Comparison of anti-siphon devices-how do they affect CSF dynamics in supine and upright posture?

Prospective evaluation of flow-regulated valves for idiopathic normal pressure hydrocephalus: 1-year results

OBJECTIVE

Overdrainage and frequent reprogramming are common problems with programmable valves after ventriculoperitoneal shunt surgery for idiopathic normal pressure hydrocephalus (iNPH). Non-adjustable, flow-regulated valves offer a potential solution to these problems, but there is limited data on their efficacy. This study will evaluate neurological improvement and overdrainage rates within one year of treatment with a flow-regulated valve.

PATIENTS AND METHODS

This prospective study analyzes 45 iNPH patients (median age: 73 years) treated with a flow-regulated valve. Clinical evaluations were performed at baseline, postoperatively, and at 3, 6, and 12 months after surgery. The primary efficacy endpoint was improvement of at least 5 points on the iNPH grading scale at follow-up. The safety endpoint was radiographic evidence of overdrainage.

RESULTS

All patients presented with gait disturbance, 35 (78 %) had cognitive impairment, and 35 (78 %) had urinary incontinence. The median duration of symptoms was 24 months. The total iNPH score improved in 33/41 (81 %) at 3 months, in 29/34 (85 %) at 6 months, and in 22/29 (64 %) at 12 months. Overall, 40/45 (89 %) patients had a significant improvement on the iNPH scale. Secondary worsening of symptoms after initial improvement was observed in 5 (11 %) patients. Overdrainage occurred in one patient (2 %) requiring surgical evacuation.

CONCLUSION

Treatment of iNPH patients with flow-regulated valves resulted in a good neurological outcome with minimal rates of overdrainage. These results are encouraging and justify the clinical use of these valve types.

17 years of experience with shunt systems in normal pressure hydrocephalus - From differential pressure to gravitational valves

Objective

Complication rate of shunting for normal pressure hydrocephalus (NPH) has significantly improved over the last decades. Especially the use of overdrainage protection has reduced the incidence of subdural hematoma and collections. However, gravitational valves were associated with other complications of shunt dysfunction. We present our 17 years of experience with patients with normal pressure hydrocephalus who changed from a differential pressure valve to a gravitational valve system.

Methods

We retrospectively identified all patients with the diagnosis of normal pressure hydrocephalus, in whom primary shunt implantation was performed between 2004 and 2020. Shunt implantation was performed as per our internal standard. Review of imaging, charts and patient reports was performed.

Results

In total, 409 patients were included in the analysis. Mean age was 73.0 ± 7.1years. Between 2004 and 2010, predominantly Hakim valves (n = 100, 24.4%) were implanted, whilst from 2009 until 2020, proGAV valves (n = 296, 72.4%) were used. Mean follow-up was 8.9 ± 4.5 years. Initial subjective improvement of symptoms was reported in 69.9%, whilst this number decreased at the last follow-up to 29.8%. No significant differences were observed between the valves in the frequency of surgery for subdural hematoma. Shunt assistant implantation was performed in 17% of patients with Hakim valve, in 9.5% of patients with proGAV, a shunt assistant was added. Shunt obstruction was significantly higher in proGAV valves (p < 0.001).

Conclusions

Our findings confirm the observation of frequent overdrainage in shunts without anti-siphon/gravitational component. Gravitational valves on the other hand may be associated with more obstruction.

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

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

Influence of head-over-body and body-over-head posture on craniospinal, vascular, and abdominal pressures in an acute ovine in-vivo model

INTRODUCTION

Optimal shunt-based hydrocephalus treatments are heavily influenced by dynamic pressure behaviors between proximal and distal ends of shunt catheters. Posture-dependent craniospinal, arterial, venous, and abdominal dynamics thereby play an essential role.

METHODS

An in-vivo ovine trial (n = 6) was conducted to evaluate communication between craniospinal, arterial, venous, and abdominal dynamics. Tilt-testing was performed between -13° and + 13° at 10-min intervals starting and ending at 0° prone position. Mean pressure, pulse pressure, and Pearson correlation (r) to the respective angle were calculated. Correlations are defined as strong: |r|≥ 0.7, mild: 0.3 <|r|< 0.7, and weak: |r|≤ 0.3. Transfer functions (TFs) between the arterial and adjacent compartments were derived.

