A new approach in the treatment of hydrocephalus

Incidence of infection rate for shunt implantation: the zero % rate is always a myth

INTRODUCTION

Paediatric CSF shunt infection rate remains a well-known complication that is not only responsible of potentially severe sequels for patients but also for economical expenses. In that study, we questioned if it is possible to attain the zero percent rate of infection that should be the goal of every paediatric neurosurgeon.

METHODS

We report our series of patients treated with a CSF device from January the first 2016 to December 31 2018.

RESULTS

In all 147 patients treated for hydrocephalus, the follow-up was of at least of 2 years from the implantation. Antibiotic-coated tubes were always used with a differential pressure valve system. A total of 172 surgical procedures were performed for 147 patients. In the follow-up time period, 4 patients presented a post-operative infection (2.3%). Two infections appeared early after the surgical procedure one after 24 h and the other after 6 days; the other two infections were diagnosed after 53 days and the other after 66 days. The germs responsible of the infections were a Staphylococcus capitals, an Escherichia coli, a Klebsiella pneumonia, and a Staphylococcus aureus.

CONCLUSIONS

Shunts will always be implanted especially in new-borns and for particular aetiologies of hydrocephalus. To reduce the rate of infection, the best thing to do is to adopt adapted protocols. Our low incidence of infection rate for shunts represent a long history to research preventive factors that helped us to improve our results during the time.

Measuring CSF shunt flow with MRI using flow enhancement of signal intensity (FENSI)

PURPOSE

To develop and validate a noninvasive imaging technique for accurately assessing very slow CSF flow within shunt tubes in pediatric patients with hydrocephalus, aiming to identify obstructions that might impede CSF drainage.

THEORY AND METHODS

A simulation of shunt flow enhancement of signal intensity (shunt-FENSI) signal is used to establish the relationship between signal change and flow rate. The quantification of flow enhancement of signal intensity data involves normalization, curve fitting, and calibration to match simulated data. Additionally, a phase sweep method is introduced to accommodate the impact of magnetic field inhomogeneity on the flow measurement. The method is tested in flow phantoms, healthy adults, intensive care unit patients with external ventricular drains (EVD), and shunt patients. EVDs enable shunt-flow measurements to be acquired with a ground truth measure of CSF drainage.

RESULTS

The flow-rate-to-signal simulation establishes signal-flow relationships and takes into account the T1 of draining fluid. The phase sweep method accurately accounts for phase accumulation due to frequency offsets at the shunt. Results in phantom and healthy human participants reveal reliable quantification of flow rates using controlled flows and agreement with the flow simulation. EVD patients display reliable measures of flow rates. Shunt patient results demonstrate feasibility of the method and consistent flow rates for functional shunts.

CONCLUSION

The results demonstrate the technique's applicability, accuracy, and potential for diagnosing and noninvasively monitoring hydrocephalus. Limitations of the current approach include a high sensitivity to motion and strict requirement of imaging slice prescription.

The Top 100 Most Cited Journal Articles on Hydrocephalus

Hydrocephalus represents a significant burden of disease, with more than 383,000 new cases annually worldwide. When the magnitude of this condition is considered, a centralized archive of pertinent literature is of great clinical value. From a neurosurgical standpoint, hydrocephalus is one of the most frequently treated conditions in the field. The focus of this study was to identify the top 100 journal articles specific to hydrocephalus using bibliometric analysis. Using the Journal of Citation Report database, 10 journals were identified. The Web of Science Core Collection was then searched using each journal name and the search term "hydrocephalus." The results were ordered by "Times Cited" and searched by the number of citations. The database contained journal articles from 1976 to 2021, and the following variables were collected for analysis: journal, article type, year of publication, and the number of citations. Journal articles were excluded if they had no relation to hydrocephalus, mostly involved basic science research, or included animal studies. Ten journals were identified using the above criteria, and a catalog of the 100 most cited publications in the hydrocephalus literature was created. Articles were arranged from highest to lowest citation number, with further classification by journal, article type, and publication year. Of the 100 articles referenced, 38 were review articles, 24 were original articles, 15 were comparative studies, 11 were clinical trials, six were multi-center studies, three were cross-sectional, and three were case reports with reviews. Articles were also sorted by study type and further stratified by etiology. If the etiology was not specified, studies were instead subcategorized by treatment type. Etiologies such as aqueductal stenosis, tumors, and other obstructive causes of hydrocephalus were classified as obstructive (n=6). Communicating (n=15) included idiopathic, normal pressure hydrocephalus, and other non-obstructive etiologies. The category "other" (n=3) was assigned to studies that included etiologies, populations, and/or treatments that did not fit into the classifications previously outlined. Through our analysis of highly cited journal articles focusing on different etiologies and the surgical or medical management of hydrocephalus, we hope to elucidate important trends. By establishing the 100 most cited hydrocephalus articles, we contribute one source, stratified for efficient referencing, to facilitate clinical care and future research on hydrocephalus.

A novel, benchtop model for quantitative analysis of resistance in ventricular catheters

INTRODUCTION

The mechanisms of catheter obstruction are still poorly understood, but the literature suggests that resistance to fluid flow plays a significant role. We developed and assessed a gravity-driven device that measures flow through ventricular catheters. We used this device to quantitatively analyze the resistances of unused ventricular catheters used in the treatment of hydrocephalus; failed hydrocephalus catheters from our catheter biorepository were also evaluated quantitatively.

METHODS

Catheters of three manufacturing companies were inserted into the benchtop model, which records time, flow rate, and pressure data using sensors. The relative resistances of catheters across six design models were evaluated. Experiments were performed to evaluate changes in the relative resistance of a catheter when the catheter's holes were progressively closed. The relative resistance of explanted catheters from our catheter biorepository was also measured.

RESULTS

Experimental results showed significant differences (P<0.05) between the relative resistances of different catheter models just after being removed from their packaging. A non-linear trend of increasing resistance was observed in experiments on catheters with artificially obstructed holes. Data from five individual benchtop models were compared, and the differences in measured data between the models were found to be negligible. A significant increase (P < 0.05) in relative resistance was observed in explanted catheters.

CONCLUSION

The current study sought to propose a novel in-vitro model and use it to examine data on differences in relative resistance among catheter models. From these experiments, we can rapidly correlate clinical patient cohorts to identify mechanisms of luminal shunt obstruction.

Development of shunt valves used for treating hydrocephalus: comparison with endoscopy treatment

The pathophysiology of hydrocephalus is not clearly defined. Thus, treatment will remain empirical until a fuller understanding of the various forms of hydrocephalus is achieved. Valve-controlled shunting has been the mainstay of therapy since the late 1950s. Initially, shunting occurred from the ventricular system to the atrium. In the 1970s, VA shunts were replaced by ventriculoperitoneal shunts as the primary location for the distal end. Multiple types of one-way valve systems have been developed in the pursuit of draining the appropriate amount of CSF that avoids either overdrainage or underdrainage while preserving normal brain development and cognition. These valves are reviewed and compared as to their function. Other locations for the distal end of the shunting system are reviewed to include pleural space and gallbladder. The lumbar subarachnoid space as the proximal location for a shunt is also reviewed. The only other surgical alternative for treating hydrocephalus is endoscopic third ventriculostomy. Since 2000, approximately 50% of children with hydrocephalus have been shown to be candidates for ETV. The benefits are the lack of need for an artificial shunt system and thus lower rates of infection and over time fewer reoperations. Future progress is dependent on improved shunt valve systems that are affordable worldwide and ready availability of ETV in developing countries. Anatomic and molecular causes of hydrocephalus need to be defined so that medications or genetic modifications become available for potential cure of hydrocephalus.

