Especially in patients with normal pressure hydrocephalus (NPH), conventional differential pressure valves are known to create unphysiologic negative intraventricular pressure values when the patient moves to an upright position, with the consequence of numerous and sometimes severe complications. The recently presented gravitational devices promise improvement primarily with respect to this disadvantage. In a prospective multicenter study, the new Miethke Dual-Switch Valve (DSV) was implanted in 128 patients with NPH. The patients were assessed before surgery and at discharge, and they were re-evaluated 6 to 9 months after surgery. The technical principle of the new device is presented. The clinical follow-up showed excellent results in 63percnt; of the patients, satisfactory results in 16percnt;, and a poor outcome in 21percnt;. The outcome correlated with the preoperative severity of NPH. Despite the clinical outcome, the computed tomography scans showed nearly no or only a minimal reduction of the ventricular size in most cases. We found a valve-related rate of overdrainage of 2.5percnt;, which is clearly lower than the results of comparable series in the literature. The clinical course of patients suffering from NPH is mainly influenced by the stage of the disease, the time of beginning the therapy, and the gravitational function of the implanted device. Based on our clinical experiences with the Miethke DSV, we underline the advantages of this valve for the treatment of hydrocephalus, especially for patients with NPH.
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