Thrombosis of Intracranial Aneurysms

Abstract

The treatment of intracranial aneurysms without craniotomy is attractive to clinicians and investigators alike. Early surgery following rupture of intracranial aneurysm carries a high mortality rate. On the other hand, the majority of the 50 per cent of aneurysms that will re-rupture do so within the first two weeks (4). This has stimulated the investigation of simple methods of thrombosing intracranial aneurysms before disastrous rupture or re-rupture occurs (3, 5). The purpose of this report is to give the preliminary results of our studies with magnetically controlled iron particles in attempts to thrombose intracranial aneurysms without craniotomy or physical trauma to the walls of the aneurysm. Procedure Meyers et al. (1) reported the use of magnetically controlled iron particles as contrast and isotopic agents. The iron particles are carbonyl iron, type SF2, in the form of 3 µ diameter spheres. These are essentially pure iron containing only small percentages of carbon, oxygen, and nitrogen. This iron is not readily ionizable except in reaction in an acid medium, and there is no contamination of the particulate matter with ionizable iron (2). It is suspended in dextran for injection. In our preliminary studies a cylindrical Alnico-5 permanent magnet was used to attract the iron particles. The femoral arteries of anesthetized dogs were exposed bilaterally, and a polyethylene catheter was inserted in one femoral artery so that the tip was above the bifurcation of the aorta. A major muscular branch of the other femoral artery was ligated approximately 5 to 10 mm beyond its origin, thus forming an “aneurysm.” With the magnet adjacent to the sac, an arteriogram was then obtained, showing the aneurysm (Fig. 1). Another arteriogram, obtained after the injection through the catheter in the contralateral femoral artery of 0.5 g of the carbonyl iron, demonstrated failure of the sac to fill with contrast material (Fig. 2). One hour after removal of the magnet a third film revealed the iron held in position in the “aneurysm” sac by thrombus (Fig. 3). Discussion The clinical application of this work would be to place a specially shaped magnet under stereotactic control so that one of its poles is next to but out-side the aneurysmal sac as demonstrated by angiography. At this time, the carbonyl iron suspension would be injected into the carotid artery. Sufficient carbonyl iron will be trapped and held in the aneurysm by the magnet to form a thrombus. Further studies are necessary and in progress to investigate the possibility of local and systemic toxicity of the agent and the permanence of the clot formed in this manner. Summary A simple method of thrombosing aneurysms is described, utilizing externally placed magnets and intra-arterially injected iron particles. Preliminary studies in dogs have been encouraging, and further studies are in progress and will be reported from time to time.