The impact of real-time ultrasound guidance on ventricular catheter placement in cerebrospinal fluid shunts – a single-center study

Abstract

Purpose

Misplacement of ventricular catheters during shunt surgery occurs in 40% of cases using a freehand technique and therefore represents a risk for early shunt failure. The goal of this retrospective, single-center study is to analyze the impact of real-time ultrasound guidance on ventricular catheter positioning and early outcome of shunt survival.

Materials and Methods

We analyzed the charts and images of all patients who underwent shunt surgery from 09/2017 to 12/2022 and compared the position of the ventricular catheter using the freehand technique and real-time ultrasound guidance. Central catheter position was graded as grade I (optimal), II (contact with ventricle structures or contralateral), and III (misplacement).

Results

A ventricular catheter was placed in 244 patients using real-time US guidance and in 506 patients using a freehand technique. The mean age (53.4 and 53.6 years, respectively) and the preoperative frontal occipital horn ratio (FOHR; 0.47 versus 0.44) were almost equal in both groups. In the study group, grade I catheter position was achieved in 64% of cases, grade II in 34%, and grade III in 2%. The control group showed grade I position in 45%, grade II in 32%, and grade III in 23% of cases (p<0.05). An early central catheter failure rate was the highest in grade III (40.5%) compared to 4% in grade I.

Conclusion

Our data demonstrate that real-time US guidance leads to a significant improvement in ventricular catheter placement. Consequently, early shunt revisions decrease significantly. Further prospective, randomized, and controlled studies comparing the standard method to real-time ultrasound catheter placement are required.

Zusammenfassung

Hintergrund

Eine fehlerhafte Platzierung von Ventrikelkathetern bei einer Shunt-Operation tritt in 40% der Fälle auf, wenn die Freihandtechnik verwendet wird, und stellt daher ein Risiko für ein frühzeitiges Shunt-Versagen dar. Ziel dieser retrospektiven Single-Center-Studie ist es, die Auswirkungen der Echtzeit-Ultraschallführung auf die Positionierung des Ventrikelkatheters und das frühe Outcome der Shunt-Funktion zu analysieren.

Material und Methoden

Wir analysierten die Diagramme und Bilder aller Patienten, die sich zwischen 09/2017 und 12/2022 einer Shunt-Operation unterzogen, und verglichen die Position des Ventrikelkatheters bei Einsatz der Freihandtechnik und der Echtzeit-Ultraschallführung. Die zentrale Katheterposition wurde als Grad I (optimal), II (Kontakt mit Ventrikelstrukturen oder kontralateral) und III (Fehlplatzierung) eingestuft.

Ergebnisse

Ventrikelkatheter wurde bei 244 Patienten unter Echtzeit-Ultraschallführung und bei 506 Patienten mittels Freihandtechnik platziert. Das Durchschnittsalter (53,4 bzw. 53,6 Jahre) und die präoperative „Frontal and Occipital Horn Ratio“ (FOHR; 0,47 bzw. 0,44) waren in beiden Gruppen nahezu gleich. In der Studiengruppe wurde in 64% der Fälle Katheterposition Grad I erreicht, in 34% Grad II und in 2% Grad III. In der Kontrollgruppe wurde in 4% der Fälle Katheterposition Grad I erzielt, in 32% der Fälle Grad II und in 23% der Fälle Grad III (p<0,05). Die Rate des frühen Katheterversagens war bei Grad III am höchsten (40,5%), im Vergleich zu 4% bei Grad I.

Schlussfolgerung

Unsere Daten zeigen, dass die Echtzeit-Ultraschallführung zu einer signifikanten Verbesserung der Platzierung von Ventrikelkathetern führt. Folglich gehen frühe Shunt-Revisionen signifikant zurück. Weitere prospektive, randomisierte und kontrollierte Studien, in denen die Standardmethode mit der Platzierung des Katheters in Echtzeit-Ultraschall verglichen wird, sind erforderlich.

