Aneurysm repair timing after aneurysmal subarachnoid haemorrhage (aSAH) was associated with lower pretreatment rebleeding rates when treatment occurred earlier, but a systematic review found no consistent independent relationship between treatment timing and mortality or functional outcomes.
The findings were drawn from 20 reports involving 11,096 participant records and examined the effect of onset to treatment timing across a range of clinical outcomes.
Researchers conducted a systematic review of studies comparing outcomes across different treatment windows following confirmed aSAH.
Timing categories ranged from less than 6 hours to 15 days or more after symptom onset.
Among the outcomes assessed, the clearest association was observed for pretreatment rebleeding.
The review found that earlier aneurysm securement reduced the opportunity for pretreatment rebleeding, particularly in analyses that included untreated patients or those whose treatment was substantially delayed.
However, comparisons limited to treated cohorts produced inconsistent findings, often due to methodological challenges including survivor bias and confounding by indication.
These factors can occur when patients with more severe disease receive treatment more urgently than those with milder presentations.
Across studies evaluating mortality and functional recovery, the evidence did not demonstrate a reproducible independent benefit of earlier treatment.
Twelve studies provided timing-based mortality analyses, with results varying substantially.
Two studies favoured earlier treatment, three favoured later treatment, four found no difference, and three reported non-significant numerical trends.
Two large observational studies analysed treatment timing as a continuous variable.
One identified a significant U-shaped association between treatment timing and mortality, with the lowest estimated mortality risk occurring at approximately 32.6 hours after onset.
Another reported a similar but non-significant pattern, with a mortality nadir near 12.2 hours.
The authors emphasised that these findings were highly susceptible to confounding and survivor bias and should not be interpreted as evidence supporting treatment delay.
Similarly, no consistent association emerged between treatment timing and functional outcome.
More methodologically robust adjusted analyses generally failed to demonstrate a clear independent effect.
The review also assessed vasospasm, delayed cerebral ischaemia, hydrocephalus, and length of stay.
Across these outcomes, no reproducible independent relationship with treatment timing was identified.
Researchers concluded that the certainty of evidence regarding mortality was very low due to serious risk of bias, inconsistency, and imprecision.
While the observed mortality patterns may generate new research hypotheses, they do not establish an optimal therapeutic window.
The authors stated that current recommendations supporting aneurysm repair as early as feasible remain appropriate.
They called for prospective multicentre studies using continuous time modelling and stronger approaches to address confounding and survivor bias before any changes to clinical practice are considered.
Reference
Fiore TFO et al. Timing of aneurysm repair and clinical outcomes after aneurysmal subarachnoid hemorrhage: a systematic review. J Neurol. 2026;DOI:10.1007/s00415-026-14063-x.
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