Treatment of Hydrocephalus

Since every case is different, and there are new developments available within shunting devices, it is likely that every neurosurgeon will have a different opinion about which hydrocephalus treatment is best. If operative procedures are mentioned they are obviously variations of procedures which have to be adapted to suit each case.

Initially, temporary measures are usually taken to lower the pressure in the skull, using medicine to decrease the production of CSF, or to increase its re-absorption. Medical treatment is not effective in the long term, and can lead to metabolic changes. Drainage of the CSF through a ventricular catheter can also be used as a temporary solution.

To decide what type of action to take, a CAT (Computed Tomography Scan) - or MRI (Magnetic Resonance Imaging)- scan is studied.

Acute hydrocephalus treatment

For initial treatment of acute hydrocephalus one will initially use medicines which reduce CSF production, and lumbar punctures. Measurements of inter-cranial pressure and the various scanning techniques are used to asses the further treatment.

If the CSF pressure does not return to normal, other methods may be used to release the pressure. These include "ventricular taps", where the CSF is drained directly from the ventricle.

After some time it will become clear whether the increase in pressure has stopped or if it has become continuous and requires surgical treatment.

Treating the causes

Treatment of the causative factors is the best strategy. When the ventricles are enlarged one needs to determine the cause. In the case of obstructive hydrocephalus, an unequal enlargement of the ventricles will point to the location of the obstruction. Causative factors for the obstruction are then searched for. Tumours or blood clots can obstruct the CSF pathways, and their removal can often re-establish a normal CSF flow pathway. Obstruction at the aqueduct or the outlets of the fourth ventricle can often be treated by surgically creating a new outlet for the ventricles, through the floor of the third ventricle (third ventriculostomy). Blockage of the foramen of Monroe with a resultant trapped lateral ventricle can be treated by surgically creating a window through the curtain of tissue separating the two lateral ventricles (septal fenestration).

Endoscopy operations involve inserting a small endoscope into the ventricle through a single small hole in the skull. The endoscope is connected via a micro-camera to a television monitor on which the surgeon can see inside the ventricles. Using these endoscopes, neurosurgeons can now create a bypass, allowing CSF to flow around certain blockages and restoring normal flow. Only certain patients are eligible for endoscopic surgery, and these patients must be selected carefully. In particular, patients with blockages within the ventricles themselves (those with obstructive hydrocephalus) are potentially candidates for endoscopic surgery.

When the CT or MRI scans show a case of hydrocephalus which cannot be dealt with using one of the above techniques, a permanent device needs to be surgically implanted to draw the fluid out of the ventricles and to carry it to some other cavity within the body where it will be reabsorbed into the blood stream. Such devices are called shunts and they became practical in the 1950's when common problems with hydrocephalus treatments were being solved. These consisted of rejection of the tubing by the body's defences, as well as infections and blockages of the tube.

The hydrocephalus shunt

A shunt is a narrow, soft and pliable piece of tubing (approximately 0.25 cm. in diameter) which is surgically implanted into the ventricle through a small hole made in the skull. All shunts have a valve system which regulates the pressure of the cerebrospinal fluid and prevents backward flow of fluid into the ventricles. It opens automatically when the pressure exceeds a certain level (usually called the 'opening pressure' of the shunt) and allows CSF to drain. The valve closes again when the pressure returns to the normal level.

Many shunts have reservoirs which can be used for removing CSF or administering drug therapy. A shunt may be pumped but this should only be done on a physician's order.

The hydrocephalus shunt has three basic components:

  1. A catheter (or tube) which is inserted into the brain ventricles
  2. A valve which regulates the flow of spinal fluid.
  3. A long catheter which carries the CSF from the head to wherever the CSF is being diverted (the peritoneal or chest cavity, the jugular vein, etc.).

There is usually also a reservoir of some type, located just beneath the skin, through which the shunt can be accessed if necessary.

The most common site to divert fluid is the peritoneal cavity (the cavity in the abdomen in which all of the intestines and abdominal organs are located) - this is called a ventriculo-peritoneal shunt. If the peritoneal cavity is not appropriate, the surgeon may choose to place the shunt in the pleural space, i.e. the cavity within the chest which surrounds the lungs. This is called a ventriculo-pleural shunt. A third common site to insert the shunt is the jugular vein in the neck, called a ventriculo-jugular (sometimes also called a ventriculo-cardiac or ventriculo-atrial) shunt. The catheter is threaded into the jugular vein and down into the heart. Rarely, other sites such as the gall bladder are selected when no other site is available.

