Christian Sprung

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. In this study, 20 patients (mean age, 69.1 years; nine men, 11 women) with idiopathic (n = 15) and secondary (n = 5) NPH were examined by cerebral multifrequency MRE and compared with 25 healthy volunteers (mean age, 62.1 years; 10 men, 15 women). Viscoelastic constants related to the stiffness (µ) and micromechanical connectivity (α) of brain tissue were derived from the dynamics of storage and loss moduli within the experimentally achieved frequency range of 25–62.5 Hz. In patients with NPH, both storage and loss moduli decreased, corresponding to a softening of brain tissue of about 20% compared with healthy volunteers (p < 0.001). This loss of rigidity was accompanied by a decreasing α parameter (9%, p < 0.001), indicating an alteration in the microstructural connectivity of brain tissue during NPH. This disease‐related decrease in viscoelastic constants was even more pronounced in the periventricular region of the brain. The results demonstrate distinct tissue degradation associated with NPH. Further studies are required to investigate the source of mechanical tissue damage as a potential cause of NPH‐related ventricular expansions and clinical symptoms. Copyright

The adjustable proGAV shunt: a prospective safety and reliability multicenter study.

OBJECTIVETo evaluate the reliability of the gravitation-assisted adjustable proGAV shunt system with a prospective multicenter study conducted in 10 German hospitals. METHODSEnrollment for this observational study began in April 2005 and concluded in February 2006. The protocol required re-examinations 3 and 6 months postoperatively and fixed the endpoint of follow-up at 12 months after implantation. Patients with different types of adult, juvenile, and pediatric hydrocephalus were included and 165 patients were enrolled; 9 died and 12 had incomplete follow-up. RESULTSOf the assessable 144 patients, 130 completed the protocol after 12 months, whereas 14 failed because of the need to explant the device, mainly because of infection. In 12 patients, components of the shunt, not the valve, were revised. In 65 of the 144 patients, there were 102 readjustments of the valve in 67 incidences because of underdrainage and in 35 because of overdrainage. In 1 case, readjustment was not possible. Determination of pressure level with the verification instrument was safe and corresponded to the required x-ray controls after adjustments. No unintended readjustments were noted. CONCLUSIONThe proGAV is a safe and reliable device.

Diffusion tensor imaging in hydrocephalus—findings before and after shunt surgery

BackgroundTo evaluate changes in diffusion tensor imaging (DTI)-derived parameters in patients with hydrocephalus (HC) before and several weeks after shunt surgery.MethodsThirteen HC patients were examined with DTI before and after shunt surgery. In a combined region of interest and whole brain voxel-based analysis, different DTI parameters were compared with an age-matched control group.ResultsAlteration of DTI parameters in HC patients and changes after shunt surgery are regionally different. HC patients show an increase in fractional anisotropy values based on increases in parallel diffusivity in the corticospinal tract. On the other hand, reduced fractional anisotropy values are found in the corpus callosum of HC patients. Following shunt surgery, all DTI parameters showed a trend towards normalization, yet differences to healthy control subjects remained.ConclusionOur results show that DTI parameter changes are regionally dependent and need a careful interpretation of the underlying diffusivities to serve as a diagnostic or follow-up measure in patients with hydrocephalus.

The Miethke Dual-Switch Valve in Patients With Normal Pressure Hydrocephalus

Especially in patients with normal pressure hydrocephalus (NPH), conventional differential pressure valves are known to create unphysiologic negative intraventricular pressure values when the patient moves to an upright position, with the consequence of numerous and sometimes severe complications. The recently presented gravitational devices promise improvement primarily with respect to this disadvantage. In a prospective multicenter study, the new Miethke Dual-Switch Valve (DSV) was implanted in 128 patients with NPH. The patients were assessed before surgery and at discharge, and they were re-evaluated 6 to 9 months after surgery. The technical principle of the new device is presented. The clinical follow-up showed excellent results in 63% of the patients, satisfactory results in 16%, and a poor outcome in 21%. The outcome correlated with the preoperative severity of NPH. Despite the clinical outcome, the computed tomography scans showed nearly no or only a minimal reduction of the ventricular size in most cases. We found a valve-related rate of overdrainage of 2.5%, which is clearly lower than the results of comparable series in the literature. The clinical course of patients suffering from NPH is mainly influenced by the stage of the disease, the time of beginning the therapy, and the gravitational function of the implanted device. Based on our clinical experiences with the Miethke DSV, we underline the advantages of this valve for the treatment of hydrocephalus, especially for patients with NPH.

