Risk factors for the formation and rupture of intracranial saccular aneurysms in Shimane,Japan

BackgroundPrevention of aneurysmal subarachnoid hemorrhage (SAH) can be achieved by reducing risk factors, which include those for aneurysm formation and aneurysm rupture. However, neither of these 2 factors has been discussed separately so far. A case control study was undertaken in Shimane, Japan, to identify modifiable risk factors for the formation and rupture of aneurysms.MethodsThis study included 858 patients with ruptured aneurysms, 285 patients with unruptured aneurysms without a history of SAH, and 798 control subjects. Hypertension, diabetes mellitus, heart disease, hypercholesterolemia, cigarette smoking, and alcohol consumption were assessed as risk factors by using conditional logistic regression.ResultsAfter adjustment for other risk factors, hypertension was the most powerful risk factor for aneurysm formation, regardless of age and sex, followed by hypercholesterolemia, heart disease, and cigarette smoking, whereas diabetes mellitus and daily drinking were insignificant for aneurysm formation. Hypertension and daily drinking were not related to the risk of aneurysm rupture, regardless of age and sex, whereas cigarette smoking was associated with an increased risk of aneurysm rupture in patients 60 years or older and in men. In contrast, hypercholesterolemia was strongly associated with a decreased risk of rupture, regardless of age and sex, and in patients with small aneurysms (<5 mm). Diabetes mellitus and heart disease were also related to a decreased risk of rupture in patients 60 years or older and in women.ConclusionIdentification of risk factors for aneurysm formation and rupture separately seems to be pivotal for reducing the incidence of SAH.     

Natural history of unruptured intracranial aneurysms: probability of and risk factors for aneurysm rupture

OBJECT: The authors conducted a study to investigate the long-term natural history of unruptured intracranial aneurysms and the predictive risk factors determining subsequent rupture in a patient population in which surgical selection of cases was not performed. METHODS: One hundred forty-two patients with 181 unruptured aneurysms were followed from the 1950s until death or the occurrence of subarachnoid hemorrhage or until the years 1997 to 1998. The annual and cumulative incidence of aneurysm rupture as well as several potential risk factors predictive of rupture were studied using lifetable analyses and Cox's proportional hazards regression models including time-dependent covariates. The median follow-up time was 19.7 years (range 0.8-38.9 years). During 2575 person-years of follow up, there were 33 first-time episodes of hemorrhage from previously unruptured aneurysms, for an average annual incidence of 1.3%. In 17 patients, hemorrhage led to death. The cumulative rate of bleeding was 10.5% at 10 years, 23% at 20 years, and 30.3% at 30 years after diagnosis. The diameter of the unruptured aneurysm (relative risk [RR] 1.11 per mm in diameter, 95% confidence interval [CI] 1-1.23, p = 0.05) and patient age at diagnosis inversely (RR 0.97 per year, 95% CI 0.93-1, p = 0.05) were significant independent predictors for a subsequent aneurysm rupture after adjustment for sex, hypertension, and aneurysm group. Active smoking status at the time of diagnosis was a significant risk factor for aneurysm rupture (RR 1.46, 95% CI 1.04-2.06, p = 0.033) after adjustment for size of the aneurysm, patient age, sex, presence of hypertension, and aneurysm group. Active smoking status as a time-dependent covariate was an even more significant risk factor for aneurysm rupture (adjusted RR 3.04, 95% CI 1.21-7.66, p = 0.02). CONCLUSIONS: Cigarette smoking, size of the unruptured intracranial aneurysm, and age, inversely, are important factors determining risk for subsequent aneurysm rupture. The authors conclude that such unruptured aneurysms should be surgically treated regardless of their size and of a patient's smoking status, especially in young and middle-aged adults, if this is technically possible and if the patient's concurrent diseases are not contraindications. Cessation of smoking may also be a good alternative to surgery in older patients with small-sized aneurysms.     

