The result of multiple sutures fusing before the brain stops growing is an increase in ICP leading to hydrocephalus.[29] 0.05%[29] Post-meningitic hydrocephalus The inflammation and scarring caused by meningitis can inhibit CSF absorption. Dandy-Walker syndrome Patients usually present with a cystic deformity of the fourth ventricle, hypoplasia of the cerebellar vermis, and an enlarged posterior fossa. The condition is a genetically heritable disease.[30] 0.003%[31] Arachnoid cyst A defect caused when CSF forms a collection that is trapped in the arachnoid membranes.