Hydrocephalus occurs at a frequency of approximately 0.5 in 1000 births [176, 177] and is characterized by abnormal flow or resorption of cerebrospinal fluid. It is considered a heterogeneous complex disorder [178] with genetic and environmental aetiologies [179, 180]. Although approximately 37% of the hydrocephalus cases have a possible genetic aetiology [180], clear susceptibility genes for hydrocephalus have not been identified yet. Studies in animal models have suggested several loci as susceptibility regions for hydrocephalus, but these regions have not yet been reported as susceptibility regions in human [reviewed in 181].