Choice of shunt

There are many different types of shunt, each with different pressure specifications, flow characteristics, and options for external adjustment. These characteristics can be matched to best solve each case.

The proximal and distal tubes must be flexible to allow for the movement of the body; soft enough to prevent damage to the ventricles and the distal placement area; and yet rigid enough to keep it from kinking or drifting out of place.

Some shunts are provided in one piece which allows for easier insertion and therefore a quicker operation. It avoids the possibility of the catheters disconnecting.

To allow for the possibility to test the shunt, a tapping or flushing chamber can be incorporated in it. This allows a neurosurgeon to test some aspects of the shunts workings.

Distal catheter site - the peritoneal cavity

The peritoneal cavity is a large cavity which is more than capable of handling any amount of CSF delivered by the shunt in all but the most unusual cases. The rhythmic contractions of the intestinal organs tend to move the tip of the shunt catheter around the abdomen, thus minimising the chances of it becoming surrounded in scar tissue and subsequently blocking.

As the child grows, changes in the length of the torso are accommodated by tubing being pulled out of the abdominal cavity. There has been an evolution of thought about how much catheter should be placed in the abdominal cavity of infants and children. Earlier, only 8 or 12 inches of tubing was placed into the cavity while now it is accepted that a neonate (new born) may have 36 or more inches in the peritoneal cavity (i.e., enough tubing to accommodate adult stature without the tube's end being pulled out of the abdominal cavity). There have been no associated complications and mandatory lengthening is no longer necessary.

Ventriculo-peritoneal shunt (VP shunt)

A ventriculo-peritoneal (VP) shunt is usually tried initially. Occasionally the abdomen cannot absorb fluid, and in these cases a Ventriculo-Atrial (VA) shunt system is used.

It may be useful for you to ask your neurosurgeon to show you an actual shunt. Be sure you know the name of the shunt.

Advantages of peritoneal shunting

With the advent of improved shunt tubing, the current site of choice for the distal tubing is in the peritoneum. Advantages of this site are:

  1. If an infection develops, it is not as potentially life threatening as with shunts in the venous system.
  2. A large amount of tubing can be placed in the abdomen to minimise the need for lengthening.
  3. The overall ease in placing peritoneal shunts in a relatively short operation.

Distal catheter site - ventriculo-atrial shunt (VA shunt)

In this system, the shunt tubing is passed from the valve to the neck where it is inserted into a vein. It is then passed through the vein until the tip of the catheter (shunt) is in the atrium (a chamber of the heart). In the heart, the CSF passes into the blood stream and is filtered along with the other bodily fluids.

When shunts were first introduced almost 40 years ago, a one-way valve drained spinal fluid directly into the right atrium of the heart via the jugular vein (ventriculoatrial shunt). Vascular shunts functioned very well, but they were prone to multiple problems. These included early and late infection; as well as rare, potentially fatal, heart failure due to blockage of blood vessels within the lungs by particles of blood clots flaking off the shunt's catheter tip. The use of the heart has been largely abandoned as an initial choice because of these problems, but it remains a viable second option when infection or surgery has rendered the abdominal cavity unaccommodating to the distal shunt catheter.

Distal catheter site - ventriculopleural shunt

The chest cavity can be used an alternative to the abdominal cavity; this is a "ventriculopleural shunt". In this case the distal catheter is placed between the linings of the lungs, called the pleural cavity. There are several possible downsides to this placement type. The pleural cavity may not be able to absorb the CSF quickly enough and this may result in difficulty breathing. Additionally, if the catheter moves it might rest on the diaphragm, which will cause irritation and hiccups.

Third ventriculostomy

Third ventriculostomy allows movement of CSF from a blocked ventricle to the subarachnoid space. The procedure involves making tiny holes in the floor of the third ventricle, allowing CSF to flow into the subarachnoid space. Third Ventriculostomy can eliminate the need for a shunt in some cases, though the procedure is not the appropriate solution in all cases.

Choroid plexectomy

This is a procedure in which a part of the choroid plexus is removed to reduce the amount of CSF being produced. This procedure is only performed in rare cases in which there is increased secretion from the choroid plexus.

Stereotaxy

Stereotaxy is a mathematical process used to find the position from where a surgeon should insert the surgical tools when he wants to operate at a precise location. Traditionally the entry position and angle was calculated from CT scans, after which a frame would be fixed to the patients head to ensure the correct insertion of the tools. This however, does not allow for the possibility of checking the position during surgery.

Frameless stereotaxy does not require a frame, instead the head is scanned before the procedure. Using the data gathered from these scans, the surgeon can get precise information regarding the position of his instruments in relation to the patient's head.

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