Regina Eymann

Five years experience with gravitational shunts in chronic hydrocephalus of adults.

Summary.Summary. Objective: Gravitational shunts for management of chronic hydrocephalus are supposed to avoid or at least to reduce the risk of overdrainage. In order to find out if this hypothesis is correct, we did a prospective study and analysed the results of a series of 185 hydrocephalic adults, treated by using gravitational shunts. For the few cases in whom overdrainage occurred, we wanted to establish the reason for it. Especially it should be proven or excluded that overdrainage was caused by shortcomings of the principle of gravitational shunts. Another goal was to compare post-shunting changes of the ventricular size with clinical outcome. A comparably large study has not yet been published. Methods: 185 adult patients who suffered from chronic hydrocephalus were shunted between 1996–2000, either using the combination of an adjustable Codmann Hakim Valve & Miethke Shunt Assistant (35 patients) or a Miethke Dual Switch Valve (150 patients). The clinical course of each patient has been followed until the end of 2000. Average follow-up time was 26 months (range 6–60 months). Results: 88% of our patients were shunt responders, 70% had a good or excellent outcome. Overdrainage occurred in only 4%. It turned out that this complication was not a failure of the concept of gravitational shunts, but the result of a wrongly estimated intraperitoneal pressure. After shunting the ventricular size was reduced only marginally. In 92% of the patients the Evans-Index decreased less than 20% after the shunt insertion, but 69% of these patients had a good or excellent outcome. The most obvious difference comparing pre- and postoperative imaging was a better visibility of the high apical sulci after shunting. Conclusion: In our series gravitational shunts proved to be effective in preventing overdrainage. The 4% negative exceptions are mainly avoidable. There was no correlation between outcome and ventricular size reduction, and as a rule ventricular size was only marginally reduced.

Safety and efficacy of gravitational shunt valves in patients with idiopathic normal pressure hydrocephalus: a pragmatic, randomised, open label, multicentre trial (SVASONA)

Objectives To investigate whether gravitational valves reduce the risk of overdrainage complications compared with programmable valves in ventriculoperitoneal (VP) shunt surgery for idiopathic normal pressure hydrocephalus (iNPH). Background Patients with iNPH may benefit from VP shunting but are prone to overdrainage complications during posture changes. Gravitational valves with tantalum balls are considered to reduce the risk of overdrainage but their clinical effectiveness is unclear. Methods We conducted a pragmatic, randomised, multicentre trial comparing gravitational with non-gravitational programmable valves in patients with iNPH eligible for VP shunting. The primary endpoint was any clinical or radiological sign (headache, nausea, vomiting, subdural effusion or slit ventricle) of overdrainage 6 months after randomisation. We also assessed disease specific instruments (Black and Kiefer Scale) and Physical and Mental Component Scores of the Short Form 12 (SF-12) generic health questionnaire. Results We enrolled 145 patients (mean (SD) age 71.9 (6.9) years), 137 of whom were available for endpoint analysis. After 6 months, 29 patients in the standard and five patients in the gravitational shunt group developed overdrainage (risk difference −36%, 95% CI −49% to −23%; p<0.001). This difference exceeded predetermined stopping rules and resulted in premature discontinuation of patient recruitment. Disease specific outcome scales did not differ between the groups although there was a significant advantage of the gravitational device in the SF-12 Mental Component Scores at the 6 and 12 month visits. Conclusions Implanting a gravitational rather than another type of valve will avoid one additional overdrainage complication in about every third patient undergoing VP shunting for iNPH.

The ependyma in chronic hydrocephalus

H-Tx rats produce congenitally hydrocephalic offspring with varying severity of the condition. We used moderately hydrocephalic rats without evident clinical signs of hydrocephalus and normal controls from the same stock when they were at least 1.5 years old. Macroscopic anatomy was studied by MRI and in fixed brain slices and the ultrastructure of the ependyma, with REM. Apart from markedly stretched areas, where the ependyma was totally destroyed and subependymal structures directly exposed to the CSF, the density of ependymal microvilli and of tufts of cilia was reduced in proportion to the ventricular distension of a given area. A supraependymal “network”– never seen before in acute hydrocephalus – was found, whose purpose is probably to prevent further ventricular enlargement. We conclude that even in arrested hydrocephalus the ependymal sequelae of hydrocephalus are similar to those of the acute stage, illustrating the extremely limited potenctial for recovery, but the organism seems nevertheless to react with an internal stabilization of the ventricular system.

