# Outcomes following intraoperative rupture of cerebral aneurysms during microsurgical clipping: a systematic review and meta-analysis

## TL;DR

This study finds that aneurysm rupture during brain surgery significantly increases the risk of poor outcomes and death, with larger aneurysms posing greater danger.

## Contribution

The study provides a meta-analysis quantifying the impact of intraoperative aneurysm rupture on neurological outcomes and mortality.

## Key findings

- IOR increases the risk of poor neurological outcomes by 67% and mortality by 111%.
- Poor outcomes are more common in larger aneurysms, with rates rising from 15.2% for <7 mm to 81.8% for ≥25 mm.
- MCA and AComA aneurysms show similar poor-outcome rates after IOR.

## Abstract

Background: Intraoperative aneurysm rupture (IOR) during microsurgical clipping remains one of the most feared intraoperative complications, reported in approximately 7–35% of cases. IOR can precipitate abrupt hemodynamic instability, cerebral swelling, and potentially devastating neurological decline, mostly due to blind clipping of poorly seen perforators. This systematic review and meta-analysis aimed to quantify the association between IOR and poor neurological outcome and mortality, and to examine how these outcomes vary by aneurysm size and location. Methods: A comprehensive search of PubMed and Embase identified studies evaluating patients undergoing microsurgical clipping that reported IOR status and postoperative outcomes using the modified Rankin Scale (mRS) or Glasgow Outcome Scale (GOS). 19 studies met the inclusion criteria; thirteen provided comparative data for pooled analysis. Random-effects models were used to estimate pooled risk ratios (RR) for poor outcome (mRS 3–6 or GOS 1–3) and mortality. Pooled proportions of poor neurologic outcome among IOR cases were stratified by aneurysm size and location. Results: IOR was associated with a significantly higher risk of poor outcome (RR 1.67, 95% CI 1.34–2.09; I² = 59.6%; p < .001) and mortality (RR 2.11, 95% CI 1.37–3.25; I² = 42.8%; p < .001). The pooled poor-outcome rate among IOR cases was 36.6% (95% CI 29.0–44.9%). Poor-outcome proportions increased with aneurysm size: <7 mm, 15.2%; 7–12 mm, 29.3%; 13–24 mm, 62.5%; ≥25 mm, 81.8%. MCA and AComA aneurysms demonstrated similar rates (37.4% vs. 36.2%). Conclusions: IOR during microsurgical clipping confers a statistically and clinically significant increase in poor neurological outcomes and mortality. Continued refinement of intraoperative strategies and preventive techniques remains essential to mitigate IOR risk and improve patient prognosis.

The online version contains supplementary material available at 10.1007/s10143-026-04221-0.