Independent Risk Factors For Rupture Research Articles

Saccular and Fusiform Abdominal Aortic Aneurysms Treated With Endovascular Repair Differ in Presentation and Treatment Threshold: Analyses Using a National Clinical Database in Japan.

Saccular abdominal aortic aneurysms (AAAs) are considered to be at higher risk of rupture than fusiform AAAs, but not much is known about the extent of this risk. Therefore, this study aimed to compare the rupture presentation between fusiform and saccular AAAs. This is a retrospective cohort study on 27 290 patients who underwent primary endovascular repair for a degenerative AAA between 2016 and 2019, and who were registered in the National Clinical Database in Japan. At operation for nonruptured case, the aneurysm diameter was significantly smaller in saccular AAAs than in fusiform AAAs (median, 44.0 versus 51.0 mm; P<0.001). Similarly, aneurysm diameter at rupture was significantly smaller in saccular AAAs than in fusiform AAAs (median, 55.6 versus 68.0 mm; P<0.001). The likelihood of repair for rupture was significantly higher in saccular AAAs than in fusiform AAAs in the 40- to 54-mm diameter range, in which saccular morphology was found to be an independent risk factor for rupture against fusiform morphology by adjusting for sex and aneurysm diameter (odds ratio, 2.54 [95% CI, 1.75-3.69]). In addition, receiver-operating characteristic curve analysis revealed that the cutoff diameter to predict rupture was smaller in saccular AAAs than in fusiform AAAs (50.5 and 59.5 mm, respectively) based on the Youden index. Saccular AAAs presented at smaller diameters than fusiform AAAs in patients with ruptured AAAs treated with endovascular aortic repair, which supports the idea that saccular AAAs should be treated at smaller diameters.

Clinical outcomes of posterior fossa arteriovenous malformations: a single center experience

BackgroundPosterior fossa arterio-venous malformations (pfAVMs) are challenging lesions due to the anatomical particularities of the posterior fossa, and the high incidence of hemorrhagic presentation. The two most important goals when treating AVMs are preserving neurological function and preventing rupture, or a second hemorrhage. The aim of this study was to analyze the clinical and imaging features of pfAVMs to identify the factors that influence the prognosis of these patients.MethodsWe conducted a single-center retrospective observational study that included patients treated at our institution with pfAVMs between January 1997 and December 2021.ResultsA total of 48 patients were included. A good modified Rankin score (mRS) was observed in 33 cases (69%) at presentation. Thirty-four patients (71%) presented with a ruptured AVM. Out of these, 19 patients (40%) had intraventricular hemorrhage. Microsurgical resection was performed in 33 cases (69%), while in the other cases, the patients opted for conservative management (7 cases, 15%), stereotactic radiosurgery (SRS) (6 cases, 12%), or endovascular treatment (2 cases, 4%). Patients ≤ 30 years old were more prone to hemorrhagic presentation (OR: 5.23; 95% CI: 1.42–17.19; p = 0.024) and this remained an independent risk factor for rupture after multivariate analysis as well (OR: 4.81; 95% CI: 1.07–21.53; p = 0.040). Following multivariate analysis, the only factor independently associated with poor prognosis in the surgically treated subgroup was a poor clinical status (mRS 3–5) at admission (OR: 96.14; 95% CI: 5.15–1793.9; p = 0.002).ConclusionsManagement of posterior fossa AVMs is challenging, and patients who present with ruptured AVMs often have a poor clinical status at admission leading to a poor prognosis. Therefore, proper and timely management of these patients is essential.

Analysis of the Risk of Basilar Aneurysm Rupture Based on CTA Morphological Parameters

Objective: To investigate morphological risk factors of basilar aneurysm rupture based on computer tomography angiography (CTA) parameters. Materials and methods: The clinical and CTA data of 43 patients with basilar aneurysm admitted to Shaanxi Provincial People’s Hospital from January 2015 to July 2023 were analyzed. The patients were divided into “ruptured group” and “unruptured group,” and the morphological parameters of aneurysms were measured. The general data and morphological parameters between the two groups were statistically analyzed. Logistic regression was used to analyzed statistically significant parameters, and the receiver operating characteristic curve was drawn to evaluate its diagnostic effectiveness. Results: Irregular aneurysms were more likely to rupture than regular aneurysms (x² = 13.971, P &lt; 0.05). The maximum diameter (4.92 [3.37–6.94] mm), length-width ratio (1.31 [1.14–1.55]), height (4.08 [2.71–5.34] mm), aspect ratio (0.99 [0.84–1.45]), and inflow angle (133.63 ± 11.21°) of aneurysms in the ruptured group were larger than the unruptured group, and the differences were statistically significant (P &lt; 0.05). Binary logistic regression showedthat aneurysm shape (OR = 39.347, P = 0.021), length-width ratio (OR = 313.062, P = 0.033), and inflow angle (OR = 1.156, P = 0.004) were independent risk factors for rupture. The area under the curve were 0.809, 0.842. and 0.894, respectively. Conclusion: Aneurysm shape, aspect ratio, and blood flow incidence angle are independent risk factors for basilar aneurysm rupture, which means that they can be used to predict the risk of rupture to a certain extent.

