Extracranial-intracranial bypass surgery for occlusive atherosclerotic disease of the anterior cerebral circulation: protocol for a systematic review and meta-analysis
Systematic Reviews volume 9, Article number: 70 (2020)
Occlusive atherosclerotic disease of the anterior cerebral circulation is one of the most common causes of anterior circulation ischemia and stroke. Treatment options include medical therapies (including antiplatelet use, blood pressure control, lipid reduction, and lifestyle modification) and extracranial-intracranial bypass surgery (such as superficial temporal artery-middle cerebral artery bypass). However, the optimal treatment remains unclear. The objective of this study will be to compare the efficacy of and extracranial-intracranial bypass surgery with that of other medical therapy in adult patients with occlusive atherosclerotic disease of the anterior cerebral circulation.
This is the study protocol for a systematic review. We will search MEDLINE, EMBASE, Web of Science, and the Cochrane Library (from January 1980 onwards). We will include randomized controlled trials, quasi-experimental studies (non-randomized, interrupted time series), and observational studies (e.g., cohort studies and case-control studies), examining the efficacy of extracranial-intracranial bypass surgery compared to other treatments for adult patients with occlusive atherosclerotic disease of anterior cerebral circulation. Two team members will independently screen all citations, full-text articles, and abstract data. Potential conflicts will be resolved through discussion. The primary outcome will include stroke or death. The secondary outcomes will include intracranial hemorrhage, transient ischemic attack, and myocardial infarction. The study methodological quality (or bias) will be appraised using appropriate tools. If feasible, we will conduct random effects meta-analysis. Additional analyses will be conducted to explore the potential sources of heterogeneity (e.g., study design, geographical location, or risk of bias).
This review will evaluate the evidence on the efficacy of extracranial-intracranial bypass surgery for adult patients with occlusive atherosclerotic disease of the anterior cerebral circulation. We anticipate that our findings will be of interest to patients, their families, caregivers, healthcare professionals, and in making optimal treatment selection. Implications for future clinical and epidemiological research will be discussed.
Systematic review registration
Stroke is a significant global health burden cause [1,2,3]. Nearly 20% of patients with anterior circulation ischemia may have carotid artery occlusion [4,5,6]. This disease could also increase the risk of death among middle-aged and older patients . Atherosclerotic arterial occlusion could be attributed to several risk factors, including hypertension , diabetes [8,9,10], dyslipidemia [8, 11], smoking [8, 9, 12], homocysteine , chronic reactive protein (CRP) , sex , and race [15, 16]. Predominant symptoms and signs may be variable. Visual, motor, and sensory deficits are the most common symptoms . Impaired cerebral hemodynamics due to occlusive cerebrovascular lesion may increase the risk of subsequent strokes [5, 17]. Furthermore, patients with increased oxygen extraction fraction (OEF) had higher risk of future symptom onset than patients with normal OEF .
The best medical therapy (BMT) could reduce the risk of vascular events through the use of synthetic drugs involving blood pressure control, anti-antiplatelet aggregation, and hyperlipidemia management, as well as through lifestyle modification [2, 19, 20]. BMT focuses on the continuous and long-term use of synthetic drugs to prevent future stroke [2, 21]. However, some of these patients, especially those who are hemodynamically compromised, showed unsatisfactory outcomes after receiving BMT . It has been reported that 5 to 8% of these patients may have an ipsilateral ischemic stroke during the first 2 years [5, 23, 24]. At the same time, revascularization by extracranial-intracranial (EC-IC) bypass surgery was firstly performed by Yasargil . It was then utilized to treat occlusive cerebrovascular disease [18, 26]. The bypass surgery is mainly performed by connecting the superficial temporal artery (STA) to the middle cerebral artery (MCA). The surgery could improve regional cerebral blood volume as well as OEF . Therefore, EC-IC bypass surgery may be effective in stroke prevention [22, 27,28,29,30], but was hypothesized to benefit only hemodynamically compromised patients [17, 21]. In addition, a high risk of hemorrhage stroke was observed in the early postoperative period, which may obscure the true benefit of revascularization of the ischemic brain .
