What are the symptoms? Excessive production of CSF, or failure of CSF reabsorption due to obstruction of the passageways out of the fourth ventricle, leads to an accumulation of fluid in the brain ventricles. This can cause raised intracranial pressure (ICP). Hydrocephalus is present in approximately 90 per cent of people affected by DWS. And can result in the failure of parts of the cerebellum to develop correctly. A large cyst is then visible on scans of the back of the brain. Symptoms caused by ICP can include: In early infancy: slow motor developmentprogressive enlargement of the skull. In older children: irritabilityvomitingconvulsionssigns of cerebellar dysfunction, such as unsteadiness, lack of muscle coordination or jerky movements of the eyesincreased head circumferencebulging at the back of the skullproblems with the nerves that control the eyes, face and neckabnormal breathingseizures. What are the causes? In the majority of cases of DWS the cause is not known. The syndrome is most often congenital (present at birth), but it can be acquired due to infection, chemical agents and other pre-birth factors. In some families, a genetic basis has been identified. How is it diagnosed? DWS is generally picked up before birth, by ultrasound. Ultrasound scans may detect the DWS cysts. A magnetic resonance imaging (MRI) scan is usually performed for detailed evaluation of the extent of DWS as can a computed tomography (CT) scan. How is it treated? Treatment for those with DWS consists of treating the associated problems. A special tube to drain off excess fluid may be placed inside the skull. This will reduce ICP and help control swelling. Symptoms caused by elevated ICP can be relieved by shunt drainage of CSF. The shunt can be used for the cyst (cystoperitoneal), the ventricles (ventriculoperitoneal) or both. With treatment, outlook for children is good. Around 50 per cent of those children affected will develop developmental delay (see entry Global developmental Delay). Inheritance patterns and prenatal diagnosis Inheritance patternsMost cases are sporadic (with no previous family history), but there is one per cent chance of recurrence in further pregnancies. Affected families should be referred to a genetic centre for advice and information. Prenatal diagnosisUltrasound scan may detect the DWS cysts. Is there support? Information and support in the UK for Dandy-Walker syndrome is provided by SHINE (Spina Bifida•Hydrocephalus•Information•Networking•Equality; see entry Spina Bifida).