Indications for Valve-Pressure Adjustments of Gravitational Assisted Valves in Patients with Idiopathic Normal Pressure Hydrocephalus-15 Years Experience

Introduction: The aim of this retrospective analysis is to evaluate indications for valve-pressure adjustments in idiopathic normal pressure hydrocephalus (iNPH). Materials and Methods: Patients operated between 2004 and 2011 with the clinical symptoms of iNPH, Evans-Index >= 0.3, and positive invasive CSF diagnostics were included. The Kiefer scale was used to classify each patient. Follow-up exams were conducted 3, 6, and 12 months after shunt implantation and yearly thereafter. Initial valve pressure was 100 or 70mmH(2)O. A planned reduction of the valve-pressure to 70 and 50 mmH(2)O, respectively, was carried out. In addition, reactive adjustments of the valve-pressure to avoid over-and underdrainage were indicated. Results: 52 patients were provided with a Medos-Hakim valveCodman (R) with a Miethke shunt assistant Aesculap (R) and 111 patients with a Miethke-proGAV Aesculap (R). During follow-up 180 reductions of the valve pressure took place (65% reactive, 35% planned). Most patients (90 %) needed one or two adjustments of their valve-pressures for optimal results. In 41% an improvement of clinical symptoms was observed. Gait disorder was improved most often after valve pressure adjustments (33 %). 18 times an elevation of the valve pressure was necessary because of headaches, vertigo or the development of subdural hygroma. Optimal valve pressure for most patients was around 50mmH(2)O (36%). Conclusion: The goal of shunt therapy in iNPH should usually be valve pressure settings between 30 and 70mmH2O. Reactive adjustments of the valve pressure are useful for therapy of over-and underdrainage symptoms. Planned reductions of the valve opening pressure are effective even if postoperative results are already satisfactory.