Design and Characterization of an Adjustable Passive Flow Regulator and Application to External CSF Drainage

Passive valves that deliver a constant flow rate regardless of inlet pressure changes have numerous applications in research, industry, and medical fields. The present article describes a passive spring valve that can be adjusted manually to deliver the required flow rate. The valve consists of a movable rod with an engraved microchannel. The fluidic resistance of the device varies together with the inlet pressure to regulate the flow rate. A prototype was made and characterized. Flow-rate adjustment up to +/-30% of the nominal flow rate was shown. A simple numerical model of the fluid flow through the device was made to adapt the design to external ventricular drainage of cerebrospinal fluid (CSF). Some insights about the implementation of this solution are also discussed.

In vitro and in vivo assessment of a novel ultra-flexible ventriculoamniotic shunt for treating fetal hydrocephalus

Fetal aqueductal stenosis (AS) is one of the most common causes of congenital hydrocephalus, which increases intracranial pressure due to partial or complete obstruction of cerebrospinal fluid (CSF) flow within the ventricular system. Approximately 2-4 infants per 10,000 births develop AS, which leads to progressive hydrocephalus, which enlarges the head often necessitating delivery by cesarean section. Most babies born with AS are severely neurologically impaired and experience a lifetime of disability. Therefore, a new device technology for venticuloamniotic shunting is urgently needed and has been studied to ameliorate or prevent fetal hydrocephalus development, which can provide a significant impact on patients and their family's quality of life and on the decrease of the healthcare dollars spent for the treatment. This study has successfully validated the design of shunt devices and demonstrated the mechanical performance and valve functions. A functional prototype shunt has been fabricated and subsequently used in multiple in vitro tests to demonstrate the performance of this newly developed ventriculoamniotic shunt. The shunt contains a main silicone-nitinol composite tube, a superelastic 90° angled dual dumbbell anchor, and an ePTFE valve encased by a stainless-steel cage. The anchor will change its diameter from 1.15 mm (collapsed state) to 2.75 mm (deployed state) showing up to 1.4-fold diameter change in human body temperature. Flow rates in shunts were quantified to demonstrate the valve function in low flow rates mimicking the fetal hydrocephalus condition showing "no backflow" for the valved shunt while there is up to 15 mL/h flow through the shunt with pressure difference of 20 Pa. In vivo ovine study results show the initial successful device delivery and flow drainage with sheep model.

Shunt technology for infants and a lifetime

The use of cerebrospinal fluid (CSF) shunts remains a fundamental therapeutic modality in the management of hydrocephalus. Nowadays, neurosurgeons have an arsenal of different shunt technologies on their hands, with several companies producing many different configurations of them. The greatest difficulty of treating a child with hydrocephalus is to deal with a brain that will enormously change its size and hydrodynamic conditions and a body that will multiply its height and weight in a short time. Detailed knowledge of the hydrodynamic properties of shunts is mandatory for any neurosurgeon and much more for those taking care of pediatric patients. It is necessary to know that these properties of the valve may influence the evolution of the patient after shunting and it is recognized that a patient physiology-specific valve selection may yield better outcomes and decrease complications. This article provides a summary of the most common available CSF valves and overdrainage control devices, their technology, and possible combinations. The objective is to offer a quick overview of the armamentarium to facilitate the recognition of the implanted device and improve the selection of the most suitable valve for each patient.

Antisiphon device: a review of existing mechanisms and clinical applications to prevent overdrainage in shunted hydrocephalic patients

Overdrainage of cerebrospinal fluid is one of the most notorious complications after ventriculoperitoneal shunt implantation. Siphon effect plays a major role in the development of overdrainage. Various overdrainage-preventing devices have been invented to counteract the siphon effect. Though some of the devices are designed to reduce the flow instead of providing antisiphoning effect, they are generally called antisiphon devices (ASDs). The basics of siphoning, the mechanisms and physical properties of currently available devices are described in this article. The clinical efficacy, shunt survival, and considerations on patient factors are also discussed. There are three kinds of ASD design, diaphragm, gravitational, and flow reducing devices. Flow reducing ASD is always open and the flow it controls is relatively stable. On the other hand, it may not provide sufficient flow in nocturnal intracranial pressure elevations. Diaphragm and gravitational devices are sensitive to the position of the patients. Diaphragm device is sensitive to the external pressure and the relative position of the device to the mastoid process. The gravitational device is sensitive to the angle between the axis of the device and the head. Many studies showed encouraging results with gravitational devices. Studies regarding diaphragm devices either showed better or similar outcomes comparing to differential pressure valves. Clinical studies regarding flow-reducing devices and head-to-head comparison between different mechanisms are warranted. This review aims to provide a useful reference for clinical practice of hydrocephalus.

A Review of Passive Constant Flow Regulators for Microfluidic Applications

This review gives an overview of passive constant flow regulators dedicated to microfluidic applications. Without external control and energy consumption, these devices deliver a constant flow rate regardless of pressure variations, making them very attractive for various microfluidic applications, including drug delivery, flow chemistry, point-of-care tests, or microdialysis. This technical review examines progress over the last three decades in the development of these flow regulators and focuses on the working principle, fabrication methods, performance, and potential applications.

Artificial Shunting of Cerebrospinal Fluid

A compact three-stage shunt valve system (Orbis Sigma™ Valve) which operates as a flow regulator within certain differential pressure values has been clinically evaluated in the treatment of hydrocephalus. Clinical trials were performed in 134 cases, covering 128 patients aged from 1 day to 79 years with a mean age at implantation of 11.4 years. One-third of the implants was performed to replace failed DP shunts. Using actuarial statistics, 83.9% of the shunts continued to adequately manage hydrocephalus at three years. Overdrainage occurred in 2 cases (1.5%) and insufficient drainage occurred in four cases (3%). Compared with literature for conventional DP shunts, the incidence of these phenomena is extremely low. Based on the results summarized in this paper and those already reported in the literature, the OSV appears to address the overdrainage limitations of conventional shunts.

Hydrocephalus treatment in children: long-term outcome in 975 consecutive patients

OBJECTIVE Hydrocephalus remains one of the more common pathologies managed in pediatric neurosurgical units. Endoscopic third ventriculostomy (ETV) has an advantage over ventriculoperitoneal shunting as it enables patients to remain device free. Multiple shunt devices with various valve designs exist, with no one valve proven to be superior to another. The aim of this study was to describe the management of hydrocephalus and its long-term outcome. METHODS The authors retrospectively reviewed the medical records of all patients who had been treated for hydrocephalus at the Hôpital Necker-Enfants Malades in the period from 1985 to 1995. RESULTS Nine hundred seventy-five children had been treated for hydrocephalus. The mean follow-up was 11 ± 7.4 years (mean ± standard deviation). The most common cause of hydrocephalus was tumor related (32.3%), followed by malformative (24.5%) and inflammatory (20.9%) causes. Two hundred eighty patients underwent ETV as the first-line treatment. The procedure was effective in controlling hydrocephalus due to posterior fossa tumors and aqueductal stenosis. Six hundred ninety-five children had initial shunt insertion, with the majority receiving an Orbis-Sigma valve (OSV). The overall OSV shunt survival was 70% at 1 year, 58% at 10 years, and 49% at 20 years. The most common cause for mechanical shunt failure was obstruction (50.7%). Overall shunt survival was statistically different between the OSV and the differential-pressure valve (p = 0.009). CONCLUSIONS Endoscopic third ventriculostomy is effective in the management of childhood hydrocephalus. Its success is directly related to the underlying pathology. In the long term, the OSV has significantly higher event-free shunt survival than the classic differential-pressure valve systems.

