Evaluation of the Miethke dual- switch valve in patients with normal pressure hydrocephalus

Especially in patients with normal pressure hydrocephalus (NPH), conventional differential-pressure valves are known to create nonphysiological negative intraventricular pressure values (IVP) when the patient moves into the upright position, with the consequence of numerous, sometimes severe, complications. The recently presented gravitational devices promise improvement, primarily in respect to this disadvantage.

In a prospective multicenter study the new Miethke dual- switch valve (DSV) has been implanted in 128 patients with NPH. The patients have been assessed before operation, at discharge, and 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 63% of the patients, satisfactory results in 16%, and a bad outcome in 21% of the cases. The infection rate was 5%; the rate of mechanical complications including overdrainage and dislocations has been in total 9%, and underdrainage was suspected in 7 cases. The outcome correlated with the preoperative severity of NPH. Despite the clinical outcome, the computed tomography scans showed only minimal or no reduction of the ventricular size in the majority of cases. We found a valve-related rate of overdrainage of 2.5%, which is clearly lower than 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 of the therapy, and the gravitational function of the implanted device. Based on our clinical experiences with the Miethke dual-switch valve (MD-SV), we underscore the advantages of this valve for the treatment of hydrocephalus, especially for patients with NPH.