Stent-assisted WEB embolization: aneurysm characteristics, outcome and case report of a WEB delivered through a stent.

PURPOSE: Woven Endobridge (WEB) embolization has become a well-established endovascular treatment option for wide-necked bifurcation aneurysms. The objective was to analyse cases that required additional stent-implantation. METHODS: Images of 178 aneurysms ≤ 11 mm treated by WEB only or by WEB plus stent were retrospectively reviewed, evaluating aneurysm characteristics, procedural specifics, adverse events and angiographic results. Moreover, we report a case of a WEB delivered through a previously implanted stent. RESULTS: Additional stent implantation was performed in 15 patients (8.4%). Baseline patient and aneurysm characteristics were comparable between both groups. A single stent was used in 12 cases and 2 stents in Y-configuration in 3. Thromboembolic complications occurred more often with stent assistance (33.3% vs. 8.0%, p = 0.002), while ischemic stroke rates were comparable between both groups (0% vs. 1.8%, p = 1.0). Six-month angiographic follow-up showed complete occlusion, neck remnants and aneurysm remnants in 73.4%, 19.4% and 7.3% after WEB only, respectively, and in 66.7%, 20.0% and 16.7% after WEB plus stent, respectively (p = 0.538). A case report shows that WEB deployment through the struts of a previously implanted standard microstent is feasible, even if a VIA 33 microcatheter is needed. CONCLUSION: In the present study, stent-assisted WEB embolization had a comparable safety and efficacy profile compared to treatment by WEB only. However, stent-assisted WEB embolization requires long-term anti-platelet medication, which annihilates the advantages of the WEB as a purely intrasaccular device. CLINICAL TRIAL REGISTRATION NUMBER: N/A.

Impact of the weekend effect on outcome after microsurgical clipping of ruptured intracranial aneurysms.

BACKGROUND: The "weekend effect" describes the assumption that weekend and/or on-call duty admission of emergency patients is associated with increased morbidity and mortality rates. For aneurysmal subarachnoid hemorrhage, we investigated, whether presentation out of regular working hours and microsurgical clipping at nighttime correlates with worse patient outcome. METHODS: This is a retrospective review of consecutive patients that underwent microsurgical clipping of an acutely ruptured aneurysm at our institution between 2010 and 2019. Patients admitted during (1) regular working hours (Monday-Friday, 08:00-17:59) and (2) on-call duty and microsurgical clipping performed during (a) daytime (Monday-Sunday, 08:00-17:59) and (b) nighttime were compared regarding the following outcome parameters: operation time, treatment-related complications, vasospasm, functional outcome, and angiographic results. RESULTS: Among 157 enrolled patients, 104 patients (66.2%) were admitted during on-call duty and 48 operations (30.6%) were performed at nighttime. Admission out of regular hours did not affect cerebral infarction (p = 0.545), mortality (p = 0.343), functional outcome (p = 0.178), and aneurysm occlusion (p = 0.689). Microsurgical clipping at nighttime carried higher odds of unfavorable outcome at discharge (OR: 2.3, 95%CI: 1.0-5.1, p = 0.039); however, there were no significant differences regarding the remaining outcome parameters. After multivariable adjustment, clipping at nighttime did not remain as independent prognosticator of short-term outcome (OR: 2.1, 95%CI: 0.7-6.2, p = 0.169). CONCLUSIONS: Admission out of regular working hours and clipping at nighttime were not independently associated with poor outcome. The adherence to standardized treatment protocols might mitigate the "weekend effect."

Endovascular treatment of aneurysm remnants with the Contour Neurovascular System after previous treatment.

OBJECTIVE: The Contour Neurovascular System (CNS) is a novel intrasaccular flow disrupting device with a semi-3D cup-like shape for the treatment of intracranial aneurysms. This study investigates the potential and limitations of the CNS for embolization of aneurysm remnants after previous treatment. METHODS: Ten cases of aneurysm recurrence treatment with the CNS were analyzed from a single-center database. Technical success, procedural aspects, complications, and angiographic results were evaluated. RESULTS: The aneurysms (median width: 5.3 mm, median neck width: 3.8 mm) were located in the anterior communicating artery (4), basilar tip (3), internal carotid artery (1), middle cerebral artery (1), and superior cerebellar artery (1). The aneurysms were initially treated endovascularly (9) and by clipping (1). Retreatment failed in one case where the smallest available CNS proved to be too small and had to be removed. Adjunctive coiling was performed in two large remnants of partially thrombosed basilar tip aneurysms. There were no procedural complications or morbidity. At a median follow-up of nine months, 4/8 (50%) aneurysms were completely occluded, 2/8 (25%) had neck remnants, and 2/8 (25%) had aneurysm remnants. The two aneurysm remnants were retreated with coiling and stent-assisted coiling, respectively. CONCLUSIONS: CNS treatment of aneurysm remnants may be feasible, especially for shallow, wide-necked aneurysm geometries. Further studies are needed to identify aneurysm subsets that benefit from CNS retreatment and to define mid- and long-term occlusion rates.

