Observations on the physiopathology of the CSF pulse and prevention of ventricular catheter obstruction in valve shunts

Cerebrospinal fluid hydrocephalus shunting: cisterna magna, ventricular frontal, ventricular occipital

Despite advances in cerebrospinal fluid shunting technology, complications remain a significant concern. There are some contradictions about the effectiveness of proximal catheter entry sites that decrease shunt failures. We aim to compare efficiency of shunts with ventricular frontal, ventricular occipital, and cisterna magna entry sites. The systemic search was conducted in the database from conception to February 16, 2022 following guidelines of PRISMA. Between 2860 identified articles, 24 articles including 6094 patients were used for data synthesis. The aggregated results of all patients showed that "overall shunt failure rate per year" in mixed hydrocephalus with ventricular frontal and occipital shunts, and cisterna magna shunt (CMS) were 9.0%, 12.6%, and 30.7%, respectively. The corresponding values for "shunt failure rate" due to obstruction were 15.3%, 31.5%, and 10.2%, respectively. The similar results for "shunt failure rate" due to infection were 11.3%, 9.1%, and 27.2%, respectively. The related values for "shunt failure rate" due to overdrainage were 2.9%, 3.9%, and 13.6%, respectively. CMS was successful in the immediate resolution of clinical symptoms. Shunting through an occipital entry site had a greater likelihood of inaccurate catheter placement and location. Contrary to possible shunt failure due to overdrainage, the failure likelihood due to obstruction and infection in pediatric patients was higher than that of mixed hydrocephalus patients. In both mixed and pediatric hydrocephalus, obstruction and overdrainage were the most and least common complications of ventricular frontal and occipital shunts, respectively. The most and least common complications of mixed CMS were infection and obstruction, respectively.

A multicenter retrospective study of heterogeneous tissue aggregates obstructing ventricular catheters explanted from patients with hydrocephalus

BACKGROUND

Implantation of ventricular catheters (VCs) to drain cerebrospinal fluid (CSF) is a standard approach to treat hydrocephalus. VCs fail frequently due to tissue obstructing the lumen via the drainage holes. Mechanisms driving obstruction are poorly understood. This study aimed to characterize the histological features of VC obstructions and identify links to clinical factors.

METHODS

343 VCs with relevant clinical data were collected from five centers. Each hole on the VCs was classified by degree of tissue obstruction after macroscopic analysis. A subgroup of 54 samples was analyzed using immunofluorescent labelling, histology and immunohistochemistry.

RESULTS

61.5% of the 343 VCs analyzed had tissue aggregates occluding at least one hole (n = 211) however the vast majority of the holes (70%) showed no tissue aggregates. Mean age at which patients with occluded VCs had their first surgeries (3.25 yrs) was lower than in patients with non-occluded VCs (5.29 yrs, p < 0.02). Mean length of time of implantation of occluded VCs, 33.22 months was greater than for non-occluded VCs, 23.8 months (p = 0.02). Patients with myelomeningocele had a greater probability of having an occluded VC (p = 0.0426). VCs with occlusions had greater numbers of macrophages and astrocytes in comparison to non-occluded VCs (p < 0.01). Microglia comprised only 2-6% of the VC-obstructing tissue aggregates. Histologic analysis showed choroid plexus occlusion in 24%, vascularized glial tissue occlusion in 24%, prevalent lymphocytic inflammation in 29%, and foreign body giant cell reactions in 5% and no ependyma.

CONCLUSION

Our data show that age of the first surgery and length of time a VC is implanted are factors that influence the degree of VC obstruction. The tissue aggregates obstructing VCs are composed predominantly of astrocytes and macrophages; microglia have a relatively small presence.

Cerebrospinal Fluid Shunting Complications in Children

Although cerebrospinal fluid (CSF) shunt placement is the most common procedure performed by pediatric neurosurgeons, shunts remain among the most failure-prone life-sustaining medical devices implanted in modern medical practice. This article provides an overview of the mechanisms of CSF shunt failure for the 3 most commonly employed definitive CSF shunts in the practice of pediatric neurosurgery: ventriculoperitoneal, ventriculopleural, and ventriculoatrial. The text has been partitioned into the broad modes of shunt failure: obstruction, infection, mechanical shunt failure, overdrainage, and distal catheter site-specific failures. Clinical management strategies for the various modes of shunt failure are discussed as are research efforts directed towards reducing shunt complication rates. As it is unlikely that CSF shunting will become an obsolete procedure in the foreseeable future, it is incumbent on the pediatric neurosurgery community to maintain focused efforts to improve our understanding of and management strategies for shunt failure and shunt-related morbidity.

Toward a better understanding of the cellular basis for cerebrospinal fluid shunt obstruction: report on the construction of a bank of explanted hydrocephalus devices