Morphological evaluation of the risk of posterior communicating artery aneurysm rupture: a mirror aneurysm model.

The aim of this study was to use morphological parameters of mirror posterior communicating artery (PCoA) aneurysms to evaluate aneurysm rupture risk. The morphological parameters of 45 pairs of ruptured mirror PCoA aneurysms were analyzed. Conditional univariate and multivariate logistic regression of the following paired morphological parameters was performed: aneurysm with a daughter sac, aneurysm height, aneurysm width, neck width, internal carotid artery diameter, PCoA diameter, flow angle, PCoA angle, aspect ratio, bottleneck factor, size ratio, height/width ratio, fetal posterior cerebral artery, and aneurysm with height > width. A scoring system was established according to the odds ratios (ORs). The receiver operating characteristic was used to test the prediction accuracy of this scoring system in the authors' database of 523 PCoA aneurysms and the threshold value was used to define higher risk. Aneurysm width (OR 1.676, p = 0.014), aneurysm with daughter sac (OR 7.775, p = 0.016), and aneurysm with height > width (OR 9.067, p = 0.012) were independent risk factors for rupture. The scoring system consisted of aneurysm width (1 point per mm), aneurysm with a daughter sac (5 points), and aneurysm with height > width (5 points). The area under the curve (AUC) of the scoring system was 0.842, and its threshold value was 7.97. A score ≥ 8 points was defined as higher risk. The AUC using this definition was 0.802. Aneurysm width, aneurysms with height > width, and aneurysms with a daughter sac were independent risk factors for PCoA aneurysm rupture. The scoring system devised in this study accurately predicts rupture risk.

Hemodynamics-based analysis of factors associated with aneurysm rupture in different sides of the internal carotid artery

Objective: To explore the influence of hemodynamics, morphological and clinical characteristics on rupture risk of the dorsal and non-dorsal internal carotid artery aneurysms (ICAAs). Methods: A total of 111 patients diagnosed with aneurysm by digital subtraction angiography (DSA) or surgery, underwent cranial CT angiography (CTA) were retrospectively collected from January 2010 to December 2016 at the Department of Diagnostic Radiology, Jinling Clinical College of Xuzhou Medical University (General Hospital of Eastern Theater Command). Among them, 41 were males and 70 were females, ranging in age from 32 to 83 (56±11) years old. The patients were divided into the ruptured group (n=54) and unruptured group (n=57) based on the hemorrhagic manifestation on non-enhanced CT images or DSA or surgery of the head. Demographics and the morphological characteristics of the aneurysms were evaluated. Hemodynamic parameters, including wall share stress, wall share stress gradient, and others were obtained in overall using computational fluid dynamics simulation technique. Characteristics were compared between the ruptured and unruptured groups. Logistic regression analysis was applied to evaluate the independent risk factors for rupture, and the hemodynamic characteristics associated with dorsal and non-dorsal aneurysms were analyzed, respectively. Results: Compared with the unruptured group, patients in the ruptured group were younger ((54.2±11.4) years and (58.3±9.9) years, P=0.033), mostly female (74.1% vs 52.6%, P<0.05), with a higher proportion of hypertension (46.3% vs 22.8%, P=0.009). The ruptured internal carotid artery aneurysms (ICAAs) were more frequently located at the dorsal of an arterial arch (57.4% vs 36.8%, P<0.05), and the flow of the blood was more complex, concentrated, unstable, and with a smaller impingement zone (68.5% vs 33.3%,55.6% vs 10.5%,72.2% vs 26.3% and 79.6% vs 36.8%, respectively, all P<0.05). Logistic regression demonstrated that women, hypertension, dorsal, concentrated flow pattern, and unstable flow pattern were an independent risk factors for ICAAs rupture [OR=3.551 (1.080-11.679), 3.900 (1.172-12.976), 4.966 (1.504-16.401), 51.893 (7.913-340.296) and 50.015 (8.423-296.985), respectively, all P<0.05]. The ruptured ICAAs located at non-dorsal had more concentrated, unstable, and with smaller impingement zone (P<0.05), while those at dorsal had more complex, concentrated, and unstable flow patterns, and with smaller impingement zone (all P<0.05). Conclusion: Women, hypertension, dorsal concentration, and unstable flow pattern are independent risk factors for the rupture of ICAAs. The dorsal locations of ICAAs could have a higher risk of rupture.