Safety and efficacy of the Contour Neurovascular System for intracranial aneurysm treatment: a retrospective analysis of 76 patients.

OBJECTIVE: The Contour Neurovascular System (CNS) is a novel intrasaccular flow-disrupting device for the treatment of intracranial aneurysms. This study presents the authors' institutional experience and midterm follow-up results with this device. METHODS: Seventy-six consecutive patients (mean ± SD age 58.9 ± 12.4 years) were treated with the CNS for 76 aneurysms (63 unruptured, 10 recurrent, and 3 ruptured). Aneurysm characteristics, procedural details, and clinical/angiographic outcomes were retrospectively evaluated. RESULTS: The most common aneurysm locations were the basilar tip in 25 (32.9%) cases and the anterior communicating artery in 22 (28.9%). There were 18 (23.7%) sidewall aneurysms. The mean ± SD aneurysm width was 5.6 ± 2.5 mm, and 68 (89.5%) aneurysms were wide-necked. The CNS was successfully implanted in 68 (89.5%) aneurysms, with 11 cases of additional coiling and 1 case each of additional stent and balloon. There were 3 (3.9%) thromboembolic events, of which 1 (1.3%) was symptomatic (a major ischemic stroke) and resulted in morbidity. There were no hemorrhagic events or deaths. At last available follow-up (mean 12 months), 32/56 (57.1%) aneurysms were completely occluded, 16/56 (28.6%) had neck remnants, and 8/56 (14.3%) had an aneurysm remnant. Three (5.4%) aneurysms were retreated. CONCLUSIONS: The use of the CNS was safe and feasible but proper aneurysm selection appears to be required, which may be facilitated with increasing operator experience and further study of this device. Similar to other intrasaccular flow disrupters, midterm complete occlusion rates are moderate but may increase with longer follow-up.

Aneurysm Treatment With the Pipeline Vantage Embolization Device in Retrospective Evaluation: Periprocedural Results from the Pipe-VADER Study.

OBJECTIVE: The Pipeline Vantage Embolization Device is a fourth-generation flow diverter with an antithrombotic coating and a reduced profile compared to previous Pipeline versions. The objective of this study was to evaluate the procedural feasibility, safety, and efficacy of this device. METHODS: The Pipe-VADER study was designed as a retrospective, observational study of consecutive patients treated with the Vantage at 3 neurovascular centers. Patient and aneurysm characteristics, procedural parameters, early complications, and extent of postinterventional contrast retention were analyzed on an intention-to-treat basis. RESULTS: Twenty-eight patients with 31 aneurysms (median size: 5.0 mm, posterior circulation: 4 [12.9%], ruptured: 5 [16.1%]) were included. The technical success rate was 100%, with multiple stents used in 4/30 (13.3%) procedures. Of the 30 procedures, adjunctive coiling was performed in 3 (10.0%) and balloon angioplasty in 2 (6.7%). Median procedure time was 62 minutes. Procedural ischemic stroke occured in 4 (13.3%) cases, whereof 2 were major strokes (6.6%). There were no hemorrhagic complications. Initial contrast retention was observed in 29/31 (93.5%) aneurysms. All 27 overstented side vessels were patent at the end of the procedure. Short-term follow-up (median: 5 months) showed complete and favorable occlusion rates of 70% (14/20) and 80% (16/20), respectively. CONCLUSIONS: The new Pipeline Vantage appears to be safe and feasible for the treatment of intracranial aneurysms and warrants further evaluation.

Lessons learned from 12 years using the Woven Endobridge for the treatment of cerebral aneurysms in a multi-center series.

