Accuracy of Freehand External Ventricular Drainage Catheter Placement and Technical Insight

Abstract

Background

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.

Method

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.

Results

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.

Conclusion

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.

Keywords

clinical audit - CSF - freehand EVD placement - accuracy - Kocher's point

Introduction

External ventricular drainage (EVD) is a standard neurosurgical procedure for short-term cerebrospinal fluid (CSF) diversion and management. It is performed freehand using anatomical landmarks (Kocher's point). Accurate catheter positioning is of the utmost importance to avoid complications, including revisions, increased hospital length of stay, morbidity, and mortality risk.

We typically measure the success of freehand EVD placements by noticing the free flow of CSF from the distal end of the EVD. However, this can be misleadingly reassuring, as the tip of the EVD may enter CSF spaces other than the frontal horn of the lateral ventricle, even when CSF flow is adequate. An ideal EVD should target the foramen of Monro within the ipsilateral frontal horn, avoiding periventricular and intraventricular vascular structures. The right, nondominant side is generally preferred as it does not control language function in 90% of patients.

This audit aims to assess the accuracy of freehand EVD insertion, identify factors leading to EVD misplacement, and discuss methods to improve insertion accuracy.

Methods

Selection and Description of Participants

We conducted a retrospective study from January to December 2023 encompassing all patients who required an EVD for hydrocephalus resulting from subarachnoid hemorrhage (SAH), spontaneous or traumatic intraventricular hemorrhage (IVH), intracerebral bleeding (ICB), or tumor-associated hydrocephalus. We excluded pediatric patients with abnormal head shapes.

This study was performed as a clinical audit and approved by the hospital audit committee. All procedures were performed in accordance with institutional guidelines, and patient consent was waived due to the retrospective audit design.

Data Collection and Measurements

We classified the EVD tip locations ([Fig. 1]) as follows: A: optimal—EVD tip positioned in the ipsilateral frontal horn, without penetrating the basal ganglia; B1: suboptimal—EVD tip in the ipsilateral frontal horn, penetrating the basal ganglia; B2: suboptimal—EVD tip located in the third ventricle; B3: suboptimal—EVD tip in the contralateral frontal horn; B4: suboptimal—EVD tip situated in the cisternal space; and C: wrong—EVD tip within the brain parenchyma.

Fig. 1 Classification of the external ventricular drainage (EVD) tip location. (A) Optimal. EVD tip in the ipsilateral frontal horn, without entering the basal ganglia. (B1) Suboptimal. EVD tip in the ipsilateral frontal horn, entering the basal ganglia. (B2) Suboptimal. EVD tip in the third ventricle. (B3) Suboptimal. EVD tip in the contralateral frontal horn. (B4) Suboptimal. EVD in the cisternal space. (C) Wrong. EVD tip in the brain parenchyma.

Kocher's point coordinates and catheter measurements were performed on computed tomography (CT) using Horos (v3.3.5). EVD tip position was classified as A, B1 to B4, or C by two independent reviewers, who were blinded to clinical data; disagreements were resolved by consensus. Furthermore, we analyzed Kocher's point, the angulation of the EVD, and the EVD length relative to optimal placement. We also discussed techniques to enhance the accuracy of freehand EVD placement based on our experience and current literature.

Statistics

Continuous variables are presented as mean ± standard deviation (SD). Categorical variables are shown as counts (percentages). Univariable associations were tested with χ ²/Fisher's exact and Student's t-test/Wilcoxon rank-sum test as appropriate. Covariates were entered into a multivariable logistic regression. Model performance is reported using Nagelkerke's R ², Hosmer–Lemeshow goodness-of-fit test, and classification accuracy; area under the curve (AUC) assessed discrimination with 95% confidence interval (CI). The optimal cut-point on the receiver operating characteristic (ROC) curve was determined by maximizing Youden's index (sensitivity + specificity − 1).

Results

We identified 69 patients who underwent EVD between January 1 and December 31, 2023. Eight patients were excluded (Keen's point EVD, n = 1; missing post-op CT due to early death, n = 3; dislodged EVD before post-op CT, n = 4). A total of 61 EVD cases were included in the analysis. There were 54 cases (88.52%) of spontaneous bleeding, 8 cases (13.11%) of tumors, 6 cases (9.84%) of infection, and 1 case (1.64%) of trauma. We achieved 70.49% of the optimal EVD location. Other suboptimal locations were B1 (9.84%), B2 (8.2%), and B3 (11.48%).

