Natural History of Small Unruptured Anterior Circulation Aneurysms

Factors influencing management of unruptured intracranial aneurysms: an analysis of 424 consecutive patients

OBJECTIVE The choice between treating and observing unruptured intracranial aneurysms is often difficult, with little guidance on which variables should influence decision making on a patient-by-patient basis. Here, the authors compared demographic variables, aneurysm-related variables, and comorbidities in patients who received microsurgical or endovascular treatment and those who were conservatively managed to determine which factors push the surgeon toward recommending treatment. METHODS A retrospective chart review was conducted of all patients diagnosed with an unruptured intracranial aneurysm at their institution between January 1, 2013, and January 1, 2016. These patients were dichotomized based on whether their aneurysm was treated. Demographic, geographic, socioeconomic, comorbidity, and aneurysm-related information was analyzed to assess which factors were associated with the decision to treat. RESULTS A total of 424 patients were identified, 163 who were treated surgically or endovascularly and 261 who were managed conservatively. In a multivariable model, an age < 65 years (OR 2.913, 95% CI 1.298-6.541, p = 0.010), a lower Charlson Comorbidity Index (OR 1.536, 95% CI 1.274-1.855, p < 0.001), a larger aneurysm size (OR 1.176, 95% CI 1.100-1.257, p < 0.001), multiple aneurysms (OR 2.093, 95% CI 1.121-3.907, p = 0.020), a white race (OR 2.288, 95% CI 1.245-4.204, p = 0.008), and living further from the medical center (OR 2.125, 95% CI 1.281-3.522, p = 0.003) were all associated with the decision to treat rather than observe. CONCLUSIONS Whereas several factors were expected to be considered in the decision to treat unruptured intracranial aneurysms, including age, Charlson Comorbidity Index, aneurysm size, and multiple aneurysms, other factors such as race and proximity to the medical center were unanticipated. Further studies are needed to identify such biases in patient treatment and improve treatment delineation based on patient-specific aneurysm rupture risk.

Lifetime Effects of Small Unruptured Intracranial Aneurysms

BACKGROUND

Recent prospective multicenter studies have shown that the probability of rupture of unruptured aneurysms with maximal diameter <7 mm is rather low. However, the overall risks and long-term impact of unruptured aneurysms on lifetime quality of life are still unknown.

METHODS

A mathematical model of the natural history of intracranial aneurysms was constructed, in which the hypothetical individuals with or without unruptured aneurysm transit between discrete health states. The annual rupture rate of small aneurysms was assumed to be 0.5% in the baseline analysis, followed by the subsequent sensitivity analysis. The analyses were continued until cumulative death rate from subarachnoid hemorrhage or other causes reached 1.0.

RESULTS

Age-specific ratios of death of subarachnoid hemorrhage in the individuals harboring unruptured aneurysm, if dying at 60 years old, were 25% in men and 43% in women. These ratios decreased rapidly with higher age. Most (more than 90%) patients with small aneurysms were expected to die of diseases other than subarachnoid hemorrhage. In the baseline analysis (60-year-old individuals), lifetime lost to small aneurysms could be estimated as 3.8% for men and 4.2% for women, but a somewhat larger impact could be identified in the young and/or female individuals compared with in the elderly and/or male individuals.

CONCLUSIONS

Lifetime effects of small unruptured aneurysms without risk factors increasing the probability of rupture are relatively small, and most patients were expected to die of diseases other than subarachnoid hemorrhage.

Larger size ratio associated with the rupture of very small (≤3 mm) anterior communicating artery aneurysms

Background

Anterior communicating artery (AcoA) aneurysms have a high rupture risk, and ruptured AcoA aneurysms tend to be smaller than other intracranial aneurysms. We aimed to determine the incidence and morphologic predictors of aneurysm rupture of very small AcoA aneurysms.

Methods

We conducted a retrospective analysis of 519 consecutive patients with single AcoA aneurysms between December 2007 and February 2015 in our hospital. Aneurysm morphologies were re-measured using CT angiography images. Very small aneurysms were defined as those with a maximum size ≤3 mm, and small aneurysms were defined as those with a maximum size ≤5 mm. Multivariate regression analyses were used to determine the association between aneurysm morphology and aneurysm rupture status.

Results

Of the 474 ruptured AcoA aneurysms, 134 (28.3%) aneurysms were very small and 278 (58.6%) aneurysms were small. In the univariate analysis for very small aneurysms, larger aneurysm size (p=0.037), larger size ratio (p=0.002), higher aneurysm height (p=0.038), smaller vessel size (p=0.012), and dominant A1 segment configuration (p=0.011) were associated with aneurysm rupture. Multivariate analysis revealed that a larger size ratio was independently associated with the rupture status of the very small aneurysms (OR 3.69, 95% CI 1.5 to 9.0; p=0.004), and larger aneurysm size, larger size ratio, and dominant A1 segment configuration were associated with the rupture of small aneurysms.

