Hydrocephalus is an abnormal increase in cerebrospinal fluid in the ventricles and brain pools, as if a lake were rising. This results in local or total dilatation of the ventricular system, water retention, enlargement of the ventricles, pressure on the brain parenchyma, and brain dysfunction. It is characterized by poor drainage of “water”. The most common cause is obstruction of the cerebrospinal fluid channels, especially the middle cerebral aqueduct. This type of hydrocephalus is called obstructive hydrocephalus. If there is no blockage and water accumulation is seen, the clinical term for this type of hydrocephalus is traffic hydrocephalus. Congenital malformation, encephalitis, tumor, hemorrhage, trauma, poisoning, etc. can all cause hydrocephalus. The appearance of hydrocephalus in infants and young children is easy to recognize, mainly because of the enlarged head circumference, bulging fontanelle, separated bones, developmental disorders, and an oversized skull. Therefore, the folklore is long called “water head”. In adults, normal pressure hydrocephalus presents with headache, ataxia/unsteady gait, vomiting, dementia, urinary incontinence/decreased level of autonomic consciousness, visual impairment, etc. This can be accurately determined by MRI or CT. The most effective treatment for hydrocephalus is surgery to remove the brain tumor causing the blockage or a lateral ventricle-abdominal shunt, which creates an “artificial river” to drain the excess “water” for a long time and relieve the flooding.