Onyx (interventional radiology)

Onyx is a non-adhesive, liquid embolic agent used in interventional radiology to treat various types of vascular malformations, including arteriovenous malformations (AVMs) and dural arteriovenous fistulas (dAVFs). It is composed of ethylene-vinyl alcohol copolymer (EVOH), dimethyl sulfoxide (DMSO), and micronized tantalum powder to provide radiopacity. Onyx is delivered through microcatheters into the vascular malformation under fluoroscopic guidance, where it solidifies upon contact with blood, thereby occluding the abnormal vessels.

History

The development of Onyx represents a significant advancement in the field of endovascular neurosurgery and interventional radiology. Before its introduction, the treatment of vascular malformations primarily relied on surgical resection or the use of adhesive embolic agents, which had limitations in terms of precision and safety. Onyx was approved by the Food and Drug Administration (FDA) for use in the United States in the early 2000s, offering a new, minimally invasive option for patients.

Mechanism of Action

Onyx works by creating a cast of the vascular malformation from the inside. When injected, the DMSO component rapidly diffuses into the blood, causing the EVOH and tantalum to precipitate and form a spongy, cohesive mass. This mass effectively occludes the abnormal vessels, reducing the risk of bleeding and facilitating the resolution of symptoms associated with the malformation.

Clinical Applications

Onyx is primarily used in the treatment of:

• Arteriovenous malformations (AVMs) - abnormal connections between arteries and veins that can cause bleeding or seizures.
• Dural arteriovenous fistulas (dAVFs) - abnormal connections between arteries and veins in the dura mater, the outer membrane of the brain.
• Peripheral vascular malformations - including those involving the limbs or organs outside the central nervous system.

Advantages

The use of Onyx in interventional radiology offers several advantages over traditional treatments:

• It allows for the precise targeting of the vascular malformation without affecting surrounding tissues.
• It is non-adhesive, reducing the risk of catheter entrapment.
• It provides a durable occlusion, with a lower rate of recanalization compared to other embolic agents.

Risks and Complications

As with any medical procedure, the use of Onyx carries potential risks and complications, including:

• Ischemia or infarction due to unintentional occlusion of normal vessels.
• Migration of the embolic agent to unintended locations.
• Allergic reactions to the components of Onyx, particularly DMSO.

Conclusion

Onyx has revolutionized the treatment of vascular malformations by providing a safe, effective, and minimally invasive option for patients. Its development underscores the importance of innovation in the field of interventional radiology and its impact on patient care.