Keywords

shunt - US-guided - ventricular catheter

Introduction

Cerebrospinal fluid (CSF) shunt insertion is among the most common procedures in neurosurgery. In the literature the shunt failure rate reaches 30% to 40% in the first year after placement [1] [2] [3] [4] [5]. Shunt failure frequently leads to additional surgical procedures and increased morbidity and mortality, and, therefore, worsening of the overall outcome of patients. The method commonly used for ventricular catheter placement is the freehand technique, where the entry point and trajectory are selected based on anatomical landmarks, preoperative imaging, and personal experience. To improve the ventricular catheter position in the ventricle, different techniques were described. Recently, the use of real-time ultrasound guidance (US) was suggested to increase the precision of ventricular catheter placement: Data of smaller cohorts showed a decreased risk of shunt revision [6] [7] [8] [9] [10] [11]. However, prospective studies comparing conventional and US-guided placement of ventricular catheters have not yet been published.

The goal of this retrospective, single-center study is to analyze the impact of using real-time ultrasound guidance on ventricular catheter positioning and early outcome of shunt survival in a large, unselected, adult cohort for neurosurgical patients undergoing VPS placement at a tertiary referral center.

Materials and Methods

The study was approved by the local research ethics committee and institutional review board (internal study number: 4757).

Patient characteristics

The charts of all patients undergoing ventricular-peritoneal shunt (VPS) insertion between September 2017 and December 2022 were reviewed. The inclusion criteria were: (1) surgery of a VPS, (2) insertion of the ventricular catheter via a frontal burr hole at Kocher’s point, (3) 18 years of age and older, and (4) complete set of pre- and post-operative imaging (MRI or CT). All patients who underwent surgery for other forms of CSF drainage (e.g., initial external ventricular drainage prior to VPS, ventricular-atrial shunting), all pediatric patients (age < 18y), patients with multiple compartment hydrocephalus and the need for more than one ventricular catheter, as well as patients who switched from the standard freehand procedure to US guidance due to problems in standard catheter placement were excluded from the present analysis.

The decision regarding which procedure to use was surgeon-dependent and was made preoperatively mainly due to individual experience.

Surgical technique

A standard frontal burr hole was placed at Kocher’s point (about 12 cm above the nasion and 2.5 to 3 cm paramedian) using a 14-mm disposable perforator (Codman & Shurtleff Inc., Raynham, USA.) For the US-guided placement of the ventricular catheter, the burr hole was extended laterally and parallel to the coronal suture by 3–4 mm with a Kerrison rongeur ([Fig. 1]A). The dura was opened with a scalpel or bipolar forceps within the lateral extension. The optimal trajectory for catheter positioning was identified by visualizing the ventricle with ultrasound. Placement of the ventricular catheter in the freehand technique was performed by puncturing the lateral ventricle in a perpendicular direction to the cortex. Puncture of the ventricle was expected at a depth of 5 to 7 cm below the cortical surface. For all patients, an early postoperative CT scan was performed to evaluate the accuracy of the position of the ventricular catheter within one week after surgery ([Fig. 2] and [Fig. 3]).

Fig. 1 a A cranial burr hole was made using a 14-mm disposable perforator (Codman & Shurtleff INC., Raynham, USA). A lateral extension of 2–3 mm was made by a Kerrison rongeur parallel to the coronal suture, to allow the ventricular catheter to pass in the flume of the burr hole probe (white arrow). b and c The burr hole catheter holder is attached to the US probe. d Ultrasound view during catheter insertion into the lateral ventricle gained through the burr hole probe.

Fig. 2 The CT scan shows a grade I catheter position in a patient with a >3mm midline shift with the catheter tip in the ipsilateral ventricle (white arrow) placed by ultrasound guidance in a patient with post-hemorrhagic hydrocephalus after acute IVH.

Fig. 3 a–c CT scans of the brain. a shows a grade I (optimal position of the ventricular catheter in the ipsilateral ventricle surrounded by CSF), b shows a grade II (catheter tip located in the contralateral ventricle going through septum pellucidum), and c shows a grade III catheter position (catheter tip lying outside of the ventricular system).