The best treatment for occlusive atherosclerotic disease of the anterior cerebral circulation remains controversial. Firstly, the medical treatment provided in these patients had unsatisfactory outcomes, and the EC/IC Bypass Study reported disappointing results of the bypass surgery . Secondly, it was hypothesized that bypass surgery would be more suitable for hemodynamically compromised patients . However, two subsequent randomized controlled trials (RCTs), including the Japanese EC-IC bypass trial (JET)  and Carotid and Middle cerebral artery Occlusion Surgery Study (CMOSS) [34, 35] did not show that bypass surgery was superior to BMT in terms of stroke prevention. Therefore, whether bypass surgery is superior to medical therapy remains unknown. To our knowledge, only one systemic review and meta-analysis comparing the two treatment modalities were published in 2010,  and several important clinical studies have been published ever since [22, 34, 35, 37, 38].
The objective of this study will be to compare the efficacy of and extracranial-intracranial bypass surgery with that of other medical therapy in adult patients with occlusive atherosclerotic disease of the anterior cerebral circulation.
The present protocol has been registered within the PROSPERO database (registration number CRD42018105513) and is being reported in accordance with the reporting guidance provided in the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocols (PRISMA-P) statement  (see checklist in Additional file 1). This systematic review will be conducted using the methodological guidance in the Cochrane Handbook for Systematic Reviews of Interventions . Any amendments made to this protocol when conducting the study will be outlined and reported in PROSPERO and the final manuscript
Information sources and search strategy
The primary source of literature will be a structured search of major electronic databases (from January 1980 onwards): PubMed/MEDLINE, EMBASE, Web of Science, and the Cochrane Library. The secondary source of potentially relevant material will be a search of the grey or difficult to locate literature, including clinical trials registers (such as ClinicalTrials.gov). We will perform hand searching of the reference lists of included studies, relevant reviews, national clinical practice guidelines, or other relevant documents. Content experts and authors who are prolific in the field will be contacted. The literature searches will be designed and conducted by the review team which includes two experienced health information specialists. The search will include a broad range of terms and keywords related to “anterior cerebal artery,” “occlusion,” and “bypass surgery.” A draft search strategy for PubMed/MEDLINE is provided in Additional file 2.
The Population, Intervention, Comparison, Outcome (PICO) model will be used in determining the specific criteria for selecting studies .
The study participants will include patients aged 18 years or over and experienced ischemic stroke caused by occlusive atherosclerotic disease (verified by angiography) of the anterior cerebral circulation. Moreover, they should include those who underwent EC-IC bypass surgery or received BMT. The location of stenosis should be in the internal carotid artery (ICA) or subsequent branches. Meanwhile, patients with stenosis due to nonatherosclerotic etiologies, including arterial dissection, moyamoya disease, vasculitis disease, radiation-induced vasculopathy, fibromuscular dysplasia, sickle cell disease, neurofibromatosis, suspected vasospastic process, and suspected recanalized embolus, will be excluded .
Type of intervention
We will examine studies investigating EC-IC bypass surgery for atherosclerotic occlusion of the anterior cerebral circulation. The EC-IC bypass must be the primary purpose of the intervention. It includes low-flow bypass such as superficial temporal artery-middle cerebral artery (STA-MCA) bypass and high-flow bypass such as external carotid artery-radial artery-middle cerebral artery (ECA-RA-MCA) bypass.
The following primary and secondary outcomes will be evaluated.
Stroke or death during (1) perioperative period and (2) long-term follow-up (e.g., 1 and 2 years).
Intracranial hemorrhage, transient ischemic attacks, and myocardial infarction (1) during perioperative period and (2) long-term follow-up (e.g., 1 and 2 years)
We will include various types of studies, including RCTs, quasi-experimental studies (e.g., non-randomized trials and interrupted time series), and observational studies (e.g., cohort studies and case-control studies). Observational studies will be included to observe the occurrence of rare complications with a clinical value and to minimize type II error, which is due to lack of statistical power of RCTs . Case series or reports and experimental studies on animals will be excluded.