Long-term survival rates of gravity-assisted, adjustable differential pressure valves in infants with hydrocephalus

OBJECTIVE The use of adjustable differential pressure valves with gravity-assisted units in shunt therapy of children with hydrocephalus was reported to be feasible and promising as a way to avoid chronic overdrainage. In this single-center study, the authors' experiences in infants, who have higher rates of shunt complications, are presented. METHODS All data were collected from a cohort of infants (93 patients [37 girls and 56 boys], less than 1 year of age [mean age 4.1 ± 3.1 months]) who received their first adjustable pressure hydrocephalus shunt as either a primary or secondary implant between May 2007 and April 2012. Rates of valve and shunt failure were recorded for a total of 85 months until the end of the observation period in May 2014. RESULTS During a follow-up of 54.2 ± 15.9 months (range 26-85 months), the Kaplan-Meier rate of shunt survival was 69.2% at 1 year and 34.1% at 85 months; the Kaplan-Meier rate of valve survival was 77.8% at 1 year and 56% at 85 months. Survival rates of the shunt were significantly inferior if the patients had previous shunt surgery. During follow-up, 44 valves were exchanged in cases of infection (n = 19), occlusion (n = 14), dysfunction of the adjustment unit (n = 10), or to change the gravitational unit (n = 1). CONCLUSIONS Although a higher shunt complication rate is observed in infant populations compared with older children, reasonable survival rates demonstrate the feasibility of using this sophisticated valve technology. The gravitational unit of this valve is well tolerated and its adjustability offers the flexible application of opening pressure in an unpredictable cohort of patients. This may adequately address overdrainage-related complications from early in treatment.

Shunt Devices for the Treatment of Adult Hydrocephalus: Recent Progress and Characteristics

Various types of shunt valves have been developed during the past 50 years, most of which can be classified into the following categories: (1) fixed differential pressure valves; (2) fixed differential pressure (DP) valves with an antisiphon mechanism; (3) programmable DP valves; (4) programmable DP valves with an antisiphon mechanism; and (5) programmable antisiphon valves. When considering the myriad of possible postoperative condition changes, such as the onset of accidental non-related diseases or trauma in adults, and changes in normal physiological development or anticipation of future shunt removal in children, it has become standard to use the programmable valve as a first choice for cerebrospinal fluid shunting. However, it is still unclear what type of shunt valve is suitable for each individual case. Based on the results of SINPHONI and more recently SINPHONI 2 trials, the programmable DP valve is recommended as the first line shunt valve. The programmable DP valve with an antisiphon mechanism is thought to be beneficial for tall, slender patients, who have a tendency for easily developing complications of overdrainage, however, this type of valve must be used cautiously in obese patients because of the increased risk of underdrainage. Although the current evidence is still insufficient, the programmable antisiphon valve, which costs the same as the programmable DP valve, is also thought to be the first line shunt valve. The quick reference table is applicable for most shunt valves, and for patients with either the ventriculoperitoneal or the lumboperitoneal shunt.

Effect of Protein Concentration on the Flow of Cerebrospinal Fluid Through Shunt Tubing

BACKGROUND:

Protein levels in cerebrospinal fluid (CSF) are commonly thought to be related to sterile shunt malfunction.

OBJECTIVE:

To investigate the relationship between protein concentration and flow through CSF shunt tubing and a shunt valve.

METHODS:

New and explanted shunt catheters were tested with and without a shunt valve attached at various protein concentrations. The protein concentrations used were 0.5, 2, 5, and 10 g/L. A flask with artificial CSF attached to the proximal end provided flow. The flow was allowed to stabilize over 1 hour, and then the change in pressure between the proximal and distal end of the catheter was measured and recorded. The resistance to flow was calculated for new and explanted catheters for adult shunt systems, as well as with the addition of a programmable siphon control valve. The resistance was examined after the addition of various protein concentrations to a normal CSF solution.

RESULTS:

Both new and explanted catheters exhibited a decrease in the resistance to flow with higher concentrations of protein.

CONCLUSION:

In our laboratory setting, there was decreased resistance of adult CSF shunt catheters with and without a valve as the concentration of protein in the CSF increased. The decrease in the resistance of CSF shunt catheters with the addition of protein to the CSF may be related to the lowering of surface tension. This is the first study to examine the effects of varying protein concentrations across different lengths of shunt tubing for both new and explanted catheters.

Is there an ideal shunt? A panoramic view of 110 years in CSF diversions and shunt systems used for the treatment of hydrocephalus: from historical events to current trends

OBJECT

The goal of this study is to evaluate whether an "ideal shunt" exists.

METHODS

This is a retrospective analysis based on original papers in the field of Hydrocephalus and Shunts. Patients of all age groups, who had hydrocephalus, and underwent some form of CSF diversion were included. The study has been divided into four stages: from 1900 to 1949, 1950 to 1974, 1975 to 1999, and from 2000 to 2010.

RESULTS

In stage 1 (historical era): Saphenous vein grafts, rubber conduits, and other materials were used in CSF diversions. In 1949, the first implantable shunt tube was developed by Nulsen. In stage 2 (experimental stage): the Holter valve was developed. Newer innovations were developed in relation to the ventriculo-atrial shunt, which was the preferred CSF diversion. In stage 3 (developmental stage), a large number of different design shunt systems were developed, with the aim of reducing complications. The ventriculo-peritoneal shunt had become the preferred CSF diversion. Also, the programmable valve was born. In stage 4 (era of programmable valve, there is a preference for the use of programmable shunt systems. However, shunt failure rate at 1 year being around 25 to 40%, and shunt survival at 1 and 2 years are 50-70 and 47-53% in most series.

CONCLUSION

Every shunt is an ideal shunt provided the choice of the shunt used should be made by the matching performance of the shunt system to the altered profile of CSF dynamics of a given patient. The most important factor being the opening pressure.

The truth and coherence behind the concept of overdrainage of cerebrospinal fluid in hydrocephalic patients

INTRODUCTION

Overdrainage, siphoning, and slit-ventricle syndrome are well-documented complications of shunting in hydrocephalic patients. Despite the prevalence of these conditions, their mechanisms are still not fully understood. In this paper, the authors trace the concept of overdrainage and the related phenomena of siphoning and slit-ventricle syndrome.

PURPOSE

To provide a historical overview of overdrainage and to reignite discussion of a topic that has been settled.

METHODS AND RESULTS

A medical literature search and review were performed via Google Scholar. Of 565 publications, 3 primary papers were identified and a timeline was developed demonstrating the convergence of the aforementioned concepts. From the primary papers, 25 relevant publications were selected and further analyzed searching for hypothesis, evidence, and conclusions.

CONCLUSION

Overdrainage, siphoning, and slit-ventricle syndrome are associated concepts that have converged into a pathophysiological theory where siphoning of CSF leads to overdrainage, which is then hypothesized to cause slit-ventricle syndrome in a small subset of patients. Our data suggests that while there have been numerous reports regarding overdrainage and its consequences, the evidence is not as robust as currently presumed and this subject requires prospective exploration.

Shunt survival rates by using the adjustable differential pressure valve combined with a gravitational unit (proGAV) in pediatric neurosurgery

OBJECT

Overdrainage is a chronic complication in shunted pediatric patients with hydrocephalus. The use of adjustability of differential pressure (DP) valves in combination with antisiphoning devices may help to overcome this sequela and may diminish the rate of possible shunt failures. The purpose of this retrospective study is to report our experience on shunt survival and infection rate with an adjustable DP valve with integrated gravitational unit in pediatric hydrocephalus.

METHODS

The proGAV consists of an adjustable differential pressure (DP) valve and a gravitational unit. During the time period of July 2004 and December 2009, a total of 237 adjustable gravitational valves were used in 203 children (age, 6.5 ± 6.54; 0-27 years). In the follow-up period, valve and shunt failures as well as rate of infection were recorded.

RESULTS

Within the average follow-up time of 21.9 ± 10.3 months (range, 6-72 months), the valve survival rate was 83.8 %. The overall shunt survival rate including all necessary revisions was 64.3 %. Looking at the group of infants (<1 year of age) within the cohort, the valve survival rate was 77.3 % and the shunt survival rate was 60.9 %. The overall infection rate was 4.6 %.

