Within the human brain there are a number of spaces known as ventricles which are filled with cerebrospinal fluid. Hydrocephalus is caused by a build up of this fluid, often leading to a dilation of the ventricles. Symptoms vary greatly with the severity of the condition including: headaches, vomiting, urinary incontinence, dementia, and learning difficulties. It is a common disorder and affects around 1:1500 births.

Most cases are due to complications in pregnancy such as infection, X-ray radiation and maternal alcohol use, however some are due to genetic mutations. Two genes have been implicated, L1CAM and AP1S2. Hydrocephalus can be treated in some cases by placing a shunt into the ventricles to drain the excess fluid from the brain.