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 Blacks outcome scale at different time points of all iNPH patients operated in our center between January 2007 and December 2010. They had received either a proGAV® valve with an integrated gravitational unit, or a programmable Codman Hakim® valve without an integrated siphon regulatory device. RESULTS The postoperative course of 55 proGAV® and 45 programmable Codman Hakim® patients was analyzed. The latest documented valve setting of the proGAV® group and Codman Hakim® group was median 50mm H2O and 120 mm H2O, respectively. Overdrainage occurred among both groups in 20% of the patients, while surgical intervention for overdrainage-related complications was seen to be necessary only in 7% of the cases in the Codman Hakim® group. Clinical outcome differed in an increasing manner over the observation period (median 4 points after 3, 12 months and at final presentation in the proGAV®; median 4 points after 3 and 12 months and 3 points at final presentation in Codman Hakim® group (p=0.001)). CONCLUSION Adjustable and gravity-assisted valves like the proGAV® improve overdrainage control and enable thus low-pressure settings for the horizontal body position. We observed an improved and more sustainable functional outcome for iNPH patients with an adjustable and gravity-assisted valve compared to iNPH patients without an integrated siphon regulatory device.

Reduction of shunt obstructions by using a peel-away sheath technique? A multicenter prospective randomized trial

OBJECTIVE Shunt obstructions may partly be caused by brain debris, which intrude into the ventricular catheter during ventricle puncture. Avoiding contact between the catheter and brain tissue, by using a peel-away sheath, should reduce the number of shunt failures caused by obstruction. To test this hypothesis, we conducted a randomized, prospective multicenter study. METHODS 201 patients from 6 different neurosurgical centers in Germany receiving a ventriculo-peritoneal shunt were included in this study. Of these, 177 patients completed a 1-year follow-up period. Surgery was randomized in a 1 to 1 fashion, such that out of 177 procedures, 91 were performed using a peel-away sheath and 86 were performed without. The rate of surgical re-interventions and shunt obstructions within a 12-month period was recorded. RESULTS Within 1 year post-surgery, 17 shunt obstructions (9.6%) leading to shunt revisions were recorded. However, no difference was found between surgeries performed using a peel-away sheath (9.9%) or not (9.3%). The overall shunt infection rate was 2.8% and the shunt revision rate for overdrainage was 3.9%. CONCLUSIONS The theoretical advantages attributed to the use of a peel-away sheath to introduce a ventricular catheter could not be confirmed in this randomized study, suggesting that the proposed role of brain debris in shunt obstructions may be overestimated.

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. The telemetric ICP sensor was referenced against ICP values measured directly from a water column within a riser tube. A total of 34 comparative ICP measurements within an ICP range from 2 cm H2O to 31 mm Hg were performed. The mean difference between both measurement techniques was 0.4 mm Hg. The limits of agreement, where 95% of differences between both methods are expected, were from -2.4 to 3.1 mm Hg. The telemetric Neurovent-P-tel sensor system provides good accuracy within a broad range exceeding normal ICP values and might be useful in clinical practice.

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. METHODS The authors used 6 female pigs for the experiments. Two transdermal telemetric pressure sensors (cranial and caudal) were implanted intraperitoneally with a craniocaudal distance of 30 cm. Direct IPP measurements were supplemented with noninvasive IPP measurements (intragastral and intravesical). The IPP was measured with the pigs in the supine (0°), 30°, 60°, and vertical (90°) body positions. After the pigs were euthanized, CT was used to determine the intraperitoneal probe position. RESULTS With pigs in the supine position, the mean (± SD) IPP was 10.0 ± 3.5 cm H2O in a mean vertical distance of 4.5 ± 2.8 cm to the highest level of the peritoneum. The difference between the mean IPP of the cranially and the caudally implanted probes (Δ IPP) increased according to position, from 5.5 cm H2O in the 0° position to 11.5 cm H2O in the 30° position, 18.3 cm H2O in the 60° position, and 25.6 cm H2O in the vertical body position. The vertical distance between the probe tips (cranially implanted over caudally implanted) increased 3.4, 11.2, 19.3, and 22.3 cm for each of the 4 body positions, respectively. The mean difference between the Δ IPP and the vertical distance between both probe tips over all body positions was 1.7 cm H2O. CONCLUSIONS The IPP is subject to the position-dependent hydrostatic force. Normal IPP is able to reduce the differential pressure in patients with ventriculoperitoneal shunts.