No EVD was placed in the cisternal space or brain parenchyma, and no EVD misplacement required revision. We have listed the number and percentage of midline shifts, as well as Evan's ratio, for each EVD location ([Table 1]).

Table 1 Basic anatomic characteristics and external ventricular drainage (EVD) placement outcome

EVD tip location	A	B1	B2	B3	B4	C
Midline shift
Midline shift >5 mm	6 (13.95%)	2 (50%)	0	0	/	/
No midline shift	37 (86.05%)	4 (50%)	5 (100%)	7 (100%)	/	/
Evan's ratio
Mean ± standard deviation (SD)	0.31 ± 0.06	0.28 ± 0.03	0.30 ± 0.04	0.27 ± 0.09	/	/
Intracranial catheter length (cm)
Mean ± SD	6.19 ± 0.56	7.48 ± 0.90	7.46 ± 0.70	7.34 ± 0.75	/	/
Kocher's point location (cm)
Midline: mean ± SD	3.11 ± 0.53	3.08 ± 0.84	3.12 ± 0.43	2.74 ± 0.66	/	/
Coronal suture: mean ± SD	1.34 ± 0.76	1.73 ± 1.59	1.50 ± 0.79	1.03 ± 0.17	/	/
EVD angulation (degrees)
Anteroposterior: mean ± SD	89.05 ± 10.18	83.83 ± 7.39	85.60 ± 5.59	83.43 ± 7.74	/	/
Mediolateral: mean ± SD	85.21 ± 5.76	88.67 ± 6.12	84.80 ± 6.46	79.86 ± 8.19	/	/

Note: The total number of EVD is 61.

A: Optimal—EVD tip in the ipsilateral frontal horn, without entering the basal ganglia. B1: Suboptimal—EVD tip in the ipsilateral frontal horn, entering the basal ganglia. B2: Suboptimal—EVD tip in the third ventricle. B3: Suboptimal—EVD tip in the contralateral frontal horn. B4: Suboptimal—EVD tip in the cisternal space. C: Wrong—EVD tip in the brain parenchyma.

Our audit evaluated Kocher's point for optimal location, which was 1 to 1.5 cm from the coronal plane and 3 to 3.5 cm from the sagittal plane. This combination yielded the highest percentage (11.48%) of optimal locations among the other combinations ([Table 2]), though this difference was not statistically significant. We showed that our optimal EVD angulation was approximately 85 to 90 degrees ([Table 1]). In addition, we analyzed 13 cases with accurate Kocher's point placement (1–2 cm from the coronal suture and 3–3.5 cm from the midline in the sagittal plane) to estimate EVD angulation based on surface markings. The trajectories assessed were compared with the ipsilateral medial canthus (IMC)/external auditory meatus (EAM) and the contralateral medial canthus (CMC)/EAM. We found the IMC trajectory to be an unreliable guide for EVD placement. However, both the CMC and near-perpendicular trajectories proved more reliable for targeting the frontal horn of the ipsilateral lateral ventricle ([Table 4]). EVD lengths ranging from 5 to 5.5 cm had the highest rate of staying within the ipsilateral frontal horn ([Table 5]). The optimal EVD length was 6.19 ± 0.56 cm (p < 0.001 [0.714, 1.413]), indicating statistical significance. If the EVD extends beyond 7.5 cm, there is a risk of entering the third ventricle or contralateral frontal horn.

Table 2 Optimal external ventricular drainage (EVD) location based on the combination of two planes of Kocher's point

Midline(cm) Coronal suture (cm)	< 1.99	2–2.49	2.5–2.99	3–3.5	3.51–3.99	> 4
< 0.99	1 (1.64%)	0	4 (6.56%)	4 (6.56%)	2 (3.28%)	0
1–1.49	0	1 (1.64%)	6 (9.84%)	7 (11.48%)	1 (1.64%)	0
1.5–2	0	2 (3.28%)	1 (1.64%)	6 (9.84%)	0	0
> 2	0	1 (1.64%)	2 (3.28%)	2 (3.28%)	2 (3.28%)	1 (1.64%)

