A simple bedside risk score for early prediction of aseptic meningitis after microvascular decompression

Background Aseptic meningitis (AM) is a common complication after microvascular decompression (MVD), without targeted multivariate tools for early prediction. This study developed and internally validated an objective bedside risk score for post-MVD AM. Methods This single-center retrospective cohort included 416 consecutive MVD patients diagnosed via composite AM criteria. Subjective intraoperative assessments (e.g., arachnoid adhesion, vascular calcification) and operator-related variables were excluded from candidate predictors; patients who received glucocorticoids or NSAIDs within 48 hours postoperatively were excluded from the cohort. Firth penalized logistic regression was used to reduce small-sample bias. A 1,000-bootstrap internal validation was conducted, and a beta-coefficient weighted risk score was established. Results AM occurred in 63 patients (15.1%). Four independent predictors were diabetes (OR=15.46, 95%CI 7.76–32.12), postoperative day-1 NLR>3 (OR=4.10, 95%CI 2.08–8.29), operative time>4 hours (OR=4.45, 95%CI 2.25–9.16), and ASA grade≥III (OR=2.47). Male sex was retained as an auxiliary factor (OR=1.99, 95%CI 0.92–4.59, P =0.083). The model had outstanding discrimination (raw AUC=0.877, optimism-corrected AUC=0.868, 95%CI 0.825–0.928) and favorable calibration (slope=0.954, intercept=-0.047, Brier score=0.079). The beta-weighted risk score (0-10 points) stratified patients into low-risk (0-1 point, 2.3%), medium-risk (2 points, 7.1%), and high-risk (≥3 points, 52.9%) groups ( P < 0.001). Conclusion Diabetes, elevated postoperative day-1 NLR, prolonged surgery and ASA grade≥ III are independent AM risk factors, with male sex as an auxiliary indicator. This risk score provides a simple tool for early risk stratification after MVD and requires prospective multicenter external validation.