Liquid Biopsy for Cerebral Aneurysms: Circulating RNA as Diagnostic and Prognostic Tools—A Systematic Review of Current Evidence and Perspectives

Intracranial aneurysms (IAs) are potentially devastating cerebrovascular lesions, and predicting rupture risk remains a major clinical challenge. Conventional radiological and clinical scores offer only partial risk stratification, highlighting the need for complementary approaches. Liquid biopsy represents a promising non-invasive strategy to identify circulating biomarkers that reflect aneurysm biology and instability. We conducted a systematic review according to PRISMA 2020 guidelines, screening PubMed, Scopus, and Web of Science up to August 2025. Forty-eight eligible studies, encompassing 3515 IA patients, evaluated circulating RNA species, including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs) in serum, plasma, blood, or cerebrospinal fluid. Multiple candidates emerged as consistently dysregulated: upregulation of miR-21, miR-126, and miR-200a-3p, and downregulation of miR-143 and let-7b-5p were recurrently observed across independent cohorts. LncRNAs, such as MALAT1 and MIAT, and circRNAs, including circ_0000690 and circ_0021001, demonstrated diagnostic and prognostic potential, with some correlating with rupture status and clinical severity indices. Despite encouraging findings, heterogeneity in study design, sample handling, and analytic methods limits reproducibility. Large-scale, multicenter validation studies are essential to translate these biomarkers into clinical practice.