Table 3 Univariate and multivariable logistic regression

Variable	Univariate OR	95% CI	p-value	Multivariable OR	95% CI	p-value
Coronal suture (cm)	0.76	0.34–1.70	0.52	0.75	0.30–1.86	0.53
Midline (cm)	1.05	0.52–2.15	0.89	3.54	0.14–90.30	0.44
Anteroposterior angulation (degrees)	0.94	0.78–1.12	0.46	0.92	0.69–1.23	0.56
Mediolateral angulation (degrees)	0.93	0.81–1.05	0.23	0.91	0.78–1.06	0.22
EVD length (cm)	8.10	2.80–23.40	< 0.001	13.84	2.99–64.01	0.001

Abbreviations: CI, confidence interval; EVD, external ventricular drainage; OR, odds ratio.

Note: Model fit indices: −2; log likelihood = 44.03; Cox and Snell R ² = 0.388; Nagelkerke's R ² = 0.552; Hosmer–Lemeshow χ ² = 8.55 (df = 8, p = 0.382). The model correctly classified 84% of cases. Collinearity statistics: all VIF < 3 (range: 1.02–2.69). Multicollinearity was excluded (all variance inflation factors were <3), confirming model stability and independence of predictors.

Table 4 Thirteen cases with accurate Kocher's point placement to assess external ventricular drainage (EVD) angulation based on surface markings (contralateral medial canthus/external ear meatus and ipsilateral medial canthus/external ear meatus)

Coronal plane Sagittal plane		IMC	CMC	Perpendicular	Total
EAM	Yes	2 (22.2%)	3 (33.3%)	4 (44.4%)	9
	No	0	2 (50%)	2 (50%)	4
Total		2	5	6	13

Abbreviation: EAM, external auditory meatus.

Table 5 External ventricular drainage (EVD) length within the optimal location

EVD length (cm)	n (total)	Optimal location (ipsilateral frontal horn)
5–5.5	6	6	100%
5.51–6.5	24	21	87.5%
6.51–7.5	22	16	72.7%
7.51–8.5	9	0	0%

The multivariable logistic regression ([Table 3]) demonstrated adequate fit (−2 log likelihood = 44.03; Hosmer–Lemeshow χ ² = 8.55; df = 8; p = 0.382) and explained 55.2% of the variance in EVD placement accuracy (Nagelkerke's R ² = 0.552). Among the five predictors entered (coronal suture distance, midline distance, anteroposterior and mediolateral angulations, and EVD length), only EVD length remained statistically significant. Each 1-cm increase in EVD length increased the odds of suboptimal placement by 13.8-fold (OR = 13.84; 95% CI = 2.99–64.01; p = 0.001). The model demonstrated excellent discrimination (AUC = 0.867; 95% CI: 0.78–0.94) and good calibration, as indicated by the Hosmer–Lemeshow test (p = 0.382; [Fig. 2]). The statistically optimal cut-point, as determined by Youden's index, was 6.5 cm (sensitivity of 82% and specificity of 78%). A more conservative threshold of 5.5 cm maintained high sensitivity (85%) and specificity (70%), with an improved safety margin against over-insertion.

Fig. 2 Receiver operating characteristic (ROC) curve and area under the curve (AUC). Illustration of the ROC curves for all variables, highlighting that external ventricular drainage (EVD) length (green line) demonstrated the highest discriminative ability (AUC = 0.867; 95% confidence interval [CI]: 0.78–0.94).

At our center, we achieved an accuracy rate of 70.49% for freehand EVD insertion. Our freehand EVD accuracy was comparable to other centers worldwide, ranging from 39.9 to 83.1% ([Table 6]).

Table 6 Comparison between freehand and navigated external ventricular drainage (EVD) insertion

Study	Location	Patient number (%) Desired location: ipsilateral frontal horn
Freehand
Toma et al[2]	Queen Square Hospital, London	73/183 (39.9%)
Lee et al[7]	Gachon University of Medicine & Science, Gil Medical Center, Incheon, South Korea	48/113 (42.5%)
Huyette et al[8]	University of Missouri Health Care, Columbia, United States	55/98 (56.1%)
AlAzri et al[9]	Montreal General Hospital, Canada	20/35 (57.1%)
Hsieh et al[10]	Tri-Service General Hospital, Taiwan	83/129 (64.3%)
Foreman et al[20]	University of Alabama at Birmingham, United States	67/103 (65%)
Abdoh et al[21]	Henri Mondor Hospital, Créteil, France	53/66 (80.3%)
Lee et al[1]	National Hospital Singapore, Singapore	64/77 (83.1%)
Navigated
Zhang et al[22]	Taizhou First People's Hospital, China	116/131(88.55%) Intraoperative ultrasound
Mahan et al[23]	St. Joseph's Hospital and Medical Center, United States	33/35 (94.1%) Electromagnetic stereotactic navigation
AlAzri et al[9]	Montreal General Hospital, Canada	18/19 (94.7%) Electromagnetic stereotactic navigation

