Abstract
Background
Unruptured intracranial aneurysms are relatively common lesions in the general population, with a prevalence of 3.2%, and are being diagnosed with greater frequency as non‐invasive techniques for imaging of intracranial vessels have become increasingly available and used. If not treated, an intracranial aneurysm can be catastrophic. Morbidity and mortality in aneurysmal subarachnoid hemorrhage are substantial: in people with subarachnoid hemorrhage, 12% die immediately, more than 30% die within one month, 25% to 50% die within six months, and 30% of survivors remain dependent. However, most intracranial aneurysms do not bleed, and the best treatment approach is still a matter of debate.
Objectives
To assess the risks and benefits of interventions for people with unruptured intracranial aneurysms.
Search methods
We searched CENTRAL (Cochrane Library 2020, Issue 5), MEDLINE Ovid, Embase Ovid, and Latin American and Caribbean Health Science Information database (LILACS). We also searched ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform from inception to 25 May 2020. There were no language restrictions. We contacted experts in the field to identify further studies and unpublished trials.
Selection criteria
Unconfounded, truly randomized trials comparing conservative treatment versus interventional treatments (microsurgical clipping or endovascular coiling) and microsurgical clipping versus endovascular coiling for individuals with unruptured intracranial aneurysms.
Data collection and analysis
Two review authors independently selected trials for inclusion according to the above criteria, assessed trial quality and risk of bias, performed data extraction, and applied the GRADE approach to the evidence. We used an intention‐to‐treat analysis strategy.
Main results
We included two trials in the review: one prospective randomized trial involving 80 participants that compared conservative treatment to endovascular coiling, and one randomized controlled trial involving 136 participants that compared microsurgical clipping to endovascular coiling for unruptured intracranial aneurysms.
There was no difference in outcome events between conservative treatment and endovascular coiling groups.
New perioperative neurological deficits were more common in participants treated surgically (16/65, 24.6%; 15.8% to 36.3%) versus 7/69 (10.1%; 5.0% to 19.5%); odds ratio (OR) 2.87 (95% confidence interval (CI) 1.02 to 8.93; P = 0.038). Hospitalization for more than five days was more common in surgical participants (30/65, 46.2%; 34.6% to 58.1%) versus 6/69 (8.7%; 4.0% to 17.7%); OR 8.85 (95% CI 3.22 to 28.59; P < 0.001). Clinical follow‐up to one year showed 1/48 clipped versus 1/58 coiled participants had died, and 1/48 clipped versus 1/58 coiled participants had become disabled (modified Rankin Scale > 2). All the evidence is of very low quality.
Authors' conclusions
There is currently insufficient good‐quality evidence to support either conservative treatment or interventional treatments (microsurgical clipping or endovascular coiling) for individuals with unruptured intracranial aneurysms. Further randomized trials are required to establish if surgery is a better option than conservative management, and if so, which surgical approach is preferred for which patients. Future studies should include consideration of important characteristics such as participant age, gender, aneurysm size, aneurysm location (anterior circulation and posterior circulation), grade of ischemia (major stroke), and duration of hospitalizations.
Plain language summary
Treatments for unruptured intracranial aneurysms
Background
Intracranial aneurysms are abnormal swellings of blood vessels in the brain. They can be present without causing any symptoms, but a small proportion will eventually cause bleeding, which can cause death or serious disability. Treatment approaches for intracranial aneurysms include conservative management (treat risk factors such as blood pressure), microsurgical clipping (an operation where a clip is placed across the aneurysm), and endovascular coiling (a minor operation where a coil is placed inside the aneurysm to cause it to block). Each approach carries different potential risks and benefits, and at present there is uncertainty about the ideal approach.
Review question
We looked at the effectiveness of performing conservative treatment compared with interventional treatments (microsurgical clipping or endovascular coiling) and microsurgical clipping compared with endovascular coiling for individuals with unruptured intracranial aneurysms.
Date of search
The search is current up to 25 May 2020.
Study characteristics
We included two trials in the review: one randomized trial (a type of study in which participants are assigned to one of two or more treatments groups using a random method) published in 2011 with 80 participants, which assessed conservative treatment with endovascular coiling, and another randomized trial published in 2017 with 136 participants, which assessed microsurgical clipping compared with endovascular coiling for individuals with unruptured intracranial aneurysms.
Key results
The limited evidence available did not show differences in illness at one year for conservative treatment or interventional treatment (endovascular coiling or microsurgical clipping) of unruptured intracranial aneurysms.
Quality of the evidence
We found little evidence on the best treatment for unruptured intracranial aneurysms. The overall quality of the evidence was very low due to the small number of participants as well as to missing outcome data. Further studies with a larger number of participants are needed.
Summary of findings
Background
Description of the condition
Unruptured intracranial aneurysms are relatively common lesions in the general population (Alshekhlee 2010; Sharma 2013). In a population without comorbidity with a mean age of 50 years, the prevalence of unruptured intracranial aneurysms is 3.2%, and is influenced by the presence of polycystic disease, a positive family history, age (higher in people aged 30 years or older), sex (female), and the presence of hypertension (Thompson 2015; Vlak 2011).
If untreated, an intracranial aneurysm can be catastrophic. There is a worldwide subarachnoid hemorrhage incidence of 700,000 person‐years (Hackenberg 2018). A nationwide study in Sweden showed that the 5‐, 10‐, and 15‐year risks of death after subarachnoid hemorrhage were 12.9%, 23.6%, and 35.4%, respectively (Sharma 2013). Morbidity and mortality in aneurysmal subarachnoid hemorrhage are substantial: in people with subarachnoid hemorrhage, 12% die immediately, more than 30% die within one month, 25% to 50% die within six months, and 30% of survivors remain dependent (Rackauskaite 2018). In people with previous subarachnoid hemorrhage, the annual rate of aneurysm formation from a new site is reported to range from 0.2% to 1.8% (Etminan 2016).
