Long-term outcome of surgically treated unruptured cerebral aneurysms

Transition of intracranial aneurysmal wall enhancement from high to low wall shear stress mediation with size increase: A hemodynamic study based on 7T magnetic resonance imaging

Background

Wall shear stress (WSS) has been proved to be related to the formation, development and rupture of intracranial aneurysms. Aneurysm wall enhancement (AWE) on magnetic resonance imaging (MRI) can be caused by inflammation and have confirmed its relationship with low WSS. High WSS can also result in inflammation but the research of its correlation with AWE is lack because of the focus on large aneurysms limited by 3T MRI in most previous studies.This study aimed to assess the potential association between high or low WSS and AWE in different aneuryms. Especially the relationship between high WSS and AWE in small aneurysm.

Methods

Forty-three unruptured intracranial aneurysms in 42 patients were prospectively included for analysis. 7.0 T MRI was used for imaging. Aneurysm size was measured on three-dimensional time-of-flight (TOF) images. Aneurysm-to-pituitary stalk contrast ratio (CRstalk) was calculated on post-contrast black-blood T1-weighted fast spin echo sequence images. Hemodynamics were assessed by four-dimensional flow MRI.

Results

The small aneurysms group had more positive WSS-CRstalk correlation coefficient distribution (dome: 78.6 %, p = 0.009; body: 50.0 %, p = 0.025), and large group had more negative coefficient distribution (dome: 44.8 %, p = 0.001; body: 69.0 %, p = 0.002). Aneurysm size was positively correlated with the significant OSI-CRstalk correlation coefficient at the dome (p = 0.012) and body (p = 0.010) but negatively correlated with the significant WSS-CRstalk correlation coefficient at the dome (p < 0.001) and body (p = 0.017).

Conclusion

AWE can be mediated by both high and low WSS, and translate from high WSS- to low WSS-mediated pathways as size increase. Additionally, AWE may serve as an indicator of the stage of aneurysm development via different correlations with hemodynamic factors.

Surgical outcomes of patients with unruptured anterior vs. inferior circulation aneurysms: A meta‑analysis

The treatment option for unruptured intracranial aneurysms (UIAs) depends on their natural history-related risk of rupture vs. the risk of surgical management. The present meta-analysis sought to assess the association between the surgical outcomes of anterior and posterior circulation UIAs. The present study investigated the comparative articles involving the surgical treatment of anterior vs. posterior circulation UIAs through electronic databases, including the Cochrane Library, PubMed (1980 to March, 2023), Medline (1980 to March, 2023) and EMBASE (1980 to March, 2023). Quoting all exclusion and inclusion criteria, nine articles finally remained for statistical analysis. The entire number of patients included in these nine articles was 3,253 (2,662 in the anterior and 591 in the posterior circulation UIAs group). The present meta-analysis proposes that the surgical treatment of anterior circulation UIAs is associated with better outcomes compared with the surgical management of posterior circulation UIAs.

Trends in the Age of Patients Treated for Unruptured Intracranial Aneurysms from 1990 to 2020

BACKGROUND

The decision for treatment for unruptured intracranial aneurysms (UIAs) is often difficult. Innovation in endovascular devices have improved the benefit-to-risk profile especially for elderly patients; however, the treatment guidelines from the past decade often recommend conservative management. It is unknown how these changes have affected the overall age of the patients selected for treatment. Herein, we aimed to study potential changes in the average age of the patients that are being treated over time.

METHODS

A systematic search of the literature was performed to identify all studies describing the age of the UIAs that were treated by any modality. Scatter diagrams with trend lines were used to plot the age of the patients treated over time and assess the presence of a potential significant trend via statistical correlation tests.

RESULTS

A total of 280 studies including 83,437 UIAs treated between 1987 and 2021 met all eligibility criteria and were entered in the analysis. Mean age of the patients was 55.5 years, and 70.7% were female. There was a significant increasing trend in the age of the treated patients over time (Spearman r: 0.250; P < 0.001), with a 1-year increase in the average age of the treated patients every 5 years since 1987.

CONCLUSIONS

The present study indicates that based on the treated UIA patient data published in the literature, older UIAs are being treated over time. This trend is likely driven by safer treatments while suggesting that re-evaluation of certain UIA treatment decision scores may be of great interest.