Data extraction, synthesis and analysis
The EndNote X7 software will be used to manage literature searches. Potentially eligible studies will be identified by two independent authors by reviewing the titles and abstracts. Then, in accordance with the above inclusion criteria, two authors will assess all potentially eligible studies by screening of the full text. Consulting a third review author will be necessary if discrepancies are found. The reasons for excluding the studies from the review will be provided. Information about ongoing trials and duplication will also be provided. The process of selecting relevant studies process will be reported by using a PRISMA flow chart.
Data extraction will be performed by two independent reviewers. A standardized electronic form for data extraction will be used. We will extract all relevant data of interest from the included studies for comparison, such as (1) study and patients’ characteristics, (2) group by intervention type, (3) detailed information of surgery techniques and medical treatment plan, and (4) primary and secondary outcomes with observation time points. If there were disagreements on data extraction between the two reviewers, a team group discussion would be organized for a final decision.
Dichotomous data will be documented as frequencies, while continuous data will be documented as mean value and standard deviation, along with the number of patients in each group. When encountering a necessary outcome that is inaccessible for direct data extraction, we will try to contact the authors by sending an email. If we do not receive a response from the author, a second email will be sent. We will exclude the study if there will be no responses to both emails, and the condition will be documented in the PRISMA flow chart.
Assessment of risk of bias
Two reviewers will independently assess the risk of bias for each study with risk of bias 2.0 tool for RCTs and quasi-experimental studies  and the Newcastle-Ottawa Scale (NOS, Additional file 3) for observational studies at study level [44, 45]. A third reviewer will help resolve any conflict through discussion. We will assess the risk of bias of RCTs and quasi-experimental studies according to the following seven domains:
•Random sequence generation
•Blinding of participants and personnel
•Blinding of outcome assessment
•Incomplete outcome data
•Selective outcome report
•Other possible bias
We will assess the risk of bias of observational studies through three domains including selection, compatibility, and exposure. We will grade the risk of bias as high, low, or unclear for each domain. We will also provide information from the study report together with a justification for our judgment in the “Risk of bias” tables.
Data synthesis and analysis
We will synthetize primary studies to explore heterogeneity descriptively rather than statistically such as structured narratives, summary tables, and measures of treatment effects. Then, a meta-analysis for quantitatively synthesis on one specific result will be performed when at least two suitable studies are included. Since clinical and epidemiological heterogeneity is expected a priori, meta-analyses will be conducted using the random effects model when data are appropriate. The random effects model assumes the treatment effects follow a normal distribution, considering both within-study and between-study variation. The analysis will be conducted using the Review Manager software . When a meta-analysis was not feasible due to an insufficient number of studies, we provided a narrative description of the study results. We will create a “Summary of findings” table using the following outcomes: stroke or death (during perioperative period and long-term follow-up), intracranial hemorrhage, transient ischemic attacks, and myocardial infarction (during perioperative period and long-term follow-up). Continuous outcomes will be expressed as standardized mean difference (SMD) along with its 95% confidence interval (CI). Dichotomous outcomes will be expressed as relative risk (RR) along with its 95% CI. Forest plots will be used to visualize pooled estimates and the extent of heterogeneity among studies. Heterogeneity will be assessed using the I2 test. We will quantify statistical heterogeneity by estimating the variance between studies using I2 statistic. The I2 statistic is the proportion of variation in prevalence estimates that is due to genuine variation in prevalence rather than sampling (random) error. I2 statistic ranges between 0 and 100%, with values of 0–25% and 75–100%, respectively, taken to indicate low and considerable heterogeneity. We will also report Tau2 and Cochran Q test with a P value of < 0.05 considered statistically heterogeneity. When heterogeneity was found, we will conduct a subgroup analysis of the following variables if the data were sufficient, such as study design, geographical location, or risk of bias.
