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[Significance of hydrostatic valves in therapy of chronic hydrocephalus].

Earlier design changes in hydrocephalus valves focusing on reducing overdrainage failed. Since the middle of the 1990s, hydrostatic valve constructions have been available which are claimed to solve this problem. The objective of this study was to evaluate the efficiency of these constructions. Clinical status and ventricular size were evaluated in 45 patients with chronic hydrocephalus before and 1, 6, and 26 weeks after operation. In 35 of these, a Miethke dual-switch valve was implanted (treatment group 1), and the others received a combination of a programmable Codman-Hakim valve and a Miethke shunt assistant as the hydrostatic element of the configuration (treatment group 2). A third group (n = 6) had already been shunted but suffered from overdrainage symptoms which could not be overcome by conservative measures. In these cases, the only operative treatment was the implantation of a Miethke shunt assistant adjunctively to the existing valve. In groups 1 and 2, there was a significant permanent improvement in the clinical state in nearly 80% of cases and a moderate permanent improvement in about 10%. Mild clinical and radiological signs of overdrainage occurred in three patients during the first postoperative week but resolved without further operative measures within the next 5 weeks. Typically, the ventricular width was not or only marginally reduced in these 45 patients. In the patients treated for symptoms of overdrainage (group 3), complaints resolved within the first week after implantation of the shunt assistant. The study indicates that gravitational shunts may be very effective in preventing overdrainage in chronic hydrocephalus, and therefore these constructions could represent the gold standard in the treatment of chronic hydrocephalus.