Analysis of Risk Factors for Anterior Communicating Artery Aneurysm Rupture: A Single-Center Study

Congenital hypoplasia or aplasia of the A1 segment of the anterior cerebral artery is associated with an increased incidence of berry aneurysms at the anterior communicating artery (ACoA) complex. We analyzed the factors contributing to ACoA aneurysm rupture. We retrospectively analyzed the data of patients with ACoA aneurysms who had undergone cerebral angiography from July 2008 to January 2020. The risk factors for rupture were identified using univariate and multivariate logistic regression models. We used the imaging data of patients without intracranial aneurysms as the control population. We confirmed 253 aneurysms in 253 patients, including 137 men (54.2%) and 116 women (45.8%), with a mean age of 54.6 ± 12.7 years. Of the 253 aneurysms, 218 (86.2%) were ruptured and 35 (13.8%) were unruptured, with a mean diameter of 4.56 ± 1.96 mm and 3.24 ± 1.79 mm, respectively. Of the 253 aneurysms, 176 (69.6%) were <5 mm in diameter, 146 (83%) of which were ruptured. Of the 253 patients, 141 (55.7%) exhibited A1 segment hypoplasia or aplasia: 106 (41.9%) on the right side of the circle of Willis and 35 (13.8%) on the left. Multivariate logistic regression analysis identified the aneurysm diameter (odds ratio, 4.11; 95% confidence interval, 1.601-16.07; P= 0.003) and age <65 years (odds ratio, 0.17; 95% confidence interval, 0.062-0.48; P < 0.001) as independent predictors of rupture. ACoA aneurysms are small (<5 mm) and have a high risk of rupture. A1 segment hypoplasia or aplasia is a risk factor for ACoA aneurysm formation; however, it was uncorrelated with aneurysm diameter or rupture risk. The strongest independent risk factors for rupture were age <65 years and aneurysm diameter.

Effect of miR-126 on intracranial aneurysms and its predictive value for rupture of aneurysms.

This study aimed to investigate the effect of miR-126 on intracranial aneurysm (IA) and its predictive value for aneurysm rupture. Altogether 102 patients (patient group) with IA diagnosed in the Jinhua Municipal Central Hospital from July 2016 to April 2018, and 80 healthy people (normal group) who underwent physical examination during the same period were collected. QRT-PCR was used to detect the expression of miR-126 in serum, analyze the expression of miR-126 in IA, and explore the predictive value on IA rupture. Potential target genes of miR-126 were analyzed by target gene prediction website, and David was used to analyze the enrichment of miR-126 target gene GO and KEGG. The expression of miR-126 in serum of patient group was significantly higher than that of normal group (p < 0.05), ROC curve area was 0.966. The high expressions of miR-126 were directly related to the possibility of large lesions (p < 0.05). Multivariate analysis showed that lesion size and miR-126 expression were independent risk factors for rupture of IA patients. ROC curve showed that lesion size and miR-126 expression area under the curve were 0.707 and 0.827. Altogether 520 potential target sites were found by Venn diagram of Targetscan, miRDB, and Starbase online miR-126 prediction website. GO enrichment and KEGG analysis by David online software found that miR-126 target genes were mainly enriched in 169 biological processes, such as nucleus, transcription, DNA-templated, transcription factor activity, sequence-specific DNA binding, protein binding, and phosphatidylinositol phosphorylation. KEGG analysis found that miR-126 target genes were significantly enriched in MAPK signaling pathway, pathways in cancer, ErbB signaling pathway, MicroRNAs in cancer, and Thyroid hormone signaling pathway. MiR-126 can be used as a potential diagnostic and predictive indicator for IA occurrence and IA rupture.

