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

Research priorities for improving cognitive and neuropsychological outcomes in hydrocephalus

Hydrocephalus is a neurological disorder that impacts approximately 85 per 100,000 individuals worldwide and is associated with motor and cognitive impairments. While many advances in surgical interventions have helped substantially improve the survival rates and quality of life of those affected, there continues to be significant gaps in our understanding of the etiology of this heterogeneous condition as well as its specific neuropsychological and functional challenges across different phases of life. To address these limitations, the Hydrocephalus Association and Rudi Schulte Research Institute organized a workshop titled, "Improving Cognitive and Psychological Outcomes in Hydrocephalus", composed of top academics in the fields of hydrocephalus, cognition, and neuropsychology, as well as individuals with hydrocephalus or their caregivers. The purpose was to review the available evidence and propose pertinent areas of further research to improve the cognitive functioning, functional status, and quality of life of individuals with hydrocephalus. These topics included cognitive and neuropsychological assessments and daily-life function of children and adults living with hydrocephalus, biomarkers of cognitive function, animal modeling of hydrocephalus, and the longitudinal impact of hydrocephalus treatment. The following paper outlines four primary areas that warrant research: (1) neuropsychological phenotypes, (2) treatment-focused research considerations, (3) translational pre-clinical tools, and (4) establishing pathways for longitudinal care. Through the efforts of this group, the goal of this manuscript is to inspire and direct scientific and clinical inquiry towards these noted research priorities to further improve the lives of individuals with hydrocephalus and their families.

Evaluation of ventriculoperitoneal shunt infections and risk factors in children

INTRODUCTION

To evaluate the demographic, clinical, diagnostic, and treatment data of pediatric patients with ventriculoperitoneal shunt infection and risk factors for ventriculoperitoneal shunt infection and recurrence of ventriculoperitoneal shunt infection.

METHODS

Patients aged 0-18 years who were diagnosed with ventriculoperitoneal shunt infection at Cukurova University Faculty of Medicine Hospital between 2016 and 2021 were included in the study. Demographic, clinical, laboratory, and treatment data of the patients were evaluated retrospectively. Risk factors for the development and recurrence of ventriculoperitoneal shunt infection were evaluated. Patients who underwent ventriculoperitoneal shunt but did not develop any shunt infection were selected as the control group.

RESULTS

Eighty-five patients with a diagnosis of ventriculoperitoneal shunt infection were included in the study. Fever (58.8%), anorexia (58.8%), vomiting (56.5%), and altered consciousness (54.1%) were the most common complaints at admission. The control group consisted of 48 patients. The number of shunt revisions was statistically significantly higher in the group that developed ventriculoperitoneal shunt infection compared to the control group (p < 0.001). In patients with ventriculoperitoneal shunt infection, C-reactive protein and cerebrospinal fluid protein values before shunt insertion were found to be statistically significantly higher than the control group (p < 0.001).

CONCLUSION

Ventriculoperitoneal shunt infection occurs most frequently in the first months after shunt application. Therefore, it is extremely important to prevent colonization and contamination during surgery in preventing the development of ventriculoperitoneal shunt infection. In the present study, cerebrospinal fluid protein elevation and C-reactive protein elevation before shunt application were found to be significant in terms of the development and recurrence of ventriculoperitoneal shunt infection.

Practical techniques for safely removing long-term implanted ventricular catheters to minimize bleeding

INTRODUCTION

Removing ventricular catheters, particularly those implanted for extended periods, poses significant challenges for neurosurgeons due to potential complications such as bleeding from adhesions to the ependyma or choroid plexus.

OBJECTIVE

This study aimed to review various techniques for safely removing ventricular catheters, emphasizing methods that minimize the risk of hemorrhagic complications.

METHODS

A comprehensive narrative review focused on techniques developed and documented in the literature for safely detaching ventricular catheters adhered to brain structures.

