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.

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.

Generation of Periventricular Reactive Astrocytes Overexpressing Aquaporin 4 Is Stimulated by Mesenchymal Stem Cell Therapy.

Aquaporin-4 (AQP4) plays a crucial role in brain water circulation and is considered a therapeutic target in hydrocephalus. Congenital hydrocephalus is associated with a reaction of astrocytes in the periventricular white matter both in experimental models and human cases. A previous report showed that bone marrow-derived mesenchymal stem cells (BM-MSCs) transplanted into the lateral ventricles of hyh mice exhibiting severe congenital hydrocephalus are attracted by the periventricular astrocyte reaction, and the cerebral tissue displays recovery. The present investigation aimed to test the effect of BM-MSC treatment on astrocyte reaction formation. BM-MSCs were injected into the lateral ventricles of four-day-old hyh mice, and the periventricular reaction was detected two weeks later. A protein expression analysis of the cerebral tissue differentiated the BM-MSC-treated mice from the controls and revealed effects on neural development. In in vivo and in vitro experiments, BM-MSCs stimulated the generation of periventricular reactive astrocytes overexpressing AQP4 and its regulatory protein kinase D-interacting substrate of 220 kDa (Kidins220). In the cerebral tissue, mRNA overexpression of nerve growth factor (NGF), vascular endothelial growth factor (VEGF), hypoxia-inducible factor-1 (HIF1α), and transforming growth factor beta 1 (TGFß1) could be related to the regulation of the astrocyte reaction and AQP4 expression. In conclusion, BM-MSC treatment in hydrocephalus can stimulate a key developmental process such as the periventricular astrocyte reaction, where AQP4 overexpression could be implicated in tissue recovery.

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.

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.

Genetics and Molecular Pathogenesis of Human Hydrocephalus.

Hydrocephalus is a neurological disorder with an incidence of 80-125 per 100,000 live births in the United States. The molecular pathogenesis of this multidimensional disorder is complex and has both genetic and environmental influences. This review aims to discuss the genetic and molecular alterations described in human hydrocephalus, from well-characterized, heritable forms of hydrocephalus (e.g., X-linked hydrocephalus from L1CAM variants) to those affecting cilia motility and other complex pathologies such as neural tube defects and Dandy-Walker syndrome. Ventricular zone disruption is one key pattern among congenital and acquired forms of hydrocephalus, with abnormalities in cadherins, which mediate neuroepithelium/ependymal cell junctions and contribute to the pathogenesis and severity of the disease. Given the relationship between hydrocephalus pathogenesis and neurodevelopment, future research should elucidate the genetic and molecular mechanisms that regulate ventricular zone integrity and stem cell biology.

Analysis of N-acetyl cysteine modified polydimethylsiloxane shunt for improved treatment of hydrocephalus.

A major cause of hydrocephalus shunt failure is cell adhesion and obstruction of shunt catheter holes. An estimated 50% of pediatric shunts fail in the first 2 years of insertion, decreasing cell attachment and catheter obstruction can prolong the lifetime and effectiveness of the device. From previous studies, it was shown that treatment of the polydimethylsiloxane (PDMS) surface of a standard catheter with an N-acetyl-cysteine (NAC/1-ethyl-3-(3-dimethylanimopropyl)carbodiimide hydrochloride/N-hydroxysuccinimide) layer increases the wettability of the surface and has been shown to decrease cell adhesion. Other studies indicate that NAC's antioxidant behavior induces glutathione and in turn modulates cell inflammatory pathways. The current study explores the longevity of the NAC coating from the surface of the catheter over time and shows its effect on valve function. Using SEM imaging, contact angle testing, and nanodrop spectrophotometry, this release was quantified for shunt samples incubated for 0, 10, 30, 60, and 90 days. Contact angle showed a significant increase in wettability of the surface when shunts were treated with NAC, confirming successful surface modification. Pressure assays determined that if the coating is release it had no detrimental downstream effects, such as on the shunt valve mechanism. SEM imaging revealed slight deformations in surface coating indicative of salt deposition on the modified shunt samples, while nanodrop spectrophotometry and contact angle data trends suggested some discharge of the NAC coating from the catheter surfaces. The effects of NAC on cell activity may transform the way hydrocephalus is treated in the future by increasing the longevity of the shunt to protect from obstruction.

