MicroRNAs in Aneurysmal Subarachnoid Hemorrhage: A Stage-Specific Model Linking Rupture, Vasospasm, and Outcome.

Aneurysmal subarachnoid hemorrhage (aSAH) is a life-threatening cerebrovascular condition characterized by a dynamic clinical course spanning distinct pathophysiological stages, including aneurysm rupture, early brain injury (EBI), delayed cerebral vasospasm, and long-term neurological outcome. Despite extensive research, no clinically applicable molecular biomarkers exist to predict disease trajectory across these stages. MicroRNAs (miRNAs), small non-coding RNA molecules detectable in blood and cerebrospinal fluid (CSF), have emerged as promising candidates due to their stability and close association with vascular, inflammatory, and neuronal processes. However, existing studies have largely evaluated miRNAs in isolation, without integrating findings into a unified temporal framework. This review provides a structured, translational synthesis of miRNA dynamics in aSAH and proposes a stage-specific conceptual model integrating prospective clinical evidence with the broader literature. Dual-biofluid profiling has identified miR-29a, miR-200a-3p, and miR-451a as robust rupture-associated biomarkers, with distinct compartment-specific expression patterns. CSF-based profiling has demonstrated that miR-221-3p, miR-9-3p, and miR-183-5p predict vasospasm within 24 h of hemorrhage, while miR-24 and miR-21-5p correlate with disease severity and poor outcome. Integrating these findings with the broader literature, we categorize miRNA signatures across four stages: rupture discrimination, early brain injury, vasospasm prediction, and outcome stratification. This stage-specific framework highlights the biological continuum linking endothelial injury, vascular dysfunction, and secondary brain damage. The proposed model provides a foundation for multi-marker biomarker development, prospective validation studies, and future precision medicine strategies in aSAH.