University Hospital Southampton NHS Foundation Trust


Hydrocephalus is commonly known as water on the brain. A fluid known as cerebro-spinal fluid (CSF) is produced constantly inside each of the four ventricles (spaces) inside the brain. This fluid flows through small pathways from one space to another, around the outside of the brain and then down the spinal cord. From here it is absorbed into the bloodstream.

If these pathways become blocked at any point then fluid will build up within the spaces and cause them to swell. Occasionally the hydrocephalus may be due to an over production of CSF. The effect of the swelling is to put pressure on the surrounding brain tissue. 

What causes Hydrocephalus?

Congenital Hydrocephalus can occur in all age groups, and there are many different reasons why a baby may devlop it, which include:

  • Congenital Hydrocephalus - This means it may be present at birth. Often, there is no known cause of this.
  • Prematurity - Premature babies have very fragile blood vessels within their brains. Sometimes there can be a bleed from these vessels which occasionally leads to a clot of blood blocking the flow of CSF. 
  • Infection - Hydrocephalus can sometimes occur after an infection such as meningitis. It may also be associated with infections in the mother before birth such as toxoplasmosis.
  • Spina Bifida - Most babies with Spina Bifida have Hydrocephalus.
  • Tumours - These cause swelling of brain tissue which can result in poor drainage of the CSF.
  • Dandy Walker Cysts - These are fluid filled cysts within the system that again result in poor drainage.
  • Trauma - Rarely, Hydrocephalus may develop after a traumatic delivery as a result of bleed within the brain.

How do we recognise Hydrocephalus?

Antenatally - Sometimes Hydrocephalus can be identified on antenatal ultrasound scans. We may see enlarged ventricles or maybe an increase in the size of the head.

Postnatally - It can detected by an increase in the head size greater than expected or by an ultrasound scan of the baby’s head. This is normally before the baby demonstrates any other symptoms.

Before any treatment a further scan (either CT or MRI) is normally necessary.

What are the symptoms associated with Hydrocephalus?

These are varied and often the problem is identified before physical signs become apparent. The symptoms include:

Increase in head circumference over and above the normal growth expected, fontanelle (the soft spot on top of the baby’s head) may be tense, vomiting, irritability, high-pitched cry, poor feeding and drowsiness, Sunset Eyes (it is more difficult for these babies to look upwards) and fits (these are not due to the Hydrocephalus itself but are usually associated with the underlying cause).

What treatment is necessary?

Sometimes Hydrocephalus does not seem to worsen and the baby can be observed and regular measurements of its head taken. However more frequently further active treatment is necessary. The two types of treatment normally used are the insertion of a shunt or a ventriculostomy. Treatment prevents the condition from becoming worse but it does not cure the Hydrocephalus. Any damage that has been caused to the brain tissue will remain.

Ventriculo-peritoneal shunt insertion

A shunt is a device to drain the CSF from the pathways and return it to the blood stream. This involves putting in a tube into one of the ventricles of the brain. Usually the shunt is placed under the skin above the ear and tunnelled under the skin to the abdomen (tummy).

Insertion of shunts is fairly straightforward and is undertaken by a specialised surgeon. However sometimes these shunts do not function well and need replacing. There is also a risk of infection occurring either at the time of the operation or at a later date.

IIIrd Ventriculostomy

During an operation a small telescope is passed through the fontanelle of the baby’s head. A drainage pathway is made by making a small hole through the floor of the IIIrd ventricle which should allow the CSF to drain away and be absorbed back into the bloodstream.

The main risk of this procedure is bleeding which is normally minor but occasionally more severe. Risk of infection is much lower as there is no implanted shunt left behind. Sometimes it is apparent that this procedure has not controlled the Hydrocephalus and then it would be necessary to insert a shunt.

Not all types of Hydrocephalus are suitable to be treated by this method.

What are the Effects of Hydrocephalus?

There can be learning difficulties associated with Hydrocephalus such as problems with concentration, reasoning and short-term memory. Hydrocephalus can also result in subtle effects: giving problems with co-ordination, motivation and organisational skills but the effects vary greatly from one baby to another. Physical effects such as visual impairment may also be possible.


University Hospital Southampton NHS Foundation Trust produce guidelines as an aid to good clinical practice. They represent recognised methods and techniques of clinical practice, based on published evidence. The ultimate judgement regarding a particular clinical procedure or treatment must be made by the clinician in the light of the clinical data presented by the patient and the diagnostic or treatment options available. The guidelines issued are not intended to be prescriptive directions defining a single course of management and departure from the local guidelines should be fully documented in the patient's case notes at the time the relevant decision is taken.