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.     

Natural history of unruptured cerebral aneurysms of the unoperated and observed cases

PURPOSE: Natural history of unruptured cerebral aneurysms is still a matter of discussion. In this study, we investigated the prognosis of unruptured cerebral aneurysms of unoperated cases in a prospective design. METHODS: Between September, 1992 and December, 2001, we have encountered a 256 cases of unruptured cerebral aneurysms. Among them, 118 cases were observed and were checked every year for their status. The endpoint was designed as their death and aneurysm rupture. Their rupture rate, mortality due to aneurysm death, and the cause of death other than aneurysm were investigated. Univariate analysis, chi-square test was used as statistics. A p-value less than 0.05 was considered as significant. RESULTS: Annual rupture rate of unoperated unruptured cerebral aneurysms of size below 5 mm, between 5-15 mm, and over 15 mm increased according to the aneurysm size, 0.4%, 3.3% and 9.9% respectively. The sole risk factor for the feasibility of rupture of unruptured aneurysms was their size (p < 0.001). Aneurysm related mortality, however, was high in posterior circulation aneurysms. In patients under 70 years of age, 45% of patients died of cerebral aneurysms, but this rate decreased to 17% for patients over 70 years of age. CONCLUSION: The rupture rate of unruptured cerebral aneurysms over 5 mm in size is not low. Unruptured aneurysms of the posterior circulation may have a much higher risk of rupture, so further investigation is necessary.     

Unruptured intracranial aneurysm: possible therapeutic strategies?

Intracranial unruptured aneurysm (ICUA) has become a common condition for patient consultation. The mortality rate after fissuration is estimated to be between 52% and 85.7%. The final therapeutic decision results from a balance between the risk of rupture and risks related to the aneurysmal exclusion. Analysis of the risk of rupture risk enables a classification of risk factors. Depending on the circumstances of diagnosis, we considered the ICUA at high risk of rupture for incidental ICUA larger than 7 mm and in the event of associated aneurysms. Classifying by morphologic features, high-risk ICUA were located in the vertebrobasilar system (RR: 4.4; 95%CI: 2.7-6.8), those with a size between 7 and 12 mm (RR: 3.3; 95%CO: 1.3-8.2), larger than 12 mm (RR: 17; 95%CI: 8-36.1), those that were multilobular or a larger size and those ones with a index P/L superior to 3.4 (risk x20). Familial ICUA would expose to a major rupture risk (2 to 7 times sporadic ICUA). Some systemic factors were related to ICUA rupture: arterial hypertension (RR: 1.46; 95%CI: 1.01-2.11) and smoking addiction (RR: 3.04; 95%CI: 1.21-7.66). After microsurgical exclusion, the morbidity and mortality rates were 10% and 2% respectively. Some microsurgical morbidity factors were identified: age (32%>65 years), size (14%>15 mm), vertebrobasilar location and temporary occlusion. The rupture incidence after microsurgical exclusion was estimated 0.26%/year. After endovascular exclusion, the morbidity and mortality rates were 8% and 1% respectively. The complete exclusion rate varied between 47% and 67%. The rupture risk was estimated at 0.9%/year. Treatment recommendations were classified into 3 categories.     

Factors associated with aneurysm size in patients with subarachnoid hemorrhage: effect of smoking and aneurysm location