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.

Neural stem cell therapy of foetal onset hydrocephalus using the HTx rat as experimental model.

Foetal onset hydrocephalus is a disease starting early in embryonic life; in many cases it results from a cell junction pathology of neural stem (NSC) and neural progenitor (NPC) cells forming the ventricular zone (VZ) and sub-ventricular zone (SVZ) of the developing brain. This pathology results in disassembling of VZ and loss of NSC/NPC, a phenomenon known as VZ disruption. At the cerebral aqueduct, VZ disruption triggers hydrocephalus while in the telencephalon, it results in abnormal neurogenesis. This may explain why derivative surgery does not cure hydrocephalus. NSC grafting appears as a therapeutic opportunity. The present investigation was designed to find out whether this is a likely possibility. HTx rats develop hereditary hydrocephalus; 30-40% of newborns are hydrocephalic (hyHTx) while their littermates are not (nHTx). NSC/NPC from the VZ/SVZ of nHTx rats were cultured into neurospheres that were then grafted into a lateral ventricle of 1-, 2- or 7-day-old hyHTx. Once in the cerebrospinal fluid, neurospheres disassembled and the freed NSC homed at the areas of VZ disruption. A population of homed cells generated new multiciliated ependyma at the sites where the ependyma was missing due to the inherited pathology. Another population of NSC homed at the disrupted VZ differentiated into ßIII-tubulin+ spherical cells likely corresponding to neuroblasts that progressed into the parenchyma. The final fate of these cells could not be established due to the protocol used to label the grafted cells. The functional outcomes of NSC grafting in hydrocephalus remain open. The present study establishes an experimental paradigm of NSC/NPC therapy of foetal onset hydrocephalus, at the etiologic level that needs to be further explored with more analytical methodologies.

Feasibility of fast brain diffusion MRI to quantify white matter injury in pediatric hydrocephalus.

OBJECTIVE: Traditionally, diffusion MRI (dMRI) has been performed in parallel with high-resolution conventional MRI, which requires long scan times and may require sedation or general anesthesia in infants and young children. Conversely, fast brain MRI permits image acquisition without the need for sedation, although its short pulse sequences, susceptibility to motion artifact, and contrast resolution have limited its use to assessing ventricular size or major structural variations. Here, the authors demonstrate the feasibility of leveraging a 3-direction fast brain MRI protocol to obtain reliable dMRI measures. METHODS: Fast brain MRI with 3-direction dMRI was performed in infants and children before and after hydrocephalus treatment. Regions of interest in the posterior limbs of the internal capsules (PLICs) and the genu of the corpus callosum (gCC) were drawn on diffusion-weighted images, and mean diffusivity (MD) data were extracted. Ventricular size was determined by the frontal occipital horn ratio (FOHR). Differences between and within groups pre- and posttreatment, and FOHR-MD correlations were assessed. RESULTS: Of 40 patients who met inclusion criteria (median age 27.5 months), 15 (37.5%), 17 (42.5%), and 8 (20.0%) had posthemorrhagic hydrocephalus (PHH), congenital hydrocephalus (CH), or no intracranial abnormality (controls), respectively. A hydrocephalus group included both PHH and CH patients. Prior to treatment, the FOHR (p < 0.001) and PLIC MD (p = 0.027) were greater in the hydrocephalus group than in the controls. While the mean gCC MD in the hydrocephalus group (1.10 × 10-3 mm2/sec) was higher than that of the control group (0.98), the difference was not significant (p = 0.135). Following a median follow-up duration of 14 months, decreases in FOHR, PLIC MD, and gCC MD were observed in the hydrocephalus group and were similar to those in the control group (p = 0.107, p = 0.702, and p = 0.169, respectively). There were no correlations identified between FOHR and MDs at either time point. CONCLUSIONS: The utility of fast brain MRI can be extended beyond anatomical assessments to obtain dMRI measures. A reduction in PLIC and gCC MD to levels similar to those of controls was observed within 14 months following shunt surgery for hydrocephalus in PHH and CH infants. Further studies are required to assess the role of fast brain dMRI for assessing clinical outcomes in pediatric hydrocephalus patients.