Natural history of unruptured intracranial aneurysms: probability of and risk factors for aneurysm rupture

OBJECT: The authors conducted a study to investigate the long-term natural history of unruptured intracranial aneurysms and the predictive risk factors determining subsequent rupture in a patient population in which surgical selection of cases was not performed. METHODS: One hundred forty-two patients with 181 unruptured aneurysms were followed from the 1950s until death or the occurrence of subarachnoid hemorrhage or until the years 1997 to 1998. The annual and cumulative incidence of aneurysm rupture as well as several potential risk factors predictive of rupture were studied using life-table analyses and Cox's proportional hazards regression models including time-dependent covariates. The median follow-up time was 19.7 years (range 0.8-38.9 years). During 2575 person-years of follow up, there were 33 first-time episodes of hemorrhage from previously unruptured aneurysms, for an average annual incidence of 1.3%. In 17 patients, hemorrhage led to death. The cumulative rate of bleeding was 10.5% at 10 years, 23% at 20 years, and 30.3% at 30 years after diagnosis. The diameter of the unruptured aneurysm (relative risk [RR] 1.11 per mm in diameter, 95% confidence interval [CI] 1-1.23, p = 0.05) and patient age at diagnosis inversely (RR 0.97 per year, 95% CI 0.93-1, p = 0.05) were significant independent predictors for a subsequent aneurysm rupture after adjustment for sex, hypertension, and aneurysm group. Active smoking status at the time of diagnosis was a significant risk factor for aneurysm rupture (RR 1.46, 95% CI 1.04-2.06, p = 0.033) after adjustment for size of the aneurysm, patient age, sex, presence of hypertension, and aneurysm group. Active smoking status as a time-dependent covariate was an even more significant risk factor for aneurysm rupture (adjusted RR 3.04, 95% CI 1.21-7.66, p = 0.02). CONCLUSIONS: Cigarette smoking, size of the unruptured intracranial aneurysm, and age, inversely, are important factors determining risk for subsequent aneurysm rupture. The authors conclude that such unruptured aneurysms should be surgically treated regardless of their size and of a patient's smoking status, especially in young and middle-aged adults, if this is technically possible and if the patient's concurrent diseases are not contraindications. Cessation of smoking may also be a good alternative to surgery in older patients with small-sized aneurysms.     

Screening of risk groups for discovering intracranial aneurysms before rupture

In development of intracranial aneurysms contribute genetic factors together with smoking, hypertension, diabetes mellitus. Epidemiology studies suggest that as many as 5% of people harbour a cerebral aneurysm by age 75. Rupture of cerebral aneurysm is the most frequent cause of spontaneous subarachnoid haemorrhage (up to 80%.) Annual incidence of SAH is 10-14/100 000, but only 15-20% of aneurysms will rupture, and that will happen probably between 40-60 years. The morbidity and mortality of aneurismal subarachnoid (SAH) continues to be high. It is not possible to predict who has aneurysm and is it going to bleed or not, but it is possible to reveal high risk groups (polycystic kidney disease, Ehlers-Danlos sy, Marphan sy, family history of cerebral aneurysms, suspect de novo aneurysm formation in patients with prior history of cerebral aneurysm). Reviewing data from literature and reporting cases from each group with high risk, that have been screened and aneurysms discovered, authors wish to focus interest on this matter and propose screening program for these groups of patients. The mortality and morbidity in cases treated before rupture is significantly lower than after SAH, so screening programs could save many lives. According to our preliminara data, mostly based on control angiographies after 8-10 zears in patients previouslz operated for intracranial aneurysmas, from 15 angipgraphies 4 revealed new aneurysms (26% in 10 years period) with total number of 6 de novo formed aneurysms, which is not valid due to small number of patients but strongly suggests the importancy of screening program for risk groups.     

Computational fluid dynamics analysis of intracranial aneurysms treated with flow diverters: A case report

IntroductionIntracranial aneurysms (IAs) are localized dilatations of intracranial arteries due to weaknesses of the endothelial layer. IAs may be treated by flow diverters (FDs), alternatively to stents and coils combination. FD is a method for the treatment of IAs especially for large, wide-necked or fusiform aneurysms. In this case report, we described a 65-year-old woman with IA who were treated by FD.Case presentationA 65-year-old woman was diagnosed with a giant aneurysm at the posterior inferior cerebellar artery segment of the left internal carotid artery. Then based on the computed tomography data of this woman, aneurysm vascular stent model was constructed before and after FD, and internal pressure, velocity, wall shear stress (WSS) of aneurysms were determined by CFD analysis. Standard boundary conditions were applied. It was found that a single FD stent and double FD stents decreased the blood flow and WSS of aneurysm. The effect of single FD stent + 30% filling on blood flow was more obvious, but the aneurysm rupture was caused by excessive coil packing. So, a single stent + 10% coil packing rate was the best option for treating aneurysms.ConclusionsCFD analysis for flow velocity and WSS have protection on aneurysms.     