OBJECTIVE: Intracranial aneurysm size is an important determinant of risk of rupture and outcome after rupture. Risk factors influencing aneurysm formation and growth are not well defined. In this study, we examined the association between known risk factors for cerebrovascular disease and size of intracranial aneurysms in patients with aneurysmal subarachnoid hemorrhage. METHODS: We analyzed prospectively collected data from the placebo-treated group in a multicenter clinical trial conducted at 54 neurosurgical centers in North America. The presence, location, and size of intracranial aneurysms were determined by review of the admission angiograms. Pertinent information regarding the presence of various cerebrovascular risk factors was collected for each patient. Using logistic regression analysis, we identified independent determinants of aneurysm size from demographic, clinical, and angiographic characteristics of the participants. The impact of aneurysm size on 3-month mortality was analyzed after adjusting for potential confounding factors. RESULTS: For 298 patients admitted with subarachnoid hemorrhage, the ruptured aneurysms were graded as small (<13 mm) in 235 patients (79%) and large (> or =13 mm) in 63 patients (21%). In the logistic regression model, both smoking at any time (odds ratio, 2.2; 95% confidence interval, 1.1-4.5) and middle cerebral artery origin (odds ratio, 2.5; 95% confidence interval, 1.3-4.9) were independently associated with large aneurysms. Neither hypertension, diabetes mellitus, nor alcohol and illicit drug use were associated with large-sized aneurysms. After adjusting for initial Glasgow Coma Scale score and age in the logistic regression model, the presence of large-sized aneurysms was independently associated with 3-month mortality (odds ratio, 2.3; 95% confidence interval, 1.1-4.8). CONCLUSION: Cigarette smoking and middle cerebral artery origin seem to increase the risk for developing large aneurysms in patients predisposed to intracranial aneurysm formation. Further studies are required to investigate the mechanism underlying the association between cigarette smoking and intracranial aneurysm formation.     

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.     

The natural history of abdominal aortic aneurysms and their risk of rupture

The UK Small Aneurysm Trial has shown that ultrasound surveillance is a safe management option for patients with small abdominal aortic aneurysms (4.0 to 5.5 cm in diameter), with an annual rupture rate of only 1%. We investigated baseline risk factors associated with aneurysm rupture in the 1090 trial patients and an additional 1167 patients enrolled in the UK Small Aneurysm Study. In this cohort of 2257 patients there were 103 cases of aneurysm rupture. After 3 years the annual rate of rupture was 2.2% (95% CI 1.7 to 2.8). The risk of rupture was independently and significantly associated with female sex (p < 0.001), larger initial aneurysm diameter (p < 0.001), current smoking (p = 0.01) and higher mean blood pressure (p = 0.01). Age, body mass index, serum cholesterol concentration and ankle/brachial pressure index were not associated with an increased risk of aneurysm rupture. The most surprising finding was that women had a 3-fold higher risk of aneurysm rupture than men. Effective control of blood pressure and cessation of smoking are two simple measures that are likely to diminish the risk of aneurysm rupture and improve the cardiovascular health of patients with abdominal aortic aneurysm.     

Size of cerebral aneurysms and related factors in patients with subarachnoid hemorrhage

BACKGROUND: As the indication for surgical treatment of incidentally discovered small aneurysms remains controversial. METHODS: We retrospectively investigated the characteristics of small ruptured aneurysms and examined the relationship between the size and location of ruptured intracranial aneurysms and the sex, age, lifestyle, and medical history of 280 patients with ruptured aneurysm treated at our institute. RESULTS: The mean diameter of ruptured aneurysms in this series was 7.6 mm. In diameter, 135 (48.2%) ranged between 5 and 10 mm; 73 (26.1%) were smaller than 5 mm. The size of the ruptured aneurysms was significantly smaller (mean 6.5 mm) in patients with non- or poorly controlled hypertension than in normotensive patients (mean 8.3 mm) (p < 0.05). Ruptured aneurysms in the anterior communicating artery (AcomA) and anterior cerebral artery (ACA) were significantly smaller (p < 0.01) than those in the internal carotid artery or middle cerebral artery. Among 58 patients with multiple aneurysms, only 7 (12%) suffered rupture of aneurysms smaller than 5 mm (p < 0.01). Patients younger than 40 years and patients with a family history of subarachnoid hemorrhage appeared to predispose to the rupture of small-sized aneurysms, although those did not affect the statistical significance. CONCLUSIONS: This study shows that even aneurysms smaller than 10 mm may rupture. However, treatment decisions for unruptured aneurysm should not be based solely on the size of the unruptured aneurysms. Our data implies that even small aneurysms in the AcomA and ACA had an increased tendency for rupture, and that hypertensive patients were at higher risk for the rupture of small aneurysms.     