Conclusions

About one-third of ruptured AcoA aneurysms were very small. A larger size ratio, rather than other aneurysm morphologies, was independently associated with the rupture of very small AcoA aneurysms.

Natural History of Unruptured Intracranial Aneurysms : A Retrospective Single Center Analysis

Objective

We conducted a retrospective cohort study to elucidate the natural course of unruptured intracranial aneurysms (UIAs) at a single institution.

Methods

Data from patients diagnosed with UIA from March 2000 to May 2008 at our hospital were subjected to a retrospective analysis. The cumulative and annual aneurysm rupture rates were calculated. Additionally, risk factors associated with aneurysmal rupture were identified.

Results

A total of 1339 aneurysms in 1006 patients met the inclusion criteria. During the follow-up period, 685 aneurysms were treated before rupture via either an open surgical or endovascular procedure. Six hundred fifty-four UIAs were identified and not repaired during the follow-up period. The mean UIA size was 4.5±3.2 mm, and 86.5% of the total UIAs had a largest dimension <7 mm. Among these UIAs, 18 ruptured at a median of 1.6 years (range : 27 days to 9.8 years) after day 0. The annual rupture risk during a 9-year follow-up was 1.00%. A multivariate Cox proportional hazards analysis revealed that the aneurysm size and a history of subarachnoid hemorrhage (SAH) were statistically significant risk factors for rupture. For an aneurysms smaller than 7 mm in the absence of a history of SAH, the annual rupture risk was 0.79%.

Conclusion

In our study, the annual rupture risk for UIAs smaller than 7 mm in the absence of a history of SAH was higher than that of Western populations but similar to that of the Japanese population.

Morphological Risk Factors for Rupture of Small (<7 mm) Posterior Communicating Artery Aneurysms

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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 Growth of Intracranial Aneurysms: A Systematic Review and Meta-Analysis

BACKGROUND AND PURPOSE

Understanding risk factors for intracranial aneurysm growth is important for patient management. We performed a meta-analysis examining risk factors for intracranial aneurysm growth in longitudinal studies and examined the association between aneurysm growth and rupture.

MATERIALS AND METHODS

We searched the literature for longitudinal studies of patients with unruptured aneurysms. We examined the associations of demographics, multiple aneurysms, prior subarachnoid hemorrhage, family history of aneurysm or subarachnoid hemorrhage, smoking, and hypertension; and aneurysm shape, size, and location with aneurysm growth. We studied the association between aneurysm growth and rupture. A meta-analysis was performed by using a random-effects model by using summary statistics from included studies.

RESULTS

Twenty-one studies including 3954 patients with 4990 aneurysms with 13,294 aneurysm-years of follow-up were included. The overall proportion of growing aneurysms was 3.0% per aneurysm-year (95% CI, 2.0%-4.0%). Patient risk factors for growth included age older than 50 years (3.8% per year versus 0.9% per year, P < .01), female sex (3.2% per year versus 1.3% per year, P < .01), and smoking history (5.5% per year versus 3.5% per year, P < .01). Characteristics associated with higher growth rates included cavernous carotid artery location (14.4% per year), nonsaccular shape (14.7% per year versus 5.2% per year for saccular, P < .01), and aneurysm size (P < .01). Aneurysm growth was associated with a rupture rate of 3.1% per year compared with 0.1% per year for stable aneurysms (P < .01).

CONCLUSIONS

Observational evidence provided multiple clinical and anatomic risk factors for aneurysm growth, including age older than 50 years, female sex, smoking history, and nonsaccular shape. These findings should be considered when counseling patients regarding the natural history of unruptured intracranial aneurysms.

Rupture of Very Small Intracranial Aneurysms: Incidence and Clinical Characteristics

Objective

Unruptured intracranial aneurysms are now being detected with increasing frequency in clinical practice. Results of the largest studies, including those of the International Study of Unruptured Intracranial Aneurysms, indicate that surgical and endovascular treatments are rarely justified in small aneurysms. However, we have encountered several cases of rupture of small and very small aneurysms in our clinical practice. This retrospective study analyzed the incidence and clinical characteristics of very small ruptured aneurysms.

Materials and Methods

A total of 200 patients with aneurysmal subarachnoid hemorrhage between January 2012 and December 2014 were reviewed. Various factors were analyzed, including the aneurysm location and size as well as the associated risk factors.

Results

The mean age of patients was 56.31 ± 13.78 (range, 25-89) years, and the male to female ratio was 1:2.1. There were 94 (47%) small-sized (< 5 mm), 91 (45.5%) medium-sized (5-9.9 mm), and 15 large-sized (> 10 mm) aneurysms. Of these, 30 (15%) aneurysms were very small-sized (< 3 mm). The most frequent site of aneurysms was the anterior communicating artery (ACoA). However, the proportion of aneurysms at the ACoA was significantly high in very small aneurysms (53.3%, p = 0.013). Hypertension was a significant risk factor for rupture of very small aneurysms (p < 0.001).