The value of early and comprehensive diagnoses in a human fetus with hydrocephalus and progressive obliteration of the aqueduct of Sylvius: Case Report.

BACKGROUND: Mutant rodent models have highlighted the importance of the ventricular ependymal cells and the subcommissural organ (a brain gland secreting glycoproteins into the cerebrospinal fluid) in the development of fetal onset hydrocephalus. Evidence indicates that communicating and non-communicating hydrocephalus can be two sequential phases of a single pathological phenomenon triggered by ependymal disruption and/or abnormal function of the subcommissural organ. We have hypothesized that a similar phenomenon may occur in human cases with fetal onset hydrocephalus. CASE PRESENTATION: We report here on a case of human fetal communicating hydrocephalus with no central nervous system abnormalities other than stenosis of the aqueduct of Sylvius (SA) that became non-communicating hydrocephalus during the first postnatal week due to obliteration of the cerebral aqueduct. The case was followed closely by a team of basic and clinic investigators allowing an early diagnosis and prediction of the evolving pathophysiology. This information prompted neurosurgeons to perform a third ventriculostomy at postnatal day 14. The fetus was monitored by ultrasound, computerized axial tomography and magnetic resonance imaging (MRI). After birth, the follow up was by MRI, electroencephalography and neurological and neurocognitive assessments. Cerebrospinal fluid (CSF) collected at surgery showed abnormalities in the subcommissural organ proteins and the membrane proteins L1-neural cell adhesion molecule and aquaporin-4. The neurological and neurocognitive assessments at 3 and 6 years of age showed neurological impairments (epilepsy and cognitive deficits). CONCLUSIONS: (1) In a hydrocephalic fetus, a stenosed SA can become obliterated at perinatal stages. (2) In the case reported, a close follow up of a communicating hydrocephalus detected in utero allowed a prompt postnatal surgery aiming to avoid as much brain damage as possible. (3) The clinical and pathological evolution of this patient supports the possibility that the progressive stenosis of the SA initiated during the embryonic period may have resulted from ependymal disruption of the cerebral aqueduct and dysfunction of the subcommissural organ. The analysis of subcommissural organ glycoproteins present in the CSF may be a valuable diagnostic tool for the pathogenesis of congenital hydrocephalus.

An update on research priorities in hydrocephalus: overview of the third National Institutes of Health-sponsored symposium "Opportunities for Hydrocephalus Research: Pathways to Better Outcomes".

Building on previous National Institutes of Health-sponsored symposia on hydrocephalus research, "Opportunities for Hydrocephalus Research: Pathways to Better Outcomes" was held in Seattle, Washington, July 9-11, 2012. Plenary sessions were organized into four major themes, each with two subtopics: Causes of Hydrocephalus (Genetics and Pathophysiological Modifications); Diagnosis of Hydrocephalus (Biomarkers and Neuroimaging); Treatment of Hydrocephalus (Bioengineering Advances and Surgical Treatments); and Outcome in Hydrocephalus (Neuropsychological and Neurological). International experts gave plenary talks, and extensive group discussions were held for each of the major themes. The conference emphasized patient-centered care and translational research, with the main objective to arrive at a consensus on priorities in hydrocephalus that have the potential to impact patient care in the next 5 years. The current state of hydrocephalus research and treatment was presented, and the following priorities for research were recommended for each theme. 1) Causes of Hydrocephalus-CSF absorption, production, and related drug therapies; pathogenesis of human hydrocephalus; improved animal and in vitro models of hydrocephalus; developmental and macromolecular transport mechanisms; biomechanical changes in hydrocephalus; and age-dependent mechanisms in the development of hydrocephalus. 2) Diagnosis of Hydrocephalus-implementation of a standardized set of protocols and a shared repository of technical information; prospective studies of multimodal techniques including MRI and CSF biomarkers to test potential pharmacological treatments; and quantitative and cost-effective CSF assessment techniques. 3) Treatment of Hydrocephalus-improved bioengineering efforts to reduce proximal catheter and overall shunt failure; external or implantable diagnostics and support for the biological infrastructure research that informs these efforts; and evidence-based surgical standardization with longitudinal metrics to validate or refute implemented practices, procedures, or tests. 4) Outcome in Hydrocephalus-development of specific, reliable batteries with metrics focused on the hydrocephalic patient; measurements of neurocognitive outcome and quality-of-life measures that are adaptable, trackable across the growth spectrum, and applicable cross-culturally; development of comparison metrics against normal aging and sensitive screening tools to diagnose idiopathic normal pressure hydrocephalus against appropriate normative age-based data; better understanding of the incidence and prevalence of hydrocephalus within both pediatric and adult populations; and comparisons of aging patterns in adults with hydrocephalus against normal aging patterns.