Morphological and clinical risk factors for the rupture of posterior communicating artery aneurysms: significance of fetal-type posterior cerebral artery

Posterior communicating artery (PcomA) aneurysm can be classified into sidewall or bifurcation types based on the anatomical variation of fetal-type posterior cerebral artery (fPCA). The aims of this study were to investigate the significance of fPCA as an independent risk factor for the rupture of PcomA aneurysm and to evaluate other associated morphological and clinical risk factors. We retrospectively reviewed clinical and radiological findings of 255 patients with PcomA aneurysms, which were treated in a single tertiary institute between January 2009 and December 2016. Univariate and multivariate analyses were performed to evaluate the associations between morphological and clinical variables and rupture status. Subgroup analysis was also performed based on the aneurysms with and without fPCA. Fifty-five out of 255 PcomA aneurysms (21.6%) were associated with fPCA. Multivariate logistic regression analysis showed that the superior direction of aneurysm dome (OR 9.106, p = 0.007), the presence of a bleb (OR 4.780, p < 0.001), a high aspect ratio (OR 1.878, p = 0.045), and fPCA (2.101, p = 0.040) were significantly associated with PcomA aneurysm rupture. In the fPCA group, only the presence of a bleb varied significantly between ruptured and unruptured PcomA aneurysms. However, in the non-fPCA group, larger aneurysms, the superior direction of dome, the presence of a bleb, and a high aspect and dome-to-neck ratio were significantly higher in the ruptured aneurysm group than in the unruptured aneurysm group. The results demonstrate that fPCA may be an independent risk factor for rupture, especially together with the presence of a bleb.

Morphological characteristics associated with the rupture risk of mirror posterior communicating artery aneurysms

ObjectivePatient related clinical factors and intracranial aneurysms (IAs) at different locations may lead to statistical bias when investigating the rupture risk of IAs. Thus the purpose of this study was...

Geometric Parameter Analysis of Ruptured and Unruptured Aneurysms in Patients with Symmetric Bilateral Intracranial Aneurysms: A Multicenter CT Angiography Study.

Previous studies of geometric and morphologic parameters of intracranial aneurysms have been conducted to determine rupture risk, which remains incompletely defined due to patient-specific risk factors, such as sex, hypertension, and age. To this end, we compared characteristics of ruptured and unruptured aneurysms in the same patients with symmetric bilateral intracranial aneurysms. Between January 2008 and March 2014, 2361 patients with 2674 aneurysms were diagnosed by CT angiography or surgical findings at 4 medical centers. Geometric and morphologic parameters examined for symmetric bilateral intracranial aneurysms comprised aneurysm wall regularity, size, neck width, aspect ratio, size ratio, neck-to-parent artery ratio, and area ratio. Univariate and multivariate statistical analyses were performed to determine independent risk factors for rupture. Sixty-three patients (48 women, 15 men; mean age, 62.5 ± 9.8 years) with symmetric bilateral aneurysms were eligible for the study and were included. The most frequent aneurysm location was the posterior communicating artery. Univariate analysis disclosed that aneurysm size, aspect ratio, size ratio, area ratio, and irregular wall differed between patients with ruptured and unruptured aneurysms. Multivariate analysis indicated that aspect ratio of ≥1.6 (adjusted OR, 9.521; 95% CI, 2.182-41.535), area ratio of ≥1.5 (adjusted OR, 4.089; 95% CI, 1.247-13.406), and irregular shape (adjusted OR, 10.443; 95% CI 3.394-32.135) were significant predictive factors for aneurysm rupture after adjustment for aneurysm size. An aspect ratio of ≥1.6, area ratio of ≥1.5, and irregular wall are associated with aneurysm rupture independent of aneurysm size and patient characteristics. These characteristics alone can help in distinguishing ruptured bilateral intracranial aneurysms from unruptured ones.

Morphological Risk Factors for Rupture of Small (

The management of small, unruptured intracranial aneurysms is still controversial. Given the distinctive natural history of aneurysm at different locations, location-specific analysis might be a reasonable approach. This study aimed to investigate morphological discriminators for rupture status by focusing on only posterior communicating artery (PcomA) aneurysms smaller than 7 mm. In 108 small PcomA aneurysms (68 ruptured, 40 unruptured), clinical and morphological characteristics were compared between the ruptured and unruptured groups. Multivariate logistic regression analysis was performed to determine the independent predictors for the rupture status of small PcomA aneurysms. None of the clinical characteristics were significantly different between the ruptured and unruptured groups (P > 0.05). The ruptured group revealed a significantly larger size (P = 0.009), aspect ratio (P = 0.009), size ratio (P = 0.002), dome-to-neck ratio (P = 0.002), inflow angle (P < 0.001), and proportion of bleb formation (P = 0.039). Bottleneck factor (P = 0.154), diameter of PcomA (P = 0.302), and fetal-type PcomA (P = 0.832) showed no significance. With multivariate analyses, size ratio (P = 0.012) and inflow angle (P = 0.001) were shown to be independently associated with the rupture status of small PcomA aneurysms. Morphological characteristics were closely related with the rupture status of small PcomA aneurysms. Size ratio and inflow angle were independent risk factors for rupture and might be useful in clinical risk stratification of small PcomA aneurysms.

