- ABOUT HYDROCEPHALUS
one of four cavities found within the brain where CSF can be accessed
A shunt is a narrow tube that allows excess cerebrospinal fluid (CSF) that has built-up inside the skull to drain out into another part of the body, such as the heart or abdomen (belly). To drain excess CSF, shunts are inserted into an opening or pouch inside the brain called a ventricle, just above where the blockage is that is preventing the CSF from flowing properly.
Shunts are named according to where they are inserted in the brain and where they are inserted to let the excess CSF drain out. A ventriculo-peritoneal (VP) shunt drains into the abdomen or peritoneum (belly). Most shunts are VP shunts. A ventriculo-pleural shunt drains into the space surrounding the lung. A ventriculo-atrial (VA) shunt drains into the atria of the heart.
Shunts are made of soft, flexible plastic tubing that is about 1/8-inch (3mm) in diameter. The shunt is inserted into the body by a neurosurgeon during a short and usually simple surgical procedure.
All shunts perform two functions. They allow CSF to flow in only one direction, to where it is meant to drain. And they all have valves, which regulate the amount of pressure inside the skull. When the pressure inside the skull becomes too great the valve opens, lowering the pressure by allowing excess CSF to drain out.
There are two main types of shunts:
Fixed pressure shunts have a valve that is pre-set to respond to a specific pressure, such as low, medium, or high. If the pressure requirement changes after surgery, the shunt must be replaced with a new one that matches the new pressure requirement.
Programmable shunts allow the neurosurgeon to set the pressure at which the valve will open, allowing the shunt to be programmed for the individual needs of each person. If needed, the pressure setting can be easily changed by the doctor during an office visit.
A shunt has 4 main parts:
Upper Catheter -This is the top-most part of the shunt. It is a small, narrow tube that is inserted into the ventricle (a small opening or pouch) inside the brain that contains the cerebrospinal fluid (CSF).
Reservoir - This is where the excess CSF is collected until it drains into the bottom portion of the shunt. The reservoir also lets the doctor remove samples of CSF for testing, and to inject fluid into the shunt to test for flow and to make sure the shunt is working properly.
Valve - This controls how much CSF is allowed to drain from the brain. The valve can be set to open at a specific pressure (a fixed pressure valve) or it can be set by the neurosurgeon to meet the individual needs of the person with hydrocephalus (a programmable valve).
Lower Catheter - This is the bottom-most part of the shunt. It is a small, narrow tube that carries the excess CSF into the part of the body where it will be absorbed, such as into the abdomen (belly) or the heart.