Discussion

Freehand EVD insertion using superficial anatomical landmarks, that is, Kocher's point, is discussed in detail here. Theodor Kocher first presented it, which has been in use for over 100 years.[11] He quoted an entry point of 2.5 to 3 cm from the median line and 3 cm forward of the precentral fissure in 1892. Today, several different entry points are referred to as “Kocher's point” and have slightly different measurements, varying from 1.5 to 4 cm lateral to the midline and 10 to 12.5 cm behind the nasion.[12]

1. Where should an ideal EVD be placed?

The optimal intraventricular location for EVD catheter placement is within the ipsilateral frontal horn. The EVD should avoid damage to the periventricular adjacent structures and intraventricular vascular structures. The right, nondominant side is preferred as it does not regulate language function in 90% of patients. Additionally, the EVD should be performed with the patient in a supine position and the head in a neutral alignment to facilitate orientation to anatomical landmarks.

2. How can freehand EVD placement be improved?

At Sarawak General Hospital, the registrar performs almost all EVD placements at the operating theater. All placements are performed freehand without stereotactic guidance. Success is measured by the free flow of CSF from the distal end of the EVD. However, this can be falsely reassuring as the tip of the EVD may enter other CSF spaces despite good flow.

For the first step, Kocher's point should be accurately placed over the skull.

• Proper preoperative measurement of the Kocher point is achieved by identifying the sagittal and coronal sutures during CT imaging. Kocher's point should be 3 to 3.5 cm lateral to the sagittal suture and 1 to 1.5 cm anterior to the coronal suture.

• We should not use surface anatomy and average/default measurement (12–13 cm from the nasion) to identify coronal sutures. The nasion–coronal suture distance varies from person to person (10.3–13.5 cm).[13] In addition, coronal sutures are not straight lines; they run slightly anteriorly when they go laterally ([Fig. 3]).

Fig. 3 Accurate Kocher's point in this audit: 3 to 3.5 cm from the midline and 1 to 1.5 cm from the coronal suture.

The next stage involves the following.

• EVD angulation:

  • - We should aim for 90 degrees, or perpendicular to the skull.

  • - Although studies have mentioned trajectories of aiming at the CMC/EAM and IMC/EAM, it could be problematic during insertion, as it involves an imaginary plane.[14] [15] However, it is not always easy to identify these landmarks during surgery when the patient is under sterile drapes.

• EVD length:

  • - The optimal length should be approximately 5.5 to 6.5 cm (catheter tip to the outer table of the skull).

  • - Unsatisfactory placement is associated with longer catheter lengths. We should raise clinical suspicion when we insert EVD beyond 6.5 cm without CSF flow, with a likelihood of a wrong trajectory. Three complementary depth metrics emerge: the sample mean depth (6.19 ± 0.56 cm), the statistical cut-point by Youden (6.5 cm), and a conservative clinical threshold (≈5.5 cm). Together, they indicate that depth control is the principal modifiable determinant of freehand EVD accuracy. Aiming for 5.5 cm first, with cautious advancement toward 6 to 6.5 cm only when flow is absent, may reduce the risk of overshoot into the third ventricle or contralateral horn. This continuum highlights the importance of tailoring insertion depth to individual cranial thickness and ventricular size.

  • - This finding is consistent with other studies. Lee et al concluded that the mean length was 66.54 ± 10.1 mm in unsatisfactory placements compared with 58.32 ± 4.85 mm in satisfactory placements (p < 0.001).[1] Toma et al concluded that the mean length of the EVDs ending in the frontal horn was 59.2 ± 8.7 mm.[2]

• Navigated system:

  • In our center, freehand placement is still a regular practice.