Intrasaccular flow disruption with the Woven Endobridge (WEB) has become a well-established endovascular technique for the treatment of intracranial aneurysms. This study presents our 12-year experience with the WEB and evaluates its evolving indications, procedures, and outcomes. A consecutive series of 324 aneurysms treated with WEB between 2011 and 2023 at three neurovascular centers was retrospectively analyzed and the study group was divided into four treatment periods. Uni- and multivariate analyses were performed to evaluate factors associated with technical success, thromboembolic complications, and angiographic outcome. The mean aneurysm size was 7.0 ± 3.6 mm and decreased during the study period, while the proportion of atypical sites for WEB implantation increased. WEB implantation was technically successful in 96.0%, and the ratio of WEB width to dome width increased during the study period, indicating oversizing. The neurological complication rate was 4.9% (1.5% major, 3.4% minor) and the mid-term complete occlusion rate was 60.6% (81.9% adequate occlusion), with no statistical differences in either outcome measure between the study periods. In multivariate analyses, the use of WEB 17 was associated with increased technical success (HR: 7.4, 95%CI: 2.4-23.6, p<0.01), whereas ruptured aneurysm status (HR: 2.5, 95%CI: 1.0-6.0, p=0.04) and the use of additional stents (HR: 4.8, 95%CI: 1.6-14.4, p<0.01) predicted thromboembolic complications. Appropriate oversizing of the WEB favored mid-term complete occlusion (HR: 10.5, 95%CI: 1.3-83.3, p=0.03). The results suggest an expansion of the indications for WEB implantation and highlight the importance of oversizing for treatment efficacy.

Safety and efficacy of coated flow diverters in the treatment of cerebral aneurysms during single antiplatelet therapy: A multicenter study.

OBJECTIVE: This multicenter study evaluates the safety and efficacy of coated flow diverters (cFDs) for the treatment of cerebral aneurysms under single antiplatelet therapy (SAPT). METHODS: This is a retrospective, observational study of 41 patients (median age: 58 years) with 41 aneurysms (median size: 7 mm, 29 [71%] saccular, 9 [22%] ruptured) treated with cFDs at four neurovascular centers between 2020 and 2023. Scheduled cases received continuous SAPT starting seven days before the procedure. Emergency cases were treated with tirofiban followed by SAPT loading. The safety endpoint was ischemic complications occurring during the procedure and within four months of clinical follow-up. RESULTS: The Pipeline Vantage or Flex Shield was used in 26 (63%) procedures, the FRED X in 12 (29%), the p48/64 Hydrophilic Polymer Coating in 2 (5%), and the Derivo Embolization Device 2heal in 1 (2%). Single antiplatelet therapy consisted of prasugrel in 27 (66%) patients, ticagrelor in 9 (22%), and ASA in 5 (12%). There were 2 (5%) early ischemic complications (one minor stroke and one transient ischemic attack). There were no late ischemic complications in the four-month follow-up of 35 patients. The six dropouts included four nontreatment-related deaths after subarachnoid hemorrhage and two patients with a poor outcome after subarachnoid hemorrhage. Complete and favorable occlusion rates (median: 7 months) were 75% (27/36) and 89% (32/36), respectively. CONCLUSIONS: Coated flow diverter implantation in the setting of SAPT was safe and effective and warrants confirmation in a prospective comparative trial.

Multicenter Experience with the Pipeline Flex and Vantage with Shield Technology for Intracranial Aneurysm Treatment.

BACKGROUND AND PURPOSE: The Pipeline Embolization Device is a safe and effective treatment option for intracranial aneurysms. The newer Pipeline generations have received structural refinements and a surface modification to improve deliverability, procedural safety, and angiographic outcomes. This multicenter study evaluated the clinical safety and efficacy of the 2 surface-modified Pipeline iterations, Pipeline Vantage and Pipeline Flex with Shield Technology (PFS). MATERIALS AND METHODS: Consecutive patients treated between 2017 and 2023 were retrospectively reviewed for aneurysm characteristics, procedural details, complications, and angiographic outcomes. The safety end point was the rate of procedural and postprocedural major neurologic events occurring during the hospital stay. The efficacy end point was the rate of complete occlusion at last follow-up. RESULTS: One hundred forty-one patients underwent 112 Pipeline Vantage procedures and 32 PFS procedures for 147 aneurysms with a mean size of 8.0 (SD, 5.9) mm (11% ruptured, 16% posterior circulation, 18% nonsaccular morphology). All procedures were technically successful with a mean of 1.2 devices implanted. Balloon angioplasty was required in 20/144 (13.9%) procedures. Major neurologic adverse events occurred in 6/144 (4.2%) procedures (all ischemic stroke), resulting in death in 2 (1.4%) patients. There were no hemorrhagic complications. At a mean of 11 months, complete occlusion was achieved in 85/112 (75.9%) aneurysms, 15/112 (13.4%) had an entry remnant, and 12/112 (10.7%) had an aneurysm remnant. CONCLUSIONS: The results demonstrate high feasibility, procedural safety, and efficacy of the surface-modified Pipeline flow diverters.