Microsurgical treatment of basilar apex aneurysms: perioperative and long-term clinical outcome

OBJECTIVE: We sought to analyze the perioperative and long-term clinical outcome data for patients with microsurgically treated basilar apex aneurysms. METHODS: We identified 98 consecutively treated basilar apex aneurysms in patients prospectively enrolled in a cerebral aneurysm database. RESULTS: Fifty patients presented with subarachnoid hemorrhage, and 19 aneurysms were giant. Eighty-four of 98 aneurysms were directly clipped. Surgical morbidity was 19.4% for the entire cohort and 8.8% for the unruptured, nongiant subgroup. The most common complication resulting in long-term morbidity was perforator injury. Sixty-seven percent of patients with clipped aneurysms were independent at discharge; this fraction increased to 79.0% at the 3-month follow-up examination. Good long-term outcomes (modified Rankin Scale score < or =2) were achieved in 56 (70%) of 80 cases. The mean Barthel Index of surviving patients was 95.8 +/- 15.0 (median = 100, n = 66). Patients with unruptured, nongiant lesions fared considerably better than patients in other cohorts. Ninety-three percent of this subgroup was independent at discharge; this fraction increased to 100% at the 3-month follow-up examination (n = 27). In univariate analyses, poor clinical grade, giant aneurysm size, major operative complications, and operations performed early in the series were associated with worse outcomes. In the multivariate analysis, unruptured giant aneurysm status was found to confer a tremendous risk for poor outcome (risk ratio, 80.0; 95% confidence interval, 8.0-800.7; P < 0.01). Surviving patients were observed for a mean clinical follow-up period of 7.4 +/- 3.7 years. The annual rate of postoperative subarachnoid hemorrhage was 0.18% for all clipped aneurysms and 0% for completely clipped lesions. CONCLUSION: In comparison to data from the existing literature regarding Guglielmi detachable coil embolization of basilar apex aneurysms, the data presented suggest that surgical clipping should be an important component of a multimodality approach to the treatment of patients with basilar apex aneurysms.     

Cigarette smoking increases the risk of developing a cerebral aneurysm and of subarachnoid hemorrhage]

Despite recent advances in diagnostic and therapeutic techniques, subarachnoid hemorrhage (SAH) is still a serious condition associated with high mortality and morbidity. There are no effective treatments other than surgical intervention. However, another option for decreasing the occurrence of SAH may be prevention of aneurysms formation and of their rupture by controlling risk factors. Cigarette smoking has been recently shown to be one of the major risk factors for SAH. We investigated whether cigarette smoking increased the risk of developing cerebral aneurysms and of SAH. Degree of smoking was investigated in 182 patients with SAH and in 123 patients with an unruptured cerebral aneurysm incidentally detected during investigation of other diseases. Sixty-nine patients with other diseases who were shown to be free of cerebral aneurysms through MR angiography served as controls. Smoking significantly increased the risk of both aneurysm formation and SAH; The odds ratio for SAH was 2.4, and for unruptured cerebral aneurysm 1.7. Smoking especially increased the occurrence of SAH in women and in youngsters. However, smoking did not influence the occurrence of cerebral vasospasm and multiplicity of aneurysms. These data suggest the importance of avoiding smoking to prevent the occurrence of cerebral aneurysms and of SAH.     

Comparison of ruptured vs unruptured aneurysms in recanalization after coil embolization

