There are several spaces in the human brain called ventricles, which contain a clear fluid called cerebrospinal fluid. If too much cerebrospinal fluid is produced, or if its absorption is impaired, the ventricles enlarge and compress the brain parenchyma between the ventricles and the skull bones, making them thin. In infants, a large head is formed because the internal pressure is increased and the skull bone gap is enlarged. What are the causes of hydrocephalus? There are many causes of hydrocephalus, for example, if the brain tissue is invaded by Toxoplasma gondii in the mother and the channels for cerebrospinal fluid circulation are blocked, then the child is born with hydrocephalus already caused. The presence of intracranial hemorrhage before and after birth and subsequent enlargement of the ventricles can be detected by a cranial CT. What are the symptoms of hydrocephalus? In young children or older children, hydrocephalus may begin in infancy but is mild and progresses slowly, so symptoms appear later. It may also be secondary to a post-inflammatory lesion such as a narrowing of the aqueduct, which is usually a partial obstruction, with symptoms and progression depending on the degree of obstruction. The clinical presentation is different from the aforementioned. In slowly progressive hydrocephalus, for example, paralysis of one or both abductor muscles is often seen. As the lesion progresses, hyperreflexia of the lower limbs may appear, motor function may be delayed, and mental retardation is a late manifestation. In hydrocephalus caused by partial cerebrospinal fluid obstruction, headache is often aggravated when resting in bed for a long time, so there is often a phenomenon of headache in the morning that disappears after getting up and moving around, probably because the cerebrospinal fluid passes through the narrowed part when physical activity helps, and this phenomenon is also seen in children with posterior cranial fossa tumors. After the enlargement of the ventricles is obvious, signs of cerebellar or brainstem involvement may appear, as well as symptoms such as impairment of upward rotation of both eyes and damage to the cone bundle. How to treat hydrocephalus? Hydrocephalus must be treated early and without delay. Medication is indicated in cases that cannot be treated surgically or as a preoperative preparation. General treatment, not as good as for hydrocephalus caused by intracranial infections such as meningitis, can be given by intrathecal injection of dexamethasone or orally, which may be effective for recent patients. Restriction of water intake and application of drugs such as acetazolamide, dihydrocotrimoxazole, and aminopterin to reduce CSF secretion and increase water excretion can be helpful in temporary hydrocephalus. Surgical treatment is more effective. There are various types of surgery, including surgery to reduce cerebrospinal fluid formation, intracranial and extracranial shunts of cerebrospinal fluid, bypass surgery of the distal and proximal ends of ventricular system obstruction and surgery to remove the cause of obstruction.