Hydrocephalus and Shunts
Hydrocephalus and Shunts in the Person with Spina Bifida
Hydrocephalus means there is a build-up of fluid around the brain. Like a bathtub with the water on and a partially clogged drain, this fluid on the brain can’t drain fast enough. This fluid is made by special brain cells to protect the brain and spinal cord. When there is too much fluid, it can be dangerous.
Most of the time, it is easy for doctors to see that there is too much fluid on the brain. There are special fluid-filled pockets, or cavities, called ventricles, that get too big when there is too much liquid. In some cases, it isn’t as easy to see. There are cases where there may be a little more fluid than normal, and the person has little or no signs of a problem. In these rare cases, neurosurgeons might treat the problem where other types of doctors would not. Part of the reason why this might happen is because experts disagree on when the best time is to treat the problem.
The most common treatment for hydrocephalus is to insert a tube, called a shunt, to drain excess fluid from the head to another place where the body can remove it naturally. Shunts have valves that regulate both the direction and amount of fluid that is drained. All shunts have three parts: 1) a ventricular catheter to reach the area where there is too much fluid, 2) a valve to control flow (there are many types) and 3) tubing to carry the fluid from one place in the body to another.
Types of shunts
There are several types of shunt valves. All of them work by controlling the amount of fluid that is drained. Most are made to work automatically when fluid pressure in the head gets too high. Some valves also may have special devices to keep too much fluid from draining.
Experts have not yet learned which type of shunt is best for whom. So neurosurgeons usually pick ones that they think are best. Shunts can be put into one of these places in the head:
Experts don’t know if one place is better than another. So where to put the shunt also is up to what the surgeon thinks is best.
About 80 percent of people with Spina Bifida have hydrocephalus that needs treatment. Almost all shunts are put in during the first days or weeks after birth. Sometimes the shunt will be inserted at the time of the initial back closure. A child who doesn’t need a shunt by the time they are five months old probably will never need one.
Signs of shunt problems
A head ultrasound, Computed Tomography (CT) scan or a Magnetic Resonance Imaging (MRI) scan will show this fluid build-up, but a shunt still may not be working right even if it doesn’t show up on a CT or MRI scan. New, long-term treatments using small endoscopes may eliminate the need for a shunt. All patients with hydrocephalus should be seen by a neurosurgeon at least every one to two years.
Most people with Spina Bifida and shunted hydrocephalus will need the shunt for life. The most common problem with shunts is that they can get blocked up, break or come apart. About 40 percent of shunts will fail and need changing (or revision) within one year, 60 percent within five years and 80-85 percent within 10 years. About 20 percent of people with Spina Bifida will need more than one shunt revision.
The signs of shunt problems in people with Spina Bifida are different for each person. This can make it hard for families and health care providers to know what’s going on. The most common sign of a shunt problem is headache. Vomiting and nausea can happen, too, but not always.
Less common signs of a shunt problem include:
Shunt malfunction can look like any of the signs of a Chiari malformation or spinal cord tethering. In fact, when brain or spinal cord function gets worse and there is no other clear cause, health care providers should check to see if there are shunt problems.
To see if there is a problem with a shunt, health care providers will study images of the brain (usually a CT scan or, for children under one year, a head ultrasound). MRI scans can show shunt problems, but they usually are not necessary, are more expensive and may require sedation or anesthesia. When ventricles start to get too big, it is a strong sign that the shunt is not working right. It is important to know that some people (between 5 and 15 percent) with Spina Bifida may have very few signs or even no visible change in the size of the ventricles when the shunt is not working correctly.
On the other hand, some people with shunted hydrocephalus can develop the slit (or stiff) ventricle syndrome. For these people, too much fluid drainage leads to very small (or slit) ventricles. In these cases, experts think that the walls of the ventricles temporarily block the shunt catheter. This leads to a series of temporary shunt malfunctions without any visible increase in the size of the ventricles. Families and health care providers must pay close attention to a person’s symptoms, especially if they are similar to those that were present with previous shunt problems.
Additional signs of an infection include:
The diagnosis can be checked by putting a small needle into the valve or a chamber of the shunt and taking out fluid for study.
Infections are commonly treated with antibiotics and with removal and replacement of the shunt system. There are two ways of doing this. The first is to take out the shunt system and then put in a temporary external drainage tube at the same time that antibiotics are given. When the treatment is done, the tube is taken out and a new shunt is put back in. This almost always stops the infection, but it takes two operations. The second (assuming that the shunt is working) is to keep the infected shunt in until the end of the antibiotic treatment. Then the infected shunt is removed and replaced with a new one. The second way only takes one operation, but it does not get rid of the infection as often as the first.
This information does not constitute medical advice for any individual. As specific cases may vary from the general information presented here, SBA advises readers to consult a qualified medical or other professional on an individual basis.