Unruptured intracranial aneurysms are being diagnosed with greater frequency as non‐invasive techniques for imaging of intracranial vessels have become increasingly available and used. However, the best treatment is still a matter of debate (Gerlach 2007; Vlak 2011).
With unruptured aneurysms, the decision whether to treat is often unclear. Preventive treatment of intracranial aneurysms carries a risk (fatality and morbidity of up to 5%). Neurosurgical treatment has a higher risk of complications than endovascular treatment, but the risk of rupture after endovascular treatment is slightly higher than after surgery, with annual rupture rates of 0.2%. The risks of treatment must be carefully balanced against the risk of rupture. The mean observed one‐year risk of aneurysm rupture is 1.4%, and the five‐year risk is 3.4%. Variables that can influence aneurysm rupture include age, hypertension, history of subarachnoid hemorrhage, aneurysm size, aneurysm location, and geographical region (North America, Europe (except Finland), Finland, and Japan), and should be take into account before treatment (Greving 2014).
Description of the intervention
The management of unruptured intracranial aneurysms remains controversial. The following three options are available: conservative treatment (observation and treatment of risk factors), microsurgical clipping, and endovascular coiling (Barker 2004). The goal of the last two options is to exclude the aneurysm from the circulation (Regli 1999).
The conservative approach monitors the aneurysm size by performing serial images, angiography, magnetic resonance imaging angiography (angioMRI), or computed tomography angiography (angioCT). Many prognostic factors for aneurysm rupture have been proposed: the Population, Hypertension, Age, Size, Earlier subarachnoid hemorrhage, and Site (PHASES) aneurysm risk score found that age, hypertension, history of subarachnoid hemorrhage, aneurysm size, aneurysm location, and geographical region provide prognostic information. PHASES provides a score based on the presence of these variables and the risk of rupture (Greving 2014).
Microsurgical clipping is a neurosurgical technique that allows direct surgical clipping after a craniotomy is performed. In 1937, Walter Dandy performed the first surgical treatment of an aneurysm using a vascular clip designed by Harvey Cushing (Cowan 2007; Qureshi 2007).
Endovascular coiling is a more recent, less invasive method that allows the aneurysms to be filled with coils, which avoids rupture. It was created in the 1980s when Guglielmi and colleagues formally introduced electrolytic detachable platinum coils into the aneurysm sac. The coil mass protected against rupture by buffering the hemodynamic stress against the fundus of the aneurysm (Cowan 2007; Qureshi 2007).
How the intervention might work
Conservative treatment consists of close observation and risk factor treatment without intervention. It is usually considered in cases where the procedures are judged to have a high risk compared with the natural history of the disease (Gerlach 2007).
Microsurgical clipping is an established operation that can be used to treat intracranial aneurysms, allowing drainage of bleeding in case of aneurysm rupture during the procedure, and avoiding intracranial hypertension. Microsurgical clipping also treats the mass effect of giant aneurysmal sacs in cranial nerves and in the brain parenchyma, and allows for vascular reconstruction in complex aneurysms, keeping vascular branches free. Microsurgical clipping has a higher complete aneurysm occlusion rate and lower aneurysm rupture and vessel sacrifice rate in middle cerebral artery aneurysms (Smith 2015). However, microsurgical clipping is associated with a higher risk of adverse outcomes, such as neurological deficit, cranial nerve palsy, infection, and longer hospital stays (Alshekhlee 2010; Bhatia 2011; Hoh 2009; Johnston 2001; Niskanen 2005).
Endovascular coiling is a newer form of treatment that seeks to reduce the operative risks of intracranial aneurysm treatment. It has the following advantages compared with traditional microsurgery: minimal invasion, decreased procedural and anesthesia time, and multiple, simultaneous treatments at disparate sites. Endovascular coiling causes less blood loss during the procedure, and is usually associated with a shorter hospital stay (Bhatia 2011), and less risk of adverse outcomes (neurological deficit, cranial nerve palsy, infection, severe disability) and in‐hospital death (Alshekhlee 2010; Johnston 2001; Niskanen 2005; Smith 2015). However, endovascular treatment is not without risks. The risk of stroke and intraprocedural rupture are real. The primary disadvantage of endovascular coiling is its durability. As a result, endovascular treatment requires more follow‐up imaging and has increased recurrence rates and a greater need for retreatment. Also, some aneurysms have angioarchitectural features that make them less amenable to endovascular techniques, in particular middle cerebral artery aneurysms. Endovascular coiling does not allow hematomas to be drained in case of aneurysmal rupture, and does not treat mass effect in cranial nerves and brain parenchyma, so the patient may have seizures, cranial nerve palsy, neurological focal deficits, and intracranial hypertension. It is also a more expensive procedure (Hoh 2009; Smith 2015).
Why it is important to do this review
There is uncertainty in the management of unruptured intracranial aneurysms, as morbidity and mortality of therapy must be balanced with the risk of rupture, and it cannot be accurately predicted when an aneurysm will rupture.
Most patients who have undergone preventive treatment (clipping or coiling) of unruptured intracranial aneurysms have done so on the basis of fear of ruptures. However, unruptured intracranial aneurysms are much more frequent than ruptured aneurysms (approximately 1% to 2% of the world population as compared to 0.01%). Because the hemorrhagic risks of unruptured intracranial aneurysms are much lower than the risks of re‐rupture of ruptured aneurysm (1% per year compared to 30% to 50% within the first year), the main question is not whether one treatment option is better than another, but whether any risky preventive treatment is justified (TEAM Trial).
In general, small aneurysms (< 7 mm) are treated conservatively because they have less chance of rupture. However, special attention is required in patients with risk factors (polycystic kidney disease, type IV Ehlers‐Danlos syndrome, Marfan syndrome, cigarette smoking, family history of subarachnoid hemorrhage or aneurysm in more than two relatives, and patients with other aneurysms that have already ruptured in another location) (Thompson 2015).