Risk factors for rupture of intracranial aneurysm

Objective To investigate the risk factors of rupture of intracranial aneurysms. Methods Two hundred and seventy eight patients with cerebral aneurysms admitted from January 2000 to December 2013 were enrolled in study, including 122 cases with ruptured intracranial aneurysm (rupture group) and 156 cases without rupture (non-rupture group). The clinical data were collected from two groups, risk factors of aneurysm rupture were studied by univariate analysis and multivariate logistic regression analysis. Results The rates of female gender, smoking history, hypertension and atherosclerosis in rupture group were significantly higher than those in non-rupture group [70.5%(86/122) vs. 59.0% (92/156), 42.6% (52/122) vs. 29.5% (46/156), 63.9% (78/122) vs. 51.9% (81/156) and 69.7% (85/122) vs. 51.3% (80/156); χ2=3.943, 5.175, 4.034 and 4.319, respectively, all P 8 mm were 63.4%(64/101), 40.9%(38/93), 25.0%(20/84), respectively, Z=27.180, P=0.000; the rates of aneurysm rupture in patients with aneurysm neck width of <4 mm was higher than that with width ≥ 4 mm [67.3% (66/98) vs. 31.1%(56/180), χ2=33.832, P=0.000]. Multivariate logistic regression analysis showed that aneurysm diameter is an independent risk factor for rupture of intracranial aneurysm (OR=3.759, 95CI: 1.638-6.879, P=0.001). Conclusions The diameter of intracranial aneurysm in an independent risk factor for aneurysm rupture. Female gender, history of smoking, underlying hypertension and atherosclerosis, and the width of aneurysm neck may also related to the rupture of intracranial aneurysms. Key words: Intracranial aneurysm; Rupture; Risk factors

Impact of hypertension and smoking on the rupture of intracranial aneurysms and their joint effect

BackgroundIn general population, the prevalence of intracranial aneurysm reaches as high as three percent. The goal of the study was to analyze retrospectively the independent risk factors for the rupture of intracranial aneurysms and their joint effect. MethodsThe records and angiographies of continuous 519 intracranial aneurysm patients treated at our center between February 2013 and July 2014 were retrospectively analyzed. Ruptured group and unruptured group were included in the study according to their clinical and imaging information. Univariate analysis and multivariate logistic regression analysis was used to identified independent risk factors for the rupture of intracranial aneurysms. We assessed the joint effect of independent risk factors for the rupture of intracranial aneurysms with an additional logistic regression analysis. ResultsThe results of multivariate analysis show that hypertension (odds ratio [OR], 1.51; 95% confidence interval [CI], 1.05–2.18) and smoking (odds ratio [OR], 1.57; 95% confidence interval [CI], 1.06–2.33) were independent risk factors for rupture of intracranial aneurysms. The joint risk of hypertension and smoking was higher (OR, 2.28; 95% CI, 1.29–4.02) than the risks of hypertension (OR, 1.74; 95% CI, 1.11–2.72) and smoking (OR, 1.86; 95% CI, 1.05–3.29) independently. ConclusionsHypertension and smoking increase of the rupture risk of intracranial aneurysms. And the joint risk of hypertension and smoking was higher than the risks of hypertension and smoking independently.

A Novel Craniotomy Simulator Provides a Validated Method to Enhance Education in the Management of Traumatic Brain Injury