Cell Junction Pathology of Neural Stem Cells Is Associated With Ventricular Zone Disruption, Hydrocephalus, and Abnormal Neurogenesis.

Fetal-onset hydrocephalus affects 1 to 3 per 1,000 live births. It is not only a disorder of cerebrospinal fluid dynamics but also a brain disorder that corrective surgery does not ameliorate. We hypothesized that cell junction abnormalities of neural stem cells (NSCs) lead to the inseparable phenomena of fetal-onset hydrocephalus and abnormal neurogenesis. We used bromodeoxyuridine labeling, immunocytochemistry, electron microscopy, and cell culture to study the telencephalon of hydrocephalic HTx rats and correlated our findings with those in human hydrocephalic and nonhydrocephalic human fetal brains (n = 12 each). Our results suggest that abnormal expression of the intercellular junction proteins N-cadherin and connexin-43 in NSC leads to 1) disruption of the ventricular and subventricular zones, loss of NSCs and neural progenitor cells; and 2) abnormalities in neurogenesis such as periventricular heterotopias and abnormal neuroblast migration. In HTx rats, the disrupted NSC and progenitor cells are shed into the cerebrospinal fluid and can be grown into neurospheres that display intercellular junction abnormalities similar to those of NSC of the disrupted ventricular zone; nevertheless, they maintain their potential for differentiating into neurons and glia. These NSCs can be used to investigate cellular and molecular mechanisms underlying this condition, thereby opening the avenue for stem cell therapy.

Effect of delayed intermittent ventricular drainage on ventriculomegaly and neurological deficits in experimental neonatal hydrocephalus.

PURPOSE: Evidence-based guidelines do not indicate when ventricular reservoirs should be placed in children with neonatal hydrocephalus, and delayed intervention is common. We hypothesize that delayed ventricular drainage has adverse effects on structural development and functional outcomes. METHODS: Using a well-established animal model of kaolin-induced obstructive hydrocephalus, we evaluated neurologic deficit after early (~1 week post-kaolin) or late (~2 weeks post-kaolin) placement of ventricular reservoirs which were tapped according to strict neurologic criteria. RESULTS: Progressive ventriculomegaly was similar in early- and late-reservoir implantation groups. The average neurologic deficit scores (NDSs) over the experimental period were 0 (n=6), 2.74 (n=5), and 2.01 (n=3) for the control, early-, and late-reservoir groups, respectively. At reservoir placement, early-group animals displayed enlarged ventricles without neurologic deficits (mean NDS=0.17), while the late group displayed ventriculomegaly with clinical signs of hydrocephalus (mean NDS=3.13). The correlation between ventriculomegaly severity and NDS in the early group was strongly positive in the acute (before surgery to 3 weeks post-reservoir placement) (R(2)=0.65) and chronic (6 to 12 weeks post-reservoir placement) (R(2)=0.65) phases, while the late group was less correlated (acute R(2)=0.51; chronic R(2)=0.19). CONCLUSIONS: Current practice favors delaying reservoir implantation until signs of elevated intracranial pressure and neurologic deficit appear. Our results demonstrate that animals in early and late groups undergo the same course of ventriculomegaly. The findings also show that tapping reservoirs in these neonatal hydrocephalic animals based on neurologic deficit does not halt progressive ventricular enlargement and that neurologic deficit correlates strongly with ventricular enlargement.

A cell junction pathology of neural stem cells leads to abnormal neurogenesis and hydrocephalus.

