In hydrocephalus, the fluid that bathes the brain and spinal cord builds up pressure. As the fluid builds up, the pressure in the head rises. This can require shunting. Symptoms of hydrocephalus will eventually start showing. Symptoms vary with age, disease progression and individual differences in intolerances of the cerebral spinal fluid.
There are many designs of shunts. The surgeon determines what type of shunt is needed in any given circumstance. Routine check ups with the neurosurgeon may be necessary to insure the shunt is working properly. The shunt has 3 components. The first portion is the called the shunt catheter or proximal portion of the shunt. This is a small narrow tube (catheter), which is implanted into the ventricle of the brain, above where the obstruction has occurred. It is then connected to the valve and reservoir. The valve controls how much fluid is withdrawn from the brain, it is then stored in the reservoir until it is released to drain down the distal (bottom) end. The distal end is a small, narrow piece of tubing (catheter) which leads to the point where the excess CSF will drain and be absorbed by the body.
The absorption site is usually the abdomen. This is the preferred location for the placement of the distal end of the shunt. This type of shunt implantation is referred to as a ventriculo-peritoneal (VP) shunt. The pleural (lung) cavity (ventriculo-pleural) shunt, or the atria of the heart, ventriculo- artial (VA) shunt can be used also. The gallbladder or bladder can be used, but this is only when there is no other site that is suitable.
Shunts are composed of a silicone elastomer (plastic) and are often impregnated with barium. In general, there are fixed shunts or programmable shunts. The fixed shunts usually have a choice of three different types of valves (low, medium, and high).
A programmable shunt allows your physician a greater range of choices in choosing the pressure at which the fluid drains. A Codman Hakim Programmable Valve gives your doctor a choice of 18 different programmable pressure settings. It is the same size as traditional fixed pressure valves and is implanted in exactly the same way. Using an exclusive external programming device, the surgeon selects the initial pressure setting prior to the procedure, and can then easily adjust the setting at any time and as many times as necessary without further surgery. The large range of pressure settings allows the surgeon to make very fine adjustments in the pressure in order to get the best resolution of symptoms after the valve is implanted. The totally non-invasive adjustments take only seconds and can be done right in the office with little or no patient discomfort.
The device used to adjust the pressure setting of the programmable shunt valve is simply called a Programmer. The programmer includes an electrical box connected to a round transmitter head. Using the transmitter head, the valve is programmed to a certain pressure chosen by the surgeon prior to being implanted in the patient. Upon pushing a button, the valve is changed to the selected pressure in 5 to 10 seconds. No additional surgeries or hospital visits are needed in order to reprogram the valve.
You should know that the shunt performs two functions. It allows fluid to go only in one direction and the valve allows fluid to flow out only when the pressure in the head has exceeded some value (usually referred to as the "opening pressure"). This system regulates the amount of the CSF in the body so that not too much is taken, nor too little.
Having a shunt is a lifetime commitment. Once a shunt is implanted, it is not a "one time" operation. Life expectancy of a shunt averages 10 years. However, a shunt can last 5 minutes to many years. It is wise to always be aware of the warning signs for a "shunt malfunction."
Once a VP shunt is working properly, a consideration that comes up with the growth of the child is whether the shunt needs to be lengthened, and if so what age this should be done. The obvious question that must be answered in these situations is whether the child is shunt dependent and continues to need the shunt, as it becomes short. Most children are shunt dependent after they are shunted, and the dictum "once a shunt, always a shunt" is probably true for most children. Despite this, careful thought should be given in lengthening the shunt to allow for the growth of the child.
Despite the advances in shunt technology and surgical techniques, there are many cases in which shunts are inadequate. Shunts are subject to complications such as blockage, breakage and infection. For this reason, in selected cases, a third ventriculostomy is preferable to a shunt.
Endoscopic Third ventriculostomy [an intracranial shunt as opposed to the extracranial (outside the brain) shunting] is another form of treatment in which a tiny perforation is made in the wall of the third ventricle, thus allowing movement of CSF out of the blocked ventricle and into the subarachnoid (one of the coverings of the central nervous system) space. The objective of the procedure is to reduce pressure on the brain from excess fluid in the ventricle without having to use a shunt. Unlike "extracranial" shunts, which may require revisions, a third ventriculostomy is a one time procedure and patients have to meet a certain criteria and be a candidate for the surgery.
Shunting has improved the outcome of patients with hydrocephalus dramatically. In the absence of any complex developmental syndrome, and with careful and systematic treatment and follow-up, patients with hydrocephalus are expected to survive and reach adulthood. In all forms of hydrocephalus, continuous careful monitoring is required for shunts because, at 10 years, up to 80% of them require revision because of some form of failure.
Significant effort in research and development is directed at shunt valve design. Although significant advancements have been achieved in the last 2 decades, room for improvement still exists