OBJECTIVE Shunt obstruction by cells and/or tissue is the most common cause of shunt failure. Ventricular catheter obstruction alone accounts for more than 50% of shunt failures in pediatric patients. The authors sought to systematically collect explanted ventricular catheters from the Seattle Children's Hospital with a focus on elucidating the cellular mechanisms underlying obstruction. METHODS In the operating room, explanted hardware was placed in 4% paraformaldehyde. Weekly, samples were transferred to buffer solution and stored at 4°C. After consent was obtained for their use, catheters were labeled using cell-specific markers for astrocytes (glial fibrillary acidic protein), microglia (ionized calcium-binding adapter molecule 1), and choroid plexus (transthyretin) in conjunction with a nuclear stain (Hoechst). Catheters were mounted in custom polycarbonate imaging chambers. Three-dimensional, multispectral, spinning-disk confocal microscopy was used to image catheter cerebrospinal fluid-intake holes (10× objective, 499.2-μm-thick z-stack, 2.4-μm step size, Olympus IX81 inverted microscope with motorized stage and charge-coupled device camera). Values are reported as the mean ± standard error of the mean and were compared using a 2-tailed Mann-Whitney U-test. Significance was defined at p < 0.05. RESULTS Thirty-six ventricular catheters have been imaged to date, resulting in the following observations: 1) Astrocytes and microglia are the dominant cell types bound directly to catheter surfaces; 2) cellular binding to catheters is ubiquitous even if no grossly visible tissue is apparent; and 3) immunohistochemical techniques are of limited utility when a catheter has been exposed to Bugbee wire electrocautery. Statistical analysis of 24 catheters was performed, after excluding 7 catheters exposed to Bugbee wire cautery, 3 that were poorly fixed, and 2 that demonstrated pronounced autofluorescence. This analysis revealed that catheters with a microglia-dominant cellular response tended to be implanted for shorter durations (24.7 ± 6.7 days) than those with an astrocyte-dominant response (1183 ± 642 days; p = 0.027). CONCLUSIONS Ventricular catheter occlusion remains a significant source of shunt morbidity in the pediatric population, and given their ability to intimately associate with catheter surfaces, astrocytes and microglia appear to be critical to this pathophysiology. Microglia tend to be the dominant cell type on catheters implanted for less than 2 months, while astrocytes tend to be the most prevalent cell type on catheters implanted for longer time courses and are noted to serve as an interface for the secondary attachment of ependymal cells and choroid plexus.

Computational fluid dynamics of ventricular catheters used for the treatment of hydrocephalus: a 3D analysis

INTRODUCTION

The most common treatment for hydrocephalus remains the ventriculoperitoneal shunt. Yet, the most frequent complication is ventricular catheter obstruction, which may account for 50-80 % of newly inserted shunts. Although many factors contribute to this, the main one is related to flow characteristics of the catheter within the hydrocephalic brain. A landmark study by Lin et al. addressed the problem of fluid characteristics in ventricular catheters using a two-dimensional simulation program of computational fluid dynamics (CFD).

METHODS

The authors have studied five current commercially available ventricular catheter designs using CFD in three-dimensional automated designs. The general procedure for the development of a CFD model involves incorporating the physical dimensions of the system to be studied into a virtual wire-frame model. The shape and features of the actual physical model are transformed into coordinates for the virtual space of the computer and a CFD computational grid (mesh) is generated. The fluid properties and motion are calculated at each of these grid points. After grid generation, flow field boundary conditions are applied, and the fluid's thermodynamic and transport properties are included. At the end, a system of strongly coupled, nonlinear, partial differential conservation equations governing the motion of the flow field are numerically solved. This numerical solution describes the fluid motion and properties.

RESULTS

The authors calculated that most of the total fluid mass flows into the catheter's most proximal holes. Fifty to 75 % flows into the two most proximal sets of inlets of current commercially available 12-32-hole catheters. Some flow uniformity was disclosed in Rivulet-type catheter.

CONCLUSIONS

Most commercially available ventricular catheters have an abnormally increase flow distribution pattern. New catheter designs with variable hole diameters along the catheter tip will allow the fluid to enter the catheter more uniformly along its length, thereby reducing the probability of its becoming occluded.

Effect of electromagnetic navigated ventriculoperitoneal shunt placement on failure rates

OBJECTIVE

To evaluate the effect of electromagnetic (EM) navigation system on ventriculoperitoneal (VP) shunt failure rate through comparing the result of standard shunt placement.

METHODS

All patients undergoing VP shunt from October 2007 to September 2010 were included in this retrospective study. The first group received shunt surgery using EM navigation. The second group had catheters inserted using manual method with anatomical landmark. The relationship between proximal catheter position and shunt revision rate was evaluated using postoperative computed tomography by a 3-point scale. 1) Grade I; optimal position free-floating in cerebrospinal fluid, 2) Grade II; touching choroid or ventricular wall, 3) Grade III; tip within parenchyma.

RESULTS

A total of 72 patients were participated, 27 with EM navigated shunts and 45 with standard shunts. Grade I was found in 25 patients from group 1 and 32 patients from group 2. Only 2 patients without use of navigation belonged to grade III. Proximal obstruction took place 7% in grade I, 15% in grade II and 100% in grade III. Shunt revision occurred in 11% of group 1 and 31% of group 2. Compared in terms of proximal catheter position, there was growing trend of revision rate according to increase of grade on each group. Although infection rate was similar between both groups, the result had no statistical meaning (p=0.905, chi-square test).

CONCLUSION

The use of EM navigation in routine shunt surgery can eliminate poor shunt placement resulting in a dramatic reduction in failure rates.

Protein adsorption to hydrocephalus shunt catheters: CSF protein adsorption

OBJECTIVE

To assess the quantity and nature of the proteins that adsorb to hydrocephalus shunt catheters after implantation, and to determine whether sufficient could accumulate to obstruct the catheter.

DESIGN

Elution of proteins from 102 explanted shunt catheters, with protein assay and electrophoresis of the eluate, and scanning electron microscopy (SEM) of the catheters.

RESULTS

The amount of protein elutable was extremely low, and significant protein, apart from a thin film, was not found on SEM. Qualitative analysis disclosed that most of the adsorbed protein was albumin.

CONCLUSIONS

Protein deposition on hydrocephalus catheters does not occur in sufficient quantities to cause catheter obstruction.