The adverse effects of flow-diverter stent-like devices on the flow pattern of saccular intracranial aneurysm models: computational fluid dynamics study

Background  

Stent deployment across the aneurysmal neck has been established as one of the endovascular methods to treat intracranial aneurysms with or without coils.     

Incidence and risk factors for multiple intracranial saccular aneurysms in patients with subarachnoid hemorrhage in Izumo City,Japan

Background  

A community-based study was conducted to estimate the incidence rates of multiple aneurysms and to investigate the factors related to multiplicity.     

Angiographic characteristics of ruptured paraclinoid aneurysms: risk factors for rupture

Background

The diagnosis and treatment of unruptured paraclinoid aneurysms has been increasing with the recent advent of diagnostic tools and less invasive endovascular therapeutic options. Considering the low incidence of rupture, investigation of the characteristics of ruptured paraclinoid aneurysm is important to predict rupture risk of the paraclinoid aneurysms. The objective of this study is to evaluate probable factors for rupture by analyzing the characteristics of ruptured paraclinoid aneurysms.

Methods

A total of 2,276 aneurysms (1,419 ruptured and 857 unruptured) were diagnosed and treated endovascularly or microsurgically between 2001 and 2011. Among them, 265 were paraclinoid aneurysms, of which 37 were ruptured. Removing 12 blister-like aneurysms, 25 ruptured and 228 unruptured saccular aneurysms were included and the medical records and radiological images were retrospectively analyzed.

Results

Of 25 aneurysms, 16 (64.0 %) were located in the superior direction. Five were inferior located lesions (20 %) and four were medially located lesions (16.0 %). Laterally located lesions were not found. The mean size of aneurysms was 9.4?±?5.6 mm. Ten aneurysms (40.0 %) were ≥?10 mm in size. Thirteen aneurysms (52.0 %) were lobulated. The superiorly located aneurysms were larger than the other aneurysms (10.3?±?5.8 mm vs. 7.7?±?4.9 mm) and more frequently lobulated (ten of 16 vs. three of nine). In a comparative analysis, the ruptured aneurysms were located more in the superior direction compared with unruptured aneurysms (64 vs. 23.2 %, p?<?0.0001). Large aneurysms (36.0 vs. 7.9 %, p?<?0.0001), longer fundus diameter (mean 9.4?±?5.6 vs. 4.8?±?3.3 mm, p?=?0.001), dome-to-neck ratio (mean 1.8?±?0.9 vs. 1.2?±?0.5, p?<?0.0001), and lobulated shape aneurysms were more likely to be ruptured aneurysms (13 of 25 ruptured aneurysms, 52.0 %, p?=?0.001).

Conclusions

Rupture risk of the paraclinoid aneurysm is very low. However, superiorly located paraclinoid aneurysms appear more likely to rupture than other locations. Angiographically, more conservative indication for the treatment of paraclinoid aneurysm should be recommended except for superior located lesions.     

Predicting the risk of rupture of intracranial aneurysms based on anatomical location

Summary The location of intracranial aneurysms may be a significant independent risk factor for predicting aneurysm rupture. A recent report found high bleed rates from posterior communicating artery aneurysms which had not previously been noted. On this distinction hangs the decision whether to treat a large number of unruptured aneurysms.In the recent publication by the International Study of Unruptured Intracranial Aneurysms (ISUIA), two bleeds from small incidental posterior communicating artery aneurysms were noted and these aneurysms were reported to have a similar risk to aneurysms of the posterior circulation and as a result were grouped with them. This was a post hoc analysis so the justification for this assertion is tenuous. The hypothesis that posterior communicating aneurysms are of similar risk to posterior circulation aneurysms requires further testing on other data before it can be confidently accepted.A review of the literature was undertaken to define relative risks of rupture for different anatomical locations and to test the above hypothesis. Eleven papers were found to contain sufficient data to calculate rupture rates for anatomical sub groups. Studies contained a total of 30,204 patient years of follow up.Results showed the internal carotid artery to be the commonest site for unruptured aneurysms (38%). Aneurysms located in the posterior circulation had an overall annual bleed rate of 1.8%. This compares with 0.49% for the anterior circulation. The bleed rate from aneurysms of the posterior communicating artery (0.46% per year) was similar to that of the rest of the anterior circulation.The ISUIA post hoc hypothesis fails when tested on these data and the ISUIA data should be re-analysed with posterior communicating artery aneurysms grouped with the anterior circulation where they more traditionally belong.     

