Outcome analysis of the randomized multi-center study on idiophatic normal pressure hydrocephalus (SVASONA)

Johannes Lemcke^a and Ullrich Meier^a, Cornelia Müller^b, Michael Fritsch^b, Uwe Kehler^c, Niels Langer^c, Michael Kiefer^d, Regina Eymann^d, Martin U Schuhmann^e, Andreas Speil^e, Friedrich Weber^f, Victor Remenez^f, Veit Rohde^g, Hans-Christoph Ludwig^g, Dirk Stengel^h

Departments of Neurosurgery at the ^aUnfallkrankenhaus Berlin, ^bErnst-Moritz-Arndt-University of Greifswald, ^cAsklepios Hospital Altona, Hamburg, ^dSaarland Medical University, Homburg/Saar, ^eEberhard-Karls-University of Tübingen, ^fHospital Cologne-Merheim, ^gGeorg-August-University of Göttingen and the ^hCenter for Clinical Research, Unfallkrankenhaus Berlin and Ernst-Moritz-Arndt-University of Greifswald, Germany

Background The Dutch hydrocephalus study in the 1990s proved the superiority of low pressure valves (LPVs) in the therapy of the idiopathic normal pressure hydrocephalus and simultaneously uncovered the enormous risk of overdrainage complications for the use of low pressure valves without a gravitational compensation. The aim of the SVASONA study was to prove, that an excellent clinical outcome and a low rate of overdrainage complications can be achieved with gravitational valves. The aim of the outcome analysis is to underline the findings about the relation between LPVs and a favourable clinical outcome.

Methods In seven german centers experienced in the treatement of iNPH, patients were enrolled in the SVASONA study after passing clinical examination, radiological assessment and cerebrospinal fluid (CSF) infusion test, CSF tap test and / or continuous ICP measurement. Those patients with a diagnosed iNPH were randomly assigned in a treatment group with a ventriculoperitoneal (vp) shunt with a programmable valve without a gravitational unit or a treatment group with a programmable valve with a gravitational unit. The patients were followed up 3, 6 and 12 month after surgery. The primary endpoint was the incidence of overdrainage complications. Secondary endpoint was the clinical outcome after 6 and 12 months.

Results From 2006 to 2010 150 patients were included in the study. The baseline parameters were equal in both treatment groups. Due to a significantly lower risk of overdrainage complications in the treatment group with gravitational units, the study was stopped according to the protocol after the planned interim analysis.

69% of the patients in the treatment group without a gravitational valve and 86% of the patients in the group with gravitational valves showed an excellent, improved or fair outcome according to the Black grading scale after 6 months. After 12 months 75% respectively 86% were registered. The difference was not significant.

According to the Kiefer score, a significant clinical improvement war recorded in the group without gravitational valves (baseline 7.5; 6 months 4.8; 12 months 3.8) and in the group with gravitational valves (baseline 7.6; 6 months 3.8; 12 months 3.5). The difference between the treatment groups was also not significant.

Discussion Whereas a significant difference between the complication rates of the two treatment groups was evident, there is only a tendency in the difference between the outcomes measured by specific iNPH scores. These findings underline that gravitational valves prevents the risk of overdrainage but do not supress the favourable outcomes achieved with LPVs.

HYDROCEPHALUS