Treatment of Hydrocephalus

How is hydrocephalus treated?

Due to that every case of hydrocephalus is a different, that there are new development in the available shunting devices, it probable that every neurosurgeon will have differing oppinions about the which treatments are the 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 usualy taken to lower the pressure skull. Medicine to decrease the production of CSF, or to increase its reabsorbtion. Mecical 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 descide what type of action to take a CAT (Computed Tomography Scan)- or MR (Magnetic Resonance Imaging)- scan is studied.

Treatment of accute hydrocephalus

To treat the acute hydrocephalus daily lumbar punctures are initially tried, aswell as drugs to lower the pressure. The head size, signs of elevated ICP(inter-cranial pressure), and cranial sonograms are followed to determine further treatment. If the lumbar puncture fails to adequately relieve the excess CSF, ventricular taps through the lateral aspect of the anterior fontanelle can be performed. Since repeated ventricular taps can cause a needle tract porencephaly, it is our practice to insert a ventricular tapping device, which is an implanted internal 2-3 cm catheter attached to a small reservoir. This can be tapped as often as needed through the skin with a 23-gauge butterfly needle, withdrawing roughly 15cc of CSF. In time it will become clear if the hydrocephalus is resolving, or if a permanent VP shunt will be needed. When it becomes apparent that a shunt will be required, it is useful to wait until the infant weighs at least 1800 Gms., and the CSF protein falls to approximately 250 mg%. When shunting a premature infant, a very low pressure shunt should be selected. The system needs to be very low profile so that it doesn't erode through the skin.Antibiotics should be used to try and offset the 25-50% shunt infection rate in this population.

Treating the causes

The treatment of the causative factors is the best strategy for treatment. When the ventricles are enlarged, the cause is searched for. 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. Tumors or blood clots can obstruct the CSF pathways and their removal can often reestablish a normal CSF flow pathway. Obstruction at the aqueduct or the outlets of the fourth ventricle can often be treated by surgically creating an 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 tiny incision and a single small hole in the skull. The endoscope is connected, via a microcamera, 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 CSF flow. Only certain patients are eligible for endoscopic surgery, and the 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 CAT or MR scans show a hydrocephalus which cannot be dealt with using one of the above techniques, a permanent diversionary device needs to be surgically implanted to draw the fluid out of the ventricles and carry it to some other cavity within the body where it will be reabsorbed into the blood stream. Such a device is called a shunt. Shunts became practical in the 1950's when the problems of rejection of the tubing by the body's defences, infections of the tube, and blockages of hte tube whree being solved.

Shunting

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 pressure(usually called the 'opening pressure' of the shunt) and allows CSF to drain. The valve closes again when the pressure returns to the permitted 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 shunt has three basic components:

a catheter (or tube) which is inserted into the brain ventricles,
a valve which regulates the flow of spinal fluid,
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.).

Usually there is also a reservoir of some type, through which the shunt can be accessed through the skin if necessary.

The most common site to divert fluid is to 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 into the pleural space (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 into 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:

Despite the large amount of different shunt systems, particularly valves with different pressures and flow characteristics, it is not thought that they play a major role in the success of shunting operation, but there are features which are advantageous. The distal and proximal tubing must be designed so that it will be flexible enough move with the body, soft enough so that is doesn't cause damage to either the ventricular wall or the distar location, but yet is must be rigid enough to keep it from kinking or drifting out of place.

A one piece shunt system is easier to insert, with a quicker operation, and it avoids the possibility of shunt disconnection or disintegration associated with a connector. A connector will also prevent the extra tubing from elongating, since the connector will become fixed in its position subcutaneously due to ingrowth of scar tissue.
The shunt should also have a right angle ventricular catheter valve just distal to the right angle. This enables the surgeon to easily have access to the shunt catheter. It avoids having to work underneath a reservoir with a catheter that becomes partially embedded in the brain.
The valve system should have incorporated in it some sort of flushing or tapping chamber to have an access to tapping a shunt, as well as ability to pump and test a shunt in the neurosurgeon's office.
This mechanism needs to have either a proximal and distal occluder system, so that the proximal and distal portions of the shunt can be tested separately, or a double bubble configuration which also allows separate testing of both proximal and distal limbs of the shunt.

Distal catheter site - The peritoneal cavity

The peritoneal cavity is a large cavity, 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 minimizing the chances of it becoming sequestered 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 in thought about how much catheter should be placed in the abdominal cavity of infants and children. Whereas a few years ago only 8 or 12 inches of tubing was placed into the cavity, it is now 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 your child's shunt.

Advantages of Peritoneal Shunting.

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

If an infection develops, it is not as potentially life threatening, as with shunts in the venous system.
A large amount of tubing can be place intra-peritoneal to minimize the need for elective lengthening.
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 other body 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 including 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 clot 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 of the distal shunt catheter.

Distal catheter site - Ventriculopleural Shunt

The chest cavity is another cavity which can be used as a backup to the abdominal cavity (ventriculopleural shunt). The catheter is placed inside the rib cage between its inner lining and the outer lining of the lungs. Occasionally, this cavity cannot resorb the CSF rapidly and the lung becomes compressed by the excess CSF resulting in difficulty in breathing. The catheter must be moved to a different cavity is such cases. Rarely, the catheter can rest on the diaphragm (the muscle at the base of the lungs used for breathing), causing irritation and hiccups.

Third Ventriculostomy

Third Ventriculostomy allows movement of CSF from a blocked ventricle to the aubarachnoid 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 apropriate solution in all cases.

Stereotaxy

Stereotaxy is a mathematical process used to find the exact position from where a surgeon should insert the surgical tools, when one wants to operate at a exact position. Traditionaly the entry position and angle was calcuted from CT scans, then a frame would be fixed to the patients head to ensure the correct insertion of the tools, this did not allow for checking the possition during surgery.
Frameless stereotaxy does not require a frame, instead the head is scanned before the proceedure, and using the information gathered from these scans(stored in a computer in the operating room), the surgeon can get precise information about the position of a "wand" in relation to the patients head. After anaestesia a number fixed points are fed into the computer which allow the computer to know the exact postion of the wand in relation to the patients head.