Conclusion

About half of our cases of ruptured aneurysms involved the rupture of small and very small aneurysms. The most common site of rupture of very small aneurysm was the ACoA. Rupture of small and very small aneurysms is unpredictable, and treatment may be considered in selected high-risk patients according to factors such as young age, ACoA location, and hypertension.

Endovascular and surgical treatment of internal carotid bifurcation aneurysms: comparison of results, outcome, and mid-term follow-up

BACKGROUND

Aneurysms of the internal carotid artery (ICA) bifurcation are rare, and no studies have compared patient outcomes after endovascular vs surgical treatment.

OBJECTIVE

To report the safety, efficacy, and follow-up outcome of these 2 treatment options for patients with ICA bifurcation aneurysms.

METHODS

Patient and aneurysm characteristics, treatment results, and follow-up outcomes (at 30 months) were analyzed from patient records and review of imaging findings.

RESULTS

A total of 58 patients with ICA bifurcation aneurysms were treated. By interdisciplinary consensus, 30 aneurysms were assigned for coiling and 28 for clipping. Patients who underwent surgical clipping were younger and had larger aneurysms. More patients were assigned to coiling if their aneurysms originated only from the ICA bifurcation or projected superiorly. For the combined angiographic endpoint, complete and nearly complete occlusion (Raymond-Roy I + II), similar rates of 96% (coiling) or 100% (clipping) could be achieved. Raymond-Roy I occlusion occurred more often after clipping (79% vs 41% coiling). Follow-up of the endovascular group showed minor recanalization of the aneurysm neck (Raymond-Roy II) in 42%. One patient (4%) showed a major recanalization (Raymond-Roy III) and needed re-treatment. For incidental findings, no bleeding complications or new persistent neurological deficits occurred during follow-up.

CONCLUSION

Treatment of ICA bifurcation aneurysms after interdisciplinary assignment to clipping or coiling is effective and safe. Despite significantly more minor recanalizations after coiling, the re-treatment rate was very low, and no bleeding was observed during follow-up. Multivariate analysis revealed that origin only from the ICA bifurcation was an independent predictor of aneurysm recanalization after endovascular treatment.

Guidelines for the Management of Patients With Unruptured Intracranial Aneurysms: A Guideline for Healthcare Professionals From the American Heart Association/American Stroke Association

PURPOSE

The aim of this updated statement is to provide comprehensive and evidence-based recommendations for management of patients with unruptured intracranial aneurysms.

METHODS

Writing group members used systematic literature reviews from January 1977 up to June 2014. They also reviewed contemporary published evidence-based guidelines, personal files, and published expert opinion to summarize existing evidence, indicate gaps in current knowledge, and when appropriate, formulated recommendations using standard American Heart Association criteria. The guideline underwent extensive peer review, including review by the Stroke Council Leadership and Stroke Scientific Statement Oversight Committees, before consideration and approval by the American Heart Association Science Advisory and Coordinating Committee.

RESULTS

Evidence-based guidelines are presented for the care of patients presenting with unruptured intracranial aneurysms. The guidelines address presentation, natural history, epidemiology, risk factors, screening, diagnosis, imaging and outcomes from surgical and endovascular treatment.

Hypertension predisposes to the formation of saccular intracranial aneurysms in 467 unruptured and 1053 ruptured patients in Eastern Finland

OBJECTIVE

Hypertension associates with subarachnoid hemorrhage from saccular intracranial aneurysm (sIA-SAH) when compared to matched controls or general population. Few series compare hypertension in unruptured sIA versus sIA-SAH, so its impact on the sIA disease remains uncertain.

METHODS

Kuopio sIA Database ( www.uef.fi/ns ) contains all cases of unruptured and ruptured sIAs admitted to Kuopio University Hospital from its Eastern Finnish catchment population. We compared the age-adjusted incidence of drug-treated hypertension in 467 unruptured and 1053 ruptured sIA patients admitted to Kuopio University Hospital from 1995 to 2007, using the national registry of prescribed medicines.

RESULTS

Antihypertensive medication was more frequent in the unruptured (73% versus 62%) with higher age-adjusted incidence. At sIA diagnosis, the sIA-SAH group had more often untreated hypertension (29% versus 23%). The size of unruptured sIAs increased with age at sIA diagnosis, independently of hypertension. Multiple sIAs, familial sIA, and sIA-SAH were not associated with hypertension in multivariate analysis. Results indicate that drug-treated hypertension associates with the formation of sIAs rather than their growth or rupture.

CONCLUSION

Hypertension is highly prevalent in the carriers of unruptured sIAs when compared to those with ruptured sIA. Hypertension may associate with the sIA formation, and may predispose to the rupture of sIA if untreated.