CONCLUSION

In a concept of avoiding chronic overdrainage by using the proGAV in hydrocephalic children, we observed a good rate of valve and shunt survival. Compared to previous reported series, we experienced the proGAV as a reliable tool for the treatment of pediatric hydrocephalus.

Hydrodynamic properties of the Certas hydrocephalus shunt

OBJECT

Independent testing of hydrocephalus shunts provides information about the quality of CSF drainage after shunt implantation. Moreover, hydrodynamic parameters of a valve assessed in the laboratory create a comparative pattern for testing of shunt performance in vivo. This study sought to assess the hydrodynamic parameters of the Certas valve, a new model of a hydrocephalus shunt.

METHODS

The Certas valve is an adjustable ball-on-spring hydrocephalus valve. It can be adjusted magnetically in vivo in 7 steps, equally distributed within the therapeutic limit for hydrocephalus, and the eighth step at high pressures intended to block CSF drainage. The magnetically adjustable rotor is designed to prevent accidental readjustment of the valve in a magnetic field, including clinical MRI.

RESULTS

The pressure-flow performance curves, as well as the operating, opening, and closing pressures, were stable, fell within the specified limits, and changed according to the adjusted performance levels. The valve at settings 1-7 demonstrated low hydrodynamic resistance of 1.4 mm Hg/ml/min, increasing to 5.1 mm Hg/ml/min after connection of a distal drain provided by the manufacturer. At performance Level 8 the hydrodynamic resistance was greater than 20 mm Hg/ml/min. External programming of the valve proved to be easy and reliable. The valve is safe in 3-T MRI and the performance level of the valve is unlikely to be changed. However, with the valve implanted, distortion of the image is substantial. Integration of the valve with the SiphonGuard limits the drainage rate.

CONCLUSIONS

In the laboratory the Certas valve appears to be a reliable differential-pressure adjustable valve. Laboratory evaluation should be supplemented by results of a clinical audit in the future.

Posture-independent piston valve: a novel valve mechanism that actuates based on intracranial pressure alone

OBJECT

Shunt valves are intended to maintain physiological intracranial pressure (ICP). A variety of mechanisms have been designed to accomplish this goal but have had limited success. Siphoning, in particular, has been a problem not effectively solved by proposed or manufactured valves. Poor control of ICP results in headache, neurological disturbances, decreased cognition, shunt malfunction, slit ventricles, subdural hematomas, decreased cranial volume, and maldevelopment. The authors of this study describe a prototype valve that was machined and tested ex vivo and that actuates based on ICP alone regardless of the presence of a siphon. Their object was to determine if a novel shunt mechanism that actuates perpendicular to the flow of fluid would eliminate the effect of siphoning in a valve for the treatment of hydrocephalus.

METHODS

A posture-independent piston valve (PIPV) was anchored to a graduated reservoir. Opening pressure was measured by noting the fluid level in the reservoir when the piston moved. Measurements were made using a 90-cm and a 120-cm water-filled siphon tube (1.3-mm standard distal catheter) to simulate an upright posture. A recumbent posture was simulated by the absence of a siphon.

RESULTS

Opening pressure of the valve did not change regardless of the presence or absence of a water-filled siphon.

CONCLUSIONS

The PIPV was triggered only by the pressure head at the inlet and did not actuate in the presence of a siphon, demonstrating proof of principle of the perpendicular actuating mechanism. The PIPV is a purely mechanical device that has practical application in the treatment of hydrocephalus.

Analysis of the risk of shunt failure or infection related to cerebrospinal fluid cell count, protein level, and glucose levels in low-birth-weight premature infants with posthemorrhagic hydrocephalus

OBJECT

Premature, low-birth-weight infants with posthemorrhagic hydrocephalus have a high risk of shunt obstruction and infection. Established risk factors for shunt failure include grade of the hemorrhage and age at shunt insertion. There is anecdotal evidence that the amount of red blood cells or protein levels in the CSF may affect shunt performance. However, this has not been analyzed specifically for this cohort of high-risk patients. Therefore, the authors performed this study to examine whether any statistical relationship exists between the CSF constituents and the rate of shunt malfunction or infection in this population.

METHODS

A retrospective cohort study was performed on premature infants born at Riley Hospital for Children from 2000 to 2009. Inclusion criteria were a CSF sample analyzed within 2 weeks prior to shunt insertion, low birth weight (< 1500 grams), prematurity (birth prior to 37 weeks estimated gestational age), and shunt insertion for posthemorrhagic hydrocephalus. Data points included the gestational age at birth and shunt insertion, weight at birth and shunt insertion, history of CNS infection prior to shunt insertion, shunt failure, shunt infection, and the levels of red blood cells, white blood cells, protein, and glucose in the CSF. Statistical analysis was performed to determine any association between shunt outcome and the CSF parameters.

RESULTS

Fifty-eight patients met the study entry criteria. Ten patients (17.2%) had primary shunt failure within 3 months of insertion. Nine patients (15.5%) had shunt infection within 3 months. A previous CNS infection prior to shunt insertion was a statistical risk factor for shunt failure (p = 0.0290) but not for shunt infection. There was no statistical relationship between shunt malfunction or infection and the CSF levels of red blood cells, white blood cells, protein, or glucose before shunt insertion.

CONCLUSIONS

Low-birth-weight premature infants with posthemorrhagic hydrocephalus have a high rate of shunt failure and infection. The authors did not find any association of shunt failure or infection with CSF cell count, protein level, or glucose level. Therefore, it may not be useful to base the timing of shunt insertion on CSF parameters.

The surgical management of pediatric hydrocephalus

The surgical management of hydrocephalus has undergone incredible changes over the past generation of neurosurgeons, including dramatic improvements in imaging, especially computed tomographic scanning and magnetic resonance imaging, and remarkably innovative advances in cerebrospinal fluid valve technology, complex computer models, and endoscopic equipment and techniques. In terms of overall patient outcomes, however, one could conclude that things are a little better, but "not much." This frustrating yet fascinating dichotomy between technological advancements and clinical outcomes makes hydrocephalus, first described by the ancients, as one of the most understated and complex disorders that neurosurgeons treat. The challenge to the next generation of neurosurgeons is to solve this vexing problem through better understanding of the basic science, improved computer models, additional technological advances, and, most importantly, a broad-based, concerted multidisciplinary attack on this disorder. This review focuses on the evolution of surgery for hydrocephalus over the last 30 years, the current state of the art of hydrocephalus treatment, and what appear to be the most promising future directions.

Preliminary study of shunt related death in paediatric patients

Hydrocephalus is a condition commonly encountered in paediatric and adult neurosurgery and cerebrospinal fluid (CSF) shunting remains the treatment of choice for many cases. Despite improvements in shunt technology and technique, morbidity and mortality remain. The incidence of early shunt obstruction is high with later failures seen less frequently. This review aims to examine mortality associated with mechanical failure of CSF shunts within Queensland. Neurosurgical and Intensive Care databases were reviewed for cases of mortality associated with shunt failure. Eight cases were identified between the years of 1992 and 2002 with the average age at death 7.7 years. Deaths occurred on average 2 years after last shunt revision. Seven of the eight patients lived outside the metropolitan area. Shunting remains an imperfect means of treating hydrocephalus. Mortality may be encountered at any time post surgery and delays to surgical intervention influence this. Alternative measures such as third ventriculostomy or the placement of a separate access device should be considered. In the event of emergency, a spinal needle could be used to access the ventricle along the course of the ventricular catheter.

Pediatric gravitational shunts: initial results from a prospective study

OBJECT

The authors' goal in this paper was to evaluate prospectively the efficacy and safety of a new pediatric gravitational shunt to determine whether it warrants inclusion in a randomized, controlled trial with other shunts.

