Comparison of outcomes after direct extracranial-to-intracranial bypass for moyamoya disease and non-moyamoya pathology: A systematic review and meta-analysis

Q: What is the clinical evidence from this study?

Study design: Meta-Analysis. Population: Moyamoya disease and non-moyamoya steno-occlusive cerebrovascular disease (n=1354). Intervention: Direct EC-IC bypass for Moyamoya disease (MMD) vs. Direct EC-IC bypass for non-Moyamoya pathology (N-MMD). Primary outcome: Graft patency (OR 0.81, 95% CI 0.54-1.21).

Q: What does this research mean for the field?

Technical and postoperative outcomes, including graft patency, stroke, intracranial hemorrhage, and hyperperfusion syndrome, do not significantly differ between patients undergoing direct EC-IC bypass for moyamoya disease versus non-moyamoya steno-occlusive diseases. Novelty: ClaimNovelty.SYNTHESIS. Consensus alignment: ConsensusAlignment.NEUTRAL.

Noel F. Manalil; T Buddhavarapu; Kyle Sporn; Joshua M. Lee; Jonathan C. Collard de Beaufort; Hanish Polavarapu; Nickalus R. Khan; Haydn Hoffman

doi:10.1007/s10143-026-04544-y

October 18, 2026Neurosurgical ReviewOpen Access

Comparison of outcomes after direct extracranial-to-intracranial bypass for moyamoya disease and non-moyamoya pathology: A systematic review and meta-analysis

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Key result

Direct EC-IC bypass shows no difference in graft patency between moyamoya and non-moyamoya disease.

OR 0.81
95% CI 0.54-1.21
n=1,354

Why the study?

Outcomes after direct EC-IC bypass for moyamoya disease compared to non-moyamoya steno-occlusive pathologies had not been systematically reviewed or compared in a meta-analysis.

Does direct extracranial-to-intracranial bypass result in different rates of graft patency, postoperative stroke, intracranial hemorrhage, or hyperperfusion syndrome in adults with moyamoya disease compared to non-moyamoya steno-occlusive pathologies?

Key Points

To compare graft patency and postoperative complications following direct extracranial-to-intracranial bypass between patients with moyamoya disease and non-moyamoya steno-occlusive pathologies.
Conducted a systematic review and meta-analysis across PubMed, Embase, Scopus, and Web of Science (PROSPERO CRD420251170971), analyzing 17 studies comprising 1,354 adult patients and 1,451 hemispheres.
Categorized indications into moyamoya disease or syndrome (52.6%) versus non-moyamoya pathologies, primarily intracranial atherosclerotic disease (46.3%) and carotid occlusion (3.1%).
Calculated pooled odds ratios using random-effects models for graft patency, postoperative stroke or transient ischemic attack, intracranial hemorrhage, and hyperperfusion syndrome.
Graft patency did not differ between moyamoya and non-moyamoya groups (OR 0.81, 95% CI 0.54–1.21; I2 = 0%), with a pooled overall graft patency rate of 94.4% (95% CI 87–98).
Postoperative stroke or transient ischemic attack rates showed no significant difference between groups (OR 0.68, 95% CI 0.33–1.41; I2 = 23%; pooled overall rate 5.7%, 95% CI 3.6–8.9).
No significant differences were identified for postoperative intracranial hemorrhage (OR 1.46, 95% CI 0.34–6.26; I2 = 61.4%; pooled rate 5.3%) or hyperperfusion syndrome (OR 1.69, 95% CI 0.67–4.26; I2 = 0; pooled rate 16.2%).

Study Design

Type

Meta-Analysis (n=1,354)

Multicenter

Yes

Structured PICO

Does direct extracranial-to-intracranial bypass result in different rates of graft patency, postoperative stroke, intracranial hemorrhage, or hyperperfusion syndrome in adults with moyamoya disease compared to non-moyamoya steno-occlusive pathologies?

P

Population

1,354 adults (1,451 hemispheres; weighted mean age 49.1 years, 56.7% female) across 17 retrospective studies undergoing direct EC-IC bypass for moyamoya disease/syndrome (52.6%) or non-moyamoya steno-occlusive pathology (46.3% ICAD, 3.1% carotid occlusion), followed for a weighted mean of 498 days.