Two independent team members will also examine possible meta-biases, including publication bias, selective outcome reporting, and dual co-authorship [47, 48]. Handling of heterogeneity for meta-analyses and other potential sources of bias will be described.
Confidence in cumulative evidence
The quality of a body of evidence will be evaluated in according to the principle of the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system  through the five considerations (study limitations, consistency of effect, imprecision, indirectness, and publication bias). We will use methods and recommendations described of the Cochrane Handbook for Systematic Reviews of Interventions and the GRADEpro GDT software.
The planned systematic review and meta-analysis may shed light on the strategy selection when treating patients with occlusive atherosclerotic disease of the anterior cerebral circulation, especially those who are hemodynamically compromised. As many recent studies recommended that bypass surgery may only be suitable for patients with impaired cerebral hemodynamics, an update of clinical evidence of comparing the two modalities is necessary. We anticipate that our findings will be of interest to patients, their families, caregivers, and healthcare professionals in making optimal treatment selection. There are several strengths and limitations of our planned systematic review methods. We will comprehensively evaluate both randomized and epidemiological data characteristics, including detailed information of interventions and primary and secondary outcomes. We hope that we will identify knowledge gaps to be filled by new researches. On this regard, implications for future research will be discussed in the final manuscript. A key challenge is that based on knowledge of the review team, we anticipate identifying studies using different study designs, populations, contexts, and with a variable quality of reporting methods and results. So, we will keep the stringent rules in the assessment of study risk bias and extraction of data to minimize the unfavorable impact on outcomes comparison by observational study inclusion. Results will be disseminated through conference presentations and publication in a peer-reviewed journal.
Availability of data and materials
Data sharing is not applicable to this article as no datasets were generated or analyzed during the current study.
Chronic reactive protein
Oxygen extraction fraction
Best medical therapy
Superficial temporal artery
Middle cerebral artery
Randomized controlled trial
Japanese EC-IC bypass trial
Carotid and Middle cerebral artery Occlusion Surgery Study
International prospective register of systematic reviews
Preferred Reporting Items for Systematic Reviews and Meta-Analyses
Population, Intervention, Comparison, Outcome
Superficial temporal artery-middle cerebral artery
External carotid artery-radial artery-middle cerebral artery
Standardized mean difference
Raggi A, Leonardi M. Burden of brain disorders in Europe in 2017 and comparison with other non-communicable disease groups. Journal of neurology, neurosurgery, and psychiatry 2019 doi: 10.1136/jnnp-2019-320466 [published Online First: 2019/06/19].
Barrett KM, Brott TG. Stroke caused by extracranial disease. Circ Res 2017;120(3):496-501. doi: 10.1161/CIRCRESAHA.117.310138 [published Online First: 2017/02/06].
Saposnik G, Hachinski V. The pathway towards an effective reduction of stroke burden worldwide: teamwork. The Lancet Neurology 2019;18(7):622-623. doi: 10.1016/s1474-4422(19)30198-x [published Online First: 2019/06/17].
Thiele BL, Young JV, Chikos PM, et al. Correlation of arteriographic findings and symptoms in cerebrovascular disease. Neurology 1980;30(10):1041-1046. doi: 10.1212/wnl.30.10.1041 [published Online First: 1980/10/01].
Klijn CJ, Kappelle LJ, Tulleken CA, et al. Symptomatic carotid artery occlusion. a reappraisal of hemodynamic factors. Stroke 1997;28(10):2084-93. [published Online First: 1997/10/28].
Flaherty ML, Flemming KD, McClelland R, et al. Population-based study of symptomatic internal carotid artery occlusion: incidence and long-term follow-up. Stroke 2004;35(8):e349-52. doi: 10.1161/01.STR.0000135024.54608.3f [published Online First: 2004/07/03].
Sex-specific relevance of diabetes to occlusive vascular and other mortality: a collaborative meta-analysis of individual data from 980 793 adults from 68 prospective studies. The lancet Diabetes & endocrinology 2018;6(7):538-46. doi: 10.1016/s2213-8587(18)30079-2 [published Online First: 2018/05/13].
