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Also known as “water on the brain,” Hydrocephalus is one of the most frequently seen problems in a busy pediatric neurosurgical practice. The term “water on the brain” is actually more of a misnomer. In reality, most cases of Hydrocephalus represent a build-up of spinal fluid inside the brain.

Everyone produces spinal fluid inside their brains every minute of their lives. This fluid is very similar to the liquid portion of blood and contains various salts and products such as sodium and glucose. The fluid is primarily produced in connected chambers within the brain, known as ventricles. This fluid circulates through the ventricles and around the brain and spinal cord. Eventually it is reabsorbed over the surface of the brain into large veins which carry the fluid back to the heart.

This orderly cycle of spinal fluid production, flow and absorption maintains a protective environment to the nervous system. In addition, there is no loss of fluids or the salts contained in the spinal fluid. Hydrocephalus is that state in which something has occurred to prevent this orderly procession of events.

When this occurs, there is a relative build-up of spinal fluid in the brain, which can lead to injury or even death if not treated. It is very important to realize that Hydrocephalus is the result of some event on the nervous system and that a child’s prognosis is not so much based on the Hydrocephalus as the cause of the Hydrocephalus.

What causes Hydrocephalus?

Hydrocephalus usually results either from:

an imbalance between CSF production and absorption (Communicating Hydrocephalus) or; a blockage within the ventricular system, such as a tumor, that prevents CSF circulation (Obstructive Hydrocephalus)

While many cases have no clear cause, the following have been associated with the development of Hydrocephalus: bleeding, infection, trauma, tumors, vascular problems and structural problems. Some occur during pregnancy and others after birth. In addition, a small number can be transmitted genetically.

What are the symptoms of Hydrocephalus?

In early infancy, Hydrocephalus is often detected by the pediatrician. The most common sign is a rapidly enlarging head circumference. This may or may not be associated with symptoms such as vomiting, failure to thrive, irritability, and delay or loss of developmental milestones. Later in infancy and into childhood, there are rarely rapid changes in head size, but rather symptoms as already described.

How is Hydrocephalus diagnosed?

Depending on the child’s age at the time of discovery, various radiographic techniques are available to confirm the diagnosis. In the first six to twelve months of life, the diagnosis can often be made with an ultrasound of the brain. After the skull fuses, the diagnosis is best made with an MRI or CT. Each of these two tests has their own advantages and disadvantages but, overall, most neurosurgeons would favor an MRI scan. While this test takes longer than a CT scan and usually requires sedation, it gives a much better picture of the brain and the possible cause of the Hydrocephalus. This information may affect the treatment options for the child.

It is important to realize that, while Hydrocephalus is very treatable, the underlying cause may not be treatable. It is important for the doctors taking care of a child with Hydrocephalus to determine if the problem is ongoing or if it has resolved but left enlarged but stable ventricles. This can sometimes be difficult to tell and often the decision will be based on many factors including symptoms, eye exams and changes in the level of activity or school performance. In addition to this, often the child will have repeated (serial) radiographic exams to look for changes in the ventricles.

If Hydrocephalus is diagnosed, almost all cases require surgery. If a definable mass is disrupting the flow, it is sometimes possible to remove the mass and allow for normal flow and resolution of the Hydrocephalus. Often the blockage cannot be removed and the fluid needs to bypass the normal circulation.

Normal MRI

Hydrocephalus on MRI

As discussed earlier, most neurosurgeons use various types of shunts to channel the fluid from the ventricles to other sites in the body, such as the abdominal cavity, chest cavity or the heart. Each of these sites has various pros and cons but the most popular distal site for a shunt is the abdominal cavity. Here the spinal fluid is absorbed onto the surface of the bowels to be returned to the blood stream along with the vital salts and other products it contains.

Treatment of Hydrocephalus

CSF Shunts

There are many different shunt systems on the market. Most neurosurgeons are comfortable with one or more systems and utilize these almost exclusively.

In its most simplistic form, a shunt is a silicone tube, less than an eighth of an inch thick, and allows fluid to flow through it. There is usually a valve system that regulates the flow, as well as a reservoir or “bubble” which can be felt through the skin. This reservoir allows for sampling of the spinal fluid (with the use of a tiny needle) to test for function or infection. Like all foreign bodies, the shunts can malfunction or become infected, which will lead to the replacement of the shunt system.

Endoscopic Third Ventriculostomy

Another common operation used in many pediatric neurosurgical centers to combat Hydrocephalus is an endoscopic third ventriculostomy (ETV).

An ETV is a hole that is created in the floor of the third ventricle, like creating a “new drain” in the bottom of a plugged sink. This procedure is most successful in older children with Non-Communicating Hydrocephalus. The advantage of this procedure is it may avoid the implantation of a foreign body. Like a shunt, however, there is also a chance that the ETV can “seal” over and the hydrocephalic patient may become symptomatic again.