RESULTS

Strong correlations were observed between posture and: mean carotid/femoral arterial (r = - 0.97, r = - 0.87), intracranial, intrathecal (r = - 0.98, r = 0.94), jugular (r = - 0.95), abdominal cranial, dorsal, caudal, and intravesical pressure (r = - 0.83, r = 0.84, r = - 0.73, r = 0.99) while mildly positive correlation exists between tilt and central venous pressure (r = 0.65). Only dorsal abdominal pulse pressure yielded a significant correlation to tilt (r = 0.21). TFs followed general lowpass behaviors with resonant peaks at 4.2 ± 0.4 and 11.5 ± 1.5 Hz followed by a mean roll-off of - 15.9 ± 6.0 dB/decade.

CONCLUSIONS

Tilt-tests with multi-compartmental recordings help elucidate craniospinal, arterial, venous, and abdominal dynamics, which is essential to optimize shunt-based therapy. Results motivate hydrostatic influences on mean pressure, with all pressures correlating to posture, with little influence on pulse pressure. TF results quantify the craniospinal, arterial, venous, and abdominal compartments as compliant systems and help pave the road for better quantitative models of the interaction between the craniospinal and adjacent spaces.

Ventriculopleural shunt outcomes for pediatric hydrocephalus: a single-institution experience

PURPOSE

The aim of this study is to analyze rates of ventriculopleural (VPL) shunt failure and complications among patients with pediatric hydrocephalus, and to analyze which factors may predict early (< 1 year) or late (> 1 year) VPL shunt failure in this sample.

METHODS

A retrospective chart review was conducted of all consecutive VPL shunt placements from 2000 to 2019 at our institution. Data was collected on patient characteristics, shunt history, and shunt type. Primary endpoints include rates of VPL shunt survival and rates of symptomatic pleural effusion. The Kaplan-Meier method was used to calculate shunt survival, and Fisher's exact test and t-test were used to compare differences between categorical variables and means, respectively (p < 0.05).

RESULTS

Thirty-one patients with pediatric hydrocephalus underwent VPL shunt placement (mean age 14.2 years). Of the 27 patients with long-term follow-up (mean 46 months), VPL shunt revision was required in 19, seven of which were due to pleural effusion. Overall shunt survival rates at 1, 3, 5, and 7 years were 76%, 62%, 55%, and 46%, respectively. Mean duration of shunt survival was 26.74 months. Overall pleural effusion rate was 26%. No patient-specific factors, including shunt valve type, were significantly associated with shunt survival, risk of early revision, or risk of pleural effusion.

CONCLUSIONS

Our results are comparable to those reported in the literature and represent one of the largest case series on the topic. VPL shunts are a viable second-line option when ventriculoperitoneal (VP) shunt placement is not possible or desirable, though there are high rates of shunt revision and pleural effusion.

The semi-sitting position in patients with indwelling CSF shunts: perioperative management and avoidance of complications

OBJECTIVE

Posterior fossa or midline tumors are often associated with hydrocephalus and primary tumor removal with or without perioperative placement of an external ventricular drain (EVD) is commonly accepted as first-line treatment. Shunting prior to posterior fossa surgery (PFS) is mostly reserved for symptomatic cases or special circumstances. There are limited data regarding the anticipated risk for symptomatic pneumocephalus and the perioperative management using the semi-sitting position (SSP) in such a scenario. Here, we therefore assessed the safety of performing PFS in a consecutive series of patients over a period of 15 years to allow the elaboration of recommendations for perioperative management.

METHODS

According to specific inclusion and exclusion criteria a total of 13 patients who underwent 17 operations was identified. Supratentorial pneumocephalus was evaluated with semiautomatic-volumetric segmentation. The volume of pneumocephalus was evaluated according to age and ventricular size.

RESULTS

Ten of the 13 patients had a programmable valve (preoperative valve setting range 6-14 cmH20; mean 7.5 cmH20) while 3 patients had non programmable valves. A variable amount of supratentorial air collection was evident in all patients postoperatively (range 3.2-331 ml; mean 122.32 ml). Positive predictors for the volume of postoperative pneumocephalus were higher age and a preoperative Evans ratio > 0.3. In our series, we encountered no cases of tension pneumocephalus necessitating an air replacement procedure as well as no obstruction, disconnection, infection or hardware malfunction of the shunt system.

