The pathological changes of hydrocephalus are gradual enlargement of the ventricular system, compression of the pituitary gland and optic nerve crossings by the third ventricle bulging inferiorly, penetration of the septum pellucidum, and thinning of the brain parenchyma, most obviously at the frontal lobe, and even penetration of the lateral ventricle with the subarachnoid space. The corpus callosum, pyramidal bundle, basal ganglia, tegmentum, choroid plexus and brainstem can be atrophied due to long-term compression. White matter demyelination, nerve axon compression and deformation, gliosis and degenerative neuronal cell degeneration are observed. Hydrocephalus is a general term for an excess of cerebrospinal fluid and an increase in pressure due to a disorder in the process of cerebrospinal fluid production or circulation and absorption, which expands the space occupied by normal cerebrospinal fluid, resulting in an increase in cranial pressure and enlargement of the ventricles. Most of the causes are due to obstruction in some parts of the cerebrospinal fluid circulation pathway, while excess generation is less common. It occurs mostly in infants within two years of age, and can be divided into two categories: communicative and non-communicative hydrocephalus, with communicative meaning that the absorption of cerebrospinal fluid on the brain surface is blocked; non-communicative meaning that the cerebrospinal fluid circulation in the ventricular system is blocked. There are many causes of hydrocephalus. There are several common causes: 1, congenital malformations: such as stenosis of the midbrain aqueduct, atresia of the interventricular foramen (median foramen of the fourth ventricle or lateral hollow atresia), cerebrovascular malformations, spina bifida, subhypophyseal herniation of the cerebellum, etc. 2, infection: intrauterine infections such as various viruses, protozoa and syphilis spirochete infectious meningitis are not controlled early enough, and the proliferating fibrous tissue blocks the circulatory orifice of cerebrospinal fluid, or intracranial inflammation of the fetus can also cause adhesions and occlusion of the brain pool, subarachnoid space and arachnoid granules. 3, hemorrhage: intracranial hemorrhage caused by fibrous hyperplasia, intracranial hemorrhage from birth injury malabsorption, etc. 4, tumor: can block any part of the cerebrospinal fluid circulation, more often seen near the fourth ventricle, or choroid plexus papilloma. 5, other: certain hereditary metabolic diseases, perinatal and neonatal asphyxia, severe vitamin A deficiency, etc.