METHODS

A total of 55 children between the ages of 0 and 6 years (median age 0.5 years, average age 4+/-6 years) underwent primary shunt implantation; all received the Miethke Paedi-GAV. The follow-up period ranged between 12 and 77 months (mean 47+/-21 months). The primary end point of the study was the first shunt failure necessitating revision. The 1- and 2-year shunt survival rates were 75 and 68%, respectively. The average failure-free shunt survival duration was 1423 +/- 641 days. Based on imaging findings, no slitlike ventricles occurred. The complication rate was 33%, and the median time to shunt failure was 45 days. Underdrainage occurred in one child (1.8%) and overdrainage in two children (3.6%).

CONCLUSIONS

These preliminary results prove the Miethke Paedi-GAV to be a safe and effective pediatric shunt worthy of inclusion in a randomized comparison with other shunts in the pediatric population.

Endoscopic third ventriculostomy in the treatment of shunt-related over-drainage: Preliminary experience with a new approach how to render ventricles navigable

OBJECTIVE

Endoscopic third ventriculostomy (ETV) is increasingly used for the treatment of shunt-related complications in hydrocephalic patients, particularly if the etiology of the underlying hydrocephalus is of obstructive nature.

PURPOSE

Due to the slit-like configuration of the ventricles, ventricular dilatation must be achieved prior to ETV in patients with problems due to over-drainage. This has been accomplished by ligating or explanting the shunt. Here we present an alternative procedure using a gravitational antisiphon device.

MATERIALS AND METHODS

In two patients with over-drainage due to shunted occlusive hydrocephalus ventricles were dilated by integrating an antisiphon device (Miethke ShuntAssistant, Aesculap AG, Tuttlingen, Germany) into their shunt systems. The resistance of the antisiphon device, which is available in configurations from 10 to 35 cm H2O was chosen 10 cm H2O higher than necessary to prevent siphoning in the individual patient.

RESULTS

Both patients gradually recovered from their over-drainage symptoms and the ventricles enlarged enough to allow access with an endoscope. Using a standard procedure, ETV was performed 7 days and 1 month later, respectively. In the same operative session the shunts were occluded. Shunts were removed within 6 weeks after ETV. During follow-up of more than 3 years, both patients remained free of symptoms.

CONCLUSION

The incorporation of an antisiphon device with resistance level selected 10 cm H2O higher than needed to prevent anti-siphoning into a pre-existing shunt system in patients suffering from shunt-related over-drainage is a safe and effective technique to render ventricles large enough to allow endoscopic access for ETV.

Endoscopic third ventriculostomy for chronic hydrocephalus after tuberculous meningitis

BACKGROUND

Cerebrospinal fluid diversion procedures are indicated in patients with hydrocephalus after tuberculous meningitis (TBM). We present 2 patients with hydrocephalus after TBM who were successfully treated with endoscopic third ventriculostomy (ETV).

METHODS

Two patients had been diagnosed with hydrocephalus after TBM and had undergone ventriculoperitoneal shunt surgery for the same. They presented with multiple episodes of shunt dysfunction. Endoscopic third ventriculostomy was performed (twice for one patient), and the patients were evaluated clinically and radiologically after the procedure.

RESULTS

On long-term clinical follow-up (3 and 2 years, respectively), both patients were asymptomatic after the ETV. The first patient was radiologically evaluated 7 months after the procedure and the second patient 2 years after the procedure. The first patient showed a decrease in ventricular size. The second patient did not show any significant change in the ventricular size.

CONCLUSION

Endoscopic third ventriculostomy can be considered as a safe and long-lasting solution for hydrocephalus after chronic TBM.

Does the ventricle size change after shunt operation of normal-pressure hydrocephalus?

The aim of this study was to determine whether ventricular size correlates with a positive clinical outcome following shunt placement. Hydrostatic valves (Dual-Switch-Valves) were implanted in 80 patients with NPH at Unfallkrankenhaus Berlin between September 1997 and January 2002. One year postoperatively, these patients underwent computerized tomography scanning, and their ventricular size was ascertained using the Evans-Index. Among 80% of the patients who showed no postoperative change in ventricular volume, 59% nonetheless had good to excellent clinical improvements, 17% satisfactory clinical improvement, and 24% no improvement. Furthermore, a moderate reduction in ventricular size was observed in 14% of patients in this cohort. Among these, 36% experienced a good to excellent clinical improvement, 28% a satisfactory improvement, and 36% unsatisfactory improvement. A marked reduction in ventricular size was observed in 6% of the patients. Of this group, 60% demonstrated good to excellent outcomes, whereas 40% had unsatisfactory outcomes. Favourable outcomes following the implantation of a hydrostatic shunt in patients with NPH did not correlate with decreased ventricular volume 1 year after surgery. In fact, better clinical outcomes were observed in patients with little or no alteration in ventricular size, compared with those in patients with marked decrease in ventricular size. A postoperative change in ventricular volume should be assessed differently in patients with NPH compared with those suffering from hypertensive hydrocephalus.

The gravity-assisted Paedi-Gav valve in the treatment of pediatric hydrocephalus

OBJECTIVE

A single-center, prospective, nonrandomized pilot study was performed to assess the Paedi-Gav gravity-assisted valve for the treatment of pediatric patients with hydrocephalus.

METHODS

Participants were pediatric patients (age <16 years) who were candidates for a hydrocephalus shunt system that required a valve insertion at the time of enrollment. The primary outcome event was shunt malfunction; subclassified into shunt obstruction, shunt overdrainage, loculated ventricles, or infection. The shunt obstructions were further subclassified according to site. A total of 32 patients were enrolled onto the study, with 2 undergoing first shunt insertion after failed ventriculostomy and 30 undergoing shunt revisions. On average, the patients had had 3.3 shunt procedures prior to insertion of a Paedi-Gav valve.

RESULTS

During a follow-up interval of minimum 52 weeks and a median of 24 months after the first implantation on-study, shunt revisions were required in 17 (53.1%) of the 32 patients. The 12-month shunt-survival rate without revision of any component was 53%, with a median shunt-survival time of 388 days. The most common reasons for shunt revision were shunt obstructions (12/17) and overdrainage (3/17). Shunt obstructions were caused by valve-related failures (9/12) and distal obstructions (3/12).

CONCLUSION

Although the small number of patients enrolled in this study warrants cautious conclusions, the overall results are comparable to those reported for primary shunt insertions with conventional valves in pediatric patients with hydrocephalus. Although this study provides a rationale for examining the Paedi-Gav gravity-assisted shunt valve in a larger prospective randomized controlled trial, the shunt failure pattern, with a rather high frequency of valve-related failures, may indicate potential for further improvements in the valve design and/or manufacturing.

Immune reactions associated with silicone-based ventriculo-peritoneal shunt malfunctions in children

The implantation of ventriculo-peritoneal (VP) shunting systems is the most commonly performed neurological procedure in children with hydrocephalus. Although the overall complication risk is low, the cumulative risk of shunt failure is high and unfortunately results in a high prevalence of revision surgeries. In this study, we explored the concept that some pediatric patients may develop an immune response to either the proteins attached to the silicone implant surface or to the biomaterial itself, and that this reaction may contribute to VP shunt failure in some individuals. The data displays that the sterile shunt malfunction group had a higher rate of protein deposition and increased levels of autoantibodies to the extracted surface proteins as compared to individuals with functioning shunting systems. The precise nature of the shunt-bound proteins that serve as antigens in this experiment have not yet been determined. The data also indicated that some individuals develop antibodies to polymeric substances that cross-react with partially polymerized acrylamide. The detection of significant amounts of shunt-bound protein, antibody responses to these proteins and to polymeric substances suggest that an immunological response to these proteins may play a role in the mechanism behind sterile shunt malfunctions.

