Gravity-assisted Valve Research Articles

Gravity-assisted valve (GAV) systems to prevent low-pressure headaches in patients with lumboperitoneal shunts

Objectives: Low-pressure symptoms after lumboperitoneal (LP) shunting for idiopathic intracranial hypertension (IIH) remain a significant problem. Gravity-assisted valves (GAV) operate at a higher pressure in a vertical position and therefore aim to reduce postural over-drainage. We audited patients with GAV valves inserted in their shunt system to assess their efficacy in reducing low-pressure symptoms and ascertain whether the additional cost of such device can be justified.Method: Using a standard proforma, we reviewed patient medical notes and recorded indications and post-operative outcomes in symptom control.Results: In total, 24 patients had the GAV system inserted, 12 had low-pressure symptoms after LP and had LP shunts inserted with GAV valves and 11 in developed low-pressure symptoms after insertion of plane LP shunts and had GAV valves added as secondary procedures. One patient was excluded from the study because the indication for the GAV system was secondary to the presence of low lying cerebellar tonsils (secondary Chiari) rather than headache in a patient with IIH who had undergone previous LP shunt insertion. The GAV system was introduced to prevent further tonsillar decent.Out of 23 patients, 17 patients who had the system inserted to prevent or improve low-pressure symptoms reported improvement in their symptoms.Conclusions: GAV inserted into LP shunts were effective in reducing low-pressure headaches induced by changes in posture whilst still sufficiently lowering ICP to ameliorate high-pressure symptoms.

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

ObjectiveThe 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. MethodsWe 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. They had received either a proGAV® valve with an integrated gravitational unit, or a programmable Codman Hakim® valve without an integrated siphon regulatory device. ResultsThe 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 120mm 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)). ConclusionAdjustable 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.

Experience with a gravitational valve in the management of symptomatic overdrainage in children with shunts

Symptomatic overdrainage in children with shunt-treated hydrocephalus represents one of the more difficult shunt-related diseases and may require repeated surgery. Gravity-assisted valve design has become a standard device to avoid overdrainage in many European pediatric hydrocephalus centers. However, the use of a gravitational valve for relieving symptoms associated with overdrainage has not yet been addressed. The goal of this study was to evaluate the effectiveness of a gravitational valve in the treatment of symptomatic overdrainage in children with shunts. Seventeen children with an adjustable shunt system and symptomatic overdrainage were treated by insertion of a gravitational valve. Clinical and radiological outcome were monitored for a minimum of 12 months after surgery. Implantation of a gravitational valve resulted in either resolution (n = 12) or improvement (n = 5) of the symptoms. In 1 patient, symptoms remained almost unchanged and the gravitational valve had to be upgraded, resulting in resolution of the symptoms. During follow-up, the pressure setting of the adjustable differential pressure valve had to be changed in 7 patients. The gravitational valve was effective in improving symptomatic overdrainage in the majority of patients in the present study. Because the ideal pressure setting for a given patient is hard to determine a priori, adjustable valve systems appear to be beneficial.

A Comparative Result of Ventriculoperitoneal Shunt, Focusing Mainly on Gravity-Assisted Valve and Programmable Valve

Despite rapid evolution of shunt devices, the complication rates remain high. The most common causes are turning from obstruction, infection, and overdrainage into mainly underdrainage. We investigated the incidence of complications in a consecutive series of hydrocephalic patients. From January 2002 to December 2009, 111 patients underwent ventriculoperitoneal (VP) shunting at our hospital. We documented shunt failures and complications according to valve type, primary disease, and number of revisions. Overall shunt survival time was 268 weeks. Mean survival time of gravity-assisted valve (GAV) was 222 weeks versus 286 weeks for other shunts. Survival time of programmable valves (264 weeks) was longer than that of pressure-controlled valves (186 weeks). The most common cause for shunt revision was underdrainage (13 valves). The revision rate due to underdrainage in patients with GAV (7 of 10 patients) was higher than that for other valve types. Of 7 patients requiring revision for GAV underdrainage, 6 patients were bedridden. The overall infection rate was 3.6%, which was lower than reported series. Seven patients demonstrating overdrainage had cranial defects when operations were performed (41%), and overdrainage was improved in 5 patients after cranioplasty. Although none of the differences was statistically significant, some of the observations were especially notable. If a candidate for VP shunting is bedridden, GAV may not be indicated because it could lead to underdrainage. Careful procedure and perioperative management can reduce infection rate. Cranioplasty performed prior to VP shunting may be beneficial.

Experiences with a gravity-assisted valve in hydrocephalic children

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. 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. 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. 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.