RESULTS

Various techniques have been identified that enhance the safety of catheter removal. Notably, the use of monopolar diathermy to coagulate and release adhesions has proven effective. Innovations such as insulated suction devices and the strategic use of flexible endoscopes have also contributed to safer removal procedures, minimizing the risk of damaging surrounding cerebral tissue and preventing catastrophic hemorrhage.

CONCLUSION

The removal of ventricular catheters, especially those with long-term implantation, requires precise and cautious techniques to avoid severe complications. The study underscores the importance of adopting advanced surgical techniques and the continuous evolution of safer practices in neurosurgery. These methods not only ensure patient safety but also facilitate the handling of potentially complex and life-threatening situations during catheter removal.

Ventricular catheter tissue obstruction and shunt malfunction in 9 hydrocephalus etiologies

OBJECTIVE

Hydrocephalus is a neurological disorder with an incidence of 80-125 per 100,000 births in the United States. The most common treatment, ventricular shunting, has a failure rate of up to 85% within 10 years of placement. The authors aimed to analyze the association between ventricular catheter (VC) tissue obstructions and shunt malfunction for each hydrocephalus etiology.

METHODS

Patient information was collected from 5 hospitals and entered into a REDCap (Research Electronic Data Capture) database by hydrocephalus etiology. The hardware samples were fixed, and each VC tip drainage hole was classified by tissue obstruction after macroscopic analysis. Shunt malfunction data, including shunt revision rate, time to failure, and age at surgery, were correlated with the degree of tissue obstruction in VCs for each etiology.

RESULTS

Posthemorrhagic hydrocephalus was the most common etiology (48.9% of total cases). Proximal catheter obstruction was the most frequent cause of hardware removal (90.4%). Myelomeningocele (44% ± 29%), other congenital etiologies (48% ± 40%), hydrocephalus with brain tumors (45% ± 35%), and posthemorrhagic hydrocephalus (41% ± 35%) showed tissue aggregates in more than 40% of the VC holes. A total of 76.8% of samples removed because of symptoms of obstruction showed cellular or tissue aggregates. No conclusive etiological associations were detected when correlating the percentage of holes with tissue for each VC and age at surgery, shunt revision rates, or time between shunt implantation and removal.

CONCLUSIONS

The proximal VC obstruction was accompanied by tissue aggregates in 76.8% of cases. However, the presence of tissue in the VC did not seem to be associated with hydrocephalus etiology.

Ventriculoperitoneal Shunt Failure and Cerebrospinal Fluid Protein: A Meta-Analysis and Systematic Review

Ventriculoperitoneal shunts (VPS) are used to manage hydrocephalus but suffer from high failure rates. Our objectives were to (1) conduct a meta-analysis to objectively weigh this conflicting evidence, and (2) conduct a systematic review compiling and synthesizing what is known about the association between CSF proteins and shunt failure. A literature search was performed in compliance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The Embase, PubMed, and CENTRAL databases were searched from inception to June 2023. The articles were screened based on the inclusion criteria. A meta-analysis was conducted using R statistical software (R Foundation for Statistical Computing, Vienna, Austria); heterogeneity, subgroup, sensitivity, risk of bias, and publication bias analyses were performed. Thirty-one studies were selected for the systematic review, of which eight were selected for the meta-analysis. Perioperative CSF protein level was compared between 351 shunt failures and 1,094 shunt survivals; the mean difference of 24.37 mg/dL favoring shunt failure was significant (95% confidence interval=2.44-46.29 mg/dL). Our systematic review yielded a hypothesized pathogenesis: proteins attached to imperfections in the shunt surface lead to secondary attachment of cells, particularly astrocytes, and tertiary attachment of ependymal cells and the choroid plexus. Owing to the limitations of this meta-analysis, including lack of robustness due to missing data, heterogeneity, and certainty of the evidence, future research is needed to better understand the relationship between perioperative CSF protein levels and shunt failure.