Levine SR, Welch KM. Common carotid artery occlusion. Neurology 1989;39(2 Pt 1):178-86. doi: 10.1212/wnl.39.2.178 [published Online First: 1989/02/01].
Miyazawa N, Akiyama I, Yamagata Z. Analysis of incidence and risk factors for progression in patients with intracranial steno-occlusive lesions by serial magnetic resonance angiography. Clinical neurology and neurosurgery 2007;109(8):680-5. doi: 10.1016/j.clineuro.2007.05.021 [published Online First: 2007/07/13].
Elmore EM, Mosquera A, Weinberger J. The prevalence of asymptomatic intracranial large-vessel occlusive disease: the role of diabetes. Journal of neuroimaging : official journal of the American Society of Neuroimaging 2003;13(3):224-7. [published Online First: 2003/08/02].
Noflatscher M, Schreinlechner M, Sommer P, et al. Influence of traditional cardiovascular risk factors on carotid and femoral atherosclerotic plaque volume as measured by three-dimensional ultrasound. Journal of clinical medicine 2018;8(1) doi: 10.3390/jcm8010032 [published Online First: 2019/01/04].
Calori G, D'Angelo A, Della Valle P, et al. The effect of cigarette-smoking on cardiovascular risk factors: a study of monozygotic twins discordant for smoking. Thrombosis and haemostasis 1996;75(1):14-8. [published Online First: 1996/01/01].
Malinow MR. Plasma homocyst(e)ine and arterial occlusive diseases: a mini-review. Clinical chemistry 1995;41(1):173-6. [published Online First: 1995/01/01].
Descamps-Latscha B, Witko-Sarsat V, Nguyen-Khoa T, et al. Advanced oxidation protein products as risk factors for atherosclerotic cardiovascular events in nondiabetic predialysis patients. American journal of kidney diseases : the official journal of the National Kidney Foundation 2005;45(1):39-47. [published Online First: 2005/02/08].
Elsharawy MA, Alkhadra AH, Fakhary Abdulmohsen M, et al. Impact of atherosclerotic risk factors on the extent of arterial occlusive disease among Arabian patients: a hospital based study. International angiology : a journal of the International Union of Angiology 2009;28(5):367-72. [published Online First: 2009/11/26].
Mak W, Cheng TS, Chan KH, et al. A possible explanation for the racial difference in distribution of large-arterial cerebrovascular disease: ancestral European settlers evolved genetic resistance to atherosclerosis, but confined to the intracranial arteries. Medical hypotheses 2005;65(4):637-48. doi: 10.1016/j.mehy.2005.05.017 [published Online First: 2005/07/12].
Li C, Cao X, Ma Z, et al. Effect of pre-surgery assessments on the prognosis of patients received extracranial-intracranial bypass surgery. Restorative neurology and neuroscience 2018;36(5):593-604. doi: 10.3233/rnn-180848 [published Online First: 2018/07/17].
Vilela MD, Newell DW. Superficial temporal artery to middle cerebral artery bypass: past, present, and future. Neurosurgical focus 2008;24(2):E2. doi: 10.3171/FOC/2008/24/2/E2 [published Online First: 2008/02/16].
Meschia JF, Bushnell C, Boden-Albala B, et al. Guidelines for the primary prevention of stroke: a statement for healthcare professionals from the American Heart Association/American Stroke Association. Stroke 2014;45(12):3754-832. doi: 10.1161/str.0000000000000046 [published Online First: 2014/10/31].
Kernan WN, Ovbiagele B, Black HR, et al. Guidelines for the prevention of stroke in patients with stroke and transient ischemic attack: a guideline for healthcare professionals from the American Heart Association/American Stroke Association. Stroke 2014;45(7):2160-236. doi: 10.1161/str.0000000000000024 [published Online First: 2014/05/03].
