by Michael Horowitz, MD
Chief of Neurosurgery, UPMC Presbyterian
Director, Center for Endovascular Therapy

Pittsburgh, January 15, 2008 -- Until recently, endovascular embolization of intracranial aneurysms has 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.

(A) Aneurysm with balloon across neck and catheter in aneurysm; (B) Onyx injection begins; (C) Onyx injection ends.

Aneurysm before treatment.

Aneurysm after treatment.

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.

Case reports:

Case 1

A 38-year-old African-American woman with an unruptured 8 mm (124.41 mm3) right ophthalmic aneurysm elected to undergo endovascular therapy for lesion obliteration. After induction of general anesthesia, placement of a 7F Cook Shuttle catheter into the right internal carotid artery (ICA) (Cook, Bloomington, IN), and insertion of EEG and SSEP neurophysiologic monitoring lines the patient was administered 5000 units Heparin IV (ACT 250 sec) and underwent planning angiography.

Using roadmapping techniques, the aneurysm was catheterized with a Rebar 14 microcatheter over an Xpedion 0.014 wire. A second Rapid transit microcatheter (Cordis, Miami Lakes, FL) over a Gold Tip Glide Wire (Terumo, Somerset, NJ) was advanced into the distal right middle cerebral artery (MCA). The wire was removed and a 300 cm 0.010 Accelerator wire (ev3) was advanced through the Rapid Transit catheter. The catheter was removed and 4mm x 20 mm Neuroform stent (Boston Scientific, Fremont, CA) was advanced and deployed across the aneurysm neck. An 8 mm Micrus spherical coil (Micrus Endovascular Corporation, Sunnyvale, CA) was then introduced into the aneurysm and released.

Over the 0.010 Accelerator wire a 4 mm x 30 mm Hyperglide balloon was advanced through the deployed stent and positioned across the aneurysm neck as well. At this point the aneurysm was embolized with 0.22 cc Onyx 500 using the recommended 2-3-2 technique.

Complete occlusion was achieved without complication. Procedure time was less than two hours. At the procedure’s conclusion the patient was administered 15 mg eptifibatide IV, 600 mg Plavix OG, and 325 mg ASA OG. Heparin at 500 units/hour was continued for 12 hours and the patient was discharged home the next day on ASA and Plavix with the Plavix to be discontinued in 60 days.

Case 2

A 68-year-old white woman with an asymptomatic unruptured 11 mm (222.41 mm3) right posterior communicating artery segment aneurysm elected to undergo endovascular therapy for lesion obliteration. Her procedure was performed identically to the one described in Case 1 above except for a few changes which included the use of a 6F cook shuttle catheter and the insertion of two helical ev3 Axium coils (10 mm x 20 mm; 8 mm x 20 mm). This patient also achieved complete aneurysm occlusion with Onyx in a procedure that took less than two hours to complete. She was discharged the following day.

Case 3:

A 48-year-old white woman with an asymptomatic, unruptured 9 mm left posterior carotid wall aneurysm elected to undergo endovascular therapy for lesion obliteration. Her procedure was performed identically to the one described in Case 2 above except for the insertion of three helical ev3 Axium coils (9 mm x 20 mm; 9 mm x 20 mm; 8 mm x 20 mm) and a 4.5 mm x 20 mm Neuroform stent. This patient also achieved near complete aneurysm occlusion with 0.18 cc Onyx. She was discharged the following day.