Risk factors for nosocomial meningitis in patients with external ventricular drainages

External ventricular drain (EVD)-associated infections are a significant cause of morbidity and mortality. Nosocomial meningitis (NM) poses diagnostic challenges, and its prognosis heavily relies on the timely initiation of treatment. The aim of this study was to investigate the epidemiology of NM and risk factors in ICU patients. We conducted a retrospective single-center cohort study of adult patients who received an EVD in a French ICU between 2018 and 2022. Patients were classified into those with NM or without meningitis based on biological and microbiological criteria. We assessed risk factors related to the patient, the device, and the primary pathology, treatment regimens, length of stay, and survival. Of 275 patients with EVD, 32 (11.6%) developed NM. Patients with meningitis had longer ICU stays (median 42.5 vs. 29 days; p = 0.019), though in-hospital mortality was similar between groups (29.5% vs. 21.9%; p = 0.668). A pathogen was identified in 75% of episodes. Significant risk factors associated with NM included CSF leakage at the insertion site (OR 3.47; 95% CI, 1.53–7.86; p = 0.002), longer drainage duration (OR 1.07 per day; 95% CI, 1.04–1.12; p < 0.001), β-lactam allergy (OR 6.83; 95% CI, 1.73–26.92; p = 0.002), and a cytochemical profile consistent with infection (leukocytes > 100/mm 3 , CSF-to-serum glucose ratio < 0.5, and protein > 1 g/) in the cerebrospinal fluid (OR 3.87; 95% CI 1.67–8.97; p < 0.001). We proposed a predictive model derived from these identified factors with an AUC-ROC curve of 0.89 (95% CI, 0.83–0.94) with a negative predictive value of 96.8%. Key risk factors included β-lactam allergy, CSF leakage, prolonged drainage, and cerebrospinal biological profile. This predictive model, derived from these factors, could be used for the early detection and treatment of NM.