CONCLUSIONS

Our findings indicate that a CSF shunt in situ is not a contraindication for performing PFS in the semi-sitting position and it does not increase the pre-existing risk for postoperative tension pneumocephalus. In cases of primary shunting for hydrocephalus associated with posterior fossa tumors a programmable valve set at a medium opening pressure with a gravitational device is a valid option when PFS in the semi-sitting position is opted. In patients with an indwelling shunt diversion system special caution is indicated in order to prevent and detect overdrainage especially in not adjustable valves or shunts without antisiphon devices.

Hydrocephalus Study Design: Testing New Hypotheses in Clinical Studies and Bench-to-Bedside Research

In this article, we aimed to describe some of the currently most challenging problems in neurosurgical management of hydrocephalus and how these can be reasons for inspiration for and development of research. We chose 4 areas of focus: 2 dedicated to improvement of current treatments (shunt implant surgery and endoscopic hydrocephalus surgery) and 2 dedicated to emerging future treatment principles (molecular mechanisms of cerebrospinal fluid secretion and hydrocephalus genetics).

Cerebral venous sinus thrombosis as a consequence of shunt hyperdrainage: a proposal of the pathophysiological mechanism and case report

BACKGROUND AND AIM

Shunt dysfunction is a common event, especially in children who have this intervention performed early in life. The consequences of chronic shunt overdrainage can be multiple since the cerebral hydrodynamics is altered. A thrombotic event with consequent symptoms of intracranial hypertension is discussed in this article.

MATERIAL AND METHODS

We performed a detailed review of cerebral hydrodynamics and intracranial pressure compensation mechanisms and how this can alter cerebral venous circulation. Next, we report the case of a 4-year-old child with such a clinical presentation that was conducted by our team.

RESULTS

A child with a history of hydrocephalus treated with a ventriculo-peritoneal (VP) shunt in his early childhood presented with symptoms of intracranial hypertension, initial computed tomography (CT) demonstrating reduced-sized ventricles. Complementary investigation showed bilateral papilledema, cranial suture closure, changes compatible with Chiari type I, and venous sinus thrombosis (transverse and sigmoid, bilaterally). The case was managed conservatively with full anticoagulation with enoxaparin. Four months after the onset of symptoms, there was an improvement in the clinical and imaging status.

CONCLUSION

A condition of severe headache in a patient with an apparently functioning shunt and small ventricles on initial CT should open up a range of diagnostic possibilities, with pseudotumor cerebri syndrome and cerebral venous sinus thrombosis being suggested. The therapeutic approach in these cases must be individualized.

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.

Shunt Overdrainage: Reappraisal of the Syndrome and Proposal for an Integrative Model

Although shunt overdrainage is a well-known complication in hydrocephalus management, the problem has been underestimated. Current literature suggests that the topic requires more examination. An insight into this condition is limited by a lack of universally agreed-upon diagnostic criteria, heterogeneity of published series, the multitude of different management options and misunderstanding of relationships among pathophysiological mechanisms involved. We carried out a review of the literature on clinical, radiological, intracranial pressure (ICP), pathophysiological and treatment concepts to finally propose an integrative model. Active prophylaxis and management are proposed according to this model based on determination of pathophysiological mechanisms and predisposing factors behind each individual case. As pathophysiology is progressively multifactorial, prevention of siphoning with gravitational valves or antisiphon devices is mandatory to avoid or minimize further complications. Shunt optimization or transferal and neuroendoscopy may be recommended when ventricular collapse and cerebrospinal fluid isolation appear. Cranial expansion may be useful in congenital or acquired craniocerebral disproportion and shunting the subarachnoid space in communicating venous hydrocephalus and idiopathic intracranial hypertension.

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.

Neurosurgical CSF Diversion in Idiopathic Intracranial Hypertension: A Narrative Review

The prevalence of idiopathic intracranial hypertension (IIH), a complex disorder, is increasing globally in association with obesity. The IIH syndrome occurs as the result of elevated intracranial pressure, which can cause permanent visual impairment and loss if not adequately managed. CSF diversion via ventriculoperitoneal and lumboperitoneal shunts is a well-established strategy to protect vision in medically refractory cases. Success of CSF diversion is compromised by high rates of complication; including over-drainage, obstruction, and infection. This review outlines currently used techniques and technologies in the management of IIH. Neurosurgical CSF diversion is a vital component of the multidisciplinary management of IIH.

