ObjectivesTo 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).BackgroundPatients 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.MethodsWe 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.ResultsWe 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.ConclusionsImplanting a gravitational rather than another type of valve will avoid one additional overdrainage complication in about every third patient undergoing VP shunting for iNPH.
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.
Overdrainage is a common complication observed after shunting patients with idiopathic normal-pressure hydrocephalus (iNPH), with an estimated incidence up to 25%. Gravitational units that counterbalance intracranial pressure changes were developed to overcome this problem. We will set out to investigate whether the combination of a programmable valve and a gravitational unit (proGAV, Aesculap/Miethke, Germany) is capable of reducing the incidence of overdrainage and improving patient-centered outcomes compared to a conventional programmable valve (Medos-Codman, Johnson & Johnson, Germany). SVASONA is a pragmatic randomized controlled trial conducted at seven centers in Germany. Patients with a high probability of iNPH (based on clinical signs and symptoms, lumbar infusion and/or tap test, cranial computed tomography [CCT]) and no contraindications for surgical drainage will randomly be assigned to receive (1) a shunt assistant valve (proGAV) or (2) a conventional, programmable shunt valve (programmable Medos-Codman).We will test the primary hypothesis that the experimental device reduces the rate of overdrainage from 25% to 10%. As secondary analyses, we will measure iNPH-specific outcomes (i.e., the Black grading scale and the NPH Recovery Rate), generic quality of life (Short Form 36), and complications and serious adverse events (SAE). One planned interim analysis for safety and efficacy will be performed halfway through the study. To detect the hypothesized difference in the incidence of overdrainage with a type I error of 5% and a type II error of 20%, correcting for multiple testing and an anticipated dropout rate of 10%, 200 patients will be enrolled.The presented trial is currently recruiting patients, with the first results predicted to be available in late 2008.
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