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.
In ventriculo-atrial shunt infections, fever is present in most cases though often intermittently. Anaemia is frequently present, and sometimes skin rashes, along with joint pains. In contrast to ventriculo-peritoneal shunts, such infections may not appear for months or years after the operation when they were contracted.
Various tests can be carried out for shunt infections and medical advice should always be sought if an infection is suspected.
How are shunt problems treated?
Shunt blockages which are causing illness usually require an operation to replace or adjust the affected part of the shunt. Shunt infections are usually treated by removal of the whole shunt and a course of antibiotics before insertion of a new system. Modern approaches to antibiotic therapy mean that such treatment can be expected to succeed, in most cases.
Endoscopic Third Ventriculostomy
An alternative treatment may be a third ventriculostomy, where a small hole is made in the floor of the ventricle to divert the flow of CSF. This treatment, if successful, avoids the need for a shunt. However, not all types of hydrocephalus can be treated by this method and it is not available in all neuro-surgical units.
For further information about ETV see Shine’s info sheet ‘Endoscopic Third Ventriculostomy’.
