Implantation of an internal drainage system or shunt requires use of a material that will not be rejected by the body, and which is very resilient. One such material is silicone rubber, and most shunt systems are made from this. A shunt consists of a tube that is introduced into a ventricle of the brain, a valve with a reservoir and a drainage tube leading to the abdominal cavity or to the heart. The reservoir is often referred to as the "pump", but in fact it is a pressure valve. The liquid will flow only when a certain pressure is exceeded in the brain ventricles. Within certain limitations, it is possible to tell in advance what the pressure might be, and thus there are low, medium and high pressure systems. There are also adjustable valves. What system is selected depends on a number of factors, such as age, cause of the hydrocephalus, findings from the CT scan or MRI examinations and on the neurosurgeon's preferences and experience.

Example of a shunt system.

llustration: Example of a shunt system.
A: Shunt into the abdominal cavity
B: Valve system
C: Shunt into the heart

voorbeeld van shunt

Illustration: Example of a shunt system.
1. Catheter placed into the brain ventricle
2. The actual valve
3. Catheter placed into the abdominal cavity

The operation

The operation itself is a relatively simple procedure, but it should nonetheless not be underestimated. A small hole is drilled into the skull behind the ear or further forward. The tube is inserted into the ventricle via this small access port. When the ventricles are enlarged, this is quite easy, but if they are a little narrow it can be quite difficult to place the tube in the correct position. Some of the modern aids used in the procedure include an endoscope (a tube for looking inside the patient) and position determination by means of CT or MRI and connected computer equipment (this process is called neuronavigation). It provides great precision in the placement of the tip of the tube that is to be inserted into the brain ventricle. Use of this aid is standard in our clinic, to prevent shunt problems from occurring later. If a diversion towards the heart is selected, then the route goes via a vein under the right jaw corner. The vein is opened and the tube is led into the right atrium (the smaller, upper chamber) of the heart under X-ray guidance. For abdominal shunts the surgeon creates a small opening in the abdominal wall, through which the tube is then introduced into the free areas of the abdominal cavity. The fluid is taken up via the peritoneum (the tissue that lines the abdominal wall and covers most of the organs in the abdomen). "Tunnelling" the system under the skin is done via a couple of small intermediate incisions.

The palpable bulge in the system (the actual valve, or "pump") enables the treating surgeon to test the system's functionality. Normally the "pump" can be depressed and it then quickly recovers its shape. If that is not the case, this could indicate a malfunction in the system, but this is not necessarily so. It is not recommended that patients try to test the shunt themselves.

We strongly advise against patient "testing" of the system by repeatedly depressing the pump.

In principle, patients fitted with a shunt remain under medical supervision for as long as the shunt is in operation. It can happen that the cause for the hydrocephalus disappears, the patient "outgrows" it, so that the shunt is no longer necessary. This new condition is called "compensated hydrocephalus". This situation can in turn also go wrong: the patient is then again dependent on the shunt. Patients fitted with a "pump" can lead a completely normal life and are not limited by the shunt itself in any way.

Third ventriculocisternostomy

This is a relatively new technique; the floor of the third ventricle is approached by means of an endoscope (a viewing device). It is very thin, and, especially in the presence of hydrocephalus, it is distended and almost translucent. It can be perforated without incurring any significant risks, thus creating a connection between the ventricles and the space around the brain. The aqueduct (the narrow canal between the third and fourth ventricles) is therefore bypassed. This procedure is particularly taken into consideration when there is a narrowing of the aqueduct and in relatively few cases can constitute an alternative for the placement of a shunt system. (See video).

Complications

Unlike many other surgical treatments, placing a shunt does not remove the cause for the hydrocephalus. It merely provides a solution for draining cerebral fluid that otherwise could not flow away. Problems can occur that will require a new shunt operation (called a revision).

The most common complication is an obstruction of the system. This can happen anywhere in the system. Tissue from the choroid plexus in the ventricle can get into the tube. Excessively strong drainage can cause the ventricles to collapse, causing the tip of the catheter to lie against the ventricle wall. The tubes can get loose, kink, loop or get into scar tissue. In children, growth can cause the position of one of the ends to change.

Infection is an enormous complication. A shunt system is a foreign body on which bacteria can settle. Antibiotics usually are no longer of any help at that stage. In such cases, removal of the system is the only solution. The period until a new shunt can be placed must sometimes be bridged by means of an external drain. Finally, leverage can cause too much liquor to drain through the system. This is called overdrainage. This can cause symptoms, but not always. A combination of very large ventricles and overdrainage can bring about the risk of a discharge or extravasation of blood between the brain and the meninges, causing a subdural haematoma. All the abovementioned complications mean that regular monitoring of patients fitted with shunts is essential.

Shunt dysfunction

The signs and symptoms of an improperly functioning shunt are the same as those of hydrocephalus without a shunt. They can appear slowly, but sometimes also very quickly. Rapid action is required in such cases, involving a revision of the shunt or parts of it. If the cause is unclear, a temporary external drain can be fitted.

Not all complaints of shunted patients can always be ascribed to the shunt itself or a dysfunction in it. The cause can be quite different, such as for example a flu or a cold. However, it is natural to worry, and if in doubt it is always recommended to seek the advice of a doctor.

Download the information brochure 'Shunt operations'
Please note: this document is only available in Dutch.