BACKGROUND: Aneurysm recanalization is a significant problem in coil-treated intracranial aneurysms. We hypothesize ruptured aneurysms are more likely to demonstrate this phenomenon than unruptured aneurysms. METHODS: This was a retrospective study over 4 years. Initial and follow-up angiography results were reviewed and aneurysm obliteration was classified: I, complete; II, residual neck; III, residual aneurysm; and IV, partial treatment. Recanalization was classified as significant, mild, and none. RESULTS: Two hundred twelve aneurysms were coiled in 199 patients, of which 180 patients survived to 6 months after treatment. Follow-up angiography (>6 months) was available for 116 (64.4%) aneurysms (44 ruptured, 72 unruptured). Mean angiographic follow-up was 20 months. Recanalization was significant in 16 (13.8%) aneurysms, mild in 23 (19.8%), and absent in 87 (75%). Sixteen aneurysms underwent recoiling. Factors significant for recanalization by univariate analysis were ruptured vs unruptured (53.5% vs 22.5%; P = .001), larger aneurysm size (t test, P < .0001; median, 8-mm cut point, P < .01), aneurysm location (basilar tip and ICA terminus, P < .05), posterior circulation (P < .05), and younger age (t test, P < .05), whereas aneurysm neck size (4 mm) demonstrated a trend (P = .09). Incomplete initial aneurysm obliteration (II-IV, 20.6% vs I, 4.3%; P < .05) was associated with significant recanalization. In multivariate analysis, younger age (age <52 years; OR, 2.4; 95% CI, 0.194-2.08), ruptured aneurysm (OR, 3.2; 95% CI, 1.25-8.13), and larger aneurysm size (OR, 1.14; 95% CI, 1.04-1.24 linearly; OR, 3.5; 95% CI, 1.38-8.72) significantly predicted aneurysm recanalization. Performance of recoiling was significant with larger aneurysm size (OR, 2.0; 95% CI, 0.02-3.25) and younger age (age <52, OR, 2.4; 95% CI, 0.34-3.31) by multivariate analysis, whereas ruptured aneurysm demonstrated a trend. CONCLUSIONS: In multivariate analyses, ruptured aneurysms, larger aneurysms, and younger patient age were significantly associated with recanalization. Larger aneurysms and younger age were significantly associated with recoiling.     

Computed tomographic angiography for detecting cerebral aneurysms: implications of aneurysm size distribution for the sensitivity,specificity, and likelihood ratios

OBJECTIVE: This study examined the efficacy of computed tomographic angiography (CTA) for detection of ruptured and unruptured aneurysms after adjustment for their size distributions under various conditions of aneurysm prevalence. METHODS: A systematic review was used to estimate 1) the aneurysm size-specific sensitivity and specificity of CTA, and 2) the size distributions of ruptured and unruptured aneurysms. Probabilistic computer simulation was used to estimate the efficacy of CTA in the detection of aneurysms. RESULTS: The sensitivity of CTA ranged from 53% (95% confidence interval [CI], 44-62%) for 2-mm aneurysms to 95% (95% CI, 92-97%) for 7-mm aneurysms. The overall specificity was 98.9% (95% CI, 91.5-99.99%), but there was between-study heterogeneity. The estimated negative likelihood ratios for ruptured, unruptured, and at least 6-mm unruptured aneurysms were 0.081, 0.18, and 0.012, respectively. The positive likelihood ratio for CTA was sensitive to the pretest probability, the size of the positive finding, and the clinical context. With a small pretest probability, the positive likelihood ratio for unruptured aneurysms ranged from 15 for 2-mm aneurysms to 61 for 5-mm aneurysms. The positive likelihood ratio for ruptured aneurysms with an intermediate pretest probability (50%) ranged from 3.9 to 56 for 2- to 5-mm aneurysms. CONCLUSION: Small aneurysms detected on CTA should be investigated further unless there is a high pretest probability of a ruptured aneurysm. During screening for ruptured aneurysms, a negative CTA should be investigated further. During screening for unruptured aneurysms, a negative CTA results in a very low probability of a clinically important aneurysm.     

Surgical management of unruptured aneurysms: prognostic indicators

BACKGROUND: The treatment of unruptured aneurysms (UA) remains controversial. Therefore, it has become necessary to define various prognostic indicators in the surgical treatment of unruptured aneurysms not associated with previously ruptured aneurysms. METHODS: During a 6-year period, 78 unruptured aneurysms were managed. The results of management were retrospectively reviewed to define the prognostic indicators. RESULTS: There were 104 patients with unruptured aneurysms who underwent surgical treatment. Seventy-five patients without previous subarachnoid hemorrhage (SAH) were selected for data analysis. Eighty-seven percent of the aneurysms were on the anterior circulation. The most common location was the middle cerebral artery (MCA) followed by the posterior communicating artery (PCom), ophthalmic artery, and anterior communicating artery (ACom). Six percent were found on the basilar artery. The mean size of aneurysms was 12.5 mm (range = 3-30 mm, SD = 7.4). At surgery, rupture of the aneurysm was encountered in eight cases with temporary control of the parent vessel being required in 31 procedures. In four cases, intraoperative angiography warranted clip reapplication. The Glasgow Outcome Scale (GOS) was used as an outcome measure. Surgical treatment resulted in good outcome (GOS 1) in 87% and 10.7% had fair outcome; 2.3% were in GOS 3 (severe disability) at 6 month follow-up. There was no mortality. Logistic regression identified significant relationships between GOS and intraoperative rupture (p < 0.0002), rupture and size (p < 0.003), and size and age (p < 0.01). CONCLUSIONS: Large size aneurysms were associated with intraoperative rupture, which had a strong correlation with poor outcome. Increased age showed a linear relationship with the size of the aneurysm. Overall results of treatment for UA are gratifying. There was no mortality. Early diagnosis and surgical extirpation of UA may reduce both intraoperative difficulties as well as poor outcome probability.     