E

Exposure

Direct extracranial-to-intracranial (EC-IC) bypass for moyamoya disease (MMD) or moyamoya syndrome (MMS) (all donors, recipients, and bypass configurations included)

C

Comparator

Direct extracranial-to-intracranial (EC-IC) bypass for non-moyamoya disease (N-MMD) steno-occlusive pathologies, primarily intracranial atherosclerotic disease (ICAD) and extracranial carotid occlusion (CO)

O

Outcome

Graft patency (recorded according to the imaging modality used in each study), postoperative stroke or transient ischemic attack (TIA), postoperative intracranial hemorrhage (ICH), and postoperative hyperperfusion syndrome (HPS) at a weighted mean follow-up of 498 dayshard clinical

Main Result

Odds Ratio: 0.81 (95% CI 0.54–1.21)

Limitations

All included studies were retrospective with self-reported outcomes, introducing potential selection bias and confounding
Indications for EC-IC bypass differed between cohorts, and detailed preoperative radiographic data (e.g., Suzuki grade, occlusion locations) were often unspecified
Small total number of included studies (17), with individual outcomes reported in even fewer studies, limiting statistical power and generalizability
Variable follow-up durations and inconsistent outcome definitions and imaging modalities across studies
Several studies failed to specify the exact EC-IC bypass configuration (e.g., double-barrel vs. single-donor/single-recipient)
Study period (2005–2025) spanned the publication of COSS and CMOSS trials, which may have altered surgical indications over time
All included studies were retrospective with self-reported outcomes, introducing potential selection bias, confounding, and inconsistent data quality
Only 17 studies were included, and many outcomes were reported in an even smaller subset of studies, limiting statistical power and generalizability
Detailed preoperative radiographic data (such as Suzuki grade or intracranial occlusion locations) and exact bypass configurations were not specified in many studies
Follow-up durations were variable and certain outcomes were defined differently across studies
The study period (2005–2025) spanned the publication of major trials (COSS and CMOSS), which may have altered indications for bypass in non-moyamoya patients

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Implication

This systematic review and meta-analysis demonstrates that technical graft patency and postoperative complication rates (stroke, intracranial hemorrhage, and hyperperfusion syndrome) following direct EC-IC bypass are comparable between patients with moyamoya disease and those with non-moyamoya steno-occlusive diseases.

Abstract

Background Extracranial-intracranial (EC-IC) bypass is an established technique to augment intracranial flow in patients with moyamoya disease (MMD) and other steno-occlusive diseases. The outcomes after direct EC-IC bypass for MMD compared to non-MMD pathologies (N-MMD) have not been systematically reviewed or compared in a meta-analysis. Methods We performed a systematic review and meta‑analysis of studies reporting on outcomes in adults undergoing EC-IC bypass stratified by indication. Patients were assigned to either MMD or N-MMD pathologies with the latter primarily consisting of intracranial atherosclerotic disease (ICAD) and extracranial carotid occlusion (CO). Outcomes included graft patency, postoperative stroke or intracranial hemorrhage (ICH), and hyperperfusion syndrome (HPS). Random effects models were used to obtain pooled estimates for each outcome. Results Seventeen studies met inclusion criteria comprising 1,354 patients and 1,451 hemispheres. The weighted mean age was 49.1 years and 56.7% of patients were female. The indications for bypass included MMD or MMS in 52.6% of patients. ICAD and CO comprised 46.3% and 3.1% of patients, respectively. There was no difference in graft patency rates for the MMD and N-MMD groups (OR 0.81, 95% CI 0.54–1.21; I 2 = 0%). There was also no difference in postoperative stroke (OR 0.68, 95% CI 0.33–1.41; I 2 = 23%) or ICH (OR 1.46, 95% CI 0.34–6.26; I 2 = 61.4%). There was no significant difference in the rate of HPS between the N-MMD and MMD groups (OR 1.69, 95% CI 0.67–4.26; I 2 = 0). Conclusion This meta-analysis suggests that technical and postoperative outcomes are similar whether direct EC-IC bypass is performed for moyamoya or non-moyamoya steno-occlusive diseases. Further research with large multicenter cohorts, standardized techniques, and consistent outcome reporting is required to confirm these results.

Discussion

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Cite This Study

Manalil et al. (2026) conducted a meta-analysis in Moyamoya disease and non-moyamoya steno-occlusive cerebrovascular disease (n=1,354). Direct EC-IC bypass for Moyamoya disease (MMD) vs. Direct EC-IC bypass for non-Moyamoya pathology (N-MMD) was evaluated on Graft patency (OR 0.81, 95% CI 0.54-1.21). Direct EC-IC bypass for moyamoya disease showed no significant difference in graft patency compared to non-moyamoya steno-occlusive disease (OR 0.81, 95% CI 0.54–1.21).

synapsesocial.com/papers/6aee6b6871a75948062208b4 https://doi.org/10.1007/s10143-026-04544-y

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Comparison of outcomes after direct extracranial-to-intracranial bypass for moyamoya disease and non-moyamoya pathology: A systematic review and meta-analysis

Key Points

Study Design

Structured PICO

Main Result

Limitations

Ask about this paper

Implication

Abstract

Discussion

Cite This Study

Comparison of outcomes after direct extracranial-to-intracranial bypass for moyamoya disease and non-moyamoya pathology: A systematic review and meta-analysis

Key Points

Study Design

Structured PICO

Main Result

Limitations

Ask about this paper

Implication

Abstract

Discussion

Cite This Study

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