Kataoka H, Miyamoto S, Ogasawara K, et al. Results of prospective cohort study on symptomatic cerebrovascular occlusive disease showing mild hemodynamic compromise [Japanese Extracranial-Intracranial Bypass Trial (JET)-2 Study]. Neurologia medico-chirurgica 2015;55(6):460-8. doi: 10.2176/nmc.oa.2014-0424 [published Online First: 2015/06/05].
Muroi C, Khan N, Bellut D, et al. Extracranial-intracranial bypass in atherosclerotic cerebrovascular disease: report of a single centre experience. British journal of neurosurgery 2011;25(3):357-62. doi: 10.3109/02688697.2010.551673 [published Online First: 2011/04/20].
Bozzao L, Fantozzi LM, Bastianello S, et al. Early collateral blood supply and late parenchymal brain damage in patients with middle cerebral artery occlusion. Stroke 1989;20(6):735-40. [published Online First: 1989/06/01].
Pessin MS, Duncan GW, Mohr JP, et al. Clinical and angiographic features of carotid transient ischemic attacks. The New England journal of medicine 1977;296(7):358-62. doi: 10.1056/nejm197702172960703 [published Online First: 1977/02/17].
Yasargil MG, Krayenbuhl HA, Jacobson JH, 2nd. Microneurosurgical arterial reconstruction. Surgery 1970;67(1):221-33. [published Online First: 1970/01/01].
Grubb RL, Jr. Extracranial-intracranial arterial bypass for treatment of occlusion of the internal carotid artery. Current neurology and neuroscience reports 2004;4(1):23-30. [published Online First: 2003/12/20].
Nagata S, Fujii K, Matsushima T, et al. Evaluation of EC-IC bypass for patients with atherosclerotic occlusive cerebrovascular disease: clinical and positron emission tomographic studies. Neurological research 1991;13(4):209-16. [published Online First: 1991/12/01].
Sasoh M, Ogasawara K, Kuroda K, et al. Effects of EC-IC bypass surgery on cognitive impairment in patients with hemodynamic cerebral ischemia. Surgical neurology 2003;59(6):455-60; discussion 60-3. [published Online First: 2003/06/27].
Mendelowitsch A, Taussky P, Rem JA, et al. Clinical outcome of standard extracranial-intracranial bypass surgery in patients with symptomatic atherosclerotic occlusion of the internal carotid artery. Acta neurochirurgica 2004;146(2):95-101. doi: 10.1007/s00701-003-0154-7 [published Online First: 2004/02/14].
Esposito G, Della Pepa GM, Sabatino G, et al. Bilateral flow changes after extracranial-intracranial bypass surgery in a complex setting of multiple brain-feeding arteries occlusion: the role of perfusion studies. British journal of neurosurgery 2015;29(5):723-5. doi: 10.3109/02688697.2015.1023779 [published Online First: 2015/03/27].
Chen X, Lin CL, Su YC, et al. Risk of subsequent stroke, with or without extracranial-intracranial bypass surgery: a nationwide, retrospective, population-based study. Journal of neurosurgery 2018:1-8. doi: 10.3171/2017.12.Jns172178 [published Online First: 2018/07/13].
Group EIBS. Failure of extracranial-intracranial arterial bypass to reduce the risk of ischemic stroke. Results of an international randomized trial. The New England journal of medicine 1985;313(19):1191-200. doi: 10.1056/NEJM198511073131904 [published Online First: 1985/11/07].
Ogasawara K, Ogawa A. [JET study (Japanese EC-IC Bypass Trial)]. Nihon rinsho Japanese journal of clinical medicine 2006;64 Suppl 7:524-7. [published Online First: 2007/04/28].
Powers WJ, Clarke WR, Grubb RL, Jr., et al. Extracranial-intracranial bypass surgery for stroke prevention in hemodynamic cerebral ischemia: the Carotid Occlusion Surgery Study randomized trial. Jama 2011;306(18):1983-92. doi: 10.1001/jama.2011.1610 [published Online First: 2011/11/10].