Intraoperative ultrasound

The US console (ProSound Alpha 6, Hitachi Aloka Medical Ltd., Tokyo, Japan) with the 3.0–7.5 MHz burr hole probe and a guide rail (UST-52114P, Hitachi Aloka Medical Ltd., Tokyo, Japan) were used. The burr hole catheter holder (Hitachi Aloka Medical Ltd., Tokyo, Japan) was attached to the burr hole probe, and the US probe was inserted into the burr hole with the guide rail facing towards the lateral extension ([Fig. 1]B). Using the US probe, we were able to visualize in continuous real-time the catheter advancing trough the brain parenchyma into the desired compartment of the ventricle, allowing for active correction of the catheter’s trajectory during puncture ([Fig. 1]C).

Data collection and outcome measures

Epidemiological data, data regarding the indications for VPS insertion and ventricle width, complications, as well as pre- and postoperative images were collected from charts and electronic records.

Ventricular size was quantified by calculating the frontal occipital horn ratio (FOHR) on the preoperative CT scans [12] [13]. Based on the modified classification proposed by Hsieh and coworkers in 2011, the position of the ventricular catheter was classified as follows: Grade I describes an optimal position of the ventricular catheter in the ipsilateral ventricle surrounded by CSF. Grade II characterizes all other catheter positions, i.e., catheter tip located in the contralateral ventricle or touching the septum pellucidum, or choroid plexus, or ventricular wall. Grade III refers to misplaced catheters, defined as the catheter tip or whole catheter lying outside of the ventricular system.

Early shunt failure was defined as shunt failure within the first 30 days after initial surgery requiring a surgical correction.

Statistical analysis

Pearson’s chi-squared test or Fisher’s exact test was used for nominal variables. Only two-sided p-values were reported. Student t-test was used for metric variables to compare the US group and the control group. Binary logistic regression analysis was performed to analyze independent predictors of grade I central catheter position. Data were organized and analyzed using SPSS version 25.0 (IBM Corp, Armonk, NY, USA).

Results

Patients and shunt data of 750 patients with VPS were included in the study. In 506 patients (67.5%) ventricular catheter insertion was performed using the freehand technique, while 244 patients (32.5%) underwent ventricular catheter insertion under real-time US guidance. The female-to-male ratio was almost balanced (384 female: 366 male). The mean age was 53.4 years (range: 19–80 years). Underlying diseases resulting in VPS insertion are summarized in [Table 1]. Both groups were well-balanced regarding implanted shunt hardware and underlying pathology. The mean preoperative FOHR index was 0.54 (SD ± 0.12) in the US group and 0.53 (SD ± 0.12) in the freehand group (p = 0.44, Fisher’s exact test [two-sided]). The mean duration of surgery was 52 and 49 minutes, respectively.

Table 1 Data regarding underlying diseases and shunt type.

Variable	Study group (US guidance, n=244)	Control group (ft, n=506)	P-value
US guidance: ultrasound guidance, ft: freehand technique, iNPH: idiopathic normal pressure hydrocephalus
Age (mean± SD)	53.56 ± 16.4	53.4 ± 16.7	0.93
Etiology of hydrocephalus
Posthemorrhagic	85 (34.8%)	232 (45%)	0.004
Trauma	20 (8.2%)	51 (10.1%)	0.69
iNPH	42 (17.2%)	48 (9.5%)	0.004
Stroke	22 (9.0%)	69 (13.7%)	0.07
Pseudotumor cerebri	9 (3.7%)	7 (1.4%)	0.11
Malformations	24 (9.8%)	19 (3.8%)	0.001
Tumor	42 (17.2%)	80 (15.8%)	0.67
Fohr index	0.54 ± 0.12	0.53 ± 0.12	0.44
Valve types
Medos Hakim (adjustable)	117 (48%)	343 (67.8%)
Codman Certas (adjustable)	73 (30%)	51 (10.1%)
Codman precision (100 mmH2O)	54 (22.1%)	112 (22.1%)

Accuracy of ventricular catheter placement

In the US group, a grade I catheter position was achieved in 156 patients (63.9%), while a grade I catheter position was found in 228 (45.1%) of the patients in the control group (p=0.0001). Only 5 patients (2%) in the US group and 116 patients (23%) in the control group showed a grade III catheter position (p = 0.0001; ([Table 2] and [Fig. 4]).

Table 2 Results of follow-up.

