Hydrocephalus

Overview

Hydrocephalus is a condition in which excess fluid builds up in your brain. The word hydrocephalus comes from the roots hydro meaning "water" and cephalus meaning "head." The fluid that accumulates is cerebrospinal fluid (CSF), a fluid that normally surrounds your brain and spinal cord.

In hydrocephalus, too much fluid builds up, causing abnormal enlargement of the cavities in the brain (ventricles) that contain CSF. Too much CSF in the ventricles can put too much pressure on the brain, potentially damaging the brain.

You can have hydrocephalus at birth (congenital hydrocephalus) or you can develop it later (acquired hydrocephalus). Hydrocephalus occurs in about 1 in every 500 children.

The outlook for people with hydrocephalus varies depending on how soon the condition is diagnosed, whether any other disorders are present and whether treatment is successful. Left untreated, progressive hydrocephalus is, with rare exceptions, fatal


Causes


Hydrocephalus results when the flow of CSF is disrupted or when your body doesn't absorb CSF properly. CSF provides a number of important functions, including acting as a cushion to protect your brain and bringing nutrients to your brain.

Inside your brain are four ventricles. CSF flows through the ventricles by way of channels that connect one ventricle to another. Once CSF passes through the ventricles, it flows into closed spaces (cisterns) at the base of your brain. Eventually, the CSF is absorbed into your bloodstream. Keeping the production, flow and absorption of CSF in balance is important to maintaining normal pressure inside your skull.

In adults, a variation of hydrocephalus called normal-pressure hydrocephalus may occur in which the CSF pressure is normal but the reabsorption of CSF is defective. In normal-pressure hydrocephalus, the ventricles of the brain are enlarged but not under high pressure. This type of hydrocephalus is most often seen in older adults and may be the result of injury or illness, but in the majority of cases the cause is unknown.

The causes of hydrocephalus fall into two main categories:

Obstructive (noncommunicating). This type of hydrocephalus results from an obstruction within the ventricular system of the brain that prevents CSF from flowing or "communicating" within the brain, as it normally should. An obstruction can be congenital or acquired. One of the most common types of obstructive hydrocephalus is a narrowing of a channel in the brain that connects two ventricles together (aqueductal stenosis).
Nonobstructive (communicating). This type of hydrocephalus results from problems with the production or absorption of CSF. One of the most common causes is bleeding into the subarachnoid space in the brain (subarachnoid hemorrhage). Nonobstructive hydrocephalus can also be congenital or acquired.
Doctors don't completely understand the specific causes of hydrocephalus. For congenital hydrocephalus, the causes may be genetic disposition or a developmental problem. The most common developmental problems that may lead to hydrocephalus include failure of the tissue surrounding the spinal cord to close properly (spina bifida) and herniation of the brain (encephalocele). For acquired encephalitis, the cause may be a disease or condition such as encephalitis, meningitis or a brain tumor that causes blood vessels in the brain to rupture and bleed. Or the cause may be a head injury.