The ventricular system is made up of four ventricles connected by narrow passages.. Normally, the cerebro-spinal fuid (CSF) flows through the ventricles, exits into cisterns (closed spaces that serve as reservoirs) at the base of the brain, bathes the surfaces of the brain and spinal cord, and then reabsorbs into the bloodstream.
CSF has three important life-sustaining functions: 1) to keep the brain tissue buoyant, acting as a cushion or "shock absorber"; 2) to act as the vehicle for delivering nutrients to the brain and removing waste; and 3) to flow between the cranium and spine and compensate for changes in intracranial blood volume (the amount of blood within the brain).
The balance between production and absorption of CSF is critically important. Because CSF is made continuously, medical conditions that block its normal flow or absorption will result in an over-accumulation of CSF. The resulting pressure of the fluid against brain tissue is what causes hydrocephalus.
Hydrocephalus is sometimes referred to as 'water on the brain'. A watery fluid, known as cerebro-spinal fluid or CSF, is produced continuously inside each of the four spaces or ventricles inside the brain. The CSF normally flows through narrow pathways from one ventricle to the next, then out across the outside of the brain and down the spinal cord. The CSF is absorbed into the bloodstream and recirculates. The amount and pressure are normally kept within a fairly narrow range. If the drainage pathways are blocked at any point, the fluid accumulates in the ventricles inside the brain, causing them to swell - resulting in compression of surrounding tissue. In babies and infants, the head will enlarge. In older children and adults, the head size cannot increase as the bones which form the skull are completely joined together.