This procedure is done in the operating room under general anesthesia. It takes about 1 1/2 hours. A tube (catheter) is passed from the cavities of the head to the abdomen to get rid of the excess cerebrospinal fluid (CSF). A pressure valve and an anti-syphon device ensure that just the right amount of fluid is drained.

The procedure is done as follows:

• An area of hair on the head is shaved. This may be behind the ear or on the top or back of the head.
• The surgeon makes a skin incision behind the ear. Another small surgical cut is made in the belly.
• A small hole is drilled in the skull. One end of the catheter is passed into a ventricle of the brain. This can be done with or without a computer as a guide. It can also be done with an endoscope that allows the surgeon to see inside the ventricle.
• A second catheter is placed under the skin behind the ear. It is sent down the neck and chest, and usually into the belly area. Sometimes, it stops at the chest area. In the belly, the catheter is often placed using an endoscope. The doctor may also make a few more small cuts, for instance in the neck or near the collarbone, to help pass the catheter under the skin.
• A valve is placed underneath the skin, usually behind the ear. The valve is connected to both catheters. When extra pressure builds up around the brain, the valve opens, and excess fluid drains through the catheter into the belly or chest area. This helps lower intracranial pressure. A reservoir on the valve allows for priming (pumping) of the valve and for collecting the CSF if needed.
• The person is taken to a recovery area and then moved to a hospital room.