MATERIAL and METHODS: PubMed and the Cochrane Library were searched for English-language studies published up to May 2015. Two independent reviewers screened abstracts, reviewed full-text articles and extracted data. Before conducting the metaanalysis, the studies were evaluated for publication bias and heterogeneity. Fixed and random effect models were used to estimate relative risks (RR) and the corresponding 95% confidence intervals (CIs). Subgroup analysis and sensitivity analysis were also performed.

RESULTS: One randomized controlled trial (RCT) and 33 observational studies of 16,793 participants were included in this paper. The overall methodological quality was satisfying. Results after excluding articles inconsistent with our surgery timing definition showed no significant difference for poor outcome, with early vs intermediate treatment (RR 0.86[0.68,1.09]), early vs late (RR 0.99[0.70,1.40]). Subgroup analysis based on age showed that early surgery could obtain more favorable outcomes for death rate, with non-early group as reference when age ?50 years (RR 0.52[0.29,0.93]). When less than 50 years old, patients could benefit more from early intervention for poor outcome, with intermediate group as reference (RR 0.18[0.04,0.78]).

CONCLUSION: Despite the shortcomings of this study, timing of surgery for aSAH did not put a significant impact on overall surgical outcome. But subgroup analysis indicated a trend with more benefits for early treatment. Given the risks of re-bleeding and inpatient stay, early intervention should be performed as soon as possible. However, more randomized trials with long-term followup are necessary, especially in this era of endovascular coiling. Keywords : Early surgery, Late surgery, Ruptured intracranial aneurysm, Subarachnoid hemorrhage, Timing