====== Gravitational valve ====== {{rss>https://pubmed.ncbi.nlm.nih.gov/rss/search/1hY_wykJMhumRvKwVXxs0CDmvpjn2g1LT37FcKcAkIJHeVV9Uo/?limit=15&utm_campaign=pubmed-2&fc=20240812055655}} ---- ---- Implanting a gravitational [[valve]] rather than another type of valve will avoid one additional [[overdrainage]] complication in about every third patient undergoing VP shunting for iNPH ((Lemcke J, Meier U, Müller C, Fritsch MJ, Kehler U, Langer N, Kiefer M, Eymann R, Schuhmann MU, Speil A, Weber F, Remenez V, Rohde V, Ludwig HC, Stengel D. Safety and efficacy of gravitational shunt valves in patients with idiopathic normal pressure hydrocephalus: a pragmatic, randomised, open label, multicentre trial (SVASONA). J Neurol Neurosurg Psychiatry. 2013 Aug;84(8):850-7. doi: 10.1136/jnnp-2012-303936. Epub 2013 Mar 1. PubMed PMID: 23457222; PubMed Central PMCID: PMC3717598.)). Gravitational valves (GVs) prevent overdrainage in ventriculoperitoneal shunting (VPS). However, there are no data available on the appropriate opening pressure in the shunt system when implementing a GV. ===== Adjustable Gravitational Valve ===== see [[Adjustable Gravitational Valve]]. ===== Anti-siphon device ===== [[Anti-siphon device]] ===== Complications ===== Between 1996 and 2002, Kieferand Eymann implanted 282 VP G-valves in various forms of [[adult]] [[chronic hydrocephalus]], of which 130 provided a complete data set with an annual follow-up. Adjustable and non-adjustable G-valves were used: the Miethke Dual-Switch valve, the Miethke GAV-valve and a combination of adjustable Codman-Hakim valves with the Miethke Shunt-Assistant. In cases of supposed mechanical shunt failure, the explanted shunts were examined in a bench test. The total complication rate was 21%:3% [[shunt infection]]s, 3% catheter dislocation/fracture, 5% [[underdrainage]] and 9% [[overdrainage]] occurred. Half of the overdrainage complications could be managed conservatively. Underdrainage complications resulted from the chosen opening pressure being too high (n = 3), a secondary increase in [[intraperitoneal pressure]] (n = 2) or from "real" [[shunt failure]] in one case according to bench test results. G-valves demonstrate sufficient long-term performance over multiple years, and real shunt-related complications are rare. The frequency of revision due to overdrainage is low (4.5%) ((Kiefer M, Eymann R. Gravitational shunt complications after a five-year follow-up. Acta Neurochir Suppl. 2010;106:107-12. doi: 10.1007/978-3-211-98811-4_18. PMID: 19812930.)). ====Case series==== A retrospective study in adult VPS patients with GVs, we analysed all available data, including the most recent computed tomography (CT) scans, to determine the best adjustments for alleviating any symptoms of [[overdrainage]] and underdrainage. Vertical effective opening pressure (VEOP) of the entire shunt system, including the [[differential pressure]] valve, was determined. One hundred and twenty-two patients were eligible for the study. Of these, female patients revealed a higher VEOP compared with males (mean, 35.6 cmH2O [SD ± 2.46] vs 28.9 cmH2O [SD ± 0.87], respectively, p = 0.0072, t-test). In patients older than 60 years, lower VEOPs, by a mean of 6.76 cmH2O ± 2.37 (p = 0.0051), were necessary. Mean VEOP was found to be high in idiopathic intracranial hypertension (IIH; 41.6 cmH2O) and malresorptive and congenital HC (35.9 and 36.3), but low in normal pressure HC (27.5, p = 0.0229; one-way ANOVA). In the total cohort, body mass index (BMI) and height did not correlate with VEOP. Twelve patients required a VEOP of more than 40 cmH2O, and in eight of these patients this was accomplished by using multiple GVs. All but one of these eight patients were of female gender, and none of the latter were treated for normal pressure hydrocephalus (NPH) (p = 0.0044 and p = 0.0032, Fisher's exact test). In adult VPS patients, female gender increases the risk of overdrainage requiring higher VEOPs. Initial implantation of adjustable GV should be considered in female patients treated with VP shunts for pathology other than NPH ((Diesner N, Freimann F, Clajus C, Kallenberg K, Rohde V, Stockhammer F. Female gender predisposes for cerebrospinal fluid overdrainage in ventriculoperitoneal shunting. Acta Neurochir (Wien). 2016 May 13. [Epub ahead of print] PubMed PMID: 27177735. )). ===== Miethke GAV ===== see [[Miethke GAV]]