(a) History 1. Congenital hydrocephalus is symptomatic at birth, such as the more common Dandy-Walk anomaly (atresia of the fourth ventricular foramen, dilatation of the fourth ventricle, overgrowth of the skull, or cyst formation at the end of the cerebellum blocking the posterior cranial fossa), with a family history. 2. Secondary hydrocephalus may have a history of encephalitis and meningitis, or a postnatal history of intracranial hemorrhage. 3. Most of the patients have large head, backward intelligence, depression, drowsiness, backward development and malnutrition. (2) Physical examination 1. Head circumference increases, fontanelle bulges, cranial sutures open, skull shape becomes round, percussion has broken pot sound, cranial bones become thin, even translucent. Frontal and temporal veins can be seen in anger. Positive cranial transillumination test. 2. Both eyes are sunset-like, and most patients have nystagmus. 3. Patients often have twitching, or have repeated convulsive episodes. In addition, cranial nerve palsy, limb paralysis, high muscle tone or ataxia are also seen as signs. (C) Auxiliary examinations 1. Cranial radiography or CT examination shows enlargement of cranial cavity, thinning of skull, separation of cranial sutures and enlargement of fontanelle. 2, lateral chamber injection of neutral phenol red 1m1, lumbar puncture within 2 to 12 minutes, CSF visible phenol red, suggesting non-obstructive hydrocephalus. If the phenol red is still not seen in 20 minutes CSF, it suggests obstructive hydrocephalus. 3, ventriculography, with filtered oxygen slowly injected into the ventricles, and then do X-ray examination, can be observed ventricular enlargement and cerebral cortex thinning. If the thickness of the cerebral cortex is more than 2 cm and the hydrocephalus can be relieved, it indicates that the patient can expect to recover his intelligence. Ventriculography can also help determine the site of obstruction or detect intracranial tumors. 4.Cranial ultrasound examination of the midline wave is not displaced, and the lateral ventricles or the third ventricle are enlarged. 5, fontanelle puncture Lend to exclude subdural hematoma or hydroma, both of which also often cause skull enlargement. It is also possible to find out the thickness of the cerebral cortex and the intracerebral pressure (50-60 mm water column in normal infants). The disease should be differentiated from subdural hematoma or effusion, intracranial tumors, and rickets in infants.