There are many causes of hydrocephalus, the common ones are as follows: 1. Congenital malformations. Such as midbrain aqueduct stenosis, diaphragm formation or atresia, interventricular foramen atresia malformation (median foramen of the fourth ventricle or lateral hollow atresia), cerebrovascular malformation, spina bifida, cerebellar subungual herniation, etc. 2.Infection. Fetal 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 fetal intracranial inflammation can also occlude the cerebral pool, subarachnoid space and arachnoid granule adhesions. 3.Hemorrhage. Fibroplasia caused by intracranial hemorrhage, malabsorption of intracranial hemorrhage from birth injury, etc. 4.Tumor. Can obstruct 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.