Toward the "Perfect" Shunt: Historical Vignette, Current Efforts, and Future Directions

As a concept, drainage of excess fluid volume in the cranium has been around for more than 1000 years. Starting with the original decompression-trepanation of Abulcasis to modern programmable shunt systems, to other nonshunt-based treatments such as endoscopic third ventriculostomy and choroid plexus cauterization, we have come far as a field. However, there are still fundamental limitations that shunts have yet to overcome: namely posture-induced over- and underdrainage, the continual need for valve opening pressure especially in pediatric cases, and the failure to reinstall physiologic intracranial pressure dynamics. However, there are groups worldwide, in the clinic, in industry, and in academia, that are trying to ameliorate the current state of the technology within hydrocephalus treatment. This chapter aims to provide a historical overview of hydrocephalus, current challenges in shunt design, what members of the community have done and continue to do to address these challenges, and finally, a definition of the "perfect" shunt is provided and how the authors are working toward it.

Polyvinylpyrrolidone-coated catheters decrease choroid plexus adhesion and improve flow/pressure performance in an in vitro model of hydrocephalus

PURPOSE

Proximal catheter obstruction is the leading cause of ventricular shunt failure in pediatric patients. Our aim is to evaluate various types of shunt catheters to assess in vitro cellular adhesion and obstruction.

METHODS

Four catheter types were tested: (1) antibiotic and impregnated, (2) barium-stripe polyvinylpyrrolidone coated (PVP), (3) barium-stripe, and (4) barium-impregnated. Catheters were seeded with choroid plexus epithelial cells to test cellular adhesion and inoculated with the same cells to test flow/pressure performance under choroid plexus growth conditions. Ventricular catheters were placed into a three-dimensional printed phantom ventricular replicating system through which artificial cerebrospinal fluid (CSF) was pumped. Differential pressure sensors were used to measure catheter performance.

RESULTS

PVP catheters had the lowest median cell attachment (10 cells) compared to antibiotic-impregnated (230 cells), barium stripe (513 cells), and barium-impregnated (146 cells) catheters after culture (p < 0.01). In addition, PVP catheters (- 0.247 cm H2O) and antibiotic-impregnated (- 1.15 cm H2O) catheters had significantly lower pressure in the phantom ventricular system compared to the barium stripe (0.167 cm H2O) and barium-impregnated (0.618 cm H2O; p < 0.01) catheters.

CONCLUSIONS

PVP catheters showed less cellular adhesion and, together with antibiotic-impregnated catheters, required less differential pressure to maintain a consistent flow. Our findings suggest clinical relevance for using PVP ventricular catheters in patients with recurrent catheter obstruction by choroid plexus.

Exploration of clinical predictors of the degree of ventricular catheter obstruction: a multicenter retrospective study

OBJECTIVE

The aim of this study was to explore how clinical factors, including the number of lifetime revision surgeries and the duration of implantation, affect the degree of obstruction and failure rates of ventricular catheters (VCs) used to manage hydrocephalus.

METHODS

A total of 343 VCs and their associated clinical data, including patient demographics, medical history, and surgical details, were collected from 5 centers and used for this analysis. Each VC was classified by the degree of obstruction after macroscopic analysis. Univariate, multivariate, and binned analyses were conducted to test for associations between clinical data and degree of VC obstruction.

RESULTS

VCs from patients with 0 to 2 lifetime revisions had a larger proportion of VC holes obstructed than VCs from patients with 10 or more revisions (p = 0.0484). VCs implanted for less than 3 months had fewer obstructed holes with protruding tissue aggregates than VCs implanted for 13 months or longer (p = 0.0225). Neither duration of implantation nor the number of lifetime revisions was a significant predictor of the degree of VC obstruction in the regression models. In the multinomial regression model, contact of the VCs with the ventricular wall robustly predicted the overall obstruction status of a VC (p = 0.005). In the mixed-effects model, the age of the patient at their first surgery emerged as a significant predictor of obstruction by protruding tissue aggregates (p = 0.002). VCs implanted through the parietal entry site were associated with more holes with nonobstructive growth and fewer empty holes than VCs implanted via other approaches (p = 0.001).

