Clinical experiences with the dual-switch valve in patients with normal pressure hydrocephalus

In patients with normal pressure hydrocephalus (NPH) we compared the postoperative results reference to the implanted valve type. In 117 patients diagnosed with normal pressure hydrocephalus there was placement of 47 Cordis Standard valves (CSV), 20 Cordis Orbis Sigma valves type I (OSV) and 50 Miethke Dual-switch valves (DSV). Ninety-five patients (36/19/40) were re-evaluated. Normal pressure hydrocephalus was graduated according to the results of the intrathecal infusion test in an early and late stage. There were no statistical differences in mechanical and infective complications between the different valve types. We found significant differences in overdrainages and subdural hematomas. Two patients (6%) with a CSV, 3 patients (16%) with an OSV and 1 patient (3%) with a DSV developed clinical symptoms due to this. The course of disease in patients with NPH is influenced by the stage of disease--degree of cerebral atrophy--and also by the implanted valve type. The great amount of overdrainage complications and subdural hematomas in the Cordis Orbis Sigma valve group may be an argument against this valve. Our clinical experiences with the Miethke Dual-switch valve show that this hydrostatic valve may be advantageous for patients with NPH.