Investigation of the surgically treated and untreated unruptured cerebral aneurysms of the anterior circulation

BACKGROUND: The natural history of unruptured cerebral aneurysms and the surgical risks are modified by several factors including size, location, and presence of subarachnoid hemorrhage (SAH). The main confusion arises because the backgrounds of the past reports describing the natural history or the surgical complication of unruptured cerebral aneurysms were different. The present study aimed to adjust the backgrounds and investigate the surgical indication with close monitoring of both surgically treated and untreated unruptured cerebral aneurysms. METHODS: In the past 9 years, 201 patients who had unruptured anterior circulation aneurysms were monitored. The decision of the operation was not randomized. The patients were divided into three subgroups by the size of the aneurysms (small group: below 5 mm, medium group: between 5 and 15 mm, large group: over 15 mm). In both surgically untreated and treated patients, overall mortality and morbidity corresponding to Rankin score II or worse was counted as unruptured aneurysm related event. The ratio of event free was compared between surgically treated and untreated patients using Log-rank test. RESULTS: In untreated patients, SAH was noted in 1 in the small group and 4 in the medium group. The annual rupture rate of the medium group was 12 times higher than that of the small group. In surgically treated patients, overall mortality and morbidity of the surgery was 2.3% in the small group, 3.6% in the medium group, and 20% in the large group. One surgically treated patient had SAH because of regrowth of aneurysm. When ratio of event free was compared, no significant advantage of surgery was noted in the small group and in all of the patients. However, the benefit of surgery was significant in the medium group (Log-rank p = 0.0189). CONCLUSIONS: The present results indicated that prophylactic surgery has a benefit for the medium-size aneurysms (5-15 mm) of the anterior circulation. For large aneurysms, individual investigation is necessary because of the variety of surgical difficulties, and the complex symptoms because of rupture and the mass effect as well as cerebral embolism. In small aneurysms, careful observation may be a reasonable choice unless the aneurysm is at a specially high risk of rupture.     

The significance of unruptured intracranial saccular aneurysms

The authors report the results of a long-term follow-up study of 130 patients with 161 unruptured intracranial saccular aneurysms. Their findings suggest that unruptured saccular aneurysms less than 10 mm in diameter have a very low probability of subsequent rupture. The mean diameter of the aneurysms that subsequently ruptured was 21.3 mm, compared with a diameter of 7.5 mm for aneurysms defined after rupture at the same institution. Part of the explanation for this discrepancy may be that the size of the filling compartment of the aneurysm decreases after rupture. There is also evidence from the present study that intracranial saccular aneurysms develop with increasing age of the patient and stabilize over a relatively short period, if they do not initially rupture, and that the likelihood of subsequent rupture decreases considerably if the initial stabilized size is less than 10 mm in diameter. Consequently, the critical size for aneurysm rupture is likely to be smaller if rupture occurs at the time of or soon after aneurysm formation. There seems to be a substantial difference in potential for growth and rupture between previously ruptured and unruptured aneurysms.     