In aneurysms greater than 7 mm, there is no consensus in the literature about treating unruptured intracranial aneurysms; however, the number of endovascular procedures is increasing, and some showed decreasing adverse events with their use (Johnston 2001). On the other hand, there is some evidence that microsurgical clipping can produce better results in aneurysms of the anterior circulation (Raftopoulos 2003).
There are many different variables in cerebral aneurysms (size, location, presence of calcification, lobulations, branches, comorbidities), and further studies are required to better define which treatment is the best option as well as to better understand the evolution of the disease.
Objectives
To assess the risks and benefits of interventions for people with unruptured intracranial aneurysms.
Methods
Criteria for considering studies for this review
Types of studies
We included randomized controlled trials comparing any of the strategies for managing unruptured intracranial aneurysms.
Types of participants
We included people with unruptured intracranial aneurysms, identified by angiography, magnetic resonance imaging angiography (angioMRI), or computed tomography angiography (angioCT).
Types of interventions
We included trials comparing conservative treatment, microsurgical clipping, and endovascular coiling (conservative treatment versus microsurgical clipping; conservative treatment versus endovascular coiling; and microsurgical clipping versus endovascular coiling).
Types of outcome measures
Where possible, we divided outcomes into short term (up to 30 days) and long term (up to five years).
Primary outcomes
The primary outcome is morbidity recorded using the Glasgow Outcome Scale (GOS) or equivalent scale.
Secondary outcomes
Death
Stroke
Infection rate, short term (0 to 30 days) and long term (30 to 365 days)
Blood loss during the procedure
Length of hospital stay
Procedure‐related costs (if data are available)
Search methods for identification of studies
See the methods for the Cochrane Stroke Group Specialised Register. We searched for trials in all languages and arranged for the translation of relevant articles where necessary.
Electronic searches
We searched the Cochrane Stroke Group Specialised Register (25 May 2020) and the following electronic databases.
Cochrane Central Register of Controlled Trials (CENTRAL; 25 May 2020, Issue 5) in the Cochrane Library (Appendix 1)
MEDLINE Ovid (from 1948 to 25 May 2020) (Appendix 2)
Embase Ovid (from 1980 to to 25 May 2020) (Appendix 3)
Latin American and Caribbean Health Science Information database (LILACS) (from 1982 to to 25 May 2020) (Appendix 4)
We developed the MEDLINE search strategy with the help of the Cochrane Stroke Group Information Specialist and adapted it for the other databases (Appendix 2). We combined all search strategies deployed with subject strategy adaptations of the Highly Sensitive Search Strategy designed by Cochrane for identifying randomized controlled trials and controlled clinical trials as described in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011).
We also searched the following ongoing trials registers.
US National Institutes of Health Ongoing Trials Register ClinicalTrials.gov (www.clinicaltrials.gov/; searched 25 May 2020) (Appendix 5)
World Health Organization International Clinical Trials Registry Platform (WHO ICTRP) (apps.who.int/trialsearch/; searched 25 May 2020) (Appendix 6)
Stroke Trials Registry (www.strokecenter.org/trials); searched 25 May 2020
Searching other resources
In an effort to identify further published, unpublished, and ongoing trials we:
searched the reference lists of identified studies and reviews;
contacted authors and experts in the field;
contacted relevant pharmaceutical companies;
used Science Citation Index Cited Reference Search for forward tracking of important articles.
Data collection and analysis
Selection of studies
Two review authors (FGBP and VV) independently screened the titles and abstracts of the references obtained as a result of the search and excluded obviously irrelevant reports. We retrieved the full‐text articles for the remaining references, and two review authors (FGBP and VV) independently screened the full‐text articles and identified studies for inclusion, and identified and recorded reasons for exclusion of the ineligible studies. Any disagreements were resolved through discussion or by consulting a third review author (JCCBS) if required. We collated multiple reports of the same study so that each study, rather than each reference, was the unit of interest in the review. We recorded the selection process and completed a PRISMA flow diagram.
Data extraction and management
We planned for two review authors (FGBP and VV) to independently extract the following data from the included studies, and record the information on standard data extraction forms.
Participants: sample size, age, sex, number of participants originally allocated to each treatment group, diagnostic criteria used for unruptured intracranial aneurysms, numbers of participants in each intervention group.
Intervention: type of intervention and randomization, type of anesthesia, technique of microsurgical clipping, and technique of endovascular coiling.
Outcomes: number of participants in each group with outcome events, including death and neurological deficits.
Withdrawals and adverse effects.
Length of follow‐up.
Any additional important information.
Any disagreements between review authors were resolved by discussion.
Assessment of risk of bias in included studies
Two review authors (FGBP and VV) independently assessed risk of bias for each study using the criteria outlined in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011). Any disagreements were resolved by discussion or by involving another review author (JCCBS). We assessed risk of bias according to the following domains.
Random sequence generation
Allocation concealment
Blinding of participants and personnel
Blinding of outcome assessment
Incomplete outcome data
Selective outcome reporting
Other bias
We graded the risk of bias for each domain as low, high, or unclear and provided information from the study report together with a justification for our judgement in the 'Risk of bias' tables.
Measures of treatment effect
For dichotomous variables, we calculated the odds ratio (OR) and 95% confidence intervals (CIs). For continuous data, we calculated mean differences (MDs) and 95% CIs between treatment groups if studies reported exactly the same outcomes. If similar outcomes were reported on different scales, we calculated the standardized mean difference (SMD) and 95% CI (Higgins 2021).
Unit of analysis issues
We based the unit of analysis on the individual participant (unit to be randomized for interventions to be compared), that is the number of observations in the analysis should match the number of individuals randomized.