Correlation between decreased ventricular size and positive clinical outcome following shunt placement in patients with normal-pressure hydrocephalus

OBJECT

It is well known that in patients with communicating hydrocephalus or normal-pressure hydrocephalus (NPH), ventricular size decreases following implantation of shunts with differential pressure valves. The aim of this study was to determine whether ventricular size correlates with a positive clinical outcome following shunt placement.

METHODS

Hydrostatic valves (dual-switch valves) were implanted in 80 patients with NPH at Unfallkrankenhaus, Berlin, between September 1997 and January 2002. One year postoperatively, these patients underwent computerized tomography scanning, and their ventricular size was ascertained using the Evans Index. Among 80% of the patients who showed no postoperative change in ventricular volume, 59% nonetheless had good to excellent clinical improvements, 17% satisfactory improvement, and 24% no improvement. Furthermore, a moderate reduction in ventricular size was observed in 14% of patients in this cohort. Among these, 36% experienced good to excellent clinical improvements, 28% satisfactory improvement, and 36% unsatisfactory improvement. A marked reduction in ventricular size was observed in 6% of the patients. Of this latter group, 60% demonstrated good to excellent outcomes, whereas 40% had unsatisfactory outcomes.

CONCLUSIONS

Favorable outcomes following the implantation of a hydrostatic shunt in patients with NPH did not correlate with decreased ventricular volume 1 year after surgery. In fact, better clinical outcomes were observed in patients with little or no alteration in ventricular size, compared with those in patients with a marked decrease in ventricular size. A postoperative change in ventricular volume should be assessed differently in patients with NPH compared with those suffering from hypertensive hydrocephalus.

Is decreased ventricular volume a correlate of positive clinical outcome following shunt placement in cases of normal pressure hydrocephalus?

It is well known that in patients with communicating hydrocephalus or normal pressure hydrocephalus, ventricular volume decreases following implantation of differential pressure valved shunts. Hydrostatic valves (Miethke dual-switch valves) were implanted in 60 normal pressure hydrocephalus patients at Unfallkrankenhaus Berlin between September 1997 and September 2001. One year postoperatively, these patients underwent CT scan, and their ventricular size was ascertained using the Evans index. Although 77% of these patients showed no postoperative change in ventricular volume, 65% nonetheless showed good to excellent clinical improvement, 13% satisfactory improvement and 22% no improvement. A moderate reduction in ventricular size was observed in 17% of the patients in our cohort. 40% of these patients showed good to excellent clinical improvement, 20% satisfactory improvement, and 40% unsatisfactory improvement. A marked reduction in ventricular size was observed in 6% of our patients. Of these latter patients, 50% showed good to excellent outcomes, while 50% had unsatisfactory outcomes. The favorable outcomes following implantation of a hydrostatic shunt in patients with normal pressure hydrocephalus did not correlate with decreased ventricular volume one year after operation. Better clinical outcomes were observed in patients with little or no alteration in ventricular size than in patients with a marked decrease in ventricular size. Postoperative change in ventricular volume should be assessed differently for patients with normal pressure hydrocephalus than in patients with hypertensive hydrocephalus.

Transcranial color-coded Doppler ultrasonography for evaluation of children with hydrocephalus

OBJECT

Hydrocephalus is a common disease process. Transcranial color-coded Doppler (TCCD) ultrasonography is an accepted noninvasive method with which to quantify intracranial blood flow in adults and children. The authors studied the applications of TCCD ultrasonography and the alterations of the flow velocity of the cerebral arteries in children with hydrocephalus.

METHODS

One hundred thirty-five children were divided into three groups: Group 1 comprised 40 infants with asymptomatic hydrocephalus who had well-functioning ventriculoperitoneal (VP) shunts; Group 2 comprised 10 children with symptomatic hydrocephalus who had malfunctioning shunts that were replaced; and Group 3 was a control group of 85 healthy infants. All patients underwent sequential measurements of cerebral blood flow (CBF) velocities (systolic and diastolic velocities) and resistivity index (RI). One group of patients underwent functional tests (compression of the anterior fontanelle and CO2 vasoreactivity) to determine hemodynamic changes in cerebral circulation. A significant statistical change in RI measurements, end diastolic CBF velocity, and percentage of change in RI was shown in patients with malfunctioning shunts, and in infants with a well-functioning VP shunt vasomotor reactivity was severely reduced.

CONCLUSIONS

Transcranial color-coded Doppler ultrasonography can be used to perform follow-up assessments of normal and malfunctioning shunts in children with hydrocephalus; the functional tests are a noninvasive tool for evaluating the cerebral compliance and the cerebral autoregulation in infants with hydrocephalus. The autoregulatory capacity may partly or completely be lost in cases of long-term shunt-treated hydrocephalus, and loss of cerebral vasoreactivity may be responsible for long-term deficits commonly observed in children, which help explain some of symptoms related to slit ventricles.

Treatment of hydrocephalus determined by the European Orbis Sigma Valve II survey: a multicenter prospective 5-year shunt survival study in children and adults in whom a flow-regulating shunt was used

OBJECT

The goal of this study was to evaluate the long-term results of a flow-regulating shunt (Orbis Sigma Valve [OSV] II Smart Valve System; Integra NeuroSciences, Sophia Antipolis, France) in the treatment of hydrocephalus, whether it was a first insertion procedure or surgical revision of another type of shunt, in everyday clinical practice in a multicenter prospective study.

METHODS

Patients of any age who had hydrocephalus underwent implantation of an OSV II system. The primary end point of the study was defined as any shunt-related surgery. The secondary end point was a mechanical complication (shunt obstruction, overdrainage, catheter misplacement, migration, or disconnection) or infection. The overall 5-year shunt survival rates and survival as it applied to different patient subgroups were assessed. Five hundred fifty-seven patients (48% of whom were adults and 52% of whom were children) were selected for OSV II shunt implantation; 196 patients reached the primary end point. Shunt obstruction occurred in 75 patients (13.5%), overdrainage in 10 patients (1.8%), and infection in 46 patients (8.2%). The probability of having experienced a shunt failure-free interval at 1 year was 71% and at 2 years it was 67%; thereafter the probability remained quite stable in following years (62% at the 5-year follow-up examination). No difference in shunt survival was observed between the overall pediatric (< or = 16 years of age) and adult populations. In the pediatric age group, however, there was a significantly lower rate of shunt survival in children younger than 6 months of age (55% at the 5-year follow-up examination).

CONCLUSIONS

In this prospective study the authors demonstrate the effectiveness of flow regulation in the treatment of hydrocephalus both in children and in adults. Flow-regulating shunts limit the incidence of overdrainage and shunt-related complications. The overall 5-year shunt survival rate (62%) compares favorably with rates cited in other recently published series.

Clinical experience with the low pressure Novus valve in the treatment of adult hydrocephalus

PURPOSE

The low pressure Novus valve is a pressure differential valve with a normally open siphon control mechanism. This study evaluates our experience with this valve in adult hydrocephalus and is the first published clinical review of the Novus valve.

PATIENTS AND METHODS

From June 1999, we prospectively inserted low pressure Novus valves in all patients requiring new ventriculoperitoneal and ventriculoatrial shunts and requiring shunt valve revision. In December 2000, 52 patients were retrospectively reviewed.

RESULTS

The major causes of hydrocephalus were intracranial haemorrhage (18), tumour (10), normal pressure hydrocephalus (10) and trauma (9). Forty one procedures were first shunts and eleven were revisions. The Novus valve was revised once. Complications include one infection and one sudden death from cerebral haemorrhage. No patients developed overdrainage symptoms or subdural haematomas. There were large improvements in symptoms. Ninety-three percent of the patients reported an improvement in daily function and quality of life. The remaining 7% reported no change, despite improvements in symptoms.

CONCLUSIONS

The Novus low pressure valve is an effective first choice of valve for adult hydrocephalus.