Complications of endovascular treatment of cerebral aneurysms

BACKGROUND: The International Subarachnoid Aneurysm Trial has indicated that endovascular management of acutely ruptured aneurysms may be superior to surgery. Clearly poor results ensue from both forms of treatment, and some of these are because of technical complications (not just poor patient status). This observational study was performed to determine the complications associated with the endovascular treatment of ruptured and unruptured cerebral aneurysms. METHODS: Prospective data were gathered on 118 patients undergoing 126 endovascular treatment sessions for 126 nontraumatic cerebral aneurysms (30% unruptured) over a 3-year period. The average age was 51 years (range, 12-85 years). Females comprised 75% of the population treated. RESULTS: Good outcomes were achieved with 71% of the procedures (59% for subarachnoid hemorrhage [SAH]; 97% for unruptured). No bleeding or rebleeding occurred from treated aneurysms. Vessel or aneurysm perforation occurred in 11 cases and led to adverse outcome in 3 (3%). Thromboembolic complications were felt to cause cerebral infarction in 8 cases (6%). The risk of vessel/aneurysm rupture or thromboembolic stroke was greater in patients with SAH. Eight attempts to coil (6%) were initially unsuccessful. Two of these were later successfully coiled and others had surgery. None of the failed attempts led to clinical deterioration. Balloon-assisted coiling (BAC) was not associated with an increased complication rate. CONCLUSIONS: Vessel perforation and thromboembolic stroke are significant risks of endovascular treatment, especially after SAH. In our hands, however, BAC does not add to this risk.     

Rupture of previously documented asymptomatic unruptured aneurysms--aneurysm size: risk factor for aneurysm rupture

The natural history of asymptomatic unruptured aneurysms is not clear. We conducted a follow up study of 100 patients (since 1993) with 122 asymptomatic unruptured aneurysms that had not been operated on. We report five patients with previously documented asymptomatic unruptured aneurysms smaller than 10 mm in diameter that subsequently ruptured. Among the 100 patients, five had suffered subarachnoid hemorrhage (SAH) due to rupturing of an aneurysm. Of the 5 cases, 1 was male and 4 were female, with ages ranging from 59-73 years (mean age, 68 years). The aneurysms were on the MCA in 3, on the BA-SCA in 1, on the IC-PC in 1. The maximal diameter of the aneurysms at diagnosis ranged from 4.5 to 8 mm. The period from discovery to SAH was from 4 to 69 months and the cumulative rate of rupture of the aneurysms was 1.5 percent per year. Four of the 5 cases increased in size after the rupture. In our series, 2 of the 5 cases showed enlargement and the development of an aneurysmal bleb in the follow up MRA and 3D-CTA. The present study demonstrates that five asymptomatic unruptured aneurysms less than 10 mm in diameter subsequently ruptured. We ought to seriously consider the assertion published in the New England Journal of Medicine (Dec. 10, 1998), that unruptured aneurysms less than 10 mm in diameter have a very low probability of subsequent rupture.     

Predicting aneurysm rupture probabilities through the application of a computed tomography angiography-derived binary logistic regression model

OBJECT:The goal of this study was to establish a biomathematical model to accurately predict the probability of aneurysm rupture. Biomathematical models incorporate various physical and dynamic phenomena that provide insight into why certain aneurysms grow or rupture. Prior studies have demonstrated that regression models may determine which parameters of an aneurysm contribute to rupture. In this study, the authors derived a modified binary logistic regression model and then validated it in a distinct cohort of patients to assess the model's stability. METHODS:Patients were examined with CT angiography. Three-dimensional reconstructions were generated and aneurysm height, width, and neck size were obtained in 2 orthogonal planes. Forward stepwise binary logistic regression was performed and then applied to a prospective cohort of 49 aneurysms in 37 patients (not included in the original derivation of the equation) to determine the log-odds of rupture for this aneurysm. RESULTS:A total of 279 aneurysms (156 ruptured and 123 unruptured) were observed in 217 patients. Four of 6 linear dimensions and the aspect ratio were significantly larger (each with p < 0.01) in ruptured aneurysms than unruptured aneurysms. Calculated volume and aneurysm location were correlated with rupture risk. Binary logistic regression applied to an independent prospective cohort demonstrated the model's stability, showing 83% sensitivity and 80% accuracy. CONCLUSIONS:This binary logistic regression model of aneurysm rupture identified the status of an aneurysm with good accuracy. The use of this technique and its validation suggests that biomorphometric data and their relationships may be valuable in determining the status of an aneurysm.     