Size-Dependent Distribution of Patient-Specific Hemodynamic Factors in Unruptured Cerebral Aneurysms Using Computational Fluid Dynamics

PURPOSE

To analyze size-dependent hemodynamic factors [velocity, shear rate, blood viscosity, wall shear stress (WSS)] in unruptured cerebral aneurysms using computational fluid dynamics (CFD) based on the measured non-Newtonian model of viscosity.

METHODS

Twenty-one patients with unruptured aneurysms formed the study cohort. Patient-specific geometric models were reconstructed for CFD analyses. Aneurysms were divided into small and large groups based on a cutoff size of 5 mm. For comparison between small and large aneurysms, 5 morphologic variables were measured. Patient-specific non-Newtonian blood viscosity was applied for more detailed CFD simulation. Quantitative and qualitative analyses of velocity, shear rate, blood viscosity, and WSS were conducted to compare small and large aneurysms.

RESULTS

Complex flow patterns were found in large aneurysms. Large aneurysms had a significantly lower shear rate (235 ± 341 s^-1)) than small aneurysms (915 ± 432 s^-1) at peak-systole. Two times higher blood viscosity was observed in large aneurysms compared with small aneurysms. Lower WSS was found in large aneurysms (1.38 ± 1.36 Pa) than in small aneurysms (3.53 ± 1.22 Pa). All the differences in hemodynamic factors between small and large aneurysms were statistically significant.

CONCLUSIONS

Large aneurysms tended to have complex flow patterns, low shear rate, high blood viscosity, and low WSS. The hemodynamic factors that we analyzed might be useful for decision making before surgical treatment of aneurysms.

High WSS or low WSS? Complex interactions of hemodynamics with intracranial aneurysm initiation, growth, and rupture: toward a unifying hypothesis

SUMMARY

Increasing detection of unruptured intracranial aneurysms, catastrophic outcomes from subarachnoid hemorrhage, and risks and cost of treatment necessitate defining objective predictive parameters of aneurysm rupture risk. Image-based computational fluid dynamics models have suggested associations between hemodynamics and intracranial aneurysm rupture, albeit with conflicting findings regarding wall shear stress. We propose that the "high-versus-low wall shear stress" controversy is a manifestation of the complexity of aneurysm pathophysiology, and both high and low wall shear stress can drive intracranial aneurysm growth and rupture. Low wall shear stress and high oscillatory shear index trigger an inflammatory-cell-mediated pathway, which could be associated with the growth and rupture of large, atherosclerotic aneurysm phenotypes, while high wall shear stress combined with a positive wall shear stress gradient trigger a mural-cell-mediated pathway, which could be associated with the growth and rupture of small or secondary bleb aneurysm phenotypes. This hypothesis correlates disparate intracranial aneurysm pathophysiology with the results of computational fluid dynamics in search of more reliable risk predictors.

Endovascular coil embolization of 435 small asymptomatic unruptured intracranial aneurysms: procedural morbidity and patient outcome

BACKGROUND AND PURPOSE

Whether treatment of small asymptomatic aneurysms is appropriate or not remains controversial. We performed a retrospective study on the procedural morbidity and mortality of coil embolization of small asymptomatic unruptured intracranial aneurysms (UIAs) to obtain a more generalized estimate of procedural risk.

MATERIALS AND METHODS

A total of 435 small (maximum diameter < or = 7 mm) asymptomatic UIAs in 370 patients were treated by coil embolization. Aneurysm sizes were determined by using 3D angiograms. We assessed procedure-related morbidity and mortality, immediate postprocedural angiographic results, short-term imaging follow-up results, and clinical outcomes.

RESULTS

Initial aneurysm occlusion was complete in 334 aneurysms, near complete in 78, and incomplete in 22. One internal carotid artery (ICA) aneurysm that ruptured during the procedure was treated with parent artery occlusion. Two hundred wide-neck aneurysms were coiled with the aid of various neck-remodeling techniques. The 44 procedure-related complications were the following: 24 thromboembolisms, 11 coil protrusions or prolapses into the parent vessel, 4 intraprocedural ruptures, 3 device-related complications, and 2 femoral-access complications. We had a total of 44 (10.1%) procedure-related complications with only 1 leading to persistent neurologic deficit. Procedure-related permanent morbidity and mortality were 0.27% (1/370) and 0%, respectively.

