 4

Factors Affecting Procedural Risks

The following factors can affect the procedural risks of cerebral AVM embolization using Onyx:

• Angioarchitecture of the lesion:
  • Can predict treatment success and complications 2
• Amount of Onyx injected:
  • Higher amounts increase the bleeding risk 2
• Technique used:
  • The proximal plug technique has a series of drawbacks that can lead to serious adverse outcomes 4
  • The coil-augmented Onyx injection technique can improve the safety of the procedure 6
• Operator experience:
  • The control of Onyx demands operators accumulate a considerable learning curve 6