Zsolt Kulcsár, MD Department of Neuroradiology, Hirslanden Clinic, Zurich, Switzerland Stephan G. Wetzel, MD Department of Neuroradiology, University Hospital of Basel, Basel, Switzerland Luca Augsburger, PhD Laboratory of Hemodynamics and Cardiovascular Technology, Federal Institute of Technology, Lausanne, Switzerland Andreas Gruber, MD, PhD Department of Neurosurgery, University of Vienna, Vienna, Austria Isabel Wanke, MD, PhD Department of Neuroradiology, Hirslanden Clinic, Zurich, Switzerland; and Department of Neuroradiology, University of Essen, Essen, Germany Daniel Andre Rüfenacht, MD, PhD Department of Neuroradiology, Hirslanden Clinic, Zurich, Switzerland Reprint requests: Zsolt Kulcsár, MD, Neuroradiologie, Klinik Hirslanden, Witellikerstrasse 40, 8032, Zürich, Switzerland. E-mail: kulcsarzsolt22@gmail.com Received, July 28, 2009. Accepted, January 20, 2010. Copyright © 2010 by the Congress of Neurological Surgeons S ubarachnoid hemorrhage (SAH) related to very small (< 2 mm) intradural aneurysms is not common and poses significant diag- nostic and therapeutic challenges. These lesions may be blisterlike, dissecting, or saccular type. Endovascular treatment with coils is difficult and may pose significant technical problems in achiev- ing endosaccular occlusion because there is a high risk that these lesions may be too small and frag- ile for safe catheterization and implant insertion. Parent vessel occlusion can be considered as an alternative if collateral pathways are sufficient. Stent redirection of blood flow in the parent ves- sel to allow aneurysm thrombosis and reverse remodeling of the wall might be an alternate and simpler treatment option. The structural design and high porosity of con- ventional stents may not be optimal to facilitate complete vascular reconstruction, although some have reported success. 1 With the advent of flow diverter (FD) implants, the technical ability to improve vascular remodeling became possible. These prostheses have a much finer mesh that evenly covers the orifice of the aneurysm regard- less of its size. Such an FD device is the SILK (BALT Extrusion, Montmorency, France; Figure 1). This flexible, self-expanding device is specifically designed to produce a hemodynamic flow diver- sion and to reconstruct laminar flow in the par- ent artery. The device is a braided mesh cylinder with flared ends composed of 48 nickel-titanium alloy (NiTinol) and platinum microfilaments. Fully deployed in a target vessel, the FD expands to appose the vessel wall and cover the aneurysm ori- fice. The porosity is significantly lower than that of conventional intracranial stents. The small HISTORICAL LIBRARY NEUROSURGERY VOLUME 67 | NUMBER 3 | SEPTEMBER 2010 | 1 Effect of Flow Diversion Treatment on Very Small Ruptured Aneurysms BACKGROUND: Ruptured aneurysms of < 2 mm are not amenable to endovascular coil- ing and therefore pose a significant treatment challenge. OBJECTIVE: To test recently introduced flow diverters that allow endovascular reconstruc- tion via another method and may represent a new treatment option for such lesions. PATIENTS AND METHODS: Three female patients presented with acute subarachnoid hemorrhage. An aneurysm of < 2 mm was identified in all patients as the cause of bleed- ing. The aneurysms were located at the C2 segment of the internal carotid in 2 patients and on the basilar bifurcation in the other. All patients had failed early endovascular treat- ment attempts. Flow diversion with the SILK flow diverter was offered as an alternative in each patient. RESULTS: SILK deployment successfully eliminated the aneurysms in all 3 instances. One of the aneurysms was excluded from contrast material visualization immediately after stent deployment. Transient thrombotic complication was observed in the case of the basi- lar artery aneurysm. It resolved with the administration of intraarterial tirofiban. There was no treatment-related morbidity, and none of the aneurysms reruptured after SILK implan- tation during a clinical follow-up of at least 4 months (range, 4-10 months). Imaging follow- up showed complete vessel remodeling in all cases. CONCLUSION: Flow diversion treatment prevented rebleeding during the follow-up period. Reverse remodeling of the concerned vascular segment with delayed disappearance of the aneurysm was observed in each case. KEY WORDS: Cerebral aneurysm, Flow diversion, SILK, Subarachnoid hemorrhage, Uncoilable Neurosurgery 00:000-000, 2010 DOI: 10.1227/01.NEU.0000372920.39101.55 www.neurosurgery-online.com ABBREVIATIONS: DSA, digital subtraction angiog- raphy; FD, flow diverter; SAH, subarachnoid hemor- rhage