CONCLUSIONS

In this series of small unruptured asymptomatic aneurysms, endovascular treatment was achieved with good short-term angiographic outcome and low permanent neurologic impairment. The goal of this study was not to provide a conclusion about treatment guidelines for small UIA but rather to help guide future recommendations by presenting a more generalized estimate of endovascular treatment risk than is currently available.

Treatment strategy for patients with unruptured intracranial aneurysms

The increased sensitivity of neuroimaging techniques has enabled the more frequent diagnosis of unruptured aneurysms. Because the most devastating complication of an unruptured aneurysm is subarachnoid hemorrhage, it has been considered desirable to treat these aneurysms before they rupture. However, the optimal treatment strategy for patients with unruptured aneurysms remains controversial. The management decision requires knowledge of the natural history and an accurate assessment of the risks related to various treatment options. On December 10, 1998 the New England Journal of Medicine published an article by the International Study of Unruptured Intracranial Aneurysms Investigators. The study retrospectively assessed the natural history of unruptured aneurysms in 1449 patients; in addition, treatment-related mortality and morbidity were examined in a prospective cohort of 1172 patients. The major finding was that the rate of rupture for aneurysms smaller than 10 mm in diameter in patients with no history of subarachnoid hemorrhage was 0.05% per year, and that the mortality and morbidity associated with surgery greatly exceeded the risk of rupture in such patients. This report has generated tremendous controversy in the treatment of unruptured aneurysms and has influenced our decision making. The results of this study are critically analyzed and potential flaws presented. To develop recommendations for treatment, the literature was reviewed. The conclusion of this search is that there is insufficient evidence to recommend a standard of management. Therapeutic guidelines are provided, particularly for patients with small incidental aneurysms and no history of subarachnoid hemorrhage.

Functional outcome after repair of unruptured intracranial aneurysms

OBJECT

Repair of unruptured aneurysms is a reasonable course of action if their expected natural history is worse than the predicted risks of treatment. The purpose of this study was to examine the presenting symptoms of unruptured aneurysms and to test the hypothesis that unruptured intracranial aneurysms can be repaired without significant functional worsening. A second hypothesis was also examined--that is, that the experience of the surgeon, the aneurysm size, and the patient age can be used to predict functional outcome.

METHODS

Consecutive patients who underwent repair of an unruptured intracranial aneurysm at a single institution between 1980 and 1998 were studied. Clinical and radiographic data were collected in all patients. Their modified Rankin Scale (mRS) score was determined before treatment (baseline), at 6 weeks, and at 6 months. The primary endpoint for analysis was the mRS score. Four hundred forty-nine aneurysms were repaired in 366 patients by 10 surgeons. The mean size of the primary lesion repaired was 14.6 + 10.4 mm and 27% were judged to be symptomatic. Aneurysm treatment involved either microsurgical clipping (78%), wrapping (4%), trapping with or without bypass (5%), hunterian ligation with or without bypass (9%), or other methods (4%). The mRS scores at 6 weeks were worse than at baseline (p < 0.0001), but there was no significant difference between the baseline and 6-month mRS score. At 6 months, 94% of patients showed no significant functional worsening as a result of treatment. The number of aneurysms treated by a specific surgeon was a strong predictor of better functional outcome (r = 0.99, p = 0.05). Increasing patient age (r = 0.16, p = 0.003) and increasing aneurysm size (r = 0.15, p = 0.004) were predictors of worsened functional outcome.

CONCLUSIONS

Many unruptured aneurysms produce symptoms. Unruptured intracranial aneurysms can be treated without significant permanent functional worsening. The surgeon's experience, aneurysm size, and patient age are predictors of functional outcome.

Unruptured Intracranial Aneurysms: Appraisal of the Literature and Suggested Recommendations for Surgery, Using Evidence-based Medicine Criteria

OBJECTIVE

The literature on unruptured intracranial aneurysms is reviewed, and an attempt is made to stratify it according to the weight of the evidence. Recommendations for surgery are suggested, using evidence-based criteria.

METHODS

A MEDLINE search was performed for 1966 to 1999. The focus was restricted to surgical management rather than other types of management, such as endovascular treatments. Each article was classified as Class I, II, or III according to the weight of the evidence. Some articles, such as literature reviews and data analyses, did not fit this classification and were grouped separately. Recommendations are based on the evidence available.

