Hydrocephalus is one of the most common disorders in children. It is simply understood to mean that there is too much cerebrospinal fluid and it affects the brain tissue. Before we get into hydrocephalus, let’s understand a little about cerebrospinal fluid. It brings nutrients to the central nervous system, transports waste products, regulates the acid-base balance of the environment, buffers the brain and spinal cord from the shock of pressure, and protects and supports the central nervous system. All cerebrospinal fluid is connected. The area where the cerebrospinal fluid surrounds the brain tissue is called the subarachnoid space, where in some places the subarachnoid space is larger and the cerebrospinal fluid is more aggregated, it is called the cerebral pool, which also includes the lumbar pool, and the four largest pools are called the ventricles. Cerebrospinal fluid is like the water inside a swimming pool, and is dynamically circulating, secreting an average of about 20 ml per hour. In children, the brain and spinal cord together have about 100-150 ml of cerebrospinal fluid, so the cerebrospinal fluid is renewed 3-4 times a day to keep the cerebrospinal fluid clean and functional. Most of the cerebrospinal fluid is secreted from the choroid plexus (equivalent to an inlet) within the ventricles, which flows through the two symmetrical lateral ventricles into the three ventricles and through the narrow midbrain aqueduct into the fourth ventricle, which has three outlets. Through the median foramen, it can flow to the spinal subarachnoid space and lumbar pool in the spinal canal, and through the two lateral foramina of the fourth ventricle, it can flow back to the subarachnoid space of the brain. Finally, the arachnoid granules (equivalent to the outlet) in the parsagittal sinus absorb the cerebrospinal fluid into the venous system. The diagram above illustrates the ventricular system and cerebrospinal fluid circulation The normal secretion and absorption of cerebrospinal fluid are matched and balanced by dynamic circulation through a fixed pathway. If cerebrospinal fluid is produced relatively more than it is absorbed, or if there is an obstruction in the circulation pathway, too much cerebrospinal fluid can accumulate and reach a certain point where the ventricles become dilated and hydrocephalus is formed. We call the situation when there is more secretion than absorption as traffic hydrocephalus, meaning that the cerebrospinal fluid circulation pathway is normal and all cerebrospinal fluid is still connected to each other; the situation when the circulation pathway is obstructed as obstructive hydrocephalus, meaning that the cerebrospinal fluid circulation pathway is blocked and the cerebrospinal fluid is not connected to each other. Hydrocephalus can occur alone or secondary to various congenital malformations, hemorrhage, trauma, infection, tumors, cysts, and other diseases. Hydrocephalus can have a significant impact on children, especially infants and young children whose brain tissue is developing rapidly, leading to restricted brain tissue development, reduced brain function, cranial nerve dysfunction, cranial hypertension, and even life-threatening conditions that require aggressive treatment. Different causes and types of hydrocephalus require different treatment options. Traffic hydrocephalus often requires a ventriculo-abdominal shunt to drain the cerebrospinal fluid into the abdominal cavity by placing a tube to help absorb the fluid because it is secreting more cerebrospinal fluid than can be absorbed. Obstructive hydrocephalus, on the other hand, can be solved by simply opening up the cerebrospinal fluid circulation and is most commonly treated with an endoscopic triple ventriculostomy. Most hydrocephalus caused by tumors or cysts is obstructive, and most hydrocephalus can be relieved by removing the tumor or cyst.