Safety and effectiveness of bolt-mounted versus tunnelled external ventricular drains: A systematic review, meta-analysis and trial-sequential analysis

Background

External ventricular drains (EVDs) are fundamental to neurocritical care, yet substantial procedural heterogeneity persists, particularly regarding bolt-mounted versus tunnelled catheter fixation. The relative safety and effectiveness of these approaches remain unclear, with conflicting data from observational studies and a lack of trial-level evidence.

Objective

To compare bolt-mounted and tunnelled EVDs across accuracy, reoperation, and key safety outcomes using systematic review, meta-analysis, and trial-sequential analysis.

Methods

Following PRISMA guidelines, PubMed, Embase, and CENTRAL databases were searched (November 2025) for randomised or observational studies comparing bolt-mounted with tunnelled EVDs in adults. Two reviewers independently screened studies, extracted data, and assessed risk of bias. Primary outcomes were optimal catheter placement (Kakarla Grade I) and reoperation for EVD-related complications. Secondary outcomes included iatrogenic intracranial haemorrhage (ICH), cerebrospinal fluid (CSF) infection, CSF leak, catheter obstruction or malfunction, accidental discontinuation, and drainage duration. Random-effects meta-analyses were conducted using restricted maximum likelihood estimation. Heterogeneity was quantified, and certainty of evidence was assessed using GRADE. Trial-sequential analysis was performed for reoperation to determine whether available data met required information size thresholds.

Results

Ten studies encompassing 2008 patients (800 bolt-mounted, 1208 tunnelled) were included. Bolt-mounted EVDs demonstrated significantly higher optimal catheter accuracy (RR 1.27; 95% CI: 1.06–1.51; P < 0.01; I² = 29.6 %). Reoperation was numerically lower with bolt-mounted systems (RR 0.51; 95% CI: 0.22–1.36; P = 0.19; I² = 85 %), although trial-sequential analysis showed the cumulative Z-curve crossed the monitoring boundary without reaching the required information size, indicating insufficient evidence for definitive inference. Bolt-mounted EVDs were associated with lower CSF leak risk (RR 0.13; 95% CI: 0.04–0.47; P < 0.01) and reduced catheter obstruction (RR 0.46; 95% CI: 0.25–0.83; P < 0.05). No significant differences were observed in iatrogenic ICH (RR 1.23; 95% CI: 0.54–2.81; P = 0.62), CSF infection (RR 0.88; 95% CI: 0.71–1.09; P = 0.23), accidental discontinuation (RR 0.41; 95% CI: 0.11–1.59; P = 0.20), or drainage duration (MD 0.56 days; 95% CI = -1.02–2.13; P = 0.49).

Conclusions

Bolt-mounted EVDs were associated with higher catheter accuracy, reduced CSF leak, and improved mechanical reliability without increased infection or haemorrhage. Although reoperation may be lower with bolt-mounted systems, current evidence remains underpowered for firm conclusions. These findings challenge historical assumptions regarding tunnelled catheters and may inform context-specific device selection in contemporary neurocritical care.