Is normal pressure hydrocephalus a valid concept in 2002? A reappraisal in five questions and proposal for a new designation of the syndrome as "chronic hydrocephalus"

The authors question the current validity of the traditional concept of normal pressure hydrocephalus (NPH) as it was described by Adams and Hakim in 1965. The classic features of the disease are addressed. It is concluded that most of the historical statements made three decades ago need to be revised. Especially, the term "normal pressure" hydrocephalus probably does not match the actual manometric profile of patients with NPH. Similarly, the terms"curable"and "reversible" dementia are inadequate to designate the mental alterations of NPH. That NPH is non-specific to the adult population is also stressed, since it may be not uncommonly encountered in paediatrics, especially in an implanted shunt malfunction. The term "chronic hydrocephalus" without reference to cerebrospinal fluid pressure and to the age of the patient is proposed instead of NPH, which seems out of step with current knowledge of the pressure profile and with the diagnosis and decision making context in patients with so called NPH.

Idiopathic normal pressure hydrocephalus: a systematic review of diagnosis and outcome

OBJECTIVE

Patient selection for cerebrospinal fluid diversion is difficult, because idiopathic normal pressure hydrocephalus (INPH) mimics other neurodegenerative disorders and no findings reliably predict outcome. The literature was reviewed to identify diagnostic criteria that predict shunt response and to formulate prognostic expectations.

METHODS

MEDLINE was searched, and 44 articles meeting predetermined criteria were included.

RESULTS

Clinical series were frequently retrospective with small patient numbers and unstandardized outcome evaluation. Clinical findings suggestive of shunt responsiveness were the complete triad (gait disturbance, urinary incontinence, and dementia) with early gait disturbance. Degree of hydrocephalus was not correlated with clinical improvement. Reduction of the subcortical low-blood flow area was correlated with improvement in three small studies. Clinical response to prolonged cerebrospinal fluid drainage predicted shunt outcome in all cases in two small series. Overall, 59% (range, 24-100%) of patients improved after shunting, and 29% (range, 10-100%) of patients experienced prolonged improvement. Complications occurred in 38% (range, 5-100%) of patients, additional surgery was required in 22% (range, 0-47%) of patients, and there was a 6% (range, 0-35%) combined rate of permanent neurological deficit and death.

CONCLUSION

Shunting INPH is associated with an approximately 29% rate of significant improvement and a 6% significant complication rate. Enlargement of the subcortical low-flow area and clinical improvement secondary to prolonged lumbar drainage may provide additive predictive value above clinical and computed tomographic criteria. A multicenter clinical trial that focuses on the value of ancillary tests, defines the clinical course of a patient with a ventriculoperitoneal shunt, and evaluates the cost effectiveness of shunting INPH is needed to better describe outcome from shunting in INPH.

Treatment of hydrocephalus in adults by placement of an open ventricular shunt

OBJECT

Ventricular shunt placement is the neurosurgical procedure most frequently associated with complications. Over the years, it has been a growing concern that the performance of most shunting devices does not conform to physiological parameters. An open ventriculoperitoneal (VP) bypass with a peritoneal catheter for which the cross-sectional internal diameter was 0.51 mm as a distinctive element for flow resistance was evaluated for use in the treatment of adult patients with hydrocephalus.

METHODS

During a 2-year period, open shunts were surgically implanted in 54 adults with hydrocephalus; conventional shunts were implanted in 80 matched controls. Periodic evaluations were performed using neuroimaging studies and measures of clinical status. All patients were followed from 12 to 36 months. 18.5 +/- 4 months for patients with the open shunt and 19.1 +/- 8.1 months for controls (mean +/- standard deviation). The device continued to function in 50 patients with the open shunt (93%) and in 49 controls (61%: p < 0.001). The Evans index in patients with the open shunt was 0.33 +/- 0.09 throughout the follow up. No cases of infection, overdrainage, or slit ventricles were observed: the index in controls was 0.28 +/- 0.08; 60% of them developed slit ventricles. During the follow-up period occlusion occurred in four patients with the open shunt (7%) and in 31 controls (39%: p < 0.001).

CONCLUSIONS

The daily cerebrospinal fluid (CSF) drainage through the open VP shunt is close to 500 ml of uninterrupted flow propelled by the hydrokinetic force generated by the combination of ventricular pressure and siphoning effect. It complies with hydrokinetic parameters imposed by a bypass connection between the ventricular and peritoneal cavities as well as with the physiological archetype of continuous flow and drainage according to CSF production. The open shunt is simple, inexpensive, and an effective treatment for hydrocephalus in adults.

Laboratory evaluation of the phoenix CRx diamond valve

OBJECTIVE

To assess the long-term hydrodynamic properties of a new cerebrospinal fluid flow-regulating hydrocephalus shunt called the CRx Diamond valve (Phoenix Biomedical Corp., Valley Forge, PA).

METHODS

Three samples of a Diamond valve were tested in the United Kingdom Shunt Evaluation Laboratory during a 40-day period. Tests were performed for long-term pressure-flow performance, overdrainage, susceptibility to ambient temperature changes, external pressure, reflux, presence of small particles in the reagent, mechanical durability, and magnetic resonance imaging compatibility.

RESULTS

Tests demonstrated that the Diamond valve stabilized flow within the range of 0.36 to 0.62 ml/min when pressure varied from 14 to 23 mm Hg. Hydrodynamic resistance demonstrated pressure-dependent variability from 20 to 78 mm Hg/(ml/min). The time drift of hydrodynamic parameters was significant (P < 0.001). The valve was insensitive to changes in temperature, external pressure, rapid fluctuations of differential pressure, small particles in fluid, and reflux.

CONCLUSION

The Diamond valve demonstrated the intended variable resistance, which increased as the pressure increased. This property may help it limit overdrainage related to body posture as well as nocturnal vasogenic waves. Flow through the valve stabilizes within a wide range, which may contribute to the prevention of excessive pressure buildup after implantation. However, shunt placement should be avoided in patients who present with normal baseline intracranial pressure but an increased incidence of high vasogenic intracranial pressure waves.

Risk factors for repeated cerebrospinal shunt failures in pediatric patients with hydrocephalus

OBJECT

Repeated cerebrospinal fluid (CSF) shunt failures in pediatric patients are common, and they are a significant cause of morbidity and, occasionally, of death. To date, the risk factors for repeated failure have not been established. By performing survival analysis for repeated events, the authors examined the effects of patient characteristics, shunt hardware, and surgical details in a large cohort of patients.

METHODS

During a 10-year period all pediatric patients with hydrocephalus requiring CSF diversion procedures were included in a prospective single-institution observational study. Patient characteristics were defined as age, gender, weight, head circumference, American Society of Anesthesiology class, and cause of hydrocephalus. Surgical details included whether the procedure was performed on an emergency or nonemergency basis, use of antibiotic agents, concurrent surgical procedures, and duration of the surgical procedure. Details on shunt hardware included: the type of shunt, the valve system, whether the shunt system included multiple or complex components, the type of distal catheter, the site of the shunt, and the side on which the shunt was placed. Repeated shunt failures were assessed using multivariable time-to-event analysis (by using the Cox regression model). Conditional models (as established by Prentice, et al.) were formulated for gap times (that is, times between successive shunt failures). There were 1183 shunt failures in 839 patients. Failure time from the first shunt procedure was an important predictor for the second and third episodes of failure, thus establishing an association between the times to failure within individual patients. An age younger than 40 weeks gestation at the time of the first shunt implantation carried a hazard ratio (HR) of 2.49 (95% confidence interval [CI] 1.68-3.68) for the first failure, which remained high for subsequent episodes of failure. An age from 40 weeks gestation to 1 year (at the time of the initial surgery) also proved to be an important predictor of first shunt malfunctions (HR 1.77, 95% CI 1.29-2.44). The cause of hydrocephalus was significantly associated with the risk of initial failure and, to a lesser extent, later failures. Concurrent other surgical procedures were associated with an increased risk of failure.