Variable	Study group (ultrasound guidance, n=244)	Control group (freehand technique, n=506)	P-value
Early shunt revisions	5 (2.1%)	63 (12.5%)	0.0001
Reason for shunt failure
Proximal blockage	5 (2.1%)	47 (9.3%)	0.0001
Valve blockage	0 (0.0%)	16 (3.2 %)	0.002
Failure related to catheter positioning
Grade I	0 (0.0%)	0 (0.0%)	0.99
Grade II	0 (0.0%)	41 (8.1%)	0.0001
Grade III	5 (2.0%)	22 (4.3%)	0.14
Catheter position
Grade I	156 (63.9%)	228 (45.1%)	0.0001
Grade II	83 (34%)	162 (32%)	0.62
Grade III	5 (2%)	116 (229%)	0.0001
Postoperative complications
Bleeding	3 (1.2%)	7 (1.4%)	0.87
Shunt infection	2 (0.8%)	4 (0.8%)	0.80
Wound infection	3 (1.2%)	4 (0.8%)	0.91

Fig. 4 Ventricular catheter position in the US-guided and freehand technique.

Multivariate analysis with consideration of the operative technique (US guidance or freehand technique) and etiology of the hydrocephalus regarding the achievement of a grade I central catheter position was performed. US-guided central catheter positioning was the only statistically significant variable in the binary logistic regression analysis to achieve a grade I central catheter position (adjusted odds ratio: 2.29, 95% CI: 1.66–3.16, p<0.001), ([Table 3]).

Table 3 Multivariate analysis regarding factors that influence grade I position of central catheter.

Variable	Adjusted OR	95% CI	P-value
OR: odds ratio, posth. hydrocephalus: posthemorrhagic hydrocephalus, iNPH: idiopathic normal pressure hydrocephalus
Ultrasound-guided technique	2.29	1.66–3.16	<0.001
Posth. hydrocephalus	1.16	0.76–1.77	0.51
iNPH	1.36	0.64–2.88	0.42
Malformations	1.02	0.37–2.82	0.98

Influence of catheter positioning to shunt failure rates

Early failure of a ventriculoperitoneal shunt requiring surgical revision was observed in 68/750 patients (9%). The early central catheter failure rate was the highest in grade III (27/121; 22.3%) compared to 0% (0/384) in grade I (p = 0.0001). Detailed results are presented in [Table 2]. Early shunt revisions were more common in the control group. Shunt failures associated with central catheter position were observed in 5 patients (2.0%) in the US group and in 63 patients (12.5%) in the control group. Therefore, US guidance resulted in a significantly lower early shunt failure rate due to the central catheter position as compared to the freehand technique (p=0.0001). The reason for the shunt failure was either a proximal blockage of the catheter or a valve blockage because of the obstruction caused by debris, protein, and cellular ingrowth mainly due to catheter misplacement.

Postoperative surgery-related complications

The overall rate of surgery-related complications, including bleeding along the catheter trajectory, infection, and wound infection, was 3.1% (n=23). Both groups had similar postoperative complication rates with no significant difference (p >0.05) [Table 2].

Discussion

This study represents the largest cohort study in the literature with 750 included patients over a 5-year period. It compares US-guided and freehand ventricular catheter placement depending on objective standardized radiological evidence using the modified Hsieh classification.

There are three key findings in this study: 1) more than 30% of patients who underwent ventriculoperitoneal shunting suffered from a misplaced position of the ventricular catheter (defined as grade III in accordance with the modified Hsieh classification), 2) the early central catheter failure rate was significantly related to the position of the ventricular catheter, and 3) US guidance of the catheter position was shown to be highly efficient and to lead to a significantly lower early shunt failure rate compared to the freehand technique.

Although the freehand technique is the most commonly applied method of ventricular catheter insertion, its remarkable rate of misplacement is well documented in the literature [5] [8] [14] [15] [16]. In our present study, positioning of the central catheter using the freehand technique resulted in its misplacement in nearly 23% of patients. Using this technique, the rate of inaccurately placed ventricular catheters was suggested to range between 10–40% in previous studies [5] [6] [17] [18]. Furthermore, and as confirmed by the present study, misplacement of the central catheter is a major risk factor for early shunt failure [3] [5] [8] [19] [20] [21]. Therefore, optimal positioning of the central catheter during VPS surgery is crucial. Several approaches and technical modifications have been described to improve placement of the central catheter including stereotactic, neuronavigational, and smartphone guidance [6] [8] [9] [10] [18] [22] [23] [24] [25] [26] [27] [28] [29].