CONCLUSIONS

The number of lifetime revisions and duration of implantation are correlated with the degree of VC obstruction but do not predict it. Contact of the VC with the ventricular wall and the age of the patient at their first surgery are predictors of the degree of VC obstruction, while the entry site of the VC correlates with it.

Cerebrospinal fluid shunt malfunctions: A reflective review

PURPOSE

Pediatric hydrocephalus is a common and challenging condition. To date, the ventriculoperitoneal shunt (VPS) is still the main lifesaving treatment option. Nonetheless, it remains imperfect and is associated with multiple short- and long-term complications. This paper is a reflective review of the current state of the VPS, our knowledge gaps, and the future state of shunts in neurosurgical practice.

METHODS AND RESULTS

The authors' reflections are based on a review of shunts and shunt-related literature.

CONCLUSION

Overall, there is still an urgent need for the neurosurgical community to actively improve current strategies for shunt failures and shunt-related morbidity. The authors emphasize the role of collaborative efforts amongst like-minded clinicians to establish pragmatic approaches to avoid shunt complications.

Polyvinylpyrrolidone-Coated Catheters Decrease Astrocyte Adhesion and Improve Flow/Pressure Performance in an Invitro Model of Hydrocephalus

The leading cause of ventricular shunt failure in pediatric patients is proximal catheter occlusion. Here, we evaluate various types of shunt catheters to assess in vitro cellular adhesion and obstruction. The following four types of catheters were tested: (1) antibiotic- and barium-impregnated, (2) polyvinylpyrrolidone, (3) barium stripe, and (4) barium impregnated. Catheters were either seeded superficially with astrocyte cells to test cellular adhesion or inoculated with cultured astrocytes into the catheters to test catheter performance under obstruction conditions. Ventricular catheters were placed into a three-dimensional printed phantom ventricular replicating system through which artificial CSF was pumped. Differential pressure sensors were used to measure catheter performance. Polyvinylpyrrolidone catheters had the lowest median cell attachment compared to antibiotic-impregnated (18 cells), barium stripe (17 cells), and barium-impregnated (21.5 cells) catheters after culture (p < 0.01). In addition, polyvinylpyrrolidone catheters had significantly higher flow in the phantom ventricular system (0.12 mL/min) compared to the antibiotic coated (0.10 mL/min), barium stripe (0.02 mL/min) and barium-impregnated (0.08 mL/min; p < 0.01) catheters. Polyvinylpyrrolidone catheters showed less cellular adhesion and were least likely to be occluded by astrocyte cells. Our findings can help suggest patient-appropriate proximal ventricular catheters for clinical use.

The effect of A1 and A2 reactive astrocyte expression on hydrocephalus shunt failure

Background

The composition of tissue obstructing neuroprosthetic devices is largely composed of inflammatory cells with a significant astrocyte component. In a first-of-its-kind study, we profile the astrocyte phenotypes present on hydrocephalus shunts.

Methods

qPCR and RNA in-situ hybridization were used to quantify pro-inflammatory (A1) and anti-inflammatory (A2) reactive astrocyte phenotypes by analyzing C3 and EMP1 genes, respectively. Additionally, CSF cytokine levels were quantified using ELISA. In an in vitro model of astrocyte growth on shunts, different cytokines were used to prevent the activation of resting astrocytes into the A1 and A2 phenotypes. Obstructed and non-obstructed shunts were characterized based on the degree of actual tissue blockage on the shunt surface instead of clinical diagnosis.

