WHAT IS A CSF SHUNT?
Although certain drugs, such as the carbonic hydrase inhibitors (acetazolamid…), may temporarily control communicating hydrocephalus, surgery is the only truly effective treatment.
CSF shunts have been performed for decades and still represent the most important advance made until now in the treatment of hydrocephalus when endoscopic treatment is not indicated or possible.
A CSF shunt involves establishing an accessory pathway for the movement of CSF in order to bypass an obstruction of the natural pathways.
The shunt is positioned to enable the CSF to be drained from the cerebral
ventricles or sub-arachnoid spaces into another absorption site, the right
atrium of the heart or the peritoneal cavity, through a system of small
tubes known as catheters. A regulatory device (known as a valve) which
may be more or less sophisticated, may be inserted into the pathway of
the catheters. This drainage enables the excess CSF within the brain to
be evacuated and, thereby, the pressure within the cranium to be reduced.
 |
||
 |
The
liquid must be removed, but not too much; then I will no longer suffer from headaches. |
 |
|
||
A CSF shunt system may consist of :
A proximal catheter (inserted proximally into the cerebral ventricles
or into the sub-arachnoid spaces and linked distally to either a reservoir
or a valve). This catheter is closed at its proximal end and multi-perforated
in order to enable the CSF to pass through. Many possible types and configurations
are available, the mostly widely used of which are the straight and right
angle ventricular catheters.
A reservoir, which may be attached to the valve (optional).
A unidirectional valve (or anti-reflux valve, i.e. one which prevents the flow of CSF towards the ventricles once the fluid has passed through the valve). Many types and configurations of these are available.
An anti-siphon device, which may be attached to the valve (optional).
A distal catheter (linked proximally to the valve and inserted distally into the peritoneal cavity or into the entrance to the right atrium of the heart). Again, many types and configurations are available. The distal tip is usually open and multi-perforated in order to facilitate the flow of CSF into the peritoneal (or cardiac) cavity.
Shunts are constructed from materials which have been shown to be well tolerated by the body, such as silicone, polysulphone or stainless steel.
The two small tubes known as catheters are generally made of silicone.
When present, the reservoir may be used to assess the patency of the shunt and to access the CSF for injections and/or samples.
The valve, whose function is to control the direction of flow and to maintain a specific pressure within the ventricles, is placed between the two catheters.
The valves for hydrocephalus are designed to work at different pressures, depending on the patient, in order to avoid excessive drainage of CSF.
The anti-siphon device theoretically allows sudden increases in the differential
pressure between the proximal and distal parts of the shunt to be corrected
when subjects move from lying down to standing up.
Depending on their experience, neurosurgeons choose the most appropriate operating method and valve for each patient.
The entire shunt system is positioned under the skin.
In obstructive hydrocephalus, the end of one of the catheters must imperatively be placed within the ventricular system and is known as the ventricular or proximal catheter.
In non-obstructive hydrocephalus, the proximal catheter is placed either in the ventricles (ventricular catheter) or in the sub-arachnoid space, at the level of the lumbar spinal column (lumbar catheter).
Shunt Systems & Type of Hydrocephalus
The catheter, one of the ends of which is placed in the peritoneal cavity or in the right atrium, is called the distal catheter.
From these clinical features the neurosurgeon will decide to insert the CSF shunt system from a choice of the three following types of implantation:
|
Ventriculo-Peritoneal Shunt |
Ventriculo-Atrial Shunt |
Ventriculo-Peritoneal Shunt (V-P)
The CSF is shunted from the cerebral ventricles to the
peritoneal cavity where it is reabsorbed into the blood through the peritoneum,
the membrane which lines the gastro-intestinal organs.
Ventriculo-Atrial Shunt (V-A)
The CSF is shunted from the cerebral ventricles into the right atrium of the heart. The CSF is then shunted directly into the blood circulation.
|
Lumbo-Peritoneal Shunt (L-P) The CSF is shunted from the lumbar sub-arachnoid
spaces to the peritoneal cavity. |
Lumbo-Peritoneal Shunt
|
|
Occasionally some shunts contain a reservoir between the ventricular catheter and the valve. This is used by the doctor for:
Medical Injection.
Insertion of a CSF shunt is a surgical procedure performed in the operating theatre under general anaesthesia. Neurosurgeons will choose the most appropriate operating method and valve for each patient depending on their experience.
The following stages may be identified schematically:
One of the ends of the distal catheter is positioned in the abdominal cavity or in a neck vein, leading to the right atrium of the heart.
An example of a ventriculo-peritoneal implantation is shown in the figure below.
Shunt system implantation
 |
|
 |
Top of page
|