Grubb RL, Jr., Powers WJ, Clarke WR, et al. Surgical results of the Carotid Occlusion Surgery Study. Journal of neurosurgery 2013;118(1):25-33. doi: 10.3171/2012.9.jns12551 [published Online First: 2012/10/30].
Fluri F, Engelter S, Lyrer P. Extracranial-intracranial arterial bypass surgery for occlusive carotid artery disease. Cochrane Database Syst Rev. 2010;2:CD005953. https://doi.org/10.1002/14651858.CD005953.pub2.
Teo KAC, Ning C, Sein L, et al. Long-term outcome in extracranial-intracranial bypass surgery for severe steno-occlusive disease of intracranial internal carotid or middle cerebral artery. Clinical neurology and neurosurgery 2018;169:149-53. doi: 10.1016/j.clineuro.2018.04.003 [published Online First: 2018/04/21].
Saber H, Rajah G, Palla M, et al. Utilization and safety of extracranial-intracranial bypass surgery in symptomatic steno-occlusive disorders. Brain circulation 2019;5(1):32-35. doi: 10.4103/bc.bc_33_18 [published Online First: 2019/04/20].
Shamseer L. Preferred reporting items for systematic review and meta-analysis protocols (PRISMA-P) 2015: elaboration and explanation (vol 350, g7647, 2015). Bmj-British Medical Journal. 2016;354. https://doi.org/10.1136/bmj.i4086.
GS HJ. Cochrane Handbook for Systematic Reviews of Interventions Version 5.1.0 [updated March 2011]. The Cochrane Collaboration 2011.
Huang X, Lin J, Demner-Fushman D. Evaluation of PICO as a knowledge representation for clinical questions. AMIA Annual Symposium proceedings AMIA Symposium 2006:359-63. [published Online First: 2007/01/24].
Ma Y, Gu Y, Tong X, et al. The Carotid and Middle cerebral artery Occlusion Surgery Study (CMOSS): a study protocol for a randomised controlled trial. Trials 2016;17(1):544. doi: 10.1186/s13063-016-1600-1 [published Online First: 2016/11/18].
E E. Probability of adverse events that have not yet occurred: a statistical reminder. %J BMJ (Clinical research ed.). 1995;7005(311).
Feng Y, Li L, Bai X, et al. Risk factors for new ischaemic cerebral lesions after carotid artery stenting: protocol for a systematic review and meta-analysis. BMJ open 2019;9(8):e030025. doi: 10.1136/bmjopen-2019-030025 [published Online First: 2019/08/26].
Li Z, Wang T, Yang Y, et al. Efficacy of non-invasive ventilation and oxygen therapy on immunocompromised patients with acute hypoxaemic respiratory failure: protocol for a systematic review and meta-analysis of randomised controlled trials. BMJ open 2017;7(6):e015335. doi: 10.1136/bmjopen-2016-015335 [published Online First: 2017/07/02].
Cochrane Collaboration: Review Manager (RevMan) Version 5.3. 2014.
Wang T, Yang K, Luo J, et al. Outcomes after stenting for symptomatic intracranial arterial stenosis: a systematic review and meta-analysis. Journal of neurology 2019 doi: 10.1007/s00415-018-09176-x [published Online First: 2019/01/07].
Prousali E, Mataftsi A, Ziakas N, et al. Interventions to control myopia progression in children: protocol for an overview of systematic reviews and meta-analyses. Syst Rev 2017;6(1):188. doi: 10.1186/s13643-017-0580-x [published Online First: 2017/09/13].
This work was supported by the National Key Research and Development Project (2016YFC1301703). The funder has no role in study design, data analysis, and writing the manuscript.
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Bai, X., Feng, Y., Yang, K. et al. Extracranial-intracranial bypass surgery for occlusive atherosclerotic disease of the anterior cerebral circulation: protocol for a systematic review and meta-analysis. Syst Rev 9, 70 (2020). https://doi.org/10.1186/s13643-020-01325-6