Results

The results showed a heterogeneous population of A1 and A2 reactive astrocytes on the shunts with obstructed shunts having a significantly higher proportion of A2 astrocytes compared to non-obstructed shunts. In addition, the pro-A2 cytokine IL-6 inducing proliferation of astrocytes was found at higher concentrations among CSF from obstructed samples. Consequently, in the in vitro model of astrocyte growth on shunts, cytokine neutralizing antibodies were used to prevent activation of resting astrocytes into the A1 and A2 phenotypes which resulted in a significant reduction in both A1 and A2 growth.

Conclusions

Therefore, targeting cytokines involved with astrocyte A1 and A2 activation is a promising intervention aimed to prevent shunt obstruction.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12987-022-00367-3.

Partial Obstruction of Ventricular Catheters Affects Performance in a New Catheter Obstruction Model of Hydrocephalus

OBJECTIVE

One of the major causes of cerebral ventricular shunt failure is proximal catheter occlusion. We describe a novel ventricular cerebrospinal fluid (CSF) flow replicating system that assesses pressure and flow responses to varying degrees of catheter occlusion.

METHODS

Ventricular catheter performance was assessed during conditions of partial and complete occlusion. The catheters were placed into a three-dimensionally-printed phantom ventricular replicating system. Artificial CSF was pumped through the ventricular system at a constant rate of 1 mL/min to mimic CSF flow, with the proximal end of the catheter in the phantom ventricle. Pressure transducer and flow rate sensors were used to measure intra-phantom pressure, outflow pressure, and CSF flow rates. The catheters were also inserted into silicone tubing and pressure was measured in the same manner for comparison with the phantom.

RESULTS

Pressure measured in the ventricle phantom did not change when the outflow of the ventricular catheter was partially occluded. However, the intraventricular phantom pressure significantly increased when the outflow catheter was 100% occluded. The flow through the catheter showed no significant difference in rate with any degree of partial occlusion of the catheter. At the distal end of the partially occluded catheters, there was less pressure compared with the nonoccluded catheters. This difference in pressure in partially occluded catheters correlated with the percentage of catheter hole occlusion.

CONCLUSIONS

Our model mimics the physiological dynamics of the CSF flow in partially and completely obstructed ventricular catheters. We found that partial occlusion of the catheter had no effect on the CSF flow rate, but did reduce outflow pressure from the catheter.

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.

Investigation of ventriculoperitoneal shunt disconnection for hydrocephalus treatment

OBJECTIVE

This investigation is aimed at gaining a better understanding of the factors that lead to mechanical failure of shunts used for the treatment of hydrocephalus, including shunt catheter-valve disconnection and shunt catheter fracture.

METHODS

To determine the root cause of mechanical failure, the authors created a benchtop mechanical model to mimic mechanical stressors on a shunt system. To test shunt fracture, cyclical loading on the catheter-valve connection site was tested with the shunt catheter held perpendicular to the valve. Standard methods were used to secure the catheter and valves with Nurolon. These commercial systems were compared to integrated catheters and valves (manufactured as one unit). To test complete separation/disconnection of the shunt catheter and valve, a parallel displacement test was conducted using both Nurolon and silk sutures. Finally, the stiffness of the catheters was assessed. All mechanical investigations were conducted on shunts from two major shunt companies, assigned as either company A or company B.

RESULTS

Cyclical loading experiments found that shunts from company B fractured after a mean of 4936 ± 1725 cycles (95% CI 2990-6890 cycles), while those of company A had not failed after 8000 cycles. The study of parallel displacement indicated complete disconnection of company B's shunt catheter-valve combination using Nurolon sutures after being stretched an average 32 ± 5.68 mm (95% CI 25.6-38.4 mm), whereas company A's did not separate using either silk or Nurolon sutures. During the stiffness experiments, the catheters of company B had statistically significantly higher stiffness of 13.23 ± 0.15 N compared to those of company A, with 6.16 ± 0.29 N (p < 0.001).