Most cells of the developing mammalian brain derive from the ventricular (VZ) and the subventricular (SVZ) zones. The VZ is formed by the multipotent radial glia/neural stem cells (NSCs) while the SVZ harbors the rapidly proliferative neural precursor cells (NPCs). Evidence from human and animal models indicates that the common history of hydrocephalus and brain maldevelopment starts early in embryonic life with disruption of the VZ and SVZ. We propose that a "cell junction pathology" involving adherent and gap junctions is a final common outcome of a wide range of gene mutations resulting in proteins abnormally expressed by the VZ cells undergoing disruption. Disruption of the VZ during fetal development implies the loss of NSCs whereas VZ disruption during the perinatal period implies the loss of ependyma. The process of disruption occurs in specific regions of the ventricular system and at specific stages of brain development. This explains why only certain brain structures have an abnormal development, which in turn results in a specific neurological impairment of the newborn. Disruption of the VZ of the Sylvian aqueduct (SA) leads to aqueductal stenosis and hydrocephalus, while disruption of the VZ of telencephalon impairs neurogenesis. We are currently investigating whether grafting of NSCs/neurospheres from normal rats into the CSF of hydrocephalic mutants helps to diminish/repair the outcomes of VZ disruption.

A cell junction pathology of neural stem cells leads to abnormal neurogenesis and hydrocephalus

Most cells of the developing mammalian brain derive from the ventricular (VZ) and the subventricular (SVZ) zones. The VZ is formed by the multipotent radial glia/neural stem cells (NSCs) while the SVZ harbors the rapidly proliferative neural precursor cells (NPCs). Evidence from human and animal models indicates that the common history of hydrocephalus and brain maldevelopment starts early in embryonic life with disruption of the VZ and SVZ. We propose that a "cell junction pathology" involving adherent and gap junctions is a final common outcome of a wide range of gene mutations resulting in proteins abnormally expressed by the VZ cells undergoing disruption. Disruption of the VZ during fetal development implies the loss of NSCs whereas VZ disruption during the perinatal period implies the loss of ependyma. The process of disruption occurs in specific regions of the ventricular system and at specific stages of brain development. This explains why only certain brain structures have an abnormal development, which in turn results in a specific neurological impairment of the newborn. Disruption of the VZ of the Sylvian aqueduct (SA) leads to aqueductal stenosis and hydrocephalus, while disruption of the VZ of telencephalon impairs neurogenesis. We are currently investigating whether grafting of NSCs/neurospheres from normal rats into the CSF of hydrocephalic mutants helps to diminish/repair the outcomes of VZ disruption.

Reduction of protein adsorption and macrophage and astrocyte adhesion on ventricular catheters by polyethylene glycol and N-acetyl-L-cysteine.

Cellular obstruction of poly(dimethyl)siloxane (PDMS) catheters is one of the most prevalent causes of shunt failure in the treatment of hydrocephalus. By modifying PDMS using short- and long-chain mono-functional polyethylene glycol (PEG604 and PEG5K, respectively) and N-acetyl-L-cysteine via adsorption and covalent binding (NAC and NAC/EDC/NHS, respectively), we increased surface wettability. We hypothesized that these surface modifications would inhibit protein adsorption and decrease host macrophage and astrocyte adhesion. Tested in a bioreactor set to mimic physiological flow, all modified surfaces significantly decreased albumin adsorption compared with PDMS (p < 0.05) except for PEG604-modified PDMS (p = 0.14). All four modification strategies significantly reduced (p < 0.01) fibronectin adsorption. PEG604, PEG5K, NAC, and NAC/EDC/NHS reduced the average level of macrophage adhesion by 53%, 63%, 40%, and 58% (p <.0.05 except when comparing PDMS with NAC) and astrocyte adhesion by 47%, 83%, 91%, and 72% (p < 0.05 except when comparing PDMS with PEG604), respectively. Combined with saline soak results which suggest that the surface wettability is stable over 30 days for each modification, our results are consistent with the hypothesis that these modifications decrease cell adhesion on catheters in vitro for the treatment of hydrocephalus.

Effects of surface wettability, flow, and protein concentration on macrophage and astrocyte adhesion in an in vitro model of central nervous system catheter obstruction.