Safety and efficacy of coated flow diverters in the treatment of ruptured intracranial aneurysms: a retrospective multicenter study.

BACKGROUND: This multicenter study evaluated the safety and efficacy of coated flow diverters (cFDs) for the treatment of ruptured intracranial aneurysms. METHODS: Consecutive patients treated with different cFDs for ruptured aneurysms under tirofiban at eight neurovascular centers between 2016 and 2023 were retrospectively analyzed. The majority of patients were loaded with dual antiplatelet therapy after the treatment. Aneurysm occlusion was determined using the O'Kelly-Marotta (OKM) grading scale. Primary outcome measures were major procedural complications and aneurysmal rebleeding during hospitalization. RESULTS: The study included 60 aneurysms (posterior circulation: 28 (47%)) with a mean size of 5.8±4.7 mm. Aneurysm morphology was saccular in 28 (47%), blister-like in 12 (20%), dissecting in 13 (22%), and fusiform in 7 (12%). Technical success was 100% with a mean of 1.1 cFDs implanted per aneurysm. Adjunctive coiling was performed in 11 (18%) aneurysms. Immediate contrast retention was observed in 45 (75%) aneurysms. There was 1 (2%) major procedural complication (a major stroke, eventually leading to death) and no aneurysmal rebleeding. A good outcome (modified Rankin Scale 0-2) was achieved in 40 (67%) patients. At a mean follow-up of 6 months, 27/34 (79%) aneurysms were completely occluded (OKM D), 3/34 (9%) had an entry remnant (OKM C), and 4/34 (12%) had residual filling (OKM A or B). There was 1 (3%) severe in-stent stenosis during follow-up that was treated with balloon angioplasty. CONCLUSIONS: Treatment of ruptured aneurysms with cFDs was reasonably safe and efficient and thus represents a valid treatment option, especially for complex cases.

Long-term clinical and angiographic outcome of the Woven EndoBridge (WEB) for endovascular treatment of intracranial aneurysms.

The Woven EndoBridge (WEB) is a well-established device for endovascular treatment of wide-necked bifurcation aneurysms. The objective was to evaluate the long-term angiographic outcome of the WEB and to identify factors that influence aneurysm occlusion. Patient, aneurysm and procedural characteristics of 213 consecutive patients treated with the WEB at three German tertiary care centers between 2011 and 2020 were retrospectively reviewed. Aneurysm occlusion was determined immediately after the procedure, at mid-term (≤ 12 months) and at long-term (> 12 months) follow-up. Among 182 included aneurysms (mean diameter: 7.0 ± 2.4, mean neck width: 4.3 ± 1.6 mm), 29.7% were ruptured. The novel WEB 17 was used in 41.8%, and 11.0% were treated in combination with coiling and/or stenting. Complete and adequate occlusions were observed in 101/155 (65.2%) and 133/155 (85.8%) at mid-term, respectively, and in 59/94 (62.8%) and 87/94 (92.6%) at long-term follow-up (median: 19 months), respectively. Among 92 patients available for both mid- and long-term follow-up, occlusion was stable in 72.8%, improved in 16.3% and worsened in 10.9%. There were no major recurrences leading to aneurysm remnants between mid- and long-term follow-up. Retreatment was performed in 10/155 (6.5%) during mid-term and in 1/94 (1.0%) during long-term follow-up. The WEB provides durable aneurysm occlusion at the long-term. Nevertheless, follow-up imaging is necessary to identify late recurrences that may occur in around 10%.

Intrasaccular Flow Disruption with the Woven EndoBridge for Narrow-Necked Aneurysms: A Safety and Feasibility Study.