CONCLUSIONS

Mechanical shunt failure from shunt catheter-valve disconnection or fracture is a significant cause of shunt failure. This study demonstrates, for the first time, a correlation between shunt catheters that are less mechanically stiff and those that are less likely to disconnect from the valve when outstretched and are also less likely to tear when held at an angle from the valve outlet. The authors propose an intervention to the standard of care wherein less stiff catheters are trialed to reduce disconnection.

Cerebrospinal fluid biomarkers of neuroinflammation in children with hydrocephalus and shunt malfunction

BACKGROUND

Approximately 30% of cerebrospinal fluid (CSF) shunt systems for hydrocephalus fail within the first year and 98% of all patients will have shunt failure in their lifetime. Obstruction remains the most common reason for shunt failure. Previous evidence suggests elevated pro-inflammatory cytokines in CSF are associated with worsening clinical outcomes in neuroinflammatory diseases. The aim of this study was to determine whether cytokines and matrix metalloproteinases (MMPs) contribute towards shunt failure in hydrocephalus.

METHODS

Using multiplex ELISA, this study examined shunt failure through the CSF protein concentration profiles of select pro-inflammatory and anti-inflammatory cytokines, as well as select MMPs. Interdependencies such as the past number of previous revisions, length of time implanted, patient age, and obstruction or non-obstruction revision were examined. The pro-inflammatory cytokines were IL-1β, IL-2, IL-5, IL-6, IL-8, IL-12, IL-17, TNF-α, GM-CSF, IFN-γ. The anti-inflammatory cytokines were IL-4 and IL-10, and the MMPs were MMP-2, MMP-3, MMP-7, MMP-9. Protein concentration is reported as pg/mL for each analyte.

RESULTS

Patient CSF was obtained at the time of shunt revision operation; all pediatric (< 18), totaling n = 38. IL-10, IL-6, IL-8 and MMP-7 demonstrated significantly increased concentrations in patient CSF for the non-obstructed subgroup. Etiological examination revealed IL-6 was increased in both obstructed and non-obstructed cases for PHH and congenital hydrocephalic patients, while IL-8 was higher only in PHH patients. In terms of number of past revisions, IL-10, IL-6, IL-8, MMP-7 and MMP-9 progressively increased from zero to two past revisions and then remained low for subsequent revisions. This presentation was notably absent in the obstruction subgroup. Shunts implanted for three months or less showed significantly increased concentrations of IL-6, IL-8, and MMP-7 in the obstruction subgroup. Lastly, only patients aged six months or less presented with significantly increased concentration of IL-8 and MMP-7.

CONCLUSION

Non-obstructive cases are reported here to accompany significantly higher CSF cytokine and MMP protein levels compared to obstructive cases for IL-10, IL-6, IL-8, MMP-7 and MMP-9. A closer examination of the definition of obstruction and the role neuroinflammation plays in creating shunt obstruction in hydrocephalic patients is suggested.

Bilateral Proptosis in a Child-A Rare Manifestation of Ventriculoperitoneal Shunt Obstruction

Ventriculoperitoneal shunt (VPS) obstruction may have a myriad of presentations. We reported a case of an 11-year-old girl presenting with acute, bilateral proptosis secondary to VPS obstruction. While neuroimaging was interpreted as unremarkable, fundoscopy revealed bilateral papilledema and lumbar puncture showed elevated intracranial pressure. Neurosurgical exploration demonstrated VPS valve obstruction and a new VPS was inserted. Postoperatively, she developed a recurrent extradural hematoma, which was initially evacuated and later managed conservatively. To our knowledge, this is the first report of bilateral proptosis secondary to VPS obstruction. This case highlights the value of key clinical findings and limitations of neuroimaging.

Characterization of a multicenter pediatric-hydrocephalus shunt biobank

BACKGROUND

Pediatric hydrocephalus is a devastating and costly disease. The mainstay of treatment is still surgical shunting of cerebrospinal fluid (CSF). These shunts fail at a high rate and impose a significant burden on patients, their families and society. The relationship between clinical decision making and shunt failure is poorly understood and multifaceted, but catheter occlusion remains the most frequent cause of shunt complications. In order to investigate factors that affect shunt failure, we have established the Wayne State University (WSU) shunt biobank.