Shkolniks and McLone's pioneering work in 1981 introduced the first documented instance of real-time ultrasound-guided placement of ventricular catheters, specifically in seven pediatric patients suffering from hydrocephalus [30].

Rubin and Dohrmann described this method in adults in five cases where they performed a craniotomy to facilitate the use of the ultrasound probe. Subsequently, they employed intraoperative ultrasound guidance for the placement of ventricular catheters [31].

In the year 2000, Strowitzki et al. released a series documenting 100 neurosurgical interventions conducted with intraoperative ultrasound assistance. These procedures encompassed a variety of conditions, including puncturing intracranial cysts, draining abscesses or hematomas, biopsying intracranial tumors, and, notably, ventricular system puncture in 46 patients [32].

A few years later, Strowitzki et al. conducted an analysis involving 115 patients who underwent ventricular system puncture for temporary cerebrospinal fluid (CSF) diversion, intracranial pressure monitoring, or a permanent shunt. Among these patients, 48 underwent the procedure with the utilization of intraoperative US guidance. The study did not specify the number of permanent shunts included or provide any follow-up data. Nevertheless, the authors noted an improvement in the accuracy of catheter tip placement when guided by US, although there was no significant difference in the number of attempts required to access the ventricle [33].

Whitehead et al. released a technical note outlining the procedure including enlarging the standard burr hole to accommodate the US probe. They did not conduct a comparison between the US group and a control group. They detailed the successful placement of ventricular catheters with US guidance in 10 pediatric patients [1].

In the present study, we evaluate the accuracy of US guidance for the placement of a central catheter during 750 VPS surgeries. In our study real-time ultrasound-guided placement of the ventricular catheter significantly improved the precision of the catheter position resulting in a low early shunt failure rate. Our results are in good agreement with multiple studies showing improved positioning of ventricular catheters using the guidance technique compared to the freehand technique [1] [7] [8] [9] [10] [11]. In comparison to the methods in the literature using a stereotactic approach, real-time US guidance does not require additional exposure to radiation for the planning of neuronavigation or stereotaxis. This might be advantageous for the patient regarding the need for multiple cranial CT scans over a lifetime due to suspicion of shunt dysfunction. Furthermore, real-time US guidance provides a real-time image during catheter insertion, whereas neuronavigation and stereotaxis simulate the shunt position on the preoperative CT scans.

Limitations

We acknowledge several limitations of the present study: (1) the results of our analysis are limited by the retrospective study design. To achieve more significant results, prospective data collection, randomization and stratification of hydrocephalus patients, and a controlled setup are required. (2) The present results arise from a single-center study. Other neurosurgical centers might have a lower incidence of central catheter misplacement using the freehand technique. However, the rate of incorrectly placed central catheters ranges between 10–40% in previous studies [2] [17] [34]. (3) We investigated a heterogeneous population including different subtypes of hydrocephalus. In particular, the rate of early shunt failure is likely related to the subtype of hydrocephalus: Shunting for posthemorrhagic or postinfectious hydrocephalus results more frequently in shunt failure than, e.g., shunting for normal pressure hydrocephalus. Therefore, the observed relationship between the applied technique and the shunt failure rate might be biased by a higher rate of posthemorrhagic hydrocephalus in the freehand technique group.

Conclusion

US guidance of catheter position was shown to be highly efficient and resulted in a significantly lower early shunt failure rate compared to the freehand technique. Further prospective, randomized, and controlled studies comparing the standard method to real-time ultrasound catheter placement are required.

Conflict of Interest

The authors declare that they have no conflict of interest.

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Publication History

Received: 31 March 2023

Accepted after revision: 25 June 2024

Accepted Manuscript online:
25 June 2024

Article published online:
07 November 2024