A tube that is inserted to drain excess cerebrospinal fluid from the brain to another part of the body, where it can easily be eliminated. This is to prevent a build-up of pressure on the brain, as caused by hydrocephalus. During an operation, one end of the tube will be inserted into the area of the brain where the fluid is collecting, and the other end will usually run through to the abdomen. From here it can be absorbed into the blood stream and eliminated from the body in the usual way, as urine when you go the toilet. The shunt usually has a valve to control the flow of fluid and make sure it doesn’t drain too quickly. You may be able to feel the valve under your scalp.