AIF1 and Hydrocephalus: The main findings of this study are as follows: (a) Iba‐1, CD68, and OX‐6 are expressed in epiplexus cells in sham‐operated rats; (b) induction of SAH increased the numbers of CD68‐ and Iba‐1‐positive cells, as well as Iba‐1‐positive cell soma size at 24 hours in rats; (c) Those effects were greater in rats that developed hydrocephalus after SAH; (d) Intraventricular injection of thrombin in rats also increased the number of Iba‐1‐positive and CD68‐positive cells at 24 hours.