What is hydrocephalus?

Hydrocephalus comes from the Greek hydro meaning water and cephalie, meaning brain. A watery fluid, known as cerebro-spinal fluid or CSF, is produced constantly inside each of the four spaces or ventricles inside the brain: between 400 and 600mls is produced each day. The CSF normally flows through narrow pathways from one ventricle to the next, then out over the outside of the brain and down the spinal cord. The CSF is absorbed into the bloodstream, and the amount and pressure are normally kept within a fairly narrow range.

If the drainage of CSF is prevented at any point, the fluid accumulates in the ventricles inside the brain, causing them to swell and resulting in compression of the surrounding tissue. In babies and infants, the head will enlarge. In older children and adults, the head size cannot increase as the bones which form the skull are completely joined together.

What causes hydrocephalus? 

The condition is caused by the inability of CSF to drain away into the bloodstream. There are many reasons why this can happen. Hydrocephalus can be congenital or acquired.

• Key

Cerebrum: The main part of the brain, in two halves one on each side (left and right hemispheres).

Cerebellum: The smaller part of the brain at the back of the head, involved in muscular coordination.

Ventricles: Connected spaces inside the brain, where CSF is produced. There are two lateral ventricles (one each side), a third ventricle and a fourth ventricle. CSF flows from here over the outside of the brain before being absorbed back into the bloodstream.

Choroid plexus: The organ that makes CSF.

Superior sagittal sinus: The major vein that runs over the centre of the top of the brain and collects CSF, draining it back into the central bloodstream.

Pituitary gland: A gland situated in the brain cavity but just behind the face. It is very important in secreting a large number of hormones that regulate body function and development. An example is growth hormone, and others are involved in sexual development.

Brainstem: A very important area connecting the spinal cord to the brain. It controls breathing and other vital functions.

Spinal cord: A complex trunk of nerves transmitting impulses to all parts of the body, allowing muscle movement, sensation and reflexes.

How is hydrocephalus treated?

Some forms of hydrocephalus require no specific treatment. Other forms are temporary and do not require treatment on a long-term basis. However, most forms do require treatment and this is usually surgical. Drugs have been used for many years but they may have unpleasant side effects and are not often successful.

The usual treatment is to insert a shunting device. It is important to note that this does not ‘cure’ the hydrocephalus and damage to the brain tissue remains. Shunting controls the pressure by draining excess CSF, so preventing the condition becoming worse. Symptoms caused by raised pressure usually improve but other problems of brain damage will remain.

What is a shunt?

A shunt is simply a device which diverts the accumulated CSF around the obstructed pathways and returns it to the bloodstream. It consists of a system of tubes with a valve to control the rate of drainage and prevent back-flow. It is inserted surgically so that the upper end is in a ventricle of the brain and the lower end leads either into the heart (ventriculo-atrial) or into the abdomen (ventriculo-peritoneal). The shunt may be a programmable (adjustable) type.

The device is completely enclosed so that all of it is inside the body. The fluid which is drained into the abdomen passes from there into the bloodstream. Other drainage sites such as the outer lining of the lungs (ventriculo-pleural shunt) can also be used.

Possible Complications 

In most cases, the shunts are intended to stay in place for life, although alterations or revisions might become necessary from time to time. The tube or catheter may become too short as the individual grows and an operation to lengthen it might be necessary. Occasionally, as with any implant, there can be mechanical failure. Also, it is important to be aware that problems can occur with blockage or infection of the shunt.

What symptoms should be looked for? 

These vary enormously between individuals. Previous personal experience of a shunt problem is often a reliable guide as to what to look for. 

Possible signs of acute shunt blockage may include: 
vomiting, headache, dizziness, photophobia (sensitivity to light) and other visual disturbances, drowsiness and fits. 

Possible signs of chronic shunt blockage may include: 
fatigue, general malaise, visual problems, behavioural changes, decline in academic performance, being just ‘not right’ from the carer’s point of view.

If a shunt blockage is suspected, medical advice should be sought from your neuro-surgical unit within four hours of acute symptoms starting. 
In shunt infections, symptoms vary with the route of drainage.

In ventriculo-peritoneal shunts, the symptoms often resemble those of a blockage. This is because the shunt becomes infected and the lower catheter is very often then sealed off by tissue. There may be accompanying fever and abdominal pain or discomfort or redness over the shunt site.