Abstract BACKGROUND: The middle cerebral artery (MCA) is the most frequent location for unruptured intracranial aneurysms. Controversy remains as to which unruptured MCA aneurysms should be treated prophylactically. OBJECTIVE: To identify independent topographical and morphological variables that could predict increased rupture risk of MCA aneurysms. METHODS: A retrospective analysis of computed tomography angiography data of 1009 consecutive patients with 1309 MCA aneurysms, referred between 2000 and 2009 to Helsinki University Hospital, was carried out. Morphological and topographical parameters examined for MCA aneurysms comprised aneurysm wall regularity, size, neck width, aspect ratio, bottleneck factor, height-width ratio, location along the MCA, side, distance from the internal carotid artery bifurcation, and dome projection in axial and coronal computed tomography angiography views. Univariate and multivariate logistic regression analyses were performed to determine independent risk factors for rupture. RESULTS: Of the 1309 MCA aneurysms, 69% were unruptured and 31% were ruptured. Most unruptured MCA aneurysms were smaller than 7 mm (78%), with a smooth wall (80%) and a height-width ratio of 1 (47%) and were located at the main bifurcation (57%). Ruptured MCA aneurysms, mostly 7 to 14 mm in size (55%), had an irregular wall (78%) and a height-width ratio greater than 1 (72%) and were located at the main bifurcation (77%). Thirty-eight percent of MCA bifurcation aneurysms, 74% of large aneurysms, 64% of aneurysms with an irregular wall, and 49% of aneurysms with a height-width ratio greater than 1 were ruptured. CONCLUSION: Location at the main MCA bifurcation, wall irregularity, and less spherical geometry were independently associated with rupture of MCA aneurysms with a correlation with aneurysm size.

Influence of sex on expansion rate of abdominal aortic aneurysms

The UK Small Aneurysm Trial suggested that female sex is an independent risk factor for rupture of abdominal aortic aneurysm (AAA). This study assessed the effect of sex on the growth rate of AAA. Between January 1985 and August 2005 all patients who were referred to the Royal Infirmary of Edinburgh with an AAA who were not considered for early aneurysm repair were assessed by serial abdominal ultrasonography. Maximum anteroposterior and transverse diameters of the AAAs were measured. A total of 1255 patients (824 men and 431 women) were followed up for a median of 30 (range 6-185) months. A median of six examinations (range 2-37) was performed for each patient. Median diameter on initial examination was 41 (range 25-83) mm. Median growth rate overall was 2.79 (range - 4.80-37.02) mm per year. Median growth rate of AAA was significantly greater in women than men (3.67 (range - 1.2-37.02) versus 2.03 (range - 4.80-21.00) mm per year; P < 0.01). Weighted linear regression analysis revealed that large initial anteroposterior AAA diameter and female sex were significant predictors of faster aneurysm growth rate (P < 0.001 and P = 0.006 respectively). The growth rate of AAA was significantly greater in women than in men. This may have implications for the frequency of follow-up and timing of repair of AAA in women.

Natural history of unruptured intracranial aneurysms: risks for aneurysm formation, growth, and rupture.

Several studies concerning risk factors for SAH and for subsequent rupture of an unruptured aneurysm have been published, but not risk factor studies for formation and growth rate of aneurysms. Because less than half of all aneurysms ever rupture, it is essential to know risk factors separately both for aneurysm formation and for its growth. Before 1979, unruptured aneurysms were not operated on in Helsinki. Recently, the results of risk factors for rupture of unruptured aneurysms of 142 patients (131 with a prior SAH) have been published. 89 were followed with conventional and/or 3D CT angiography, or at autopsy to define risk factors for aneurysm formation and growth. During 2575 person-years, 33 of the 142 patients (23%) suffered SAH, resulting in an annual incidence of 1.3% (95% CI, 0.9-1.7%). The cumulative rate of bleeding was 10.5% (95% CI, 5.3-15.8%) at 10 years, and 30.3% (21.1-39.6%) at 30 years. Independent risk factors for rupture were cigarette smoking (time-dependent relative risk, 3.04; 95% CI, 1.21-7.66), and size of aneurysm (1.14 per mm; 1.01-1.30) after adjustment for age, aneurysm group, and hypertension. In addition, current cigarette smoking at end of follow-up (age-adjusted odds ratio, 3.92; 95% CI, 1.29-11.93) and female gender 3.36 (1.11-10.22) were the only independent risk factors for aneurysm growth of > or = 1 mm but only current smoking (3.48, 1.14-10.64) was a risk factor for growth of > or = 3 mm. Probability of de novo aneurysm formation was 0.84% per year (95% CI, 0.47-1.37%). Female gender (adjusted odds ratio, 4.73; 95% CI, 1.16-19.38) and current smoking (4.07, 1.09-15.15) were the only significant (p < 0.05) independent risk factors for de novo aneurysm formation. Cessation of smoking is very important for these patients. It is recommended that unruptured aneurysms be operated on irrespective of their size and of patients' smoking status, in people aged < 50 to 60 years.