Female gender predisposes for cerebrospinal fluid overdrainage in ventriculoperitoneal shunting

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. We performed a retrospective analysis of hydrocephalic patients who were successfully treated with VPS which included one or more GV. In this 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 cmH(2)O [SD +/- 2.46] vs 28.9 cmH(2)O [SD +/- 0.87], respectively, p = 0.0072, t-test). In patients older than 60 years, lower VEOPs, by a mean of 6.76 cmH(2)O +/- 2.37 (p = 0.0051), were necessary. Mean VEOP was found to be high in idiopathic intracranial hypertension (IIH; 41.6 cmH(2)O) 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 cmH(2)O, 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.