Changes of intracranial pressure during the rupture of intracranial aneurysms: Prognosis for survival

The intracranial pressure at the time of rebleeding from an intracranial aneurysm was recorded in 4 patients who were undergoing conservative treatment pending clinical improvement. Two died of severe hemorrhages and the remaining two recovered. In the deceased patients, repeated rapid increases in the intracranial pressure in a short time caused by rupture of the intracranial aneurysm were observed. In the surviving patients, the intracranial pressure increased only once, owing to the rupture of the intracranial aneurysm. We suggest that sudden death following the rupture of an intracranial aneurysm may result from frequent, repeated bleeding causing an intracerebral hematoma or severe brain swelling, or both.     

Multiple intracranial aneurysms: determining the site of rupture

A retrospective hospital chart and radiograph review was performed of all patients with multiple intracranial aneurysms seen over a 52-month period. Sixty-nine patients with a total of 205 aneurysms were studied. Among the patients with aneurysms, the incidence of multiple aneurysms was 33.5%. Multiple aneurysms were much more common in women, with a female to male ratio of 5:1 for all patients and 11:1 for patients with three or more aneurysms. Common locations for multiple aneurysms were the posterior communicating artery (22%), middle cerebral artery (21.5%), anterior communicating artery (12%), and ophthalmic artery (11%). However, locations with the highest probability of rupture were the anterior communicating artery (62%), posterior inferior cerebellar artery (50%), and basilar artery summit (50%). The middle cerebral artery was the least likely site for rupture. In contrast to previous studies, in this series irregularity of contour was more important than size in identifying the site of rupture. Using a simple algorithm outlined in the text, it was possible to identify the site of aneurysm rupture in 97.5% of cases.     

Temporary arterial occlusion in the repair of ruptured intracranial aneurysms: an analysis of risk factors for stroke

OBJECT: This study was performed to further elucidate technical and patient-specific risk factors for perioperative stroke in patients undergoing temporary arterial occlusion during the surgical repair of their aneurysms. METHODS: One hundred twelve consecutive patients in whom temporary arterial occlusion was performed during surgical repair of an aneurysm were retrospectively analyzed. Confounding factors (inadvertent permanent vessel occlusion and retraction injury) were identified in six cases (5%) and these were excluded from further analysis. The demographics for the remaining 106 patients were analyzed with respect to age, neurological status, aneurysm characteristics, intraoperative rupture, duration of temporary occlusion, and number of occlusive episodes; end points considered were outcome at 3-month follow up and symptomatic and radiological stroke. CONCLUSIONS: Overall 17% of patients experienced symptomatic stroke and 26% had radiological evidence of stroke attributable to temporary arterial occlusion. A longer duration of clip placement, older patient age, a poor clinical grade (Hunt and Hess Grades IV-V), early surgery, and the use of single prolonged clip placement rather than repeated shorter episodes were associated with a higher risk of stroke based on univariate analysis. Intraoperative aneurysm rupture did not affect stroke risk. On multivariate analysis, only poorer clinical grade (p = 0.001) and increasing age (p = 0.04) were significantly associated with symptomatic stroke risk.     

A mathematical model for the mechanics of saccular aneurysms

We constructed and discussed a mathematical model of intracranial saccular aneurysms based on the static mechanics of hollow vessels and were able to focus on three variables that are fundamental to the process of enlargement and rupture of these lesions. They are blood pressure (P), wall strength (sigma), and total wall substance (VT), which, if assigned values of 150 mm Hg, 10 MPa, and 1.0 mm3, lead to model-predicted values of 8 mm for the diameter and 40 micron for the wall thickness for the critical geometry of aneurysmal rupture. These are quantitatively similar to published measurements. The model is based on the assumption of a uniform thin spherical shell for the saccular aneurysm. The interrelationship of the variables, expressed in the equation for critical size at rupture (dc) (i.e., dc = [4 sigma VT/(pi P)]1/3), draws attention to the need for quantitative studies on aneurysmal geometry and on the stereology of the structural fraction of the aneurysmal wall. We concluded that tissue recruitment from around the initial site or hypertrophy of the wall tissue is commonly involved in the aneurysmal process. We identify the paradox of elastic stiffness and stability, which are characteristic of autopsy specimens in the laboratory, in contrast to plastic behavior and irreversible strain, which are essential to the natural process of enlargement of saccular aneurysms.     