Gravitational Shunts in Longstanding Overt Ventriculomegaly in Adults

OBJECTIVE:A new entity of chronic hydrocephalus was introduced recently in the international literature: longstanding overt ventriculomegaly in adults. Previous experience with this disorder has demonstrated that shunt therapy for such patients involves a considerable risk of overdrainage. In the present study, we aimed to clarify whether this risk could be avoided by use of gravitational shunts. METHODS:A total of 26 adults (age range, 17–75 yr) with macrocephaly and progressive hydrocephalus symptoms underwent implantation of either an adjustable Codman Hakim gravity-assisted shunt (Codman Medos, LeLocle, Switzerland) plus an Aesculap-Miethke ShuntAssistant (Miethke KG, Kleinmachnow, Germany) or a nonadjustable gravitational shunt (Aesculap-Miethke gravity-assisted valve). The follow-up period averaged 29 ± 13 months (range, 6–48 mo). RESULTS:Significant sustained clinical improvement was achieved in 87% of patients. In more than 90% of patients, Evans index decreased postoperatively by less than 10%. No correlation was documented between the degree of ventricle width reduction and clinical improvement. Only two patients developed subdural hematoma, which was caused by insufficient hydrostatic pressure compensation owing to errors in estimation of intraperitoneal pressure. CONCLUSION:Unlike conventional differential pressure shunts, gravitational shunts can be used in the treatment of high-risk patients with longstanding overt ventriculomegaly in adults. Significant risk of overdrainage can be avoided. Gravitational shunts offer a viable alternative to endoscopic third ventriculostomy, provided the choice and adjustment of the shunt opening pressure is based on a correct assessment of the hydrostatic pressure to be compensated for.

Outcome predictors for normal-pressure hydrocephalus

The objective of this prospective study was to find outcome predictors for better selection for treatment of normal-pressure hydrocephalus (NPH) patients. A total of 125 patients were evaluated and provided with a gravitational shunt. Cerebrospinal fluid hydrodynamics provided better predictive values if an algorithm to shunt all patients with a pressure/volume index of < 30 mL or resistance to outflow > 13 mmHg/mL x min was used. In general, outcome became worse with increasing anamnesis duration, worse preoperative clinical state, and increasing comorbidity. If one of these parameters was lower than a critical value, the shunt-responder rate was about 90% and the normally negative influence of older age was not seen. The well-known paradigm of a worse prognosis with NPH is not the result of the hydrocephalus etiology itself, but the consequence of a typical accumulation of negative outcome predictors as a consequence of the misinterpretation of normal aging and delayed adequate treatment.

Telemetric ICP Measurement with the First CE-Approved Device: Data from Animal Experiments and Initial Clinical Experiences

The objective was to evaluate the qualification of the new telemetric intracranial pressure (ICP) measurement (t-ICP) device Raumedic(®) NEUROVENT P-Tel and S-Tel. The proof of concept was examined in a pilot animal study measuring intraperitoneal pressure with a telemetric and a conventional ICP measurement probe at five rates for 1 h each. Moderate external pressure load allowed measuring values between 0 and 40 mmHg. To estimate long-term performance 18 t-ICP devices were implanted subdurally or intraparenchymally into minipigs. Reference measurements were performed regularly using conventional ICP probes. From the short-term as well as from the long-term perspective t-ICP proved to have excellent dynamic ICP signal components perception (e.g. pulse amplitude). Some zero drift of static ICP was found, ranging between 5 and 8 mmHg. While all telemetric, intraparenchymal probes kept their functionality throughout the follow-up, 33% of the subdurals failed for reasons detailed in another paper. Raumedics NEUROVENT(®) P-Tel/S-Tel proved to provide reliable data over periods of up to 18 months. Minor zero drift can be well tolerated as the dynamic ICP signal is measured with excellent stability. Clinicians should focus more on such ICP dynamic signal information than on static ICP when using the device over longer follow-up periods.

Experiences with a gravity-assisted valve in hydrocephalic children. Clinical article.