Dealing with missing data
For missing or unavailable data, we contacted the study authors for additional information. If we received no response, irrespective of the type of data, we would report dropout rates in the 'Characteristics of included studies' tables of the review, and use intention‐to‐treat analysis (Higgins 2021).
Assessment of heterogeneity
We used I2 as the measurement of heterogeneity as per Section 10.10.2 of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2021). We considered an I2 > 75% as indicative of substantial heterogeneity. If I2 was greater than 75%, we explored the individual trial characteristics to identify potential sources of heterogeneity, as outlined in Sensitivity analysis.
Assessment of reporting biases
We planned that if we identified 10 or more studies, we would use funnel plots to assess for the potential existence of small‐study bias (Higgins 2021).
Data synthesis
If we considered studies to be sufficiently similar, we would conduct a meta‐analysis by pooling the appropriate data using Review Manager 5 (Review Manager 2020). We would pool data using the fixed‐effect model, and then use the random‐effects model if heterogeneity was significant.
Subgroup analysis and investigation of heterogeneity
We planned that if we identified an adequate number of studies (at least two), we would perform subgroup analyses according to: participants' age (< 40 versus ≥ 40), participants' sex; size of aneurysms (< 7 mm versus ≥ 7 mm); type of circulation (anterior or posterior); and location of aneurysm (carotid artery, anterior cerebral artery, middle cerebral artery, basilar apex, or posterior inferior cerebellar artery).
Sensitivity analysis
We planned that if there was an adequate number of studies (at least two), we would perform sensitivity analyses based on separation of studies according to risk of bias. We did this by excluding the trials most susceptible to bias based on our 'Risk of bias' assessment, that is those with inadequate allocation concealment; high levels of postrandomization losses or exclusions; and uncertain or unblinded outcome assessment (Deeks 2011).
Summary of findings and assessment of the quality of the evidence
We created a 'Summary of findings' table using the following outcomes: morbidity (GOS), death, stroke, infection rate (short term (0 to 30 days) and long term (30 to 365 days)), blood loss during the procedure, length of hospital stay, and procedure‐related costs (if data were available). We used the five GRADE considerations (study limitations, consistency of effect, imprecision, indirectness, and publication bias) to assess the quality of a body of evidence as it relates to the studies that contribute data to the meta‐analyses for the prespecified outcomes (Atkins 2004). We used the methods and recommendations described in Section 8.5 and Chapter 12 of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011), employing GRADEpro GDT software (GRADEpro GDT 2015). We justified all decisions to downgrade the quality of studies in footnotes, and provided comments to aid the reader's understanding of the review where necessary.
Summary of findings and assessment of the certainty of the evidence
We created a 'Summary of findings' table using the following outcomes: morbidity (GOS), death, stroke, infection rate (short term: within 30 days; and long term: greater than 30 to 365 days), blood loss during the procedure, length of hospital stay, and procedure‐related costs (if data were available). We used the five GRADE considerations (study limitations; consistency of effect; imprecision; indirectness; and publication bias) to assess the quality of a body of evidence as it relates to the studies that contribute data to the meta‐analyses for the prespecified outcomes (Atkins 2004). We used methods and recommendations described in Section 8.5 and Chapter 12 of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011) using GRADEproGDT software (GRADEpro GDT 2015). We justified all decisions to downgrade the quality of studies in footnotes, and we provided comments to aid the reader's understanding of the review where necessary.
Results
Description of studies
See: Characteristics of included studies and Characteristics of excluded studies
Results of the search
We identified a total of 16,485 articles; after removal of duplicates, we manually screened 413 records. We identified 412 articles from the search of the Cochrane Stroke Group Specialised Register. The process of study identification and selection is described in Figure 1.
1.
Study flow diagram.
Included studies
We included two trials in the review.
Darsaut 2017 included 136 participants and compared microsurgical clipping and coiling in unruptured aneurysms judged to be treatable using both methods. The primary outcome was treatment failure; secondary outcomes included neurological deficits, hospitalization longer than five days, morbidity and mortality.
TEAM Trial was a prospective randomized trial involving 80 participants, which compared conservative treatment and endovascular coiling. This study was stopped early because of poor recruitment. Outcome events and duration of follow‐up were reported.
Excluded studies
We excluded four studies that did not fulfill our inclusion criteria. None of them were randomized microsurgical clinical trials: Ruan 2015 was a meta‐analysis, whilst Gerlach 2007, Wiebers 2003, and Brilstra 2003 were prospective non‐randomized studies.
Risk of bias in included studies
Both included trials were of very low methodological quality.
TEAM Trial was assessed as having an unclear risk of bias for allocation concealment and detection bias, and a high risk of selection, performance, and attrition bias, as well as bias related to small sample size.
Darsaut 2017 was assessed as having a low risk of bias for random sequence generation, allocation concealment, detection bias, and reporting bias, and a high risk of performance and attrition bias, as well as bias related to small sample size. See Figure 2.
2.
Risk of bias summary: review authors' judgements about each risk of bias item for each included study.
Allocation
TEAM Trial had an asymmetrical allocation of management (2:1 or 3:1 in favor of endovascular coiling).
Darsaut 2017 had a parallel‐group randomization (1:1), which was concealed and generated through a web‐based platform (MedSciNet).
Blinding
The study design and the nature of the intervention and outcomes were such that health workers and participants were not blinded to treatment in either study.
Incomplete outcome data
TEAM Trial had poor recruitment (80 participants) and was therefore assessed as having a high risk of attrition bias.
In Darsaut 2017, of the 66 participants randomized to microsurgical clipping, one was not treated, and data were not available for 17. In the endovascular coiling group, one participant was not treated, and data were not available for 11. Data were analyzed on an intention‐to‐treat basis. Darsaut 2017 reported losses (1.5%) and was therefore assessed as having a high risk of attrition bias.
Selective reporting
Because of poor recruitment, and cultural and bureaucratic hurdles, TEAM Trial was stopped early and published only partial results (outcome events and duration of follow‐up).
