Acute hydrocephalus is associated with poor outcome after SAH [6]. Hydrocephalus develops within 72 h (acute hydrocephalus) in 20–63 % of SAH patients but rarely occurs in SAH patients at 3–7 days (2–3 %; subacute hydrocephalus) [9, 10]. It is generally accepted that fibrosis of the leptomeninges and arachnoid granulations cause impaired cerebrospinal flow and decreased absorption, resulting in hydrocephalus development. However, the exact mechanisms of hydrocephalus development after SAH remain poorly understood. In a clinical study, the presence of an intraventricular hemorrhage had a high statistical correlation with hydrocephalus [9] and we found that the degree of hydrocephalus correlated with the amount of intraventricular blood in a rat SAH model [15].

In addition to SAH incidence being higher in women than in men [13], more female patients develop acute hydrocephalus after SAH [19]. Female gender was also one of the parameters associated with the likelihood of needing a permanent shunt [3]. In this study, we examined the effect of gender in experimental rat SAH and found that acute hydrocephalus occurs more frequently in females. In a clinical study, acute hydrocephalus after SAH occurred 2.2-fold more frequently in women compared with men [14]. In another study, female gender was one factor associated with shunt-dependent hydrocephalus [5]. These results all suggest that the gender is the factor in the development of acute hydrocephalus after SAH.

There are some limitations to this study: (1) the time course of SAH-induced hydrocephalus in different genders after SAH was not determined and (2) it is still unknown whether estrogen has a role in hydrocephalus development.