What is hydrocephalus?

The ventricular system is made up of four ventricles connected by narrow pathways. Normally, 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 is absorbed 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 to 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. Ideally, the fluid is almost completely absorbed into the bloodstream as it circulates; however, there are circumstances which, when present, will prevent or disturb the production or absorption of CSF, or which will inhibit its normal flow. When this balance is disturbed, hydrocephalus is the result.

Hydrocephalus occurs when excess fluid builds up in your brain, most often because of an obstruction preventing proper fluid drainage. The excess fluid can push fragile brain tissues up against the skull — causing brain damage and, if left untreated, even death.

Once known as "water on the brain," hydrocephalus is sometimes present at birth, although it may develop later. About one out of 500 children are born with the disorder. The outlook for people with hydrocephalus depends on how quickly the condition is diagnosed and whether any underlying disorders are present.