OBJECT Over the past decade, a gravity-assisted valve (GAV) has become a standard device in many European pediatric hydrocephalus centers. Because past comparative clinical outcome studies on valve design have not included any GAV, the authors in this trial evaluated the early results of GAV applications in a pediatric population. METHODS For a minimum of 2 years the authors monitored 169 of 182 hydrocephalic children who received a pediatric GAV at their first CSF shunt insertion (61.5%) or as a substitute for any differential pressure valve (38.5%) at 1 of 7 European pediatric hydrocephalus centers. Outcomes were categorized as valve survival (primary outcome) or shunt survival (secondary outcome). The end point was defined as valve explantation. RESULTS Within a follow-up period of 2 years, the valve remained functional in 130 (76.9%) of 169 patients. One hundred eight of these patients (63.9%) had an uncomplicated clinical course without any subsequent surgery, and 22 (13%) were submitted to a valve-preserving catheter revision without any further complications during the follow-up period. Thirty-nine patients (23.1%) reached an end point of valve explantation: 13 valve failures from infection (7.7%), 8 (4.7%) from overdrainage, and 18 (10.6%) from underdrainage. CONCLUSIONS Compared with nongravitational shunt designs, a GAV does not substantially affect the early complication rate. Valve-preserving shunt revisions do not increase the risk of subsequent valve failure and therefore should not be defined as an end point in studies on valve design. A significant impact of any well-established valve design on the early complication rate in shunt surgery is not supported by any current data; therefore, this correlation should be dismissed. As overdrainage-related complications have been shown to occur late, the presumed advantages of a pediatric GAV remain to be shown in a long-term study.

Predictors of Subsequent Overdrainage and Clinical Outcomes After Ventriculoperitoneal Shunting for Idiopathic Normal Pressure Hydrocephalus

BACKGROUND Little is known about variables associated with overdrainage complications and neurofunctional and health-related quality of life outcomes in idiopathic normal-pressure hydrocephalus (iNPH) patients after shunt surgery. OBJECTIVE To identify candidate demographic and disease-specific predictors of overdrainage and patient-related outcomes, allowing for more personalized care of patients with iNPH. METHODS This was a secondary analysis of the dataset of the SVASONA study, a multicenter randomized trial comparing gravitational and conventional gravitational valves for treating iNPH. We evaluated the association between baseline items and the incidence of overdrainage, using different endpoint definitions. RESULTS We identified only a few variables associated with a possible increased risk of overdrainage. Apart from using conventional rather than gravitational valves, longer duration of surgery and female sex were associated with a higher risk of clinical signs and symptoms suggestive of overdrainage (hazard ratio: 1.02, 95% confidence interval: 1.01-1.04 and 1.84, 95% confidence interval: 0.81-4.16). The occurrence of clinical symptoms of overdrainage, and the need for exchanging a programmable by a gravitational valve may adversely affect disease-specific outcomes like the Kiefer score. CONCLUSION Few, if any, baseline and treatment characteristics may be helpful in estimating the individual risk of complications and clinical outcomes after shunt surgery for iNPH. Patients should be informed that longer surgery for any reason may increase the risk of later overdrainage. Also, women should be counseled about a sex-associated increased risk of the development of clinical symptoms of overdrainage, although the latter cannot be distinguished from a generally higher prevalence of headaches in the female population.

Accuracy of ultrasound-guided puncture of the ventricular system

ObjectsPuncture of the ventricular system as one of the most frequently performed operative procedures in neurosurgery is usually done in a freehand way without guiding devices. The objective of this study is to examine whether ultrasonic guidance is able to heighten the accuracy of ventricular tapping.MethodsReal-time imaging via a single burr hole approach is achieved by aid of a bajonet-like shaped transducer with a footprint of 8x8 mm only (EUP-NS32, Hitachi Medical Systems). The needle is advanced towards the frontal horn along a displayed guideline. 51 punctures in 48 patients were performed with ultrasonic guidance and compared to 85 punctures in 67 patients without a guiding device.ConclusionThe presented ultrasound method was not able to heighten the access rate of ventricular tapping, but it improved correct positioning of the catheter tip inside the frontal horn of the ventricular system significantly.

The dynamic infusion test in rats

Abstract Although the hydrocephalic H-Tx rat is a widely used model, data on the cerebrospinal fluid (CSF) dynamics in hydrocephalic rats are rare or – as the pressure volume index (PVI) – not available. We used hydrocephalic and nonhydrocephalic H-Tx rats, a stock with a high percentage of inherited hydrocephalus, for the evaluation of such data. In addition, a new, simple mathematical algorithm (”dynamic infusion test”), which has not formerly been used in animal experiments, was used as a pathophysiological model of CSF dynamics. Compared with classical methods for evaluation of these data, the dynamic infusion test gives a deeper insight into the relation between ICP and CSF dynamics. It was found that the resistance to outflow (ROF) in hydrocephalic rats was at least twice that in nonhydrocephalic rats. The PVI measured was similar in hydrocephalic and nonhydrocephalic animals, but clearly higher than the values reported in the literature. This may be attributable to the fact that the classically used bolus test, in contrast to the ”dynamic infusion test”, is representative only for the CSF compartment which is directly exposed to the bolus application.