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.

Stereotactic cysto-ventricular catheters in craniopharyngiomas: an effective minimally invasive method to improve visual impairment and achieve long-term cyst volume reduction

Craniopharyngiomas are typically located in the sellar region and frequently contain space-occupying cysts. They usually cause visual impairment and endocrine disorders. Due to the high potential morbidity associated with radical resection, several less invasive surgical approaches have been developed. This study investigated stereotactic-guided implantation of cysto-ventricular catheters (CVC) as a new method to reduce and control cystic components. Twelve patients with cystic craniopharyngiomas were treated with CVC in our hospital between 04/2013 and 05/2017. The clinical and radiological data were retrospectively analysed to evaluate safety aspects as well as ophthalmological and endocrine symptoms. The long-term development of tumour and cyst volumes was assessed by volumetry. The median age of our patients was 69.0 years and the median follow-up period was 41.0 months. Volumetric analyses demonstrated a mean reduction of cyst volume of 64.2% after CVC implantation. At last follow-up assessment, there was a mean reduction of cyst volume of 92.0% and total tumour volume of 85.8% after completion of radiotherapy. Visual acuity improved in 90% of affected patients, and visual field defects improved in 70% of affected patients. No patient showed ophthalmological deterioration after surgery, and endocrine disorders remained stable. Stereotactic implantation of CVC proved to be a safe minimally invasive method for the long-term reduction of cystic components with improved ophthalmological symptoms. The consequential decrease of total tumour volumes optimised conditions for adjuvant radiotherapy. Given the low surgical morbidity and the effective drainage of tumour cysts, this technique should be considered for the treatment of selected cystic craniopharyngiomas.

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.

A simple and cost-effective model for ventricular catheter placement training: technical note

OBJECTIVEExternal ventricular drain (EVD) placement is one of first cranial procedures neurosurgery residents are expected to perform independently. While proper training improves patient outcomes, there are few options for practicing EVD placement prior to placing the EVD in patients in a clinical setting. Proposed solutions to this include using cadaveric models and virtual simulations, but barriers exist with these as well in regard to authenticity. EVD simulators using virtual reality technologies are a promising new technique for training, but the cost of these devices poses a barrier to general/widespread accessibility among smaller programs or underserved hospitals. The authors desribe a novel, yet simple, and cost-effective technique (less than $5 per mold) for developing a brain model constructed of homemade ballistics gelatin that can be used for teaching and practicing the placement of EVD.METHODSA brain model is made with ballistics gelatin using an anatomically correct skull model as a mold. A 3D-printed ventricular system model is used to create a mold of an anatomically correct ventricular system in the brain model. A group of medical students (n = 10) were given a basic presentation about EVD placement, including standard landmarks and placement techniques, and were also shown a demonstration of EVD placement on the brain model. They were then allowed to perform an EVD placement using the brain model. The students were surveyed on their experience with using the brain model, including usability and practicality of the model. Accuracy of EVD placement by each student was also assessed, with adequate position of catheter tip being in the ipsilateral frontal horn.RESULTSThe final product is fairly inexpensive and easy to make. It is soft enough to pass a catheter through, but it is also firm enough to maintain its shape, including a cavity representing the lateral ventricles. The dense gelatin holds the catheter in its final resting position, while the two halves are separated and inspected. All participants in the test group of medical students reported that the brain model was easy to use, helped them understand the steps and technique of EVD placement, and provided good feedback on the ideal position of ventricular catheters. All of the participants in the group had adequate positioning of their ventricular catheters after one attempt.CONCLUSIONSThe presented brain model is easy to replicate, inexpensive, anatomically accurate, and provides a medium for neurosurgeons to teach and practice ventricular catheter placement in a risk-free environment.