This is a single-center, retrospective, and observational study.This retrospective study was approved by the Medical Ethics Committee of Qilu Hospital of Shandong University.Patients diagnosed with IVADA who underwent endovascular blood reconstructive treatment in the institution from December 2011 to December 2022 were eligible.Patient age, sex,index, clinical presentation, smoking, drinking, hypertension, diabetes mellitus, hyperlipidemia, modified Rankin Scale (mRS) score, aneurysm size, and arterial branch anatomy were recorded. Treatment details, complications, and angiographic and clinical outcomes were also recorded.

The optimal treatment strategy was evaluated based on the patients' neurological condition and comorbidities, the angioarchitectural features of the aneurysm, and the decision of the patient and their first degree relatives. The conventional stents included Neuroform (Stryker Neurovascular, USA), Enterprise (Cordis Neurovascular, USA), and Solitaire (ev3, USA) stents, and a low-profile visualized intraluminal support (LVIS) device (MicroVention Terumo, USA) was used. The flow diverters included Tubridge (MicroPort NeuroTech, China) and Pipeline (Medtronic, USA) devices. All EVT procedures were performed via a femoral artery approach under general anesthesia. An intravenous bolus of heparin (5000 IU) was administered before the procedure. Heparin was discontinued at the end of the procedure. A standard 6F or 8F guide catheter was advanced into the subclavian artery, proximal to the vertebral artery. An intermediate catheter (Navien, Medtronic) was then inserted into the V2 segment of the vertebral artery. A stent microcatheter was used to access the true lumen of the aneurysm in the posterior cerebral artery through the guidewire. For cases with additional coil insertion, a coil microcatheter was placed in the aneurysm sac. The stent was partially deployed to cover the aneurysm neck and temporarily jail the microcatheter, after which the aneurysm was loosely or densely packed with detachable coils before the stent was completely deployed. For long segmental lesions in which the aneurysm neck could not be covered completely with a single stent, an additional stent was extended into the bridged segment. If a single stent was not sufficient to alter the intra-aneurysmal hemodynamics, overlapping stents were used to reconstruct the lesion.

The anti-platelet drugs (aspirin 100 mg/day and clopidogrel 75 mg/day) were administered for at least 3 days prior to the procedure for patients with unruptured aneurysms. All patients with ruptured aneurysm were given aspirin and clopidogrel 300mg by oral or nasal feeding before general anesthesia was administered.The anti-platelet drugs (aspirin 100 mg/day and clopidogrel 75 mg/day) were administered for 3 months post-operatively, followed by aspirin alone for 3 months. Patients who had insufficient responses to aspirin or clopidogrel received a substitute antiplatelet agent (ticagrelor).The diameter and length of the stent were chosen according to the dimensions of the affected parent vessel.

The main complications during hospitalization were hemorrhage, infarction, or hydrocephalus requiring shunting. Procedural complications included those that occurred intraoperatively or after EVT. Periprocedural complications included those that occurred during hospitalization. Clinical follow-up was performed via neurological examinations or telephone interviews. Clinical outcomes were assigned based on the modified Rankin scale (mRS) score at the last follow-up: 0-2, favorable outcome; 3-6, unfavorable outcome. Cerebral angiography was performed at 6 months after EVT to confirm aneurysm occlusion and the patency of the VA（vertebral artery）. Aneurysm occlusions on immediate and final follow-up cerebral angiography were categorized as complete occlusion (no filling of the contrast agent in the aneurysm sac) or incomplete occlusion (residual filling of the contrast agent in the aneurysm neck or sac).

Imaging follow-up was performed using DSA（digital subtraction angiography）、CTA（Computer Tomographic Angiography）、MRA（Magnetic Resonance Angiography） approximately 6 months after stenting. The occlusion rate was evaluated using the O'KellyMarotta (OKM) grading scale . Recurrence was defined as an aneurysm that showed an increased percentage of contrast filling within the aneurysmal sac on follow-up angiography. All imaging studies were evaluated independently by two neurointerventionalists with more than 5 years of experience. Any disagreements were resolved by third neurointerventionalists with 10 years of experience. Clinical outcomes were evaluated by determining the mRS score at follow-up visits or via telephone interviews.

Using The R Programming Language software,Propensity Score Matching 1：2 (caliper value 0.05), to make it has no statistical differences between the two groups in baseline information. The matched case data will be statistically analyzed by IBM SPSS Statistics27.0(IBM Corp, New York, USA)。 The one-sample Kolmogorov-Smirnov test was used to test the normality of the data distribution for continuous variables. Continuous variables that conforming to a normal distribution are presented as mean and SD, and do not conform to the normal distribution are expressed by the median (25%,75%).Categorical variables are presented as numbers (frequency). Continuous variables were compared using the Student's t-test or Mann-Whitney U test, as appropriate. Categorical variables were compared using the chi-square test or Fisher's exact test, as appropriate. Variables identified as potential predictors in univariate analysis (p\<0.1) were included in binary logistic regression analysis (forward) to determine their status as independent predictors. A p value of \<0.05 was considered statistically significant.