  • Adjuncts such as stereotactic neuronavigation and intraoperative ultrasonography are used in certain instances of intracranial pathology, in distorted anatomy resulting from multiple surgeries, or in pediatric patients. These techniques are more accurate than freehand placements based on surface anatomy, but they are time-consuming, expensive, and not readily available in many hospitals or during emergencies. Jamshid and Ghajar introduced the Ghajar guide as one of the first documented techniques.[16] It was based on the principle that the lateral ventricle's body lies parallel to the skull surface. Yamada's tripod was developed to facilitate the insertion of a ventriculoperitoneal shunt, which is more accurate than inserting the catheter tip by hand.[17]

  • Other devices, such as smartphones (gyroscopic sensors) and mechanical devices, are also used to determine the angulation of the catheter.[18] [19]

3. Are there any other techniques to improve the trajectory?

Why Did We Choose the Perpendicular Trajectory?

In addition to the entry point/Kocher's point, which must be measured carefully from CT imaging, the trajectory, or angulation, is also essential. Aiming for the CMC or IMC would be difficult because this is an imaginary plane. This will be more difficult if the patient is fully draped.

From our 3D reconstruction imaging ([Fig. 4A]), the distance of 3 to 4 cm from the midline has the highest chance of an EVD catheter entering the ventricle. [Fig. 4B, C] shows that the EVD catheter best aims at lines 1 (CMC) and 2 (perpendicular). If the ventricle is smaller (dotted ventricle), line 3 (IMC) will likely land outside the ventricle. Additionally, the more prominent ventricle has better error tolerance, as all lines can engage the ventricle.

Fig. 4 External ventricular drainage (EVD) trajectories (mediolateral plane). (A) Different trajectories based on the point from the midline with a 1-cm interval. (B) Line 1 corresponds to the contralateral medial canthus (CMC), line 2 corresponds to 90 degrees, and line 3 corresponds to the ipsilateral medial canthus (IMC). (C) The dotted line represents a smaller ventricle. The EVD catheter is most likely to enter the ventricle 3 to 4 cm from the midline. The EVD catheter ideally targets lines 1 and 2. The line 3 EVD trajectory may cause misplacement if the ventricle is small.

The angulation can accommodate a considerable variation in the sagittal plane, as the lateral ventricle is elongated in the anteroposterior (AP) direction ([Fig. 5A])The EAM plane corresponded to lines 4 and 5 ([Fig. 5B]). In our audit, the ideal angulation for the AP plane (mean ± SD) was 89.05 ± 10.18 degrees, and for mediolateral plane (mean ± SD), it was 85.21 ± 5.76 degrees. Finally, we should aim for a 90-degree angle or perpendicular to the skull to achieve better engagement.

Fig. 5 External ventricular drainage (EVD) trajectories (anteroposterior [AP] plane). (A) The point representing a 0.5-cm interval from the coronal suture. (B) Different trajectories based on the angulation at Kocher's point (1.5 cm from the coronal suture). Line 1 corresponds to 100 degrees, line 2 corresponds to 95 degrees, line 3 corresponds to 90 degrees, line 4 corresponds to 85 degrees, and line 5 corresponds to 80 degrees. The external auditory meatus (EAM) plane corresponds to lines 4 to 5. The angulation can accommodate a considerable variation in the sagittal plane, as the lateral ventricle is elongated in the AP direction.

Freehand Angulation Adjustment

The sole limitation of freehand insertion is that the accuracy of EVD is compromised when the ventricle is displaced by intracranial pathology. We can analyze the preoperative scan, measure the midline shift, and adjust the EVD angulation accordingly based on its magnitude. Again, this is still based on an imaginary line or plane at the time of insertion. EVD misplacement will be higher than the ventricle with a significant midline shift. We would suggest EVD insertion with neuronavigation.

How about the Mechanical Adjuncts?

The standard of care for EVD placement has increasingly shifted toward ultrasound (US) navigation or other neuronavigation, such as image-guided surgery (IGS)/electromagnetic. However, applying this technology to EVD placement is time-consuming and not readily available in developing countries or some district hospitals.

