**1. Introduction**

350 Aneurysm

604-605.2004;

[15] Ho P.C., Leung C.Y.: Treatment of post-stenotic saphenous vein graft aneurysm: special considerations with the polytetrafluoroethylene-covered stent. J Invasive Cardiol 16.

> There are various intracranial aneurysms: saccular, fusiform, dissecting or mycotic. Saccular aneurysms are the most common type and account for up to 98% of all intracranial aneurysms (Yasargil, 1984). If the widest diameter of the aneurysm is equal to or exceeding 25 millimetres (mm), the aneurysm is defined by convention as giant (GIA). The etiology of GIAs is similar to smaller ones (Lemole, 2000), theories about the development of all saccular aneurysms include congenital and acquired artery defects. GIA's and other aneurysms are etiologically divided into "sidewall" and "bifurcation" aneurysms (LeRoux, 2003). In flow-related phenomena, constant enlargement of a small aneurysm in the distal part of the neck results in GIA formation. However, de novo development of GIA has also been described (Barth, 1994). The histology of GIA wall is different from smaller aneurysms: GIAs often lack a muscular layer as well as elastic laminar layers show degeneration. The incidence of intraluminal thrombosis significantly increases with the lumen size of aneurysms; in GIAs this phenomena may occur in approximately 60% of cases (LeRoux, 2003). Krings publication (Krings, 2005) was a breakthrough in large aneurysms formation knowledge; he proved that the GIA development in the internal carotid artery (ICA) and vertebral artery (VA) differ from those in other locations. Repeated subadventitial haemorrhages from vasa vasorum are a predominant factor in GIA aneurysm pathogenesis. Therefore, GIA formation can be considered as a "proliferative disease of the vessel wall induced by extravascular activity". Historically GIA rupture is known as devastating due to higher amount of extravasated blood. In contrast, recent papers indicate that rupture of some smaller aneurysms leads to more extensive SAH. The study ISUIA (Kassell, 1990) proved that the risk of rupture of GIA can reach 40% in five-year follow-up, while treatment of unruptured intracranial aneurysm carries relatively low mortality that does not exceed 2% (Molyneux, 2005). Therefore, treatment is warranted for most patients suffering from GIAs. There are two treatment modalities that can be offered to patients afflicted with GIA

© 2012 Szmuda and Sloniewski, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

pathology: endovascular or surgical. In general endovascular treatment is less invasive and has fewer complications than surgery, and therefore is preferable. Surprisingly, no randomized comparison study of these two methods in GIA treatment have been published. However, the outcome measurement and analysis may be difficult to conduct a trial in GIAs; these aneurysms constitute a heterogeneous group and they are treated using different methods in different institutions. Furthermore, there is not enough observational data in the literature discussing results of treatment and their pertinence to quality of life in patients with GIAs in comparison to smaller ones. Additionally, radiographic results assessed several years post-operatively have not been reported sufficiently. Probably it is due to the unique peculiarity of GIAs as these require extensive comprehension of the treatment strategies to achieve better results. The current study is not only aimed at describing available methods, but to compare the prognosis after treatment of GIAs versus smaller aneurysms. A new neurovascular surgeon should be accustomed to all surgical techniques for GIAs. All of the treatment possibilities, technical issues and their clinical implications are to be learned meticulously and considered preoperatively.
