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HYDROCEPHALUS A clear, saltwater-like liquid called cerebrospinal fluid surrounds the brain. This fluid protects and hydrates the brain, carries away wastes from brain cells and contains important chemicals and nutrients. Each day the brain produces about a pint of cerebrospinal fluid which flows in a continuous circuit through the brain cavities (ventricles) and over the surface of the brain and spinal cord until it is absorbed by the body. In approximately 90 percent of people with spina bifida, the flow of cerebrospinal fluid is obstructed. A blockage at the base of the brain results in a build up of fluid in the ventricles of the brain, which then expand and push against brain tissue and the bones of the skull. In an infant the plates of the skull are not yet fused together. This enables the plates to shift and accommodate the excess cerebrospinal fluid and thus lessen the amount of damage to the brain. In some babies born with hydrocephalus the condition is arrested if the blocked passage opens or the fluid is channelled elsewhere. If it continues to develop there is continuing pressure on the brain, which if untreated will cause brain damage. Hydrocephalus is usually treated by insertion of a shunt. A shunt is a device which is designed to drain excess cerebrospinal fluid from the brain and carry it to other parts of the body. A one-way valve is used, which usually sits outside the skull, but beneath the skin, somewhere behind the ear. (See diagram) Although a shunt generally works well, it may stop working if it disconnects, becomes blocked, or it is outgrown. If this happens the cerebrospinal fluid will begin to accumulate again and a number of symptoms will develop. It is important to get medical attention if any of the following symptoms appear. SYMPTOMS OF A MALFUNCTIONING SHUNT
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