A technique of clipping giant intracranial aneurysms with the preservation of the parent artery

Several methods are currently available for the treatment of giant intracranial aneurysms. In this report, we emphasize the technique of temporary trapping of the aneurysm followed by aspiration and collapse, and subsequent clipping. This method permits the preservation of the parent vessel and avoids the need for creating a microvascular bypass. Two cases are presented to illustrate this technique; in one case the patient had a giant middle cerebral artery aneurysm, and in the other a giant carotid-ophthalmic artery aneurysm. Both aneurysms were successfully clipped with preservation of the major vessels and a good result. On the basis of the configurations of their necks, giant aneurysms can be classified into three groups. The different methods of treating these aneurysms are reviewed with respect to this classification.     

A comparison of risk factors in the etiology of mirror and nonmirror multiple intracranial aneurysms

BACKGROUND: Pure mirror intracranial aneurysms represent a subgroup of multiple aneurysm patients where a congenital predisposition may play a major etiologic role. The aim of this study was to compare the pattern of prevalence of known risk factors for aneurysm disease between pure mirror and pure nonmirror multiple aneurysm populations. METHODS: Clinical records of all patients with multiple intracranial aneurysms admitted to our institution between January 1985 and September 2001 were reviewed. Age, localization of aneurysms, gender, and history of cigarette smoking or hypertension were noted and compared using Fisher's exact test and logistic regression analysis. RESULTS: There were 33 patients presented with pure mirror aneurysms (MirAn) and 49 with nonmirror multiple aneurysms (nMirAn). Average age of rupture occurred in the 5th decade in both groups. Female:male ratio was 3.1:1 in MirAn; 2.1:1 in nMirAn. In MirAn patients younger than 40 years it was 1:1. Smoking was the most prevalent risk factor in nMirAn (59.2%). In MirAn this was true only for patients in the 5th or 6th decades (65%), and hypertension was the most prevalent risk factor over that age (62.5%). A total of 80% of mirror aneurysm patients under 40 years had no known extrinsic risk factor, compared with 20% in nMirAn (p < 0.05). CONCLUSIONS: Differences in the relative prevalence of risk factors between both groups supports the hypothesis of a different etiologic process occurring in mirror aneurysm disease. Early rupture in patients with no extrinsic risk factors lends support to the role of a congenital predisposition over degenerative causes in these patients.     

Acoustic detection of intracranial aneurysms: A decision analysis

Summary We present a further evaluation of an improved recording method for the acoustic detection of intracranial aneurysms (ADA). A sensor was applied to the patient's eyes. Two measures were derived to summarize the power spectral density functions of the sound frequencies that were obtained from each patient: the power median (PM), the median of the power spectral density function, and the mean difference error (MDE), a measure of the difference between the normalized, logarithmically transformed spectra of the patient and a template, the normal spectrum. The capability of these two measures (alone or combined) to discriminate between patients with and without an intracranial aneurysm was tested in a series of 89 patients harbouring a total of 109 aneurysms and 73 controls, using multiple logistic regression analysis. When PM and MDE were combined, the accuracy of the predictions amounted to 79%. Individualized threshold values of the likelihood ratio of harbouring an aneurysm, for ordering four-vessel angiography are suggested, depending on the prior probability of harbouring an aneurysm, the risks of unnecessary angiography and the risk of living with an undetected aneurysm. Our decision analysis suggests that using these recommendations, employing acoustic detection results in a small gain in quality adjusted life expectancy (0.01 life year) for patients aged between 40 and 60, compared to no diagnostic testing, and 0.02 life year compared to angiography, which cannot be recommended. For patients with a three times increased prior risk of harbouring an intracranial aneurysm, the benefit of ADA compared to angiography increases to 0.05 life year. We conclude that acoustic detection has the potential of becoming a useful tool in the non-invasive diagnosis of occult, asymptomatic intracranial aneurysms.