The venous angle as an anatomical landmark to evaluate external ventricular catheter placement

Abstract

Background

External ventricular drain (EVD) placement is a lifesaving procedure that accesses the ventricular system. It is typically performed freehand using external craniometric landmarks. Herein, we study the utility of digital subtraction angiograms (DSA) in determining the EVD location by comparing it to the deep venous system.

Methods

A retrospective review was conducted at a single center from 2021 to 2024 to identify patients with EVD placement for communicating hydrocephalus secondary to a subarachnoid hemorrhage. Two independent reviewers assessed placement using Fargen's grade and a novel grading system. We analyzed inter-reviewer reliability.

Results

We included 48 patients (mean age 60.3 ± 12.9) in this study. Most patients presented with a modified Fisher score of 4 (76.6%) and a Hunt-Hess grade of 4 (31.9%). Based on the computed tomography (CT) scan, 33 patients had good placement, 13 had contralateral placement, and two had suboptimal EVD placement. Inter-reviewer reliability between the Fargen CT and novel DSA grading systems demonstrated 85.4% overall agreement and Cohen's κ = 0.66 (95% CI, 0.41–0.90). The novel DSA grading system demonstrated moderate discrimination among the three CT-defined categories (one-vs-all AUCs: suboptimal 0.668, contralateral 0.847, good 0.841; multiclass AUC 0.700).

Conclusion

This feasibility study suggests that EVD placement can efficiently be determined in the endovascular suite by visualizing the catheter's position in relation to the venous angle on DSA. While this may streamline emergency workflows and reduce reliance on immediate CT scans, subsequent verification with CT or magnetic resonance imaging remains essential. Prospective studies are needed to validate accuracy before wider adoption.