Evaluating the Effects of Cerebrospinal Fluid Protein Content on the Performance of Differential Pressure Valves and Antisiphon Devices Using a Novel Benchtop Shunting Model

BACKGROUND

Hydrocephalus is managed by surgically implanting flow-diversion technologies such as differential pressure valves and antisiphoning devices; however, such hardware is prone to failure. Extensive research has tested them in flow-controlled settings using saline or de-aerated water, yet little has been done to validate their performance in a setting recreating physiologically relevant parameters, including intracranial pressures, cerebrospinal fluid (CSF) protein content, and body position.

OBJECTIVE

To more accurately chart the episodic drainage characteristics of flow-diversion technology. A gravity-driven benchtop model of flow was designed and tested continuously during weeks-long trials.

METHODS

Using a hydrostatic pressure gradient as the sole driving force, interval flow rates of 6 valves were examined in parallel with various fluids. Daily trials in the upright and supine positions were run with fluid output collected from distal catheters placed at alternating heights for extended intervals.

RESULTS

Significant variability in flow rates was observed, both within specific individual valves across different trials and among multiple valves of the same type. These intervalve and intravalve variabilities were greatest during supine trials and with increased protein. None of the valves showed evidence of overt obstruction during 30 d of exposure to CSF containing 5 g/L protein.

CONCLUSION

Day-to-day variability of ball-in-cone differential pressure shunt valves may increase overdrainage risk. Narrow-lumen high-resistance flow control devices as tested here under similar conditions appear to achieve more consistent flow rates, suggesting their use may be advantageous, and did not demonstrate any blockage or trend of decreasing flow over the 3 wk of chronic use.

Risk factors for developing subdural hematoma: a registry-based study in 1457 patients with shunted idiopathic normal pressure hydrocephalus

OBJECTIVE

Subdural hematomas and hygromas (SDHs) are common complications in idiopathic normal pressure hydrocephalus (iNPH) patients with shunts. In this registry-based study, patients with shunted iNPH were screened nationwide to identify perioperative variables that may increase the risk of SDH.

METHODS

The Swedish Hydrocephalus Quality Registry was reviewed for iNPH patients who had undergone shunt surgery in Sweden in 2004-2014. Potential risk factors for SDH were recorded preoperatively and 3 months after surgery. Drug prescriptions were identified from a national pharmacy database. Patients who developed SDHs were compared with those without SDHs.

RESULTS

The study population consisted of 1457 patients, 152 (10.4%) of whom developed an SDH. Men developed an SDH more often than women (OR 2.084, 95% CI 1.421-3.058, p < 0.001). Patients on platelet aggregation inhibitors developed an SDH more often than those who were not (OR 1.733, 95% CI 1.236-2.431, p = 0.001). At surgery, shunt opening pressures had been set 5.9 mm H2O lower in the SDH group than in the no-SDH group (109.6 ± 24.1 vs 115.5 ± 25.4 mm H2O, respectively, p = 0.009). Antisiphoning devices (ASDs) were used in 892 patients but did not prevent SDH. Mean opening pressures at surgery and the follow-up were lower with shunts with an ASD, without causing more SDHs. No other differences were seen between the groups.

CONCLUSIONS

iNPH patients in this study were diagnosed and operated on in routine practice; thus, the results represent everyday care. Male sex, antiplatelet medication, and a lower opening pressure at surgery were risk factors for SDH. Physical status and comorbidity were not. ASD did not prevent SDH, but a shunt with an ASD allowed a lower opening pressure without causing more SDHs.

Gravitational shunt valves in hydrocephalus to challenge the sequelae of over-drainage

INTRODUCTION

In hydrocephalus treatment, ventriculo-peritoneal shunts (VPS) have become the most relevant therapy for seven decades among other treatment options. Due to the hydrostatic pressure in vertical position, CSF diversion is somehow non-physiological. The integration of gravitational valves in VPS was established to counteract the hydrostatic draining force and to approach a physiological condition of the cerebrospinal diverting system. Numerous clinical studies have shown that gravitational valves are able to reduce secondary complications of VPS treatment. It remains a challenge for the treating neurosurgeon to select the correct valve resistance based on individual anatomies and different etiologies of hydrocephalus as well as varying levels of activity of the patient.

