Hemorrhagic Complications of Endovascular Coil Embolization for Very Small Intracranial Aneurysms

We studied hemorrhagic complications of coil embolization for very small (less than 3 mm in maximum diameter) intracranial aneurysms from April 2006 to Dec. 2011. We treated 272 intracranial aneurysms (78 ruptured, 194 unruptured), including 12 very small aneurysms (five ruptured, seven unruptured), during this period. There were one rupture during coil embolization among 260 intracranial aneurysms larger than 3 mm in maximum diameter (0.4%), However, there were two ruptures of very small 12 aneurysms (16.7%, p<0.05). The rupture rate of very small aneurysms during coil embolization is remarkably high compared with that of aneurysms with maximum diameter larger than 3 mm. The main cause of intraoperative rupture was supposed to be unstableness of the microcatheter for the long axis of the very small aneurysms. Therefore, the coils were pushed out in an unexpected direction and resulted in rupture. Preshaping of the tip of the microcatheter to fit the long axis of the very small aneurysms is very important to prevent this serious complication.