Clinical experiences with different valve systems in patients with normal-pressure hydrocephalus: evaluation of the Miethke dual-switch valve

Objective: In patients with normal-pressure hydrocephalus (NPH) and beginning brain atrophy the conventional differential pressure valve bears the disadvantage of opening abruptly when the patient moves into an upright position. In this way severe suction on the already atrophic brain could be induced. We wished to find whether this disadvantage, and especially the complication of the overdrainage, could be reduced or solved by a hydrostatic valve? Methods: In H 5 patients diagnosed with NPH we implanted 36 Cordis standard valves (CSV), 19 Cordis-Orbis-Sigma valves type I (OSV), and 60 Miethke Dual-Switch valves (M-DSV). The patients were re-evaluated 7 months after surgical treatment. NPH was diagnosed from the clinical symptoms, the results of the CAT scan or MRI scan, the intrathecal infusion test, and the patients' recovery after a CSF tap test. Results: The clinical follow-up showed significantly better results for patients with an implanted M-DSV valve than in patients with a conventional differential pressure valve. We found clear differences in the incidences of overdrainage and subdural hematoma: 2 patients (6%) with a CSV, 3 patients (16%) with an OSV and 1 (2%) with a M-DSV exhibited clinical signs of overdrainage. Three patients (16%) with the OSV later developed subdural hematomas, for which neurosurgical treatment was necessary. One of these 3 patients (5%) died of an intraventricular hemorrhage. One patient with a CSV (3%) and I with a M-DSV (2%) had to be operated on a subdural hematoma. Conclusion: The clinical course in patients with NPH is influenced by the stage of the disease, the beginning of therapy and the implanted valve type. Although little clinical experience is so far available with the M-DSV, we have to underline the advantages of this valve for patients with NPH.