1, Objects and Methods In our department, from February 1999 to March 2006, electrolytic detachable spring coil (GDC) was applied to embolize 393 intracranial aneurysms in 361 cases, of which 314 aneurysms in 289 cases were effectively followed up. The present study focused on the analysis of 285 cases of ruptured aneurysms, including 166 females and 119 males; ages ranged from 5 to 82 years, with a mean of 50.6 years. DSA showed 285 patients with 285 ruptured aneurysms, as well as 23 unruptured aneurysms. Ruptured aneurysms were completely embolized in 114 (40.0%), subcompletely embolized in 121 (42.5%), and incompletely embolized in 50 (17.5%). Follow-up visits were conducted by letter, telephone, and outpatient clinic, and were based on patients’ symptoms and signs, focusing on whether rebleeding occurred after aneurysm embolization, and collecting as much imaging data as possible. When rebleeding cases were found, their medical history, radiographic data and treatment were retrospectively analyzed, and related factors were analyzed. 2.Results 2.1 Follow-up results The follow-up period ranged from 2 to 72 months, with an average of 28.1 months. 17 patients died due to other diseases or advanced age. During the follow-up period, 4 intracranial aneurysms ruptured again, with a cumulative rebleeding rate of 1.4%; among them, 3 aneurysms were incompletely embolized and 2 were large aneurysms. 2.2 Typical cases Case 1, female, 42 years old, Hunt-Hess grade II, DSA posterior transportation aneurysm (Figure 1A), size 12.2 mm × 9.7 mm, neck 5.2 mm, only incomplete embolization was performed for economic reasons (Figure 1B). The patient recovered well after surgery, but 8 months later, he suddenly fell into a coma, Hunt-Hess grade IV, and cranial CT showed subarachnoid hemorrhage (SAH) and a small hematoma at the original embolization site. the patient died after 2 d. The patient had been in a coma since the beginning of this case, but he was still in the hospital. Case 2, male, 34 years old, Hunt-Hess class II, DSA showed an anterior transport aneurysm (Figure 2A), size 3.1 mm × 3.4 mm, neck 2 mm. During embolization, the aneurysm ruptured and hemorrhaged, and the intracerebral blood supply ceased (Figure 2B), and embolization could not be continued. The patient recovered completely after the operation, and the DSA showed incomplete embolization (Figure 2C). The patient refused further treatment and became comatose after 45 d. A cranial CT scan showed that the aneurysm had hemorrhaged again, and the patient died on the same day. Case 3, female, 48 years old, Hunt-Hess grade II, DSA showed posterior traffic aneurysm (Figure 3A), size 3.2 mm × 5.6 mm, neck 2.1 mm, and was subjected to subtotal embolization (Figure 3B). The patient was discharged from the hospital without review, and 24 months later, the patient was in a coma, and the CT showed SAH, and the DSA showed that the original embolized aneurysm was significantly enlarged (Figure 3C), with the size of 7.5 mm × 5.1 mm, and it was surgically clamped. Case 4, male, 70 years old, Hunt-Hess grade III, DSA showed an aneurysm of the superior cerebellar artery of the basilar artery, size 11 mm × 13.5 mm, with a neck of 3 mm, incomplete embolization was performed, and the patient recovered well. Eleven months after the operation, the patient became comatose, and cranial CT showed SAH, and the patient died 3 d later. The purpose of treatment for intracranial aneurysm is to prevent re-rupture and bleeding. We used the terms “ruptured aneurysm”, “embolization” and “follow-up” to search the Medline and Pubmed search engines. A total of 35 articles, including 10 180 patients, were searched in Medline and Pubmed search engines for “rebleeding after embolization of ruptured aneurysm”; the follow-up time ranged from 3 to 70 months, and the incidence of rebleeding ranged from 0 to 8.2%, with an average of 0.95%. The average follow-up time in this group was more than 2 years, and the cumulative rebleeding rate was 1.4%. Compared with the natural rebleeding rate of intracranial ruptured aneurysms, the risk of rebleeding after embolization was substantially lower in both this group of cases and in the literature. The highest rebleeding rate reported in the literature was 8.2% [1], which was higher than that of the cases in our group, but the risk of rebleeding was also significantly lower; 13 papers showed that no rebleeding occurred [2-4], suggesting that aneurysm spring coil embolization therapy has a clear role in preventing rebleeding of aneurysms. Among the 4 cases of rebleeding in this group, 3 aneurysms were incompletely embolized, while the number of incompletely embolized aneurysms was 50 out of all 285 aneurysms, i.e., the rebleeding rate of incompletely embolized aneurysms was 6%, which was still much lower than the natural rebleeding rate of ruptured aneurysms. Thus, even if only incomplete embolization is performed for ruptured aneurysms, the probability of rebleeding is significantly reduced. Although the probability of rebleeding from an aneurysm is reduced after embolization, isolated reports are still as high as 8%. Because of the small number of rebleeding cases, there is no literature analyzing the factors associated with rebleeding. Of the rebleeding aneurysms in our group, 3 were incompletely embolized and 1 was subtotally embolized; 2 aneurysms had diameters of more than 10 mm. of the 35 papers we retrieved, individual reports of rebleeding after complete embolization of aneurysms were reported, and 14 explicitly mentioned that rebleeding occurred in incompletely embolized aneurysms [5-7]. In addition, the incidence of rebleeding in large and giant aneurysms is relatively high, with seven publications specifying rebleeding after embolization of large and giant aneurysms. The majority of patients whose aneurysms re-ruptured died immediately, with no imaging evidence of the aneurysm’s condition at the time; individual cases survived, and DSA often revealed aneurysm recanalization. In our group, 1 aneurysm was subcompletely embolized, and after bleeding, DSA showed that the aneurysm recanalized and was significantly larger than at the time of initial embolization. It is inferred that the possibility of recurrence exists in other rebleeding aneurysms. The above data suggest that rebleeding after aneurysm embolization occurs mainly in larger aneurysms, incompletely embolized aneurysms, or aneurysms in which recurrence is more obvious on imaging review. The results of clinical follow-up and literature analysis of rebleeding after embolization of intracranial ruptured aneurysms are summarized as follows: ① Minimize the proportion of incomplete embolization. ② Incomplete embolization can be used as a palliative treatment in special cases, which can also reduce the probability of rebleeding in the near future and buy time for later treatment. ③ For large and giant aneurysms, embolization should be chosen carefully. ④ For incomplete embolization and larger aneurysms, follow-up should be strengthened. ⑤ Surgical clipping should be the treatment of choice for aneurysms for which complete or subtotal embolization is not expected (including economic considerations) and for very large aneurysms.