The Source for Neurovascular News and Education

July 28, 2021


The study authors plan to develop an international database and calculate risk prediction scores for neurosurgical and endovascular treatment.


A new meta-analysis may help clinicians estimate the risk of procedural complication and death associated with endovascular and neurosurgical treatment for unruptured intracranial aneurysm, and balance that against the risk of rupture. The meta-analysis was published online December 28, 2018, ahead of print in JAMA Neurology. 


“The prevalence of saccular unruptured intracranial aneurysms (UIAs) in the general population is 3%,” write the authors, led by Annemijn M. Algra, MD (University Medical Center Utrecht, the Netherlands). “Owing to the rising availability and quality of brain imaging, the number of incidentally discovered UIAs is increasing. Many UIAs remain asymptomatic, but some rupture, causing subarachnoid hemorrhage (SAH).”


While this subtype of hemorrhagic stroke can have a case-fatality rate as high as 35%, they continue, preventive treatment of unruptured aneurysms carries its own set of risks regardless of whether an endovascular or neurosurgical approach is undertaken.


“Over the last few years, we have developed risk prediction scores to predict the risk of rupture [of unruptured aneurysms],” Algra told Neurovascular Exchange. Similarly, the group wanted to develop scores that would predict the risk of treatment complications with clipping and with endovascular treatment To do so, they needed to first update the reviews on these topics, since the most recent ones are nearly a decade old.


Algra and colleagues conducted a meta-analysis of 114 studies that reported on the clinical complications, case-fatality rate, and associated risk factors linked with undergoing endovascular or neurosurgical treatment of saccular unruptured aneurysms.


The researchers sought to reflect recent advances in endovascular techniques: all the studies included in the analysis were published in 2011-2017 and comprised at least 50 patients treated after January 1, 2000.


Female Sex, Comorbidities, Neck Size


Overall, 106,433 patients with 108,263 aneurysms were included in the analysis. In total, 74 studies evaluated endovascular interventions and 54 evaluated neurosurgical treatment.


For endovascular therapy, the pooled clinical complication risk was 4.96% (95% CI 4.00%-6.12%) and the case-fatality rate was 0.30% (95% CI 0.20%-0.40%). Factors such as sex, comorbidities, and aneurysm neck size were associated with increased risk for complications from endovascular therapy.


Endovascular Therapy Complications


Risk Factor

OR (95% CI)

Female Sex

1.06 (1.01-1.11)*


1.81 (1.05-3.13)


1.76 (1.31-2.37)

Cardiac Comorbidity

2.27 (1.53-3.37)

Wide Aneurysm Neck (> 4 mm or dome-to-neck ratio > 1.5 mm)

1.71 (1.38-2.11]

Posterior Circulation Aneurysm

1.42 (1.15-1.74)

Stent-Assisted Coiling

1.82 (1.16-2.85)


3.43 (1.45-8.09)


*Pooled risk estimate.


Algra pointed out that the increased risk associated with stenting and stent assisted coiling may simply represent the fact that these approaches are typically undertaken for the treatment of more complex aneurysms, rather than any increased risk associated with the procedures themselves.


For neurosurgical treatment, the pooled complication risk was 8.34% (95% CI 6.25%-11.10%), and the case-fatality ratio was 0.10% (95% CI 0-0.20%). Factors associated with complications from neurosurgical therapy included age, sex, cardiovascular comorbidities, and aneurysm-specific details.


Neurosurgery Complications


Risk Factor

OR (95% CI)

Age (Per Year Increase)

1.02 (1.01-1.02)

Female Sex

0.43 (0.32-0.85)


2.14 (1.13-4.06)

Use of Anticoagulation

6.36 (2.55-15.85)


1.95 (1.36-2.79)


1.45 (1.03-2.03)


2.38 (1.54-3.67)

Congestive Heart Failure

2.71 (1.57-4.69)

Posterior Aneurysm Location

7.25 (3.70-14.20)

Aneurysm Calcification

2.89 (1.35-6.18)


“We found the risk of treatment complications for neurosurgical treatment seems to be lower among women than men,” said Algra. “To be honest, I have no clue why that is. It might be selection bias. We don’t know.”


“These data confirm many of our personal experiences with treating unruptured aneurysms,” Jesse Liu, MD (Oregon Health & Science University School of Medicine, Portland), told NVX via email. “These findings can help clinicians guide and counsel patients about the treatment of unruptured aneurysms. By defining specific risk factors, clinicians may be able to modify their treatment plans to provide the best outcomes for patients.”


“This is retrospective and the data are not of very good quality, but now we are able to say that patients who, for example, have wide-neck aneurysms or cardiovascular comorbidities are at higher risk,” echoed Algra. “This is important to take into account when making treatment decisions. Now, these decisions are largely based on the risk of rupture.”


No Consensus on ‘Best’ Therapy


“People tend to want to compare endovascular treatment with neurosurgical clipping, but we should not do it because [the data are] all observational and retrospective,” warned Algra.


Commenting on the findings for NVX, Liu noted a few limitations of the study. “Due to the large data set, it is difficult to provide granular data,” he said. It would be helpful, Liu continued, to know more about the experience level of the interventionalists and to have more information about aneurysm recurrence and need for retreatment.”


He also pointed out that many of the studies predominantly reported anterior circulation aneurysms, which can potentially increase the apparent complication rate of treating posterior circulation aneurysms.


“There is not yet a consensus on the ‘best’ method of treatment for unruptured aneurysms,” concluded Liu. “This review certainly adds to the body of knowledge and will help clinicians provide better preoperative counseling. Ultimately, I believe a very detailed registry could be very helpful to strengthen these data.”


That is Algra’s plan. “The next step is building an international aneurysm database, so we can actually start predicting treatment complications,” she said.





Algra AM, Lindgren A, Vergouwen MDI, et al. Procedural clinical complications, case-fatality risks, and risk factors in endovascular and neurosurgical treatment of unruptured intracranial aneurysms: a systematic review and meta-analysis. JAMA Neurol. 2018;Epub ahead of print.



Algra and Liu report no relevant conflicts of interest.