In Darsaut 2017, outcome measures (initial failure of aneurysms treatment, intracranial hemorrhage, and residual or recurrent aneurysms) were recorded using computed tomographic angiography (CTA), magnetic resonance angiography (MRI), or digital subtraction angiography (DSA), and the modified Rankin scale for independence. All of the study’s prespecified outcomes and all expected outcomes of interest to the review were reported in the results.
Other potential sources of bias
We assessed possible bias due to the small size of both studies, as small studies have been shown to overestimate treatment effects, allowing critical criteria to be compromised. Studies were considered to be at low risk of bias if they had 200 participants or more per arm, at unclear risk if they had 50 to 200 participants, and at high risk if they had fewer than 50 participants (Dechartres 2013; TEAM Trial). We therefore considered both included studies as at high risk of bias.
Effects of interventions
Summary of findings 1. Microsurgical clipping compared to endovascular coiling for unruptured intracranial aneurysms.
| Microsurgical clipping compared to endovascular coiling for unruptured intracranial aneurysms | ||||||
|
Participants or population: people with unruptured intracranial aneurysms Setting: hospital Intervention: microsurgical clipping Comparison: endovascular coiling | ||||||
| Outcomes | No. of participants (studies) | Quality of the evidence (GRADE) | Comments | |||
| Assumed risk | Corresponding risk | |||||
| Endovascular coiling | Microsurgical clipping | |||||
| Morbidity (GOS) Short term |
7/69 (10.1%) | 16/65 (24.6%) | P = 0.038 | 134 (1 study) |
Very lowa,b,c | This outcome was poorly reported: 1 study reported higher perioperative morbidity in the surgical group. |
| Death | 1/58 (1.7%) | 1/48 (2.0%) | 106 (1 study) |
Very lowa,b,c | This outcome was poorly reported: 1 study reported no difference between groups. | |
| Stroke | 1/58 | 1/48 | P = 1.00 | 104 (1 study) |
Very lowa,b,c | This outcome was poorly reported: 1 study reported no difference between groups. |
| Infection rate Short term (0 to 30 days) |
This outcome was not reported. | Not assessed | ||||
| Infection rate Long term (30 to 365 days) |
This outcome was not reported. | Not assessed | ||||
| Blood loss during the procedure | This outcome was not reported. | Not assessed | ||||
| Length of hospital stay | 6/69 (8.7%) | 30/65 (46.2%) | P < 0.001 | 134 (1 study) |
Very lowa,b,c | This outcome was poorly reported: 1 study reported longer hospitalization in the surgical group. |
| Procedure‐related costs | This outcome was not reported. | Not assessed | ||||
| *The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: confidence interval; GOS: Glasgow Outcome Scale | ||||||
| GRADE Working Group grades of evidence High quality: Further research is very unlikely to change our confidence in the estimate of effect. Moderate quality: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate. Low quality: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate. Very low quality: We are very uncertain about the estimate. | ||||||
aDowngraded one level due to imprecision: one study with a small sample size (Darsaut 2017). bDowngraded one level due to risk of bias: incomplete outcome data. cDowngraded one level due to risk of bias: surgeons and participants not blinded.
Summary of findings 2. Conservative treatment compared with endovascular coiling for unruptured intracranial aneurysms.
| Conservative treatment compared with endovascular coiling for unruptured intracranial aneurysms | ||||||
|
Patient or population: people with unruptured intracranial aneurysms Settings: hospital Intervention: conservative treatment Comparison: endovascular coiling | ||||||
| Outcomes | Illustrative comparative risks* (95% CI) | Relative effect (95% CI) | No. of participants (studies) | Quality of the evidence (GRADE) | Comments | |
| Assumed risk | Corresponding risk | |||||
| Endovascular coiling | Conservative treatment | |||||
| Morbidity (GOS) | 0 | 0 | ‐ | 80 (1 study) |
Very lowa,b,c | No outcome events, but small sample size |
| Death | 0 | 0 | ‐ | 80 (1 study) |
Very lowa,b,c | No outcome events, but small sample size |
| Stroke | 0 | 0 | ‐ | 80 (1 study) |
Very lowa,b,c | No strokes, but small sample size |
| Infection rate Short term (0 to 30 days) |
This outcome was not reported. | Not assessed | ||||
| Infection rate Long term (30 to 365 days) |
This outcome was not reported. | Not assessed | ||||
| Blood loss during the procedure | This outcome was not reported. | Not assessed | ||||
| Length of hospital stay | This outcome was not reported. | Not assessed | ||||
| Procedure‐related costs | This outcome was not reported. | Not assessed | ||||
| *The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: confidence interval; GOS: Glasgow Outcome Scale | ||||||
| GRADE Working Group grades of evidence High quality: Further research is very unlikely to change our confidence in the estimate of effect. Moderate quality: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate. Low quality: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate. Very low quality: We are very uncertain about the estimate. | ||||||
aDowngraded one level due to imprecision: one study with a small sample size (TEAM Trial). bDowngraded one level due to risk of bias: incomplete outcome data. cDowngraded one level due to risk of bias: surgeons and participants not blinded.
Morbidity
Microsurgical clipping versus endovascular coiling
The evidence is very uncertain for morbidity. New perioperative neurological deficits were more common in participants treated surgically (16/65, 24.6%; 15.8% to 36.3%) versus 7/69 (10.1%; 5.0% to 19.5%); odds ratio (OR) 2.87 (95% confidence interval (CI) 1.02 to 8.93; P = 0.038).
Conservative treatment versus endovascular coiling
The evidence is very uncertain for morbidity. There were no outcome events, with no disease or treatment‐related neurological events in either the conservative management or endovascular group.
Death
Microsurgical clipping versus endovascular coiling
The evidence is very uncertain for death. One participant died in each group.
Conservative treatment versus endovascular coiling
The evidence is very uncertain for death. There were no differences between groups for this outcome.