OBJECTIVE: The Woven EndoBridge (WEB) received U.S. Food and Drug Administration approval for endovascular treatment of wide-necked bifurcation aneurysms. We evaluated the feasibility, safety, and efficacy of the WEB for treatment of narrow-necked aneurysms. METHODS: This multicenter study included 17 narrow-necked aneurysms, defined by a neck width <4 mm and a dome-to-neck ratio >2. Aneurysm characteristics, treatment strategies, technical success, complications, and angiographic outcomes were retrospectively assessed. RESULTS: Aneurysm locations included the internal carotid artery (7 cases), anterior communicating artery (4 cases), middle cerebral artery (4 cases), and basilar artery (2 cases). The median aneurysm size was 7.4 mm with a median neck width of 2.3 mm. The technical success rate was 100%. There were no neurological complications. Angiographic control revealed complete and adequate occlusion in 13 of 15 (86.7%) and 14 of 15 (93.3%) cases, respectively, after 6 months and in 6 of 7 (85.6%) and 7 of 7 (100%) cases, respectively, after a median of 13 months. Two aneurysms were retreated with flow diverters. CONCLUSIONS: WEB embolization of narrow-necked aneurysms was technically feasible and safe and might be considered as an alternative treatment option to conventional coiling in selected cases.

Treatment of recurrent and residual aneurysms with the low-profile Acandis Acclino stent: Multi-center review of 19 patients.

OBJECTIVE: To evaluate the safety and efficacy of the low-profile Acandis Acclino microstent for embolization of recurrent and residual intracranial aneurysms. METHODS: Consecutive patients treated with the Acclino for aneurysm remnants at three German neurovascular centers were enrolled. The technical success, complications, angiographic and clinical outcome were investigated. RESULTS: Nineteen patients (median age: 53 years) with 19 aneurysm remnants (median size: 5 mm, anterior circulation: 14) were included. Initial aneurysm treatment consisted of stand-alone coiling in 14 cases, stent-assisted coiling in 4 and clipping in 1. Acclino stent-assisted coil embolization was performed technically successfully in all patients. Morbidity occurred in one patient (5.3%) due to aneurysm perforation. At the angiographic follow-up with a median follow-up duration of 21 months (range: 5-37 months), complete occlusion was obtained in 76.9%. The retreatment rate was 7.7%. CONCLUSIONS: Retreatment of aneurysm remnants with the Acclino microstent was associated with high aneurysm occlusion rates and acceptable morbidity. Further studies will be necessary to draw a definite conclusion.

Microsurgical Clipping versus Advanced Endovascular Treatment of Unruptured Middle Cerebral Artery Bifurcation Aneurysms After a "Coil-First" Policy.

OBJECTIVE: Although intracranial aneurysms are increasingly treated endovascularly, microsurgical clipping has been the standard approach for middle cerebral artery (MCA) aneurysms. We compared microsurgical clipping and state-of-the-art endovascular treatment of unruptured MCA bifurcation aneurysms treated at a neurovascular center following a "coil-first" policy. METHODS: This single-center study included 148 patients treated for 160 unruptured MCA bifurcation aneurysms. Technical success, complications, clinical outcome, and angiographic results were retrospectively compared. RESULTS: Microsurgical clipping was performed for 120 MCA aneurysms (75%) and endovascular treatment for 40 (25%; conventional coiling: 8, stent-assisted coiling: 16, balloon-assisted coiling: 3, and flow-disruption: 13). Technical treatment success was higher in the clipping group (100%) than in the endovascular group (92.5%, P = 0.015). Overall, complications occurred in 16.7% for clipping and in 20.0% for endovascular treatment (P = 0.631). Major ischemic stroke rates were 4.2% in the clipping group and 7.5% in the endovascular group (P = 0.414). At 6 months, a favorable outcome was obtained by 99.2% after clipping and 95.0% after endovascular treatment (P = 0.154). The 6-month complete aneurysm occlusion rates were by trend higher in the clipping group (89.2%) than in the endovascular group (75.9%, P = 0.078). CONCLUSIONS: Microsurgical clipping was associated with a higher technical success rate and tendentially higher complete occlusion than endovascular treatment, with no additional morbidity and similar clinical outcome. On the basis of these results, clipping proves to be the standard treatment option for MCA bifurcation aneurysms. However, endovascular treatment represents a safe and efficient alternative treatment option for patients.

Identifying Predictors for Aneurysm Remnants After Clipping by Morphometric Analysis and Proposal of a Novel Risk Score.