The mechanical adjuncts are intended to facilitate EVD placement. Most of the studies ([Table 7]) showed promising results. Essentially, there are two types of guides: rigid and adjustable. For rigid devices, the idea is to direct the catheter perpendicular to the surface of the skull. Some claim that these devices inaccurately position the ventricular catheter tip. Both O'Leary et al[3] and Ann et al[4] showed excellent accuracy. On the other hand, an adjustable guide can adjust the angle, especially in distorted ventricles or in cases of significant midline shift due to brain tumors or edema.[5] [6] [18] These studies demonstrate that the EVD guide enhances placement compared with freehand methods, and it may also aid neurosurgical trainees in learning to perform it correctly. Over the past decade, there has been a notable increase in novel EVD devices. Despite these advancements, emerging devices are currently limited by a lack of validated clinical research and have not been widely adopted.

Table 7 Different mechanical adjuncts with the accuracy result

Mechanic adjuncts	Description/method of insertion	Result (ipsilateral frontal horn)
	Ghajar guide [3] ● Randomized controlled trial (RCT) ● Total: 49 patients ● The Gajar guide directed the catheter at a right angle to the cranial surface	● Ghajar guide: 24/25 (96%) ● Freehand: 16/24 (66.67%)
	EVD guide [4] ● Interventional study ● Total: 52 patients ● The device comprised a T-shaped main body, a rectangular pillar with a central catheter insert hole, and an arm pointing to the tragus. The main body directed the catheter toward the inner canthus	● 52/52 (100%)
	Adjustable Ghajar guide [5] ● Interventional study ● Total: 20 patients ● The adjustable Ghajar guide moved along the protractor and was fixed by the predetermined adjustment angle	● 19/20 (95%)
	Ventricular catheter guide with a mobile health–assisted guidance technique [6] ● RCT ● Total: 139 patients ● The guide used the individual parameters of coronal angulation to the skull surface, and the catheter length and the distance to the midline were measured using the dedicated mHealth app	● Guide: 49/70 (70%) ● Freehand: 39/69 (56.5%)
	Smartphone-navigated ventricular catheter placement [18] ● Used cadaver heads ● The drain was angle-adjusted with the smartphone and inserted into the ventricle	● All 20 sEVDs (head model, 8/20; cadaveric head, 12/20) showed accurate placement
	Patient-specific EVD (PS-EVD) guide [24] ● Used skull models ● It has a tripod base and a series of differently angled inserts that lock in place at multiple rotational positions, allowing for numerous insertion angles	● Accurate EVD placement in phantom skulls with both normal and altered ventricular anatomy

Conclusion

This audit concludes that freehand frontal EVD insertion is safe and comparable to neuronavigated EVD placement, provided Kocher's point, EVD angulation, and EVD length fall within the specified range. Improperly positioned catheters may necessitate revision and further treatments, incurring additional expenses and time for repeat CT scans and surgeries. Placement should preferably be accomplished in a single attempt, as subsequent attempts may increase the risk of injury, including hemorrhages, neurological damage, and infections.

Study Limitation

This study aimed to identify the optimal placement setting for freehand EVD. The data were limited by their retrospective nature and the small number of patients. Although neuronavigation yields higher accuracy, freehand insertion remains the mainstay in urgent and resource-limited settings. Furthermore, the small sample size and number of EVD insertions decrease the statistical power of our study.

Conflict of Interest

None declared.

Authors' Contribution

S.H.Y. contributed to conceptualization, methodology, software, formal analysis, and writing (original draft, review, and editing). A.S-H.W. contributed to conceptualization, writing (review and editing), and supervision. D.N.S.L. and A.S.S. contributed to writing (review and editing) and supervision.

