<Tr> <Th> MeSH </Th> <Td> D002557 </Td> </Tr> <Tr> <Td_colspan="2"> (edit on Wikidata) </Td> </Tr> <P> Cerebral shunts are commonly used to treat hydrocephalus, the swelling of the brain due to excess buildup of cerebrospinal fluid (CSF). If left unchecked, the cerebrospinal fluid can build up leading to an increase in intracranial pressure (ICP) which can lead to intracranial hematoma, cerebral edema, crushed brain tissue or herniation . The cerebral shunt can be used to alleviate or prevent these problems in patients who suffer from hydrocephalus or other related diseases . Shunts can come in a variety of forms but most of them consist of a valve housing connected to a catheter, the end of which is usually placed in the peritoneal cavity . The main differences between shunts are usually in the materials used to construct them, the types of valve (if any) used, and whether the valve is programmable or not . </P> <Table> <Tr> <Th> Valve type </Th> <Th> Description </Th> </Tr> <Tr> <Td> Delta </Td> <Td> Designed to prevent overdrainage . Remains closed until ICP reaches a predetermined level . Leaves shunted ventricle larger than the non-shunted ventricles . </Td> </Tr> <Tr> <Td> Medium pressure cylindrical </Td> <Td> Can lead to uneven drainage of ventricles . </Td> </Tr> <Tr> <Td> Nulsen and Spitz </Td> <Td> Contains two ball - valve units connected with a spring . Does not have an adjustable pressure setting . First mass - produced valve used to treat hydrocephalus in 1956 . </Td> </Tr> <Tr> <Td> Spitz - Holter </Td> <Td> Uses slits in silicone to avoid mechanical failure . </Td> </Tr> <Tr> <Td> Anti-siphon </Td> <Td> Prevents over drainage by preventing the siphon effect . The device closes when the pressure within the valve becomes negative relative to the ambient pressure . Prevents overdrainage that might occur when a patient sits, stands or rapidly changes posture . </Td> </Tr> <Tr> <Td> Sigma </Td> <Td> The Sigma valve operates on a flow - control mechanism as opposed to the pressure - control system of other valves . The device can regulate CSF flow changes without being programmed or surgically changed . The first iteration was introduced in 1987 . Valve operated in three stages to prevent over and under drainage . </Td> </Tr> </Table>

What is the purpose of a shunt in the brain