CONCLUSIONS

The patient's age at the time of initial shunt placement and the time interval since previous surgical revision are important predictors of repeated shunt failures in the multivariable model. Even after adjusting for age at first shunt insertion as well as the cause of hydrocephalus, there is significant association between repeated failure times for individual patients.

A randomized, controlled study of a programmable shunt valve versus a conventional valve for patients with hydrocephalus. Hakim-Medos Investigator Group

OBJECTIVE

A multicenter prospective randomized controlled study was performed to assess the safety and efficacy of a Codman Hakim programmable shunt valve (Codman/Johnson & Johnson, Raynham, MA) versus a conventional valve system of the surgeon's choice for the treatment of patients with hydrocephalus.

METHODS

Enrollment was stratified on the basis of whether the patient was undergoing initial shunt insertion or revision of an existing valve system at study entry. Study end points were: 1) valve explantation, and 2) shunt failure (surgical intervention for any component of the shunt). A total of 377 patients were enrolled onto the study, with 235 undergoing first shunt insertion (119 experimental, 116 control) and 142 undergoing revisions (75 experimental, 67 control).

RESULTS

During a follow-up interval of 104 weeks after the first implantation on-study, explantation of the valve was required in 62 (32%) of 194 experimental valves, compared with 71 (39%) of 183 control valves. Two-year survival rates of the original shunt without revision of any component were 52% (62 of 119) and 50% (58 of 116) in experimental and control patients, respectively, who underwent initial shunt insertion, and 43% (32 of 75) and 43% (29 of 67) in experimental and control patients, respectively, who underwent replacement of an existing valve. No statistically significant difference was observed between experimental and control patients in the survival of either the valve or the overall shunt system. Control of hydrocephalus as assessed symptomatically and by imaging was comparable in the two treatment groups. Although problems related to inability to achieve the desired pressure setting were reported in 22 experimental valves, in all but four instances no additional programming was attempted because the patients were functioning well clinically. The most common reasons cited for valve explantation and shunt revision were infection (9.8% frequency in the overall cohort) and proximal shunt malfunction, which occurred with comparable frequency in the experimental and control groups.

CONCLUSION

Safety and efficacy of the Codman Hakim programmable shunt valve is comparable to conventional valves in the overall population of patients with hydrocephalus. However, the current study was not designed to assess the efficacy of programmable versus conventional valves in the management of individual hydrocephalus problems, and it had insufficient statistical power to support such comparisons. This study provides a rationale for examining whether the theoretical advantages of a programmable valve for managing challenging hydrocephalus problems can translate into meaningful improvements in shunt and valve survival.

Change in ventricular size and effect of ventricular catheter placement in pediatric patients with shunted hydrocephalus

OBJECTIVE

The multicenter, randomized pediatric cerebrospinal fluid shunt valve design trial found no difference in the rate of shunt failure between a standard valve, a siphon-reducing valve (Delta; Medtronic PS Medical, Goleta, CA), and a flow-limiting valve (Orbis Sigma; Cordis, Miami, FL); however, the valves were expected to have different effects on ultimate ventricular size. Also, the catheter position or local environment of the ventricular catheter tip might have affected shunt failure. Therefore, we performed a post hoc analysis to understand what factors, other than valve design, affected shunt failure and to identify strategies that might be developed to reduce shunt failure.

METHODS

Ventricular size was measured at as many as six different intervals, using a modified Evans' ratio (with incorporation of the frontal and occipital dimensions), in 344 patients. Ventricular catheter location was defined as being in the frontal horn, occipital horn, body of the lateral ventricle, third ventricle, embedded in brain, or unknown. The ventricular catheter tip was described as surrounded by cerebrospinal fluid, touching brain, or surrounded by brain parenchyma within the ventricle (slit ventricle). Repeated measures analysis of variance for unbalanced data was used to analyze ventricular size. A Cox model (with incorporation of time-dependent covariates) was used to evaluate the contribution of age, etiology, shunt design, ventricular size, ventricular catheter location, and environment among the cases.

RESULTS

Ventricular volume decreased in an exponential fashion, forming a plateau at 14 months, and was similar for the three valves (P = 0.4). Frontal and occipital ventricular catheter tip locations were associated with a reduced risk of shunt failure (hazard ratios, 0.60 [P = 0.02] and 0.45 [P = 0.001], respectively). Ventricular catheter tips surrounded by cerebrospinal fluid or touching the brain were associated with a reduced risk of failure (hazard ratios, 0.21 and 0.33, respectively; P = 0.0001). Patients with myelomeningocele or large ventricles had increased risk of malfunction (hazard ratios, 1.78 [P = 0.006] and 2.33 [P = 0.03], respectively).

CONCLUSION

Decline of ventricular size over time is not affected by these different shunt valve designs. This suggests that the mechanical models of hydrocephalus on which the designs were based are inadequate. Ventricular catheter tip location and ventricular catheter environment are important. Techniques to accurately place ventricular catheters and new valve designs that effectively control ventricular size might reduce shunt malfunction.

Endoscopic aqueductoplasty: technique and results

OBJECTIVE

The purpose of this study was to determine the safety and efficacy of endoscopic aqueductoplasty in patients with hydrocephalus caused by aqueductal stenosis. The controversy of third ventriculostomy and aqueductoplasty is discussed.

METHODS

A series of 17 patients who underwent endoscopic aqueductoplasty is reported. Rigid rod-lens scopes were used for inspecting the aqueductal entry and performing balloon aqueductoplasty. With the aid of a 2.5-mm flexible endoscope, the aqueduct and fourth ventricle were explored and aqueductal membranous obstructions were perforated. Third ventriculostomies were performed simultaneously in nine patients. One aqueductal stent was inserted. In six patients, frameless computerized neuronavigation was used for an accurate approach to the aqueduct. The average duration of the endoscopic procedures was 59 minutes (range, 25-100 min).

RESULTS

There was no endoscopy-related mortality. Surgical complications included an asymptomatic fornix contusion and two injuries to the aqueductal roof, which resulted in permanent diplopia due to dysconjugate eye movement (one patient) and transient trochlear palsy (one patient). In addition, two patients developed transient dysconjugate eye movements, and one patient had an asymptomatic epidural hematoma. Eleven patients showed improvement in their symptoms. The conditions of five patients were unchanged. One patient died of stroke 1 month after the operation. No patient required shunting. The ventricles decreased in size in nine patients and were unchanged in the remaining eight patients.

CONCLUSION

Endoscopic aqueductoplasty is an effective alternative to third ventriculostomy for the treatment of hydrocephalus caused by short aqueductal stenosis. However, longer follow-up periods are necessary to evaluate long-term aqueductal patency after aqueductoplasty.

The role of endoscopic third ventriculostomy in the management of shunt malfunction

OBJECTIVE

To evaluate the effectiveness of third ventriculostomy as an alternative to shunt revision in the management of shunt malfunction and infection in obstructive hydrocephalus.

METHODS

All of the clinical notes of 30 patients treated with third ventriculostomy for malfunctioning or infected shunts between January 1, 1974, and December 31, 1996, were retrospectively reviewed. Third ventriculostomy was performed under fluoroscopic control in the first seven patients and endoscopically in the remainder. A successful outcome was achieved if further shunt revision surgery was avoided. The median follow-up duration was 8.7 years

RESULTS

Twenty-three patients (76.7%) experienced successful outcomes, resulting in shunt independence. Of the seven failures, three were technical failures at the time of surgery and the remaining four were manifest within a median of 10 days, resulting in shunt revision. There have been no delayed failures.

CONCLUSION

Third ventriculostomy is a valuable alternative to shunt revision in patients affected by obstructive hydrocephalus presenting with shunt malfunction or infection. It should be considered in all suitable cases as the first-line treatment for obstructive hydrocephalus of all causes. Because all failures were manifest within a short time, it is likely that these successes will be durable.