RESULTS

Forty-five articles were reviewed. Thirteen articles contained information on the natural history, 19 contained data on the risks of surgery, and 2 contained information on both. In addition, 11 contained analyses of costs and benefits. None met the criteria for Class I evidence. Seven articles on the natural history and 7 on the risks of surgery met the criteria for Class II evidence, and 6 and 12, respectively, met those for Class III evidence. The remainder of the articles were analyses or review articles.

CONCLUSION

There is insufficient evidence to recommend a standard of management. As a therapeutic guideline, conservative treatment is recommended for small aneurysms (&lt;10 mm) and asymptomatic nongiant aneurysms in older people, whereas surgery is recommended for larger aneurysms in younger people and symptomatic aneurysms in fit patients. Other recommendations can be justified only as therapeutic options, using evidence-based criteria. Areas for future investigation are discussed.

Embolization of incidental cerebral aneurysms by using the Guglielmi detachable coil system

OBJECT

Guglielmi detachable coil (GDC) technology is a valuable therapeutic alternative to the surgical treatment of ruptured or incidental intracranial aneurysms. The authors describe their technical and clinical experience in the use of the GDC technique in patients who underwent endovascular occlusion for the treatment of incidentally found intracranial aneurysms.

METHODS

One hundred fifteen patients with 120 incidentally found intracranial aneurysms underwent embolization by means of the GDC endovascular technique. Ninety-one patients were females and 24 were males. Patient age ranged from 13 to 80 years. In 64 patients the incidental aneurysms were discovered when unrelated nonneurological conditions signaled the need for angiography or magnetic resonance angiography (Group 1). Twenty patients who presented with incidental aneurysms that were discovered during treatment for an acutely ruptured aneurysm underwent treatment of both types of aneurysm during the acute phase of subarachnoid hemorrhage (SAH) (Group 2). Sixteen patients with incidental aneurysms were treated during the chronic phase of SAH (Group 3). Group 4 included 15 patients who had incidental aneurysms associated with brain tumors or arteriovenous malformations. Angiographic results revealed complete or near-complete occlusion in 109 aneurysms (91%) and incomplete occlusion in five aneurysms (4%). Guglielmi detachable coil embolization was attempted unsuccessfully in six aneurysms (5%). One hundred nine patients (94.8%) remained neurologically intact or unchanged from their initial clinical status. Five patients (4.3%) deteriorated as a result of immediate procedural complications. All these complications occurred in the first 50 patients treated in the series. No clinical complications were observed in the last 65 patients. In one patient, a partially embolized aneurysm ruptured 3 years postprocedure. In Groups 1 and 3, the average length of hospitalization was 3.3 days.

CONCLUSIONS

The evolution of GDC technology has proved to provide safe treatment of incidental aneurysms (a morbidity rate of 0% was achieved in the last 65 patients). The topography of the aneurysm and the clinical condition of the patient did not influence final anatomical or clinical outcomes. The GDC technology also confers a positive economic impact by decreasing hospital length of stay and by eliminating the need for postembolization intensive care.

Mortality and morbidity of surgery for unruptured intracranial aneurysms: a meta-analysis

BACKGROUND AND PURPOSE

Greater availability and improvement of neuroradiological techniques have resulted in more frequent detection of unruptured aneurysms. Because prognosis of subarachnoid hemorrhage is still poor, preventive surgery is increasingly considered as a therapeutic option. Elective surgery requires reliable data on its risks. Therefore, we performed a meta-analysis on the mortality and morbidity of surgery for unruptured intracranial aneurysms.

METHODS

Through Medline and additional searches by hand, we retrieved studies on clipping of unruptured (additional, symptomatic, or incidental) aneurysms published from 1966 through June 1996. Two authors independently extracted data. We used weighted linear regression for data analysis.

RESULTS

We included 61 studies that involved 2460 patients (57% female; mean age, 50 years) and at least 2568 unruptured aneurysms (27% >25 mm, 30% located in the posterior circulation). Mortality was 2.6% (95% confidence interval [CI], 2.0% to 3.3%). Permanent morbidity occurred in 10.9% (95% CI, 9.6% to 12.2%) of patients. Postoperative mortality was significantly lower in more recent years for nongiant aneurysms and aneurysms with an anterior location; the last 2 characteristics were also associated with a significantly lower morbidity.

CONCLUSIONS

In studies published between 1966 and 1996 on clipping of unruptured aneurysms, mortality was 2.6% and morbidity was 10.9%. In calculating the pros and cons of preventive surgery, these proportions should be taken into account.