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,< Walker–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.
The melanocytic tumours in these cases are thought to relate to the same genetic errors in the development of the embryonic neural tube that lead to the DWM, since the subsequent embryonic neural crest gives rise to melanocytes, among other cells. 10% of patients had endocrine or metabolic disorders, and 2.7% had excessive hair growth (hypertrichosis). 9% of patients (almost all with classic DWM) had musculoskeletal abnormalities, which included scoliosis or kyphoscoliosis and arthrogryposis. 5.9% of patients had underdeveloped reproductive organs, such as hypoplastic genitalia or undescended testicles (cryptorchidism). 5.3% of patients had underdeveloped or polycystic kidneys.Occipital encephalocele may occur in DWM. This has generally been found at rates between 6 and 8%. It has been suggested to occur to compensate for the increased pressure in the posterior fossa during foetal life.Syringomyelia occasionally occurs with DWM, though it is not certain how often. One review reported an occurrence of 4.3% in a sample. This may be due to herniation of the bottom of the cyst through the foramen magnum (a similar mechanism to Chiari malformation). Alternatively, it may be a result of hydrocephalus, in which it forms as a "fifth ventricle" due to an enlarged central canal.Rarely, spina bifida has been found with DWM. When it is present, it is usually spina bifida occulta. Cause
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.