AREAS COVERED

This review covers the development of gravitational shunt valves from historical, theoretical and clinical aspects for pediatric and adult etiologies of hydrocephalus. We discuss the role of gravitational shunt valves in preventing over-drainage issues and present the state-of-the-art literature. Furthermore, ongoing prospective trials are presented.

EXPERT OPINION

Counteracting the hydrostatic force by selecting the correct valve in a VPS system to achieve physiological balance in CSF diversion during vertical and horizontal body changes has become the current standard for hydrocephalus management. Gravitational shunt valves reliably address this need to minimize over-drainage events in the vertical position without affecting the CSF flow in the horizontal position. The results of ongoing prospective studies on the safety and efficacy of adjustable gravitational valves are still pending. Due to the complexity of the CSF flow, lifelong follow-up care for patients with VPS is critical.

Enhanced wall shear stress prevents obstruction by astrocytes in ventricular catheters

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

Posture related in-vitro characterization of a flow regulated MEMS CSF valve

Overdrainage in upright position is one of the most prevalent issues in treating hydrocephalus with a cerebrospinal fluid (CSF) shunt. Anti-siphon devices (ASDs) are employed to reduce this problem. A novel microelectromechanical system (MEMS)-based valve, termed Chronoflow device, aims to regulate CSF drainage indifferently of the body posture. With this study, the suitability of this MEMS-based valve is evaluated regarding its use for the treatment of hydrocephalus, particularly for the prevention of overdrainage and blockage. In total, four Chronoflow devices were tested. An established in-vitro hardware-in-the-loop (HIL) test bed was used to investigate the valves regarding their pressure-flow characteristics, their behaviors towards CSF dynamics, and their capabilities to prevent CSF overdrainage in upright position. Additionally, a contamination test was conducted to evaluate the susceptibility of the device to blockage due to particles. All valves tested regulated the drainage rate at similar nominal flows and independently of posture. The pressure-flow relation measured, however, was notably higher than numerically calculated. Regarding the CSF dynamics, the first three valves tested led to a decreased steady-state intracranial pressure in supine position and showed stable drainage rate in upright position. During the transitional phase from supine to upright and vice versa, the valves continuously adjusted the outflow resistance, which resulted in a stable transitional phase preventing overdrainage. Yet, the fourth valve showed continuous overdrainage in upright position due to an increased nominal flow. However, after several test iterations the nominal flow decreased and stabilized at a level similar to that of the first three valves tested. The contamination test showed that most particles initially adhere to the pillars and spread throughout the cavity of the valve as the concentration of particles increases, thereby affecting the displacement of the membrane. The devices generally provide a stable flow regulation and prevent overdrainage in upright position. Specifically, their drainage behaviors during the posture changes are very effective. However, they also showed high hysteresis and sensitivity towards particle contamination, which resulted in initial increased and altering nominal flows after many test iterations. This result suggests that the MEMS design presented lacks robustness. Yet, an upstream filter and specific coatings on the fluid pathway may increase significantly its reliability.

Custom Shunt System for Increased Baseline Intracranial Pressure in a Patient with Idiopathic Intracranial Hypertension

BACKGROUND

Standard treatment of idiopathic intracranial hypertension (IIH) involves reduction of intracranial pressure (ICP) to normal range, often via a ventriculoperitoneal shunt (VPS). We describe a case of a middle-aged man who presented with symptoms consistent with IIH. After ICP was normalized with a VPS, the patient had neurologic deterioration into a coma. He completely recovered after a month when his ICP was allowed to increase and remain above the normal range.

CASE DESCRIPTION

A 50-year-old man presented with daily headaches, visual loss (right > left), and increased lumbar opening pressure consistent with IIH. A VPS was inserted using a Strata II valve with a pressure setting of 1.5, lowering ICP into the normal range. The patient initially had a normal postoperative course, but then became comatose and developed imaging signs consistent with intracranial hypotension. A Codman Certas valve was placed at a setting of 7 and a distal slit-cut peritoneal catheter was used (as opposed to standard open output). This custom system drained at pressure >26 mm Hg based on intraoperative manometry. The patient tolerated this well and is currently planned for a gradual reduction in ICP with valve setting adjustments as an outpatient.

CONCLUSIONS

In patients with chronic IIH, reduction to normal ICP may unexpectedly lead to encephalopathic changes. Personalized shunts may facilitate reduction of ICP to still elevated but tolerable levels in these patients.

