Onyx Liquid Embolic Agent

Endovascular embolization of intracranial aneurysms has often involved the placement of platinum coils via a microcatheter into the lesion until no additional coils could be placed. Such introduction of coils into an aneurysm would lead to thrombosis and exclusion of the aneurysm from the native circulation. Due to the mechanics of placing coils into a three dimensional space (analogous to filling a box with Slinkys) only about 35% such a space’s volume can be filled with coils when maximum packing is achieved thus leaving numerous interstices between abutting platinum wires.

In late 2007 Onyx liquid embolic material (ev3, Irvine, CA) became the first liquid embolic agent to be available in the United States for the treatment of intracranial aneurysms. This material is an ethylene vinyl alcohol copolymer dissolved in the organic solvent dimethyl sulfoxide (DMSO) opacified with tantalum powder. Once coming into contact with an ionic solution the DMSO dissipates and the Onyx solidifies into a spongy, cohesive material. Onyx HD 500 is a viscous form of the material used for the occlusion of intracranial aneurysms. This substance is delivered to the aneurysm via a microcatheter once the neck of the aneurysm is temporarily occluded by a balloon which reduces the risk of the copolymer exiting the aneurysm and entering the native circulation.

Several European centers have reported the results and variable techniques for Onyx 500 embolization of cerebral aneurysms. Most of these studies and case reports have centered around the use of Onyx with temporary balloon occlusion of the aneurysm neck. Some however have mentioned the use of endovascular coils and stents in conjunction with balloons to achieve effective lesion obliteration.

In November 2007 the Department of Neurosurgery at the University of Pittsburgh Medical Center became the third location in the United States to use Onyx 500 for the treatment of cerebral aneurysms. Below are our first three clinical cases performed that involved treatment of intracranial aneurysms using a combination of stents, platinum coils, balloons, and Onyx.