Intracranial saccular aneurysm enlargement determined using serial magnetic resonance angiography

OBJECT: The goal of this study was to determine the frequency of enlargement of unruptured intracranial aneurysms by using serial magnetic resonance (MR) angiography and to investigate whether aneurysm characteristics and demographic factors predict changes in aneurysm size. METHODS: A retrospective review of MR angiograms obtained in 57 patients with 62 unruptured, untreated saccular aneurysms was performed. Fifty-five of the 57 patients had no history of subarachnoid hemorrhage. The means of three measurements of the maximum diameters of these lesions on MR source images defined the aneurysm size. The median follow-up period was 47 months (mean 50 months, range 17-90 months). No aneurysm ruptured during the follow-up period. Four patients (7%) harbored aneurysms that had increased in size. No aneurysms smaller than 9 mm in diameter grew larger, whereas four (44%) of the nine aneurysms with initial diameters of 9 mm or larger increased in size. Factors that predicted aneurysm growth included the size of the lesion (p < 0.001) and the presence of multiple lobes (p = 0.021). The location of the aneurysm did not predict an increased risk of enlargement. CONCLUSIONS: Patients with medium-sized or large aneurysms and patients harboring aneurysms with multiple lobes may be at increased risk for aneurysm growth and should be followed up with MR imaging if the aneurysm is left untreated.     

Small unruptured aneurysm verification (SUAVe Study, Japan)--interim report

A prospective study (SUAVe Study, Japan) is in progress at 13 national hospitals to determine the surgical indications for small unruptured intracranial aneurysm. These hospitals are observing the natural history of small unruptured aneurysms (under 5 mm diameter) without surgical treatment. Since October 2000, 455 aneurysms (393 patients) with 75 aneurysms excluded by film judgment committees have been registered, of which 380 aneurysms (329 cases) have been followed up for a mean of 13.8 months (5 aneurysms for 36 months, 68 for 24 months, 164 for 12 months, and 64 for 6 months). Four aneurysms have already ruptured (3 multiple and 1 single). The annual rupture rate was 0.8% (95% confidence interval 0.2-3%). Another 18 aneurysms have enlarged including seven aneurysms treated for enlargement over 2 mm in size. Considering this finding, the annual rupture rate might rise slightly. The important factors for rupture and enlargement were multiplicity of aneurysm, female, patient aged over 70 years old, and location of aneurysm (anterior communicating artery, basilar artery). The growth rate may be faster in multiple aneurysms than in single aneurysms.     

Late angiographic follow-up review of surgically treated aneurysms.

OBJECT: This study was undertaken to evaluate the long-term angiographic outcome of surgically treated aneurysms, which is unknown. Specifically, the incidence of recurrent aneurysms, the fate of residual necks, and the de novo formation of aneurysms were evaluated. METHODS: One hundred two patients (80 females and 22 males; mean age 49 years; range 12-78 years) harboring a total of 167 aneurysms underwent late follow-up angiography; 160 aneurysms were surgically treated. Late angiographic follow-up review was obtained at a mean of 4.4 +/- 1.6 years postsurgery (range 2.6-9.7 years). Late follow-up angiography revealed two recurrent aneurysms (1.5%) of 135 clipped aneurysms without residua. Of 12 aneurysms with known residua, there were eight "dog-ear" residua, of which two (25%) enlarged. One hemorrhage was noted, yielding a hemorrhage risk of 1.9% per year. A second subgroup with broad-based residua revealed dramatic regrowth in three of four cases. Eight de novo aneurysms were found in six patients, for an annual risk of 1.8% per year. A history of multiple aneurysms was associated with de novo aneurysm formation (p = 0.049, chi-square analysis). CONCLUSIONS: This study confirms the long-term efficacy of aneurysm clip ligation. In addition, the authors found there is a small but significant risk of de novo aneurysm formation, particularly in patients with multiple aneurysms. Most residual aneurysm rests appear to remain stable, although a subset may enlarge or rupture. These findings support the rationale for late angiographic follow-up review in patients with aneurysms.