Initial experience with silver-impregnated polyurethane ventricular catheter for shunting of cerebrospinal fluid in patients with infected hydrocephalus

Objective: Infection is a major complication and risk factor of cerebrospinal fluid (CSF) shunting procedures. Recently, antibiotic-impregnated shunt systems have been developed in an attempt to prevent or reduce the CSF infection. The aim of this study was to determine the efficacy of silver-impregnated polyurethane ventricular catheter for shunting of CSF in patients with infected hydrocephalus.Methods: Seven patients who had hydrocephalus with high protein level and positive CSF culture underwent implantation of ventriculoperitoneal shunt with silver-impregnated polyurethane ventricular catheter. All of them experienced shunt failure previously due to infection. The Silverline ventricular catheter, which was connected to the Miethke gravity-assisted valve system and peritoneal catheter, was used in all patients. The mean follow-up period after operation was 14 months. Cerebrospinal fluid samples from the reservoir of the shunts were obtained at the end of the third month after operation in all patients.Results: The CSF protein level of the patients was reduced significantly, and the CSF culture became negative after shunt placement with silver-impregnated polyurethane ventricular catheters. The mean CSF silver (Ag) level was 0.51 ng/ml [parts per billion (ppb)], and blood Ag level was 3.65 ng/ml (ppb) at the first month after operation. No shunt obstruction or infection was observed in the follow-up period.Conclusion: Silver-impregnated polyurethane ventricular catheters appear to be safe and well tolerated in patients who sustained infected hydrocephalus. Preliminary results suggest a complete improvement of infection. Longer follow-up and large number of patients are needed to more accurately assess the efficacy of these catheters.

First experiences with an adjustable gravitational valve in childhood hydrocephalus

The goal of this report was to describe the authors' initial experiences with an adjustable gravity-assisted valve (GAV) called the ProGAV in treating childhood hydrocephalus. The ProGAV was implanted in 53 children (29 boys and 24 girls, median age 7.3 years) with hydrocephalus of various origins. The ProGAV consists of a differential-pressure unit with adjustable opening pressures and a gravitational unit with a fixed opening pressure. The mean follow-up period was 15.2 months (range 6-44 months). The authors did not observe any valve-related complications. Four infections (7.5%) occurred, warranting the removal of the shunt. In 19 children, the opening pressure was changed at least once during the follow-up period, for underdrainage in 10, overdrainage in 8, and shunt weaning in 1, with substantial clinical improvement in 18 children. Overall, good clinical results were obtained in 47 (88.7%) of the 53 valve placements. With an overall success rate of 88.7%, the first experiences with the ProGAV in childhood hydrocephalus are promising and justify its further use in the pediatric population.

Valve inclination influences the performance of gravity-assisted valve

Background The performance of GAV may be affected by its inclination as a tantalum sphere in the valve, which generates a downhill force in proportion to the sine of the angle with respect to level. Accordingly, the aim of this study was to evaluate the effect of valve inclination relative to the vertical on shunt performance. Method In 24 adult patients who underwent ventriculoperitoneal shunting using a GAV for hydrocephalus, valve inclination relative to the vertical was measured using AP and lateral projections of skull x-rays that were taken in a standing position, and the relationship between valve inclination and ventricular volume change after ventriculoperitoneal shunting in CT scans was evaluated. Results The Pearson correlation coefficient between valve inclination in a sagittal plane and ventricular volume change was −0.768 ( P < .01), whereas lateral valve inclination had no correlation with ventricular volume change. Eleven patients with a posterior valve inclination relative to the vertical exhibited a greater ventricular volume reduction of 34.1% ± 8.2% compared to the volume reduction of 13.4% ± 9.2 % in 13 other patients with an anterior valve inclination ( P = .000). Two (40%) of 5 patients with a severe anterior valve inclination of more than 20° relative to the vertical underwent shunt revision for underdrainage. Conclusions A severe anterior inclination of the valve by more than 20° relative to the vertical can lead to underdrainage owing to an increased OP in a lying position, especially in patients who are nonambulatory at the time of GAV implantation.

Klinische Erfahrungen mit dem neuen programmierbaren Schwerkraftventil (proGAVAesculap®) bei Patienten mit idiopathischem Normaldruckhydrozephalus

OBJECTIVE The higher rate of overdrainage is an expensive price but is accepted to get a good outcome in the treatment of idiopathic normal-pressure hydrocephalus patients by using low-pressure valves. Is a programmable, gravity-assisted valve a solution to optimize the outcome? METHOD In a prospective follow-up study made by the Neurosurgical Department in the Unfallkrankenhaus Berlin in the period from June 2004 to July 2005, 34 patients with idiopathic normal-pressure hydrocephalus underwent shunt surgery using the new programmable gravity-assisted valve (proGAV Aesculap ®). These patients were followed-up after 6 and 12 months. RESULTS The course of disease correlates with the opening pressure of the valve . The controlled adjustment of the valve's programmable opening pressure changes in steps from initially 100 mm H 2 O to 70 mm H 2 O and finally 50 mm H 2 O after 3 months and thus allows an optimal adaption of the cerebrum to the new pressure environment and reduces the overdrainage rate. CONCLUSIONS The advantages of the new programmable, gravity-assisted valve (proGAV Aesculap ®) are its resistance to external magnetic fields which otherwise cause a misadjustment of programmable valves and the fact that reading of the adjusted opening pressure can be done by using a complementary device without exposing the patient to a skull X-ray. The disadvantage lies in the difficult early post-operative (1 - 10 days post-operatively) adjustment in 18 % of the implanted valves. From the clinical point of view, the programmable gravity-assisted valve (proGAV Aesculap ®) represents an extraordinary and consequent trend in the valve manufacturing technique.

Gravitational Shunts in Longstanding Overt Ventriculomegaly in Adults

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. 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). 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. 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.

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.