The term hydrocephalus relates to the presence of an excessive amount of cerebrospinal fluid (CSF), which may cause an increase in intracranial pressure with or without abnormal enlargement of the cerebral ventricles. Hydrocephalus can result from a variety of pathological processes or insults that cause imbalance between production and absorption of CSF. Numerous classifications and categories exist with two widely used and pragmatically helpful subdivisions: obstructive (where there is macroscopic obstruction to bulk flow of CSF within the ventricles) and communicating hydrocephalus (where there is inadequate absorption of CSF from the subarachnoid space).