In vitro testing of explanted shunt valves in hydrocephalic patients with suspected valve malfunction.

Diagnosis of symptomatic valve malfunction in hydrocephalic patients treated with VP-Shunt (VPS) might be difficult. Clinical symptoms such as headache or nausea are nonspecific, hence cerebrospinal fluid (CSF) over- or underdrainage can only be suspected but not proven. Knowledge concerning valve malfunction is still limited.

Test-Retest Reliability of Outpatient Telemetric Intracranial Pressure Measurements in Shunt-Dependent Patients with Hydrocephalus and Idiopathic Intracranial Hypertension.

Background: Some patients with hydrocephalus and idiopathic intracranial hypertension treated for elevated intracranial pressure (ICP) with a cerebrospinal fluid shunt may continue to experience symptoms or develop new symptoms despite valve adjustments. Use of telemetric ICP measurements may help confirm clinical suspicion of cerebrospinal fluid underdrainage or overdrainage in these patients. However, point in time, duration, and activity during the measurements have never been standardized.

A counterforce to diversion of cerebrospinal fluid during ventriculoperitoneal shunting: the intraperitoneal pressure. An observational study.

Background: Intraperitoneal pressure (IPP) counteracts the diversion of cerebrospinal fluid (CSF) from the cranial to the peritoneal compartment during ventriculoperitoneal shunting. Animal studies suggest that the intrinsic IPP exceeds the intraperitoneal hydrostatic pressure. The intrinsic IPP in mobile patients is relevant for shunt therapy, but data about it is not available.

EphrinB2 Activation Enhances Vascular Repair Mechanisms and Reduces Brain Swelling After Mild Cerebral Ischemia.

Objective: Cerebral edema caused by the disruption of the blood-brain barrier is a major complication after stroke. Therefore, strategies to accelerate and enhance neurovascular recovery after stroke are of prime interest. Our main aim was to study the role of ephrinB2/EphB4 signaling in mediating the vascular repair and in blood-brain barrier restoration after mild cerebral ischemia occlusion/reperfusion.

Pressure Measurement Techniques for Abdominal Hypertension: Conclusions from an Experimental Model.

Introduction. Intra-abdominal pressure (IAP) measurement is an indispensable tool for the diagnosis of abdominal hypertension. Different techniques have been described in the literature and applied in the clinical setting.

High-resolution mechanical imaging of glioblastoma by multifrequency magnetic resonance elastography.

Objective: To generate high-resolution maps of the viscoelastic properties of human brain parenchyma for presurgical quantitative assessment in glioblastoma (GB).

Methods: Twenty-two GB patients underwent routine presurgical work-up supplemented by additional multifrequency magnetic resonance elastography. Two three-dimensional viscoelastic parameter maps, magnitude |G*|, and phase angle φ of the complex shear modulus were reconstructed by inversion of full wave field data in 2-mm isotropic resolution at seven harmonic drive frequencies ranging from 30 to 60 Hz.

In vitro performance and principles of anti-siphoning devices.

Background: Anti-siphon devices (ASDs) of various working principles were developed to overcome overdrainage-related complications associated with ventriculoperitoneal shunting.

Objective: We aimed to provide comparative data on the pressure and flow characteristics of six different types of ASDs (gravity-assisted, membrane-controlled, and flow-regulated) in order to achieve a better understanding of these devices and their potential clinical application.

Methods: We analyzed three gravity-dependent ASDs (ShuntAssistant [SA], Miethke; Gravity Compensating Accessory [GCA], Integra; SiphonX [SX], Sophysa), two membrane-controlled ASDs (Anti-Siphon Device [IASD], Integra; Delta Chamber [DC], Medtronic), and one flow-regulated ASD (SiphonGuard [SG], Codman).

The Frankfurt horizontal plane as a reference for the implantation of gravitational units: a series of 376 adult patients.

Background: The in-line combination of adjustable differential pressure valves with fixed gravitational units is increasingly recommended in the literature. The spatial positioning of the gravitational unit is thereby decisive for the valve opening pressure. We aimed at providing data on factors contributing to primary overdrainage and underdrainage of cerebrospinal fluid (CSF), with special attention paid to the implantation angle of the gravitational unit.

Feasibility of telemetric ICP-guided valve adjustments for complex shunt therapy.

