Accuracy of Freehand External Ventricular Drainage Catheter Placement and Technical Insight

Abstract Freehand external ventricular drainage (EVD) remains widely used in emergent settings, but its accuracy and optimal parameters (Kocher's point, trajectory angle, and catheter length) remain variable in neurosurgical practice. We conducted a retrospective study from January to December 2023 that included all patients who required an EVD for hydrocephalus. We excluded pediatric patients with abnormal head shapes. We analyzed Kocher's point, EVD angulation, and EVD length relative to optimal placement (ipsilateral frontal horn). Univariable and multivariable logistic regression were used to identify independent predictors of suboptimal catheter tip position. Receiver operating characteristic (ROC) curve/area under the curve (AUC) and Youden's index identified optimal cut-points for catheter length. We also explored technical factors associated with optimal placement. Sixty-one EVD insertions met the inclusion criteria, out of which 70.5% (43/61) achieved optimal placement. On multivariable logistic regression, only intracranial catheter length independently predicted suboptimal placement (odds ratio [OR]: 13.84/cm; 95% confidence interval [CI]: 2.99–64.01; p = 0.001). Model performance was strong (Nagelkerke's R 2 = 0.552; Hosmer–Lemeshow p = 0.382). EVD length showed excellent discrimination (AUC: 0.867; 95% CI: 0.78–0.94). The Youden cut-point was 6.5 cm (sensitivity, 82%; specificity, 78%); a conservative clinical threshold of 5.5 cm maintained high sensitivity with added safety against over-insertion. Kocher's point combinations of 1 to 1.5 cm anterior to the coronal suture and 3 to 3.5 cm lateral to the midline were most frequently associated with optimal placement but were not statistically significant. Freehand frontal EVD insertion achieved accuracy within ranges reported for neuronavigated techniques, provided Kocher's point, trajectory, and catheter length fall within the specified parameters.