METHODS

To date, four hospital centers have contributed various components of failed shunts and CSF from patients diagnosed with hydrocephalus before adulthood. The hardware samples are transported in paraformaldehyde and transferred to phosphate-buffered saline with sodium azide upon deposit into the biobank. Once in the bank, they are then available for study. Informed consent is obtained by the local center before corresponding clinical data are entered into a REDCap database. Data such as hydrocephalus etiology and details of shunt revision history. All data are entered under a coded identifier.

RESULTS

293 shunt samples were collected from 228 pediatric patients starting from May 2015 to September 2019. We saw a significant difference in the number of revisions per patient between centers (Kruskal-Wallis H test, p value < 0.001). The leading etiology at all centers was post-hemorrhagic hydrocephalus, a fisher's exact test showed there to be statistically significant differences in etiology between center (p = 0.01). Regression showed age (p < 0.01), race (p = 0.038) and hospital-center (p < 0.001) to explain significant variance in the number of revisions. Our model accounted for 31.9% of the variance in revisions. Generalized linear modeling showed hydrocephalus etiology (p < 0.001), age (p < 0.001), weight and physician (p < 0.001) to impact the number of ventricular obstructions.

CONCLUSION

The retrospective analysis identified that differences exist between currently enrolled centers, although further work is needed before clinically actionable recommendations can be made. Moreover, the variables collected from this chart review explain a meaningful amount of variance in the number of revision surgeries. Future work will expand on the contribution of different site-specific and patient-specific factors to identify potential cause and effect relationships.

Enhanced wall shear stress prevents obstruction by astrocytes in ventricular catheters

The treatment of hydrocephalus often involves the placement of a shunt catheter into the cerebrospinal ventricular space, though such ventricular catheters often fail by tissue obstruction. While diverse cell types contribute to the obstruction, astrocytes are believed to contribute to late catheter failure that can occur months after shunt insertion. Using in vitro microfluidic cultures of astrocytes, we show that applied fluid shear stress leads to a decrease of cell confluency and the loss of their typical stellate cell morphology. Furthermore, we show that astrocytes exposed to moderate shear stress for an extended period of time are detached more easily upon suddenly imposed high fluid shear stress. In light of these findings and examining the range of values of wall shear stress in a typical ventricular catheter through computational fluid dynamics (CFD) simulation, we find that the typical geometry of ventricular catheters has low wall shear stress zones that can favour the growth and adhesion of astrocytes, thus promoting obstruction. Using high-precision direct flow visualization and CFD simulations, we discover that the catheter flow can be formulated as a network of Poiseuille flows. Based on this observation, we leverage a Poiseuille network model to optimize ventricular catheter design such that the distribution of wall shear stress is above a critical threshold to minimize astrocyte adhesion and growth. Using this approach, we also suggest a novel design principle that not only optimizes the wall shear stress distribution but also eliminates a stagnation zone with low wall shear stress, which is common to current ventricular catheters.

Overdrainage-related ependymal bands: a postulated cause of proximal shunt obstruction

OBJECTIVEVentricular shunts have an unacceptably high failure rate, which approaches 50% of patients at 2 years. Most shunt failures are related to ventricular catheter obstruction. The literature suggests that obstructions are caused by in-growth of choroid plexus and/or reactive cellular aggregation. The authors report endoscopic evidence of overdrainage-related ventricular tissue protrusions ("ependymal bands") that cause partial or complete obstruction of the ventricular catheter.METHODSA retrospective review was completed on patients undergoing shunt revision surgery between 2008 and 2015, identifying all cases in which the senior author reported endoscopic evidence of ependymal tissue in-growth into ventricular catheters. Detailed clinical, radiological, and surgical findings are described.RESULTSFifty patients underwent 83 endoscopic shunt revision procedures that revealed in-growth of ventricular wall tissue into the catheter tip orifices (ependymal bands), producing partial, complete, or intermittent shunt obstructions. Endoscopic ventricular explorations revealed ependymal bands at various stages of development, which appear to form secondarily to siphoning. Ependymal bands are associated with small ventricles when the shunt is functional, but may dilate at the time of obstruction.CONCLUSIONSVentricular wall protrusions are a significant cause of proximal shunt obstruction, and they appear to be caused by siphoning of surrounding tissue into the ventricular catheter orifices.

