Encyclopedia / H / Hydrocephalus



Hydrocephalus is a condition in which dilated cerebral ventricles inhibit normal flow of cerebrospinal fluid (CSF). The CSF accumulates in the skull and puts pressure on the brain tissue.

An enlarged head in infants and increased CSF pressure are frequent findings but are not necessary for the diagnosis. Hydrocephalus is sometimes inaccurately referred to as "water on the brain."


Normally, CSF is secreted in the cavities of the brain and absorbed by a membrane that lines the cavities. If the membrane does not absorb the fluid or if the fluid is blocked, it builds up in the cavities. The fluid buildup causes the head to become enlarged and the brain to become compressed. This condition can lead to paralysis, blindness, mental retardation, inability to speak, and convulsions.

Hydrocephalus is subdivided according to the ventricular defect and the CSF pressure, high or normal.

In communicating hydrocephalus, there is no obstruction in the ventricular system - the CSF flows readily into the subarachnoid space but is insufficiently absorbed, or perhaps produced in too great a quantity to be absorbed.

In noncommunicating (obstructing) hydrocephalus, a ventricular block to CSF flow causes dilation of the pathways upstream of the block, leading to increased CSF pressure in the skull.

Normal-pressure hydrocephalus, which affects middle-aged and older persons, is characterized by dilated ventricles but normal lumbar CSF pressure.


Hydrocephalus is usually the result of a brain infection or a malformation in the fetus prior to birth. Although the baby's head may not appear abnormally large at birth, it expands rapidly from month to month.

If untreated, the baby usually dies by the end of the second year. If the blockage of CSF is only partial, the child may live for a number of years or may even live a normal life span.


Characteristic features of hydrocephalus in children include cephalomegaly, a thin, transparent scalp, a bulging forehead with prominent fontanelles, and a downward gaze.

Other clinical findings include convulsions, abnormal reflexes, a slowed heartbeat and respiratory rate, headache, vomiting, irritability, weakness, and problems with vision.

Blindness and continuing mental deterioration from brain atrophy can result if treatment is not instituted.


Surgical correction is the only treatment for hydrocephalus. Usually, such surgery consists of insertion of a ventriculoperitoneal shunt, which transports excess fluid from the lateral ventricle into the peritoneal cavity.

A less common procedure is insertion of a ventriculoatrial shunt, which drains fluid from the brain's lateral ventricle into the right atrium of the heart, where the fluid makes its way into the venous circulation. Periodic lengthening of the shunt is necessary to accommodate growth in children. A clogged malfunctioning shunt will have to be replaced.

Complications of surgery include shunt infection, septicemia (after ventriculoatrial shunt), adhesions and paralytic ileus, shunt migration, peritonitis, and intestinal perforation (with peritoneal shunt).


What type of hydrocephalus is involved?

How dangerous is it?

Will it get worse?

Is surgery indicated?

Will a shunt be used?

What are the possible risks and complications?

Is a cure possible?