Stroke
Microsurgical clipping versus endovascular coiling
The evidence is very uncertain for stroke. One participant had an intracranial hemorrhage in each group and 1/48 clipped versus 1/58 coiled participants had become disabled (modified Rankin Scale > 2)
Conservative treatment versus endovascular coiling
The evidence is very uncertain for stroke. There were no strokes in either group.
Infection rate
No trial data were provided for this outcome.
Blood loss during the procedure
No trial data were provided for this outcome.
Length of hospital stay
Microsurgical clipping versus endovascular coiling
The evidence is very uncertain for length of hospital stay. Hospitalization for more than five days was more common in surgical participants (30/65, 46.2%; 34.6% to 58.1%) versus 6/69 (8.7%; 4.0% to 17.7%); OR 8.85 (95% CI 3.22 to 28.59; P < 0.001)
Conservative treatment versus endovascular coiling
No trial data were provided for this comparison.
Procedure‐related costs
No trial data were provided for this outcome.
Discussion
Summary of main results
Most studies comparing treatments for unruptured intracranial aneurysms were not randomized. We identified only one prospective randomized trial comparing conservative treatment and endovascular coiling (TEAM Trial), and one completed randomized study comparing microsurgical clipping and endovascular coiling (Darsaut 2017). Data were insufficient to draw any reliable conclusions on the preferred technique.
TEAM Trial found no direct evidence of clinical benefit from either conservative treatment or endovascular coiling; however, this trial was not completed and had poor recruitment and short duration of follow‐up.
Darsaut 2017 found no direct evidence of clinical benefit from either microsurgical clipping or endovascular coiling with simple observation of these lesions. The number of days hospitalized was higher in the microsurgical group than in the endovascular group.
Consequently, there is a need for further randomized trials. The TEAM Trial study showed how difficult is to conduct a randomized clinical trial on this question due to multifactorial problems such as poor recruitment and delays in trial initiation caused by bureaucratic barriers.
Overall completeness and applicability of evidence
The primary outcome of this review, that is morbidity recorded using the Glasgow Outcome Scale (GOS) or equivalent scale, with follow‐up recorded early (up to 30 days) or later (up to five years), was reported by only one study. It is therefore difficult to analyze and draw any reliable conclusions.
Quality of the evidence
Overall, the included studies were of very low methodological quality. The reasons for downgrading the quality of the evidence related to incomplete outcome data, lack of blinding of participants, and very small sample size. We downgraded the quality of the evidence for all outcomes included in Table 1 by three levels, resulting in an assessment of very low‐quality evidence for all outcomes.
Potential biases in the review process
We attempted to avoid bias in the review process by involving two review authors who worked independently at each step of the review and by performing a comprehensive search with no language restrictions.
Agreements and disagreements with other studies or reviews
Most comparable studies and reviews refer to non‐randomized studies. Gerlach 2007 found no direct evidence of clinical benefit from either treatment compared with simple observation of these lesions, causing a dilemma for both patients and physicians. Moreover, in Wiebers 2003, patients with unruptured intracranial aneurysms less than 7 mm in diameter who had no previous subarachnoid hemorrhage had a very low rupture rate (about 0% to 1% per year), and accordingly it would be difficult to improve natural history of these lesions.
Many factors are involved in the decision regarding management of patients with unruptured intracranial aneurysms. It seems that patients younger than 50 years with aneurysms that are 24 mm or less in anterior circulation have the lowest rates of surgical morbidity. On the other hand, patients older than 50 years, especially those with large aneurysms in posterior circulation, have a poor surgical outcome. Regarding number of days hospitalized, endovascular procedures showed short hospitalization, whilst long‐term risk and durability are unknown (Wiebers 2003).
Brilstra 2003 compared quality of life after treatments (microsurgical clipping versus endovascular coiling) and found that, in short‐term surgical treatment of patients with an unruptured aneurysm, there was a considerable impact on functional health and quality of life, whilst for treatment by coil embolization there was not.
We identified another systematic review, which included non‐randomized clinical trials. That meta‐analysis found no difference between microsurgical clipping and endovascular coiling (Ruan 2015).
Authors' conclusions
Implications for practice.
There is currently insufficient evidence from randomized trials of people with unruptured intracranial aneurysms to determine the relative risks and benefits of conservative management, microsurgical clipping, or endovascular coiling. Until such evidence is available, the choice of treatment will depend on other considerations.
Implications for research.
Little is known about the natural history of unruptured intracranial aneurysms and what constitutes best treatment. Further studies, preferably multicenter to obtain a larger sample, are needed to consolidate this evidence.
There is a need for further randomized controlled trials with high methodology quality (i.e. adequate report of randomization, allocation concealment, blinding, etc.), assessing the effects of these patients prospectively in an unconfounded randomized study of the best treatments for unruptured intracranial aneurysms. Future studies should standardize the observation time and stratify participants by age group, gender, grade of aneurysm size and location.
The most important outcomes are the cumulative risk of bleeding and death within 30 days of surgery, and cumulative risk of perioperative death, aneurysmal recurrence, and all strokes. Other important issues that require examination include patient age (e.g. to determine if the elderly fare worse), aneurysm size, aneurysm location (anterior circulation and posterior circulation), grade of ischemia (major stroke), gender (male versus female), and length of hospitalizations.
History
Protocol first published: Issue 4, 2019 Review first published: Issue 5, 2021
Acknowledgements
We acknowledge the support of Hazel Fraser, Cochrane Stroke Group Managing Editor, and Joshua Cheyne, Information Specialist.