Flow-regulated versus differential pressure valves for idiopathic normal pressure hydrocephalus: comparison of overdrainage rates and neurological outcome

BACKGROUND

To compare flow-regulated (FR) and differential pressure (DP) valves for treatment of patients with idiopathic normal hydrocephalus (iNPH) focusing on overdrainage and neurological outcome.

METHODS

This is a retrospective study of patients with iNPH treated with FR and DP valves at a single institution between 2008 and 2018. The neurological status was evaluated retrospectively with the Kiefer scale at baseline, after shunt placement and at the 6-month follow-up. Groups were compared using inverse probability of treatment weighting based on propensity scores.

RESULTS

The study cohort consisted of 38 patients treated with FR valves and 49 with DP valves. The mean patient age was 72.0 ± 7.6 years. Based on the Kiefer scale score, neurological improvement at the 6-month follow-up was recorded in 79.6% in the DP group and 89.5% in the FR group (p = 0.252). The overdrainage rates were higher among DP valves (10.2%) than among FR valves (2.6%, adjusted p = 0.002). Valve malfunction occurred in 2.0% in the DP group and 5.3% in the FR group (adjusted p = 0.667).

CONCLUSIONS

The current study demonstrates a comparable neurological improvement between DP and FR valves, with potentially lower overdrainage rates among FR valves. Long-term studies will be necessary to draw a definite conclusion on FR valves for treatment of iNPH patients.

Conservative and operative management of iatrogenic craniocerebral disproportion-a case-based review

INTRODUCTION

Craniocerebral disproportion (CCD) can occur as a sequela after shunting in early infancy. It can be understood as a disorder closely related to slit ventricle syndrome and chronic overdrainage syndrome. Here, we present two exemplary cases and summarize the pathophysiological, diagnostic, and therapeutic approaches to CCD.

CLINICAL PRESENTATION

Two premature babies underwent shunting for posthemorrhagic hydrocephalus and presented in later childhood with recurrent episodes of symptomatic raised intracranial pressure (ICP) at 2 and 8 years of age, respectively.

DIAGNOSIS AND MANAGEMENT

Both patients had unchanged ventricular size on cranial imaging and fulfilled the clinical diagnostic criteria of CCD. After confirming shunt patency, ICP monitoring was performed to diagnose intermittent intracranial hypertension. Different treatment pathways were pursued: While readjustment of a programmable shunt valve was sufficient to alleviate the raised ICP in the first case, a cranial expansion surgery was necessary in the second case.

OUTCOME AND CONCLUSIONS

Both children were treated successfully after thorough assessment and careful choice of treatment approaches. This review provides detailed insight into CCD and highlights the importance of individual and critical decision-making in these complex patients.

Minimizing overdrainage with flow-regulated valves - Initial results of a prospective study on idiopathic normal pressure hydrocephalus

OBJECTIVE

Overdrainage and frequent reprogramming are common issues with programmable valves after ventriculoperitoneal shunt surgery for idiopathic normal pressure hydrocephalus (iNPH). Flow-regulated valves may address these limitations, but data on their efficacy are sparse. We present our single-center experience with flow-regulated valves focusing on overdrainage and efficiency.

PATIENTS AND METHODS

Thirty-two patients with iNPH treated with the Integra® NPH Low Flow Valve were prospectively enrolled. Clinical evaluation was performed at baseline, postoperatively as well as 3 and 6 months after surgery. The outcome was assessed by employing the iNPH grading scale and the Mini Mental Status Examination (MMSE). Overdrainage was assessed clinically and radiologically by computed tomography.

RESULTS

The mean patient age was 71 years. All patients presented with gait disturbance, 29 had cognitive impairment and 25 had urinary incontinence. The mean duration of symptoms was 22.9 months. At 3-month follow-up, 25/31 patients (80.6%) improved on the total iNPH score by at least 5 points (p < 0.001). The mean MMSE score increased from 24.5 to 26.1 points (p = 0.013). After 6 months, the improvement rates of the iNPH (82.1%) and the MMSE scores (26.8 points) were stable. The rate of clinically significant overdrainage was 3.2%. One patient presented with subdural hygromas that necessitated evacuation. In the remaining patients, clinical and radiological signs of overdrainage were absent.

CONCLUSION

The use of the Integra® NPH Low Flow Valve leads to a good neurological outcome and has low overdrainage rates without the need for reprogramming. These results are encouraging and justify further investigation of this valve.