**3. The aneurysmal recurrence rate after endovascular coil embolization has improved but is still high**

While endovascular treatment is a minimally invasive treatment for cerebral aneurysms, the biggest problem is that, unlike craniotomy clipping, which is a treatment that can completely exclude cerebral aneurysms from the circulatory system, it is a method of filling coils with aneurysms while they are still in the circulatory system, which inevitably results in a relatively high postoperative recurrence rate. According to the ISAT results, the cerebral aneurysm recurrence rate after endovascular treatment is reported to be 17.4% [16]. The BRAT results also reported a 15.6% cerebral aneurysm recurrence rate after 1 year of endovascular treatment [21]. According to reports on so-called real-world data from other than these randomized controlled trials, the recurrence rate is 20–30% [22, 23]. But recent reports indicate that the rate of cerebral aneurysm recurrence after endovascular treatment is trending downward, from 10% to the 5% range [24, 25]. This is primarily due to new technological innovations such as stent-assisted coil embolization. On the other hand, as mentioned above, the number of cerebral aneurysms treated endovascularly is increasing. As the population grows, it is clear that the number of aneurysms requiring retreatment will inevitably increase, no matter how low the recurrence rate becomes.
