Hydrocephalus is a medical condition characterized by the accumulation of cerebrospinal fluid (CSF) within the cavities of the brain, leading to an increase in intracranial pressure. Cerebrospinal fluid is a clear, colorless fluid that surrounds and cushions the brain and spinal cord, providing essential nutrients and removing waste products.
As DIPG/DMG tumors grow, they may at times block the flow of CSF, causing hydrocephalus. Sometimes children with DIPGs/DMGs need procedures to control the fluid pressure.
When the fluid pressure builds up, it can cause headaches, vomiting, mental changes, and even coma. Many of these symptoms overlap the typical symptoms of DIPG/DMG.
Ventriculoperitoneal shunt (VP shunt)
The most common and well-established procedure to treat hydrocephalus is the ventriculoperitoneal shunt (VP shunt). A tube is placed from the outer surface of the head through the skull and brain into a lateral ventricle. The shunt is connected to a device—the valve—which determines how much pressure must build up before CSF starts to flow, and makes sure CSF only flows out of the ventricle and not back in. The valve sits under the skin and connects to a tube that leads to a place in the body where the CSF can be absorbed back into the blood stream (where it would have gone from the brain directly, if it could). The most common end point of shunts is the peritoneal cavity—the belly—but other times shunts go to the chest, through blood vessels to the heart, or even to the gall bladder. Effective shunts have been around for about 50 years, and they save and improve the lives of tens of thousands of kids each year.
Shunts, however, have their own problems. They are foreign to the body, so the body may react to them and block off their flow. They are also mechanical systems that can break or malfunction. The most common way they become a problem is when they become infected. Infections happen between 5 to 14 percent of the times they are implanted. (Neurosurgeons are very focused on how to reduce the rate of these infections.) When a shunt is infected, it has to be removed, and—after a period of time—replaced with a clean system.
Endoscopic Third Ventriculostomy (ETV)
Because of the problems with shunts, another way to drain fluid from the ventricles is the endoscopic third ventriculostomy (ETV), which creates an alternative pathway from the third or fourth ventricle when the normal pathway is blocked. Whether the ETV is an option depends on the particular anatomy of a child with hydrocephalus due to a DIPG. This is a matter only the surgeon can assess. (The pons sits behind the area where CSF goes after an ETV. If a DIPG can block the CSF pathway behind it, it can block the pathway in front as well.)