Rupture Risk in Small Unruptured Intracranial Aneurysms

Systematic Review and Meta-Analysis

WHAT THIS STUDY DOES

This study examines how often small unruptured intracranial aneurysms rupture when they are managed without treatment.

It brings together data from multiple global studies to provide a clear, evidence-based estimate of rupture risk.

WHY THIS MATTERS

When an aneurysm is found, a key question is:
“What is the risk if we do not treat it?”

Clinical decisions often rely on simplified assumptions about rupture risk.
This study provides a more precise estimate based on observed follow-up data.

WHAT WE FOUND

31 studies, ~13,800 aneurysms
Mean follow-up ~3.7 years

Rupture risk

For every 100 aneurysms ≤10 mm managed conservatively, approximately 1 will rupture over ~4 years (range ~0.8–1.5%)

Additional insights

Results are most applicable to 2–5 mm aneurysms, which made up the majority of included cohorts
Estimates reflect observed follow-up (~3–4 years), not lifetime extrapolation
Overall rupture risk is low, but not zero

Study quality matters

Higher-quality studies: ~1.8% over ~3.9 years
This suggests rupture risk may be underestimated in lower-quality studies

Important context

Results reflect patients selected for conservative management
Risk estimates depend on study quality and follow-up duration

These findings provide a practical, evidence-based way to communicate rupture risk over the time period for which data are available.

📈 KEY FIGURE

HOW THIS STUDY WAS DONE

Systematic review (PROSPERO registered)
4 major databases searched
Random-effects meta-analysis
Heterogeneity assessed (I²)
Meta-regression performed
Sensitivity analyses across size thresholds

Full methods are available in the paper and supplementary materials

WHY THE RESULTS ARE ROBUST

This study includes:

Large pooled dataset
Formal heterogeneity assessment
Outlier and influence analysis
Multiple sensitivity analyses

Results remained consistent across analyses

REPRODUCIBILITY

All data extraction and analysis steps are available in this repository.
To reproduce the analysis:

Load dataset
Run meta-analysis script
Generate figures

REPOSITORY CONTENTS

Extracted study-level dataset
Analysis scripts (R)
Figures and outputs
Supplementary material

REFERENCE

Chandra RV, Maingard J, Slater L-A, Cheung NK, Lai LT, Gall SL, Thrift AG and Phan TG (2022) A Meta-Analysis of Rupture Risk for Intracranial Aneurysms 10 mm or Less in Size Selected for Conservative Management Without Repair.
Frontiers in Neurology.
https://doi.org/10.3389/fneur.2021.743023

Monash Neurointervention