Fourth ventricle (E) location shown in red, between the cerebellum and the pons (B) DWM is caused by any disruption to embryonic development that affects the formation of the cerebellar vermis. This is usually a genetic mutation that results in impaired cell migration and division. A large number of genetic conditions can result in the anomaly. In a large portion of DWM cases, the condition is identified in the person affected, however in most cases the cause is not identified. At least 21% of those with DWM have a sibling with the malformation, and at least 16% have a parent with the malformation. Ciliopathic genetic conditions A genetic condition is identified in around 33% of those diagnosed with DWM after birth. In a 2017 review, 4.3% were found to have PHACE syndrome, a condition involving brain, cardiovascular and eye abnormalities, while 2.3% had Joubert syndrome, a condition involving neurological and sometimes eye and kidney abnormalities. Anywhere from 21% to 81% of those with PHACE syndrome have DWM. Other comorbid genetic conditions that were found included oculocerebrocutaneous syndrome, oral-facial-digital syndrome, Coffin–Siris syndrome, Meckel–Gruber syndrome type 7 and Kallmann syndrome, among many others. DWM has also been associated with 3C syndrome, Rubinstein–Taybi syndrome, Marden–Walker syndrome, Sheldon–Hall syndrome, Shah–Waardenburg syndrome, Fryns syndrome,<unk> –Warburg syndrome, Fukuyama congenital muscular dystrophy, Ellis–van Creveld syndrome, Fraser syndrome, Aicardi syndrome, Cornelia de Lange syndrome, Klippel–Feil syndrome and acrocallosal syndrome, among others. Many of these disorders are classified as ciliopathies, genetic disorders that affect the cellular primary cilia, thin cell projections made from microtubules that are believed to be crucial in signalling embryonic cell division and migration. DWM is one of the single largest predictors of a ciliopathic genetic disease. Other genes that have been linked to DWM include ZIC1, ZIC4, FOXC1, FGF17, LAMC1 and NID1. Chromosomal abnormalities In those who are diagnosed with DWM before birth on ultrasound, up to half are found to have a chromosomal abnormality, with the most common being Edwards syndrome (trisomy 18), at roughly 26% of prenatal DWM cases. 6.5% of those diagnosed with DWM after birth also have Edwards syndrome. Other chromosomal abnormalities that can lead to DWM include triploidy, Patau syndrome (trisomy 13), trisomy 9 and partial 3q deletion or duplication. The 3q24 region contains the ZIC1 and ZIC4 genes, known to be associated with DWM. External toxins Warfarin use during pregnancy has been known to lead to systemic defects in the fetus, including ocular dysgenesis, microcephaly, agenesis of the corpus callosum, skeletal abnormalities and heart defects. In 1985, it was also linked to DWM.
Dandy–Walker malformation
Glial tumor
Subdural hygroma
Schizencephaly
Chiari malformation
Hemimegalencephaly
Subependymoma
Hydranencephaly