AQP4 deficiency reduced cytotoxic edema produced by water intoxication, cerebral hischemia and acute bacterial meningitis [22, 32], but increases vasogenic edema caused by brain tumour, cortical freeze injury, brain abscess and kaolin-induced obstructive hydrocephalus [11, 13, 31]. The gene discussed is AQP4; the disease is obstructive hydrocephalus.