Intracranial aneurysms and delayed cerebral ischemia: Decades of evidence on unexplored event

Background: The current literature reveals a female predominance among delayed cerebral ischemia (DCI) cases and speculates the fluctuations in sex-specific hormones as an explanation for the disparity. We aimed to address the following simple question: Do older females undergoing unruptured aneurysm (UA) treatment have higher chances for DCI? Materials and methods: We conducted a literature search of PubMed, Scopus, and Web of Science from 1980 to 2024. We identified studies on evident DCI in patients who underwent treatment for UA and additionally provided another DCI case following surgery in a patient with a UA. We pooled all evidence and examined sex differences using Bayesian hierarchical models with 4 chains of 4,000 Markov Chain Monte Carlo samples. Results: Of the 5,293 publications identified, 43 were selected for the full-text review. Sixteen case series were eligible for inclusion. Modelled DCI posterior mean odds ratio (OR) was 2.4 (0.4-17.8) and 0.4 (0.1-2.3) for females and males, respectively, with posterior probabilities of 87% and 17%, respectively, for the OR exceeding 1.0. Conclusion: Our findings suggest females have a substantially greater risk for DCI, which suggests a potential impact of sex-specific hormonal variations, further justifying the observed predominance. Furthermore, we suspect that prolonged drying of the exposed vessels contributes to the onset of DCI.