Neurointerventional procedures have become an essential component in the management of numerous intracranial diseases ranging from arterial aneurysms to arteriovenous malformations. Among the critical decisions a neurointerventionalist has to make is the selection of an appropriate embolic agent. Two of the most widely used embolic agents are Ethyl-Vinyl Alcohol Liquid Embolic Agents (EVOH) and N-Butyl Cyanoacrylate (NBCA). Both these agents have their respective advantages and limitations. This article aims to compare EVOH and NBCA and determine which is a better choice for neurointerventional procedures.
EVOH Liquid Embolic Agents are hydrophobic, biocompatible, non-adhesive, and slowly degradable copolymers of ethylene-vinyl alcohol that effectively occludes the arterial flow of the targeted vessel segment. The use of EVOH agents reduces the risk of non-target embolization, and it provides better control over the density and amount of embolization. The polymerization time of EVOH is relatively longer, which demands caution while injecting the product since unwanted migration of the embolic agent may occur. Additional handling steps are necessary to increase the concentration of the embolic agent while maintaining proper viscosity. Anatomical and procedural expertise and experience are essential when using EVOH embolic agents. EVOH agents have been approved by the FDA to treat intracranial vascular lesions, as well as pulmonary arteriovenous malformations.
N-Butyl Cyanoacrylate (NBCA) is a fast and potent liquid embolic agent that rapidly polymerizes on contact with blood. NBCA is an adhesive compound, which makes it highly effective in targeting small and tortuous vessels, and in reducing re-bleeding rates, especially in cases of arteriovenous malformations and dural arteriovenous fistulas. NBCA polymerization time is relatively shorter, which limits the time the interventionalist has to reposition the catheter and injection of the embolic agent. Additionally, NBCA is highly viscous, requiring specialized mixing steps and temperature-control processes to maintain its appropriate consistency while minimizing the risk of adjacent tissue damage and non-target embolization. Studies have shown that EVOH provides long-term benefits in the occlusion of large and dysplastic arteries while minimizing the risk of non-target embolization.
In terms of procedural safety, both EVOH and NBCA have a low risk of embolization. EVOH, however, presents a significant degree of hyperdense cerebral edema up to 14 days after its injection, which may cause a delayed intracranial hemorrhage. Regarding NBCA, it has a more significant risk of tissue necrosis and non-targeted embolization. The use of NBCA requires extra caution when administered in the peddicular regions, as the possibility of unwanted migration to the spinal cord can occur.
In summary, both agents have their respective benefits and limitations. EVOH has a more prolonged polymerization time and requires careful handling, which may be challenging to some interventionalists. NBCA, on the other hand, has a shorter polymerization time, but it can be challenging to control the rate of flow, particularly in tortuous vessels. Considering the crucial role external factors, such as procedure type, patient factors, benefits, and limitations of both agents, a careful review, and individualized approach will help interventionalists select an optimal embolic agent for their patients.