While silicone devices have vastly improved an array of medical treatments, reactions at the tissue-substrate interface often impede their functionality. Insertion of a poly(dimethyl)siloxane (PDMS) catheter into the cerebral ventricles to drain excess cerebrospinal fluid (CSF) is the most common treatment of hydrocephalus, but shunting often fails because inflammatory tissue, choroid plexus cells, and debris grow into these central nervous system catheters and obstruct flow. We hypothesized that plasma oxidation of PDMS would inhibit macrophage and astrocyte adhesion under flow (0 to 0.3 mL/min) and protein (20.8 to 240 mg/dL) conditions similar to those observed in the physiological state. Oxidation (to increase wettability) had an inhibitory effect on macrophage cell binding (yielding a significant 88% change) that was generally more pronounced than the effect of flow (22% change) or protein concentration (3% change). In contrast, greater flow increased binding of astrocytes in most cases (yielding a significant 97% change); plasma oxidation (19% change), and protein concentration (60% change) had less pronounced effects. This study is the initial indicator that plasma oxidation of PDMS catheters may inhibit macrophage adhesion during CSF outflow but may not be as effective at inhibiting astrocyte binding.

Does drainage hole size influence adhesion on ventricular catheters?

PURPOSE: Ventricular catheter drainage holes of shunt systems used to treat hydrocephalus obstruct with tissue commonly comprising monocytes/macrophages, astrocytes, and giant cells. Despite high rates of obstruction, very few studies have manipulated drainage hole orientation, number, position, or diameter. By altering the hole diameter but maintaining a constant hole surface area, we manipulated shear stress through the holes, which we hypothesized would change the degree of macrophage and astrocyte attachment. METHODS: First, a hole fabrication method was chosen from two fabrication techniques including punched holes in catheter tubing and constructed holes using nanofabrication techniques. RESULTS: Punched holes were chosen to vary hole size from 282 to 975 µm because (1) samples were geometrically similar to commercially available ventricular catheters without significant microscopic differences in roughness values and (2) total macrophage and astrocyte adhesion on the punched holes was not significantly different from adhesion on the commercially available catheters. Overall adhesion from least to most adherent appeared to follow 975 < 754 ≈ 500 < 282-µm hole diameter for macrophages and 975 < 500 < 754 < 282 for astrocytes with an obvious dependency on catheter orientation with respect to the horizontal; a dependency to the proximity of the hole to the catheter tip was not observed. CONCLUSION: This study suggests that macrophage and astrocyte adhesion generally decreases with increasing hole diameter under flow conditions and underscores the necessity for future work to examine how hole diameter impacts inflammatory-based shunt obstruction.

Effects of congenital hydrocephalus on the hypothalamic gonadotrophin-releasing hormone system.

OBJECT: Despite the investigations that have linked hydrocephalus to reproductive system abnormalities, no researchers have attempted to identify the pathophysiological mechanism of this relationship. Because the role of the hypothalamic gonadotrophin-releasing hormone (GnRH) system in the regulation of reproductive functions is well established, the authors used immunohistochemical and radioimmunoassay (RIA) techniques to determine the morphological and biochemical effects of hydrocephalus on the hypothalamic GnRH system. METHODS: Hypothalamic GnRH levels, fiber density, and cell types were studied in 21- and 50-day-old control and congenitally hydrocephalic Texas rats. Results of RIA indicated a significant (8.4%) increase in GnRH in 21-day-old hydrocephalic rats (9.17 +/- 0.64 pg/ng total protein) compared with that in controls (0.97 +/- 0.74 pg/ng total protein). In addition, the 50-day-old hydrocephalic animals had a significantly higher level of GnRH compared with age-matched controls (20.4 pg/ng compared with 1.88 +/- 2.1 pg/ng total protein). This increase was accompanied by changes in the fiber appearance and a shift from low GnRH producing cells to high GnRH producing cells in the hydrocephalic animals; however, there was no significant difference in the fiber density between the control and hydrocephalic animals at 21 days. In addition, poor neurological scores correlated with the severity of hydrocephalus. CONCLUSIONS: These results demonstrated that hypothalamic GnRH levels are significantly affected by fetal-onset hydrocephalus and that the mechanisms responsible for these effects may take place at the cellular rather than the gross structural level. Furthermore, they suggest that impairments in the GnRH system may be protracted in neonates and infants with hydrocephalus, and thus may be overcome by relatively early treatment with ventricular diversion. However, the clinical implications of GnRH perturbations in shunt-dependent patients must await a forthcoming study in shunted animals.