Shunt-dependent hydrocephalus: management style among members of the American Society of Pediatric Neurosurgeons

OBJECTIVE The authors conducted a survey to evaluate differences in the understanding and management of shunt-dependent hydrocephalus among members of the American Society of Pediatric Neurosurgeons (ASPN). METHODS Surveys were sent to all 204 active ASPN members in September 2014. One hundred thirty responses were received, representing a 64% response rate. Respondents were asked 13 multiple-choice and free-response questions regarding 4 fundamental problems encountered in shunted-hydrocephalus management: shunt malfunction, chronic cerebrospinal fluid (CSF) overdrainage, chronic headaches, and slit ventricle syndrome (SVS). RESULTS Respondents agreed that shunt malfunction occurs most often as the result of ventricular catheter obstruction. Despite contrary evidence in the literature, most respondents (66%) also believed that choroid plexus is the tissue most often found in obstructed proximal catheters. However, free-text responses revealed that the respondents' understanding of the underlying pathophysiology of shunt obstruction was highly variable and included growth, migration, or adherence of choroid plexus, CSF debris, catheter position, inflammatory processes, and CSF overdrainage. Most respondents considered chronic CSF overdrainage to be a rare complication of shunting in their practice and reported wide variation in treatment protocols. Moreover, despite a lack of evidence in the literature, most respondents attributed chronic headaches in shunt patients to medical reasons (for example, migraines, tension). Accordingly, most respondents managed headaches with reassurance and/or referral to pain clinics. Lastly, there were variable opinions on the etiology of slit ventricle syndrome (SVS), which included early shunting, chronic overdrainage, and/or loss of brain compliance. Beyond shunt revision, respondents reported divergent SVS treatment preferences. CONCLUSIONS The survey shows that there is wide variability in the understanding and management of shunt-dependent hydrocephalus and its complications. Such discrepancies appear to be derived partly from inconsistent familiarity with existing literature but especially from a paucity of high-quality publications.

Reduced cell attachment to poly(2-hydroxyethyl methacrylate)-coated ventricular catheters in vitro

The majority of patients with hydrocephalus are dependent on ventriculoperitoneal shunts for diversion of excess cerebrospinal fluid. Unfortunately, these shunts are failure-prone and over half of all life-threatening pediatric failures are caused by obstruction of the ventricular catheter by the brain's resident immune cells, reactive microglia and astrocytes. Poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogels are widely used for biomedical implants. The extreme hydrophilicity of PHEMA confers resistance to protein fouling, making it a strong candidate coating for ventricular catheters. With the advent of initiated chemical vapor deposition (iCVD), a solvent-free coating technology that creates a polymer in thin film form on a substrate surface by introducing gaseous reactant species into a vacuum reactor, it is now possible to apply uniform polymer coatings on complex three-dimensional substrate surfaces. iCVD was utilized to coat commercially available ventricular catheters with PHEMA. The chemical structure was confirmed on catheter surfaces using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. PHEMA coating morphology was characterized by scanning electron microscopy. Testing PHEMA-coated catheters against uncoated clinical-grade catheters in an in vitro hydrocephalus catheter bioreactor containing co-cultured astrocytes and microglia revealed significant reductions in cell attachment to PHEMA-coated catheters at both 17-day and 6-week time points. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1268-1279, 2018.

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.