Hydrocephalus-induced neuroleptic malignant-like syndrome with reduced dopamine transporters

Key symptoms of neuroleptic malignant syndrome (NMS) are alterations of mental status or consciousness, rigidity, hyperthermia, and autonomic dysfunction [1, 2]. Symptoms of NMS can result from brain injuries in the absence of neuroleptic drugs. Symptoms of brain injury–induced neuroleptic malignant-like syndrome (NMLS) are indistinguishable from antipsychotic drug-induced NMS. They can be triggered by infections, nonconvulsive status epilepticus, midbrain lesions, or hydrocephalus [3, 4]. Hydrocephalus is known to cause extrapyramidal symptoms. Akinetic, tremulous, hypertonic, or hyperkinetic movement disorders have been reported in 75 % of symptomatic hydrocephalus patients [5, 6]. These symptoms can progress to NMLS and be classified as akinetic crisis [7, 8]. The pathophysiology of hydrocephalusinduced NMLS is unknown. In this report, we describe a dysfunction of nigrostriatal neurons in two patients with acute hydrocephalus and NMLS. Single photon emission computed tomography (SPECT) with the I-labelled dopamine transporter (DaT) ligand ioflupane was used to assess dopamine transporters in the striatum [9]. Nigrostriatal injury is associated with decrease of DaT protein. Ioflupane SPECT was performed with a MultiSPECT 3 gamma camera (Siemens) and evaluated as published [10, 11]. The binding potential of ioflupane is proportional to the density of available DaT in the striatum. Patient 1, a 31-year-old woman, presented with progredient fatigue, cognitive changes, and reduced consciousness. A ventriculoperitoneal shunt was implanted 16 years ago due to hydrocephalus of unknown etiology. In exam, there were vertical gaze palsy, hypokinesia, and rigidity. Her Glasgow Coma Scale (GCS) was 9/15 and her body temperature went up to 41 C. Brain CT showed markedly enlarged ventricles (Fig. 1a). A nonconvulsive status epilepticus was excluded in EEG. Cerebrospinal fluid exam was normal. CK (254 U/l) and myoglobin (438 U/l) were increased. Blood pressure (62/40–168/ 90 mm Hg) and heart rate (55–155/min) were fluctuating greatly. The obstructed ventriculoperitoneal shunt was replaced. The patient’s symptoms as well as ventricle size improved slowly (Fig. 1a). Symptoms of NMLS were treated with dopamine agonists, dantrolene, and l-dopa ? benserazide. Ioflupane SPECT proved reduced DaT availability in the striatum (Fig. 1b). Two years later, SPECT showed an increase of DaT availability towards the normal range (Fig. 1b). The patient recovered almost fully. Her Unified Parkinson’s Disease Rating Scale Motor Subscale was 25 before, 80 during, and 7 after the crisis. Patient 2, a 66-year-old female patient, presented with progressive reduction of her vigilance. A ventriculoperitoneal shunt had been implanted 12 years ago for treatment of hydrocephalus after operative resection of a cerebellar hemangioblastoma. Her GCS was 8/15 on admission to our D. Jussen C. Sprung Department of Neurosurgery, Charité Universitätsmedizin Berlin, Berlin, Germany

An improved reservoir for the flushing test to diagnose shunt insufficiency.

OBJECTIVE Reservoirs integrated into hydrocephalus shunts are commonly used for the removal of CSF and for intra-ventricular pressure measurement. Pumping with the reservoir to diagnose shunt sufficiency is still a matter of controversy. The authors describe an improved flushing device and its characteristic features in vitro and in vivo. METHODS The flushing reservoir is constructed with a sapphire ball in a cage as a nonresistance valve to also enable the detection of distal occlusions. The most important reservoir parameters were investigated in vitro, simulating total and partial proximal and distal shunt occlusions. Then the expected advantages were assessed in vivo by evaluating the pump test data of 360 implanted reservoirs. The results were compared with those found in the literature. RESULTS The optimization of the technical parameters of the device, such as the high stroke volume in combination with moderate suction force, are obvious advantages compared with other flushing devices. Total occlusion of the ventricular catheter and the valve could be assessed with high certainty. The detection of a total obstruction of the peritoneal catheter or any partial obstruction is also possible, depending on its exact grade and location. CONCLUSIONS Shunt obstructions can be assessed using the pumping test. The reservoir construction presented here provides a clear enhancement of that diagnostic test.