Hydrocephalus The most frequent and prominent symptoms of