Object: The advances in shunt valve technology towards modern adjustable differential pressure (DP) valves and adjustable gravitational assisted valves result in an increasing complexity of therapeutical options. Modern telemetric intracranial pressure (ICP) sensors may be helpful in their application for diagnostic purposes in shunt therapy. We present our first experiences on telemetric ICP-guided valve adjustments in cases with the combination of an adjustable DP valve and adjustable gravitational unit.

Large-scale referencing of the telemetric neurovent-P-tel intracranial pressure sensor in a porcine model.

The Neurovent-P-tel sensor is a promising device for telemetric intracranial pressure (ICP) measurements in cases of complex hydrocephalus. Data on its accuracy within a broad ICP range are missing. We applied a porcine model for large-scale manipulation of the ICP values.

Differential pressure in shunt therapy: investigation of position-dependent intraperitoneal pressure in a porcine model.

Object: The differential pressure between the intracranial and intraperitoneal cavities is essential for ventriculoperitoneal shunting. A determination of the pressure in both cavities is decisive for selecting the appropriate valve type and opening pressure. The intraperitoneal pressure (IPP)-in contrast to the intracranial pressure-still remains controversial with regard to its normal level and position dependency.

Patients benefit from low-pressure settings enabled by gravitational valves in normal pressure hydrocephalus.

Objective: The ability of siphon regulatory devices to improve overdrainage control despite low-pressure settings of the valve for the horizontal body position has been described previously. We aim to provide a systematic investigation on the ability of gravitational units as siphon regulatory devices to improve clinical outcome in shunt therapy.

Methods: We analyzed retrospectively postoperative complications, type and frequency of valve adjustments and the clinical outcome using Black's outcome scale at different time points of all iNPH patients operated in our center between January 2007 and December 2010.

MR elastography in a murine stroke model reveals correlation of macroscopic viscoelastic properties of the brain with neuronal density.

The aim of this study was to investigate the influence of neuronal density on viscoelastic parameters of living brain tissue after ischemic infarction in the mouse using MR elastography (MRE). Transient middle cerebral artery occlusion (MCAO) in the left hemisphere was induced in 20 mice. In vivo 7-T MRE at a vibration frequency of 900 Hz was performed on days 3, 7, 14 and 28 (n = 5 per group) after MCAO, followed by the analysis of histological markers, such as neuron counts (NeuN).

Evaluation of a new large animal model for controlled intracranial pressure changes induced by capnoperitoneum.

Background: A standardized large animal model for controlled ICP manipulation within a relevant range and repetitive ICP measurements is missing. We sought to develop such a model on the base of controlled IPP changes induced by capnoperitoneum.

Methods: We utilized six female pigs (mean body weight 59.

Shunting with gravitational valves--can adjustments end the era of revisions for overdrainage-related events?: clinical article.

Object: Overdrainage of CSF remains an unsolved problem in shunt therapy. The aim of the present study was to evaluate treatment options on overdrainage-related events enabled by the new generation of adjustable gravity-assisted valves.

Methods: The authors retrospectively studied the clinical course of 250 consecutive adult patients with various etiologies of hydrocephalus after shunt insertion for different signs and symptoms of overdrainage.

Alteration of brain viscoelasticity after shunt treatment in normal pressure hydrocephalus.

Introduction: Normal pressure hydrocephalus (NPH) represents a chronic neurological disorder with increasing incidence. The symptoms of NPH may be relieved by surgically implanting a ventriculoperitoneal shunt to drain excess cerebrospinal fluid. However, the pathogenesis of NPH is not yet fully elucidated, and the clinical response of shunt treatment is hard to predict.

In vivo viscoelastic properties of the brain in normal pressure hydrocephalus.

Nearly half a century after the first report of normal pressure hydrocephalus (NPH), the pathophysiological cause of the disease still remains unclear. Several theories about the cause and development of NPH emphasize disease-related alterations of the mechanical properties of the brain. MR elastography (MRE) uniquely allows the measurement of viscoelastic constants of the living brain without intervention.

Evaluation of long-term upregulation of Calbindin D28K as a preventive approach for ischaemic stroke.

Buffering of intracellular calcium peaks following an acute ischaemic stroke protects neurons from necrotic and apoptotic cell death. However, the need for on-demand delivery of protective agents due to the short therapeutic window in stroke therapy makes it difficult to apply a calcium-buffering strategy in patients. We investigated the effects of a preventive upregulation of the calcium-binding protein Calbindin D28K as a potential approach for patients at a high risk of ischaemic stroke.