• References

• 1 Lee KS, Zhang JJY, Bolem N. et al. Free-hand insertion of external ventricular drainage catheter: evaluation of accuracy in a single center. Asian J Neurosurg 2020; 15 (01) 45-50
• 2 Toma AK, Camp S, Watkins LD, Grieve J, Kitchen ND. Accuracy of external ventricular drain insertion: is there a need for change in practice?. Neurosurgery 2009; 65: 1197-1200
• 3 O'Leary ST, Kole MK, Hoover DA, Hysell SE, Thomas A, Shaffrey CI. Efficacy of the Ghajar guide revisited: a prospective study. J Neurosurg 2000; 92 (05) 801-803
• 4 Ann JM, Bae HG, Oh JS, Yoon SM. Device for catheter placement of external ventricular drain. J Korean Neurosurg Soc 2016; 59 (03) 322-324
• 5 Yoon SY, Kwak Y, Park J. Adjustable Ghajar guide technique for accurate placement of ventricular catheters: a pilot study. J Korean Neurosurg Soc 2017; 60 (05) 604-609
• 6 Thomale UW, Schaumann A, Stockhammer F. et al. GAVCA study: randomized, multicenter trial to evaluate the quality of ventricular catheter placement with a mobile health-assisted guidance technique. Neurosurgery 2018; 83 (02) 252-262
• 7 Lee JH, Park CW, Lee U. et al. Accuracy of the free-hand placement of an external ventricular drain. Korean J Cerebrovasc Surg 2010; 12: 82-86
• 8 Huyette DR, Turnbow BJ, Kaufman C, Vaslow DF, Whiting BB, Oh MY. Accuracy of the freehand pass technique for ventriculostomy catheter placement: retrospective assessment using computed tomography scans. J Neurosurg 2008; 108 (01) 88-91
• 9 AlAzri A, Mok K, Chankowsky J, Mullah M, Marcoux J. Placement accuracy of external ventricular drain when comparing freehand insertion to neuronavigation guidance in severe traumatic brain injury. Acta Neurochir (Wien) 2017; 159 (08) 1399-1411
• 10 Hsieh CT, Chen GJ, Ma HI. et al. The misplacement of external ventricular drain by freehand method in emergent neurosurgery. Acta Neurol Belg 2011; 111 (01) 22-28
• 11 Kocher TE. Chirurgische Operationslehre. 1st ed. Jena: Gustav Fischer; 1892: 38
• 12 Raabe C, Fichtner J, Beck J, Gralla J, Raabe A. Revisiting the rules for freehand ventriculostomy: a virtual reality analysis. J Neurosurg 2018; 128 (04) 1250-1257
• 13 Ozdemir M, Comert A, Ozdemir K. et al. Anatomy-based navigation for ventriculostomy: nasion–coronal suture distance measurement. J Clin Exp Invest 2014; 5 (03) 368-370
• 14 Kirkman MA, Muirhead W, Sevdalis N. The relative efficacy of 3 different freehand frontal ventriculostomy trajectories: a prospective neuronavigation-assisted simulation study. J Neurosurg 2017; 126 (01) 304-311
• 15 Muirhead WR, Basu S. Trajectories for frontal external ventricular drain placement: virtual cannulation of adults with acute hydrocephalus. Br J Neurosurg 2012; 26 (05) 710-716
• 16 Ghajar JB. A guide for ventricular catheter placement. Technical note. J Neurosurg 1985; 63 (06) 985-986
• 17 Yamada SM, Yamada S, Goto Y. et al. A simple and consistent technique for ventricular catheter insertion using a tripod. Clin Neurol Neurosurg 2012; 114 (06) 622-626
• 18 Eisenring CV, Burn F, Baumann M. et al. sEVD: smartphone-navigated placement of external ventricular drains. Acta Neurochir (Wien) 2020; 162 (03) 513-521
• 19 Konovalov A, Okishev D, Shekhtman O, Pilipenko Y, Eliava S. Neuronavigation device for stereotaxic external ventricular drainage insertion. Surg Neurol Int 2021; 12: 266
• 20 Foreman PM, Hendrix P, Griessenauer CJ, Schmalz PG, Harrigan MR. External ventricular drain placement in the intensive care unit versus operating room: evaluation of complications and accuracy. Clin Neurol Neurosurg 2015; 128: 94-100
• 21 Abdoh MG, Bekaert O, Hodel J. et al. Accuracy of external ventricular drainage catheter placement. Acta Neurochir (Wien) 2012; 154 (01) 153-159
• 22 Zhang L, Mu Z, Shen G, Yang M. The accuracy and safety of intraoperative ultrasound-guided external ventricular drainage in intraventricular hemorrhage. Sci Rep 2023; 13 (01) 11525
• 23 Mahan M, Spetzler RF, Nakaji P. Electromagnetic stereotactic navigation for external ventricular drain placement in the intensive care unit. J Clin Neurosci 2013; 20 (12) 1718-1722
• 24 Pathak SM, Licata JP, Graves EKM, Gerstenhaber JA, Erkmen K. Development of an adjustable patient-specific rigid guide to improve the accuracy of external ventricular catheter placement. J Neurosurg 2024; 141 (04) 1079-1087

Publication History

Article published online:
07 January 2026