OBJECTIVE: Although the risk of aneurysm remnants after microsurgical clipping is generally low, complete aneurysm occlusion is not always guaranteed. We performed a morphometric analysis of intracranial aneurysms to identify predictors for aneurysm remnants and to propose a novel risk score. METHODS: This is a retrospective, single-center analysis of consecutive patients with ruptured and unruptured aneurysms who underwent microsurgical clipping and postoperative digital subtraction angiography between 2010 and 2018. Based on preoperative rotational angiography, distinct morphologic aneurysm characteristics were determined and correlated with postoperative angiographic results. Factors predictive in the univariate and multivariate analyses were determined to establish a risk score for postoperative remnants after aneurysm clipping. RESULTS: Among 140 patients with 166 clipped aneurysms, aneurysm remnants were present in 19.9%. In the multivariate analysis, ruptured aneurysm status (odds ratio [OR], 7.8; 95% confidence interval [CI], 1.7-36; P < 0.01) and increased aspect ratio (OR, 1.9; 95% CI, 1.0-4.0; P = 0.07) were associated with postoperative aneurysm remnants. Anterior communicating artery location (P = 0.02), internal carotid artery location (P = 0.06), increased aneurysm inclination angle (P < 0.01), and irregular aneurysm shape (P = 0.07) were further predictors for aneurysm remnants in the univariate analysis. These factors were weighted and included into a risk sum score for postoperative aneurysm remnants (range, 0-8 points), which performed with good accuracy (area under the curve = 0.807). CONCLUSIONS: After external validation of the proposed risk score, it could help identify cases requiring angiographic control after aneurysm surgery.

Delayed hospital admission of patients with aneurysmal subarachnoid hemorrhage: clinical presentation, treatment strategies, and outcome.

OBJECTIVE: Timely aneurysm occlusion and neurointensive care treatment are key principles in the management of aneurysmal subarachnoid hemorrhage (aSAH) to prevent secondary brain injury. Patients with early (EHA) and delayed hospital admission (DHA) were compared in terms of clinical presentation, treatment strategies, aSAH-related complications, and outcome. METHODS: In this retrospective study, consecutive aSAH patients were treated at a single neurovascular center between 2009 and 2019. Propensity score matching was performed to account for divergent baseline characteristics. RESULTS: Among 509 included patients, 55 were admitted more than 48 hours after ictus (DHA group). DHA patients were significantly younger (52 ± 11 vs 56 ± 14 years, p = 0.03) and had lower World Federation of Neurosurgical Societies scores (p < 0.01) than EHA patients. In 54.5% of the cases, DHA patients presented with neurological deterioration or aggravated symptoms. Propensity score matching revealed a higher vasospastic infarction rate in the DHA group (41.5%) than in the EHA group (22.6%) (p = 0.04). A similar portion of patients in both groups achieved favorable outcome at midterm follow-up (77.3% vs 73.6%, p = 0.87). DHA patients (62.3%) received conventional coiling more often than EHA patients (41.5%) (p = 0.03). CONCLUSIONS: DHA patients are at an increased risk of cerebral infarction. Nevertheless, state-of-the-art neurointensive care treatment can result in a good clinical outcome.

Angiographic Characteristics of Lobulated Intracranial Aneurysms.

OBJECTIVE: Previous studies have indicated that lobulated aneurysms are more susceptible to rupture than are single-sac aneurysms. We aimed to determine the angiographic characteristics related to the lobulated shape of unruptured intracranial aneurysms (UIAs) and ruptured (RIAs) intracranial aneurysms. METHODS: This is a retrospective analysis of consecutive patients with UIAs (n = 143) and RIAs (n = 190) who underwent digital subtraction angiography at our institution between 2010 and 2017. Patient and aneurysm characteristics were compared between lobulated and regular single-sac aneurysms. RESULTS: Patients with lobulated UIAs were significantly older than were patients with regular aneurysms (56.5 ± 10.7 years vs. 49.3 ± 13.0 years; P = 0.003). In the multivariate analysis, lobulated morphology was significantly related to bifurcation location (69.5% vs. 27.3%; odds ratio [OR], 3.0, 95% confidence interval [CI], 1.2-7.5; P = 0.019), aneurysm size (8.1 ± 3.2 mm vs. 4.9 ± 3.0 mm; OR, 5.4; 95% CI, 1.7-17.8; P = 0.005), and inflow angle (145 ± 27° vs. 114 ± 27°; OR, 2.8; 95% CI, 1.1-7.2; P = 0.031). Bifurcation location (P = 0.031) and larger aneurysm size (P < 0.001) were confirmed as independent characteristics for lobulation in the RIA group. Compared with regular aneurysms, lobulated UIAs were more often allocated to treatment (86.6% vs. 60.3%; P < 0.001) and treated by microsurgical clipping (39.4% vs. 16.4%; P = 0.002). CONCLUSIONS: Bifurcation location, an increased aneurysm size, and a straighter aneurysm inflow angle are independently associated with lobulated aneurysms.