An abnormal build-up of fluid within the skull, also known as water on the brain

  • Age and genetics as risk factors depend on the cause
  • Gender and lifestyle are not significant factors

Hydrocephalus is an uncommon condition that occurs mainly in premature babies or with other disorders present from birth, such as spina bifida (see Neural tube defects).

Cerebrospinal fluid (CSF) is produced in the cavities of the brain and flows around the brain and spinal cord, protecting them from injury. Hydrocephalus develops if CSF builds up in the cavities of the brain, causing them to enlarge. This build-up occurs when the system that drains the CSF away from the brain is damaged or blocked or if excess CSF is produced. In such cases, the resulting increase in pressure in the skull may lead to brain damage.

Hydrocephalus may be caused by a brain defect that is present from birth. The disorder also sometimes develops as a result of meningitis, a serious infection of the membranes covering the brain and spinal cord (see Meningitis in children), or a brain tumour (see Brain and spinal cord tumours in children).

What are the symptoms?

The symptoms vary according to the age of the child, but the following may occur in all affected children:

  • Vomiting.

  • Drowsiness.

  • Reluctance to settle down.

In young babies, the skull bones are not yet fused and are able to separate to some extent to accommodate excess fluid. For this reason, the first signs of hydrocephalus in babies may be an enlarged head that grows too fast and widening of the fontanelles (the soft areas on the top of a baby’s skull). In older children with hydrocephalus, the head does not enlarge because the skull bones have fused, and headache due to pressure may be an early symptom.

Left untreated, hydrocephalus may lead to seizures and to cerebral palsy, in which movement and posture are affected. The disorder may also affect vision and hearing and can result in poor intellectual development.

How is it diagnosed?

Hydrocephalus can sometimes be diagnosed during pregnancy with routine ultrasound scanning (see Ultrasound scanning in pregnancy).

If the condition is suspected after birth, the doctor will arrange for ultrasound scanning or CT scanning of the child’s head to look for obstructions or other abnormalities.


In this CT scan, the small cavities in the centre of the brain have been enlarged by an abnormal build-up of fluid, a condition known as hydrocephalus.

What is the treatment?

A child who has hydrocephalus usually needs surgery. During the operation, a narrow flexible tube, called a shunt, is inserted into a cavity in the brain to drain away the excess fluid (see Shunt for hydrocephalus). The tube is normally left in place permanently.

In addition, the child may be prescribed drugs that will slow down the production of CSF in the brain. Underlying causes of obstruction, such as a brain tumour, will be treated.

Some children with hydrocephalus are able to lead normal lives if they are given treatment before significant brain damage occurs. However, if the condition is severe or is left untreated, resulting in physical disabilities or difficulties with learning, affected children and their families will need long-term practical and psychological support.

Parents who have a child with hydrocephalus may wish to consider genetic counselling because there is an increased risk of the condition occurring in subsequent children.

Treatment: Shunt for Hydrocephalus

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

The subjects, conditions and treatments covered in this encyclopaedia are for information only and may not be covered by your insurance product should you make a claim.

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