Appendices
Appendix 1. CENTRAL search strategy (2020, Issue 5)
ID SearchHits
#1MeSH descriptor: [Aneurysm] this term only
#2MeSH descriptor: [Intracranial Aneurysm] this term only
#3((intracranial or basilar or brain or cerebral$* or berry or saccular) NEAR/5 aneurysm*):ti,ab,kw
#4(unruptured NEAR/3 aneurysm*):ti,ab,kw
#5{OR #1‐#4}
#6MeSH descriptor: [Embolization, Therapeutic] this term only
#7MeSH descriptor: [Endovascular Procedures] this term only
#8MeSH descriptor: [Prostheses and Implants] this term only
#9MeSH descriptor: [Blood Vessel Prosthesis] this term only
#10MeSH descriptor: [Vascular Surgical Procedures] this term only
#11MeSH descriptor: [Blood Vessel Prosthesis Implantation] this term only
#12(coil* or hydrocoil* or Guglielmi*):ti,ab,kw
#13MeSH descriptor: [Neurosurgery] this term only
#14MeSH descriptor: [Neurosurgical Procedures] this term only
#15MeSH descriptor: [Craniotomy] this term only
#16(clip*):ti,ab,kw
#17{OR #6‐#16}
#18#5 AND #17
Appendix 2. MEDLINE search strategy
1. aneurysm/ or intracranial aneurysm/ 2. ((intracranial or basilar or brain or cerebral$ or berry or saccular) adj5 aneurysm$).tw. 3. (unruptured adj3 aneurysm$).tw. 4. or/1‐3 5. Embolization, Therapeutic/ or endovascular procedures/ 6. "prostheses and implants"/ or blood vessel prosthesis/ 7. vascular surgical procedures/ or blood vessel prosthesis implantation/ 8. (coil$ or hydrocoil$ or Guglielmi$).tw. 9. Neurosurgery/ 10. neurosurgical procedures/ or craniotomy/ 11. clip$.tw. 12. or/5‐11 13. 4 and 12 14. Intracranial Aneurysm/su [Surgery] 15. 13 or 14 16. randomized controlled trial.pt. 17. controlled clinical trial.pt. 18. randomized.ab. 19. placebo.ab. 20. randomly.ab. 21. trial.ab. 22. groups.ab. 23. or/16‐22 24. 15 and 23
Appendix 3. Embase search strategy
1. exp carotid artery aneurysm/ or dissecting aneurysm/ or exp intracranial aneurysm/ or saccular aneurysm/ 2. ((intracranial or basilar or brain or cerebral$ or berry or saccular) adj5 aneurysm$).tw.
3. (unruptured adj3 aneurysm$).tw.
4. 1 or 2 or 3
5. artificial embolization/ or arterial embolization/ or balloon embolization/ or coil embolization/
6. endovascular surgery/
7. angioplasty/ or bare metal stenting/ or carotid angioplasty/ or carotid artery stenting/ or laser angioplasty/ or patch angioplasty/ or percutaneous transluminal angioplasty/ or transluminal coronary angioplasty/
8. blood vessel prosthesis/ or endoprosthesis/
9. exp blood vessel transplantation/ or vascular surgery/
10. (coil$ or hydrocoil$ or Guglielmi$).tw.
11. neurosurgery/ or exp cerebrovascular surgery/ or craniotomy/
12. clip$.tw.
13. or/5‐12
14. 4 and 13
15. aneurysm surgery/ or aneurysm clipping/ or endovascular aneurysm repair/ or aneurysm clip/
16. exp intracranial aneurysm/su [Surgery]
17. aneurysm rupture/pc, su [Prevention, Surgery]
18. exp carotid artery aneurysm/su [Surgery]
19. or/15‐18
20. 14 or 19
21. Randomized Controlled Trial/ or "randomized controlled trial (topic)"/
22. Randomization/
23. Controlled clinical trial/ or "controlled clinical trial (topic)"/
24. control group/ or controlled study/
25. clinical trial/ or "clinical trial (topic)"/ or phase 1 clinical trial/ or phase 2 clinical trial/ or phase 3 clinical trial/ or phase 4 clinical trial/
26. Crossover Procedure/
27. Double Blind Procedure/
28. Single Blind Procedure/ or triple blind procedure/
29. placebo/ or placebo effect/
30. (random$ or RCT or RCTs).tw.
31. (controlled adj5 (trial$ or stud$)).tw.
32. (clinical$ adj5 trial$).tw.
33. ((control or treatment or experiment$ or intervention) adj5 (group$ or subject$ or patient$)).tw.
34. (quasi‐random$ or quasi random$ or pseudo‐random$ or pseudo random$).tw.
35. ((control or experiment$ or conservative) adj5 (treatment or therapy or procedure or manage$)).tw.
36. ((singl$ or doubl$ or tripl$ or trebl$) adj5 (blind$ or mask$)).tw.
37. (cross‐over or cross over or crossover).tw.
38. (placebo$ or sham).tw.
39. trial.ti.
40. (assign$ or allocat$).tw.
41. controls.tw.
42. or/21‐41
43. 20 and 42
Appendix 4. LILACS search satrategy
#1 MH: Intracranial Aneurysm Sinonimos ‐ Aneurysms, Intracranial OR Intracranial Aneurysms OR Aneurysm, Intracranial OR Aneurysm, Anterior Communicating Artery OR Anterior Communicating Artery Aneurysm OR Aneurysm, Basilar Artery OR Aneurysms, Basilar Artery OR Artery Aneurysm, Basilar OR Artery Aneurysms, Basilar OR Basilar Artery Aneurysms OR Basilar Artery Aneurysm OR Aneurysm, Middle Cerebral Artery OR Middle Cerebral Artery Aneurysm OR Aneurysm, Posterior Cerebral Artery OR Posterior Cerebral Artery Aneurysm OR Berry Aneurysm OR Aneurysm, Berry OR Aneurysms, Berry OR Berry Aneurysms OR Brain Aneurysm OR Aneurysm, Brain OR Aneurysms, Brain OR Brain Aneurysms OR Cerebral Aneurysm OR Aneurysms, Cerebral OR Cerebral Aneurysms OR Aneurysm, Cerebral OR Giant Intracranial Aneurysm OR Aneurysm, Giant Intracranial OR Aneurysms, Giant Intracranial OR Giant Intracranial Aneurysms OR Intracranial Aneurysm, Giant OR Intracranial Aneurysms, Giant OR Mycotic Aneurysm, Intracranial OR Aneurysm, Intracranial Mycotic OR Aneurysms, Intracranial Mycotic OR Intracranial Mycotic Aneurysm OR Intracranial Mycotic Aneurysms OR Mycotic Aneurysms, Intracranial OR Aneurysm, Anterior Cerebral Artery OR Anterior Cerebral Artery Aneurysm OR Aneurysm, Posterior Communicating Artery OR Posterior Communicating Artery Aneurysm
#2MH: microsurgery
#3MH: Embolization, Therapeutic Sinonimo – Embolotherapy OR Embolotherapies OR Therapeutic Embolization OR Embolizations, Therapeutic OR Therapeutic Embolizations
Appendix 5. ClinicalTrials.gov
US National Institutes of Health Ongoing Trials Register ClinicalTrials.gov (www.clinicaltrials.gov; searched 25 May 2020)
INFLECT EXACT "Interventional" [STUDY‐TYPES] AND Intracranial Aneurysm [DISEASE]
Appendix 6. WHO ICTRP
World Health Organization International Clinical Trials Registry Platform (apps.who.int/trialsearch)
Basic search: intracranial aneurysm
Phases are: all
Characteristics of studies
Characteristics of included studies [ordered by study ID]
Darsaut 2017.
| Study characteristics | ||
| Methods | Randomized clinical trial Multicenter 12 months follow‐up |
|
| Participants | 136 participants with unruptured intracranial aneurysms, 18 years and older if they have more than years of life expectancy | |
| Interventions | Surgical clipping Endovascular coiling |
|
| Outcomes | Primary: treatment failure Secondary: overall morbidity (mRS > 2), new perioperative (30 days) neurological deficits, perioperative morbidity (mRS), peri‐treatment hospitalization lasting > 5 days |
|
| Funding source | Funded by the CIHR (MOP 119554) and sponsored by the Centre Hospitalier de l'Universitè de Montreal | |
| Notes | No data available for 17 participants in the surgical clipping group and 11 participants in the endovascular coiling group | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Low risk | Participants were randomized by computer. |
| Allocation concealment (selection bias) | Low risk | Randomization was concealed, generated through a web‐based platform (MedSciNet). |
| Blinding of participants and personnel (performance bias) All outcomes | High risk | Not possible because of the nature of the study |
| Blinding of outcome assessment (detection bias) All outcomes | Low risk | Blinded data were examined by the Data Safety Monitoring Committee. |
| Incomplete outcome data (attrition bias) All outcomes | High risk | No data available for 17 participants in the surgical clipping group and 11 participants in the endovascular coiling group |
| Selective reporting (reporting bias) | Low risk | Data on prespecified primary and secondary outcomes are presented. |
| Other bias | High risk | Size: sample size less than 100 per treatment arm |
TEAM Trial.
| Study characteristics | ||
| Methods | Randomized clinical trial Multicenter 14 months follow‐up |
|
| Participants | 80 participants with unruptured intracranial aneurysms | |
| Interventions | Conservative treatment and endovascular coiling | |
| Outcomes | Outcome events | |
| Funding source | CIHR; UK National Institute for Health Research (NIHR) Health Technology Assessment Panel (HTA) and NINDs | |
| Notes | Non‐completed trial | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | High risk | Physicians were reluctant to question the merit of their interventions, and there was asymmetrical allocation (2:1). |
| Allocation concealment (selection bias) | Unclear risk | Not reported |
| Blinding of participants and personnel (performance bias) All outcomes | High risk | Not possible because of the nature of the study |
| Blinding of outcome assessment (detection bias) All outcomes | Unclear risk | Not reported |
| Incomplete outcome data (attrition bias) All outcomes | High risk | Poor recruitment of participants |
| Selective reporting (reporting bias) | Unclear risk | Limited information reported |
| Other bias | High risk | Size: sample size less than 100 per treatment arm |
CIHR: Canadian Institutes of Health Research
mRS: modified Rankin Scale
NINDs: National Institute of Neurological Disorders and Stroke
Characteristics of excluded studies [ordered by study ID]
| Study | Reason for exclusion |
|---|---|
| Brilstra 2003 | Not randomized |
| Gerlach 2007 | Not randomized |
| Ruan 2015 | Not randomized |
| Wiebers 2003 | Not randomized |
Differences between protocol and review
In the protocol our primary outcome was death or dependency; in the review we changed the primary outcome to morbidity (using the Glasgow Outcome Scale or equivalent scale) and made death a secondary outcome. We believed that the separation of these two outcomes allowed us to better compare the treatment options.
Contributions of authors
| Protocol stage: draft the protocol | FGBP, EMKS, JCCBS, and VV |
| Review stage: select which trials to include | FGBP, VV, and EMKS |
| Review stage: extract data from trials | FGBP and VV |
| Review stage: enter data into RevMan | FGBP and VV |
| Review stage: carry out the analysis | FGBP and EMKS |
| Review stage: interpret the analysis | FGBP and EMKS |
| Review stage: draft the final review | FGBP, VV, EMKS, and JCCBS |
| Update stage: update the review | FGBP, VV, EMKS, and JCCBS |
Sources of support
Internal sources
-
No sources of support, Other
none
External sources
-
No sources of support, Other
none
Declarations of interest
Felipe Gomes de Barros Pontes: none known.
Edina Mariko Koga da Silva: none known.
Jose Carlos Costa Baptista‐Silva: none known.
Vladimir Tonello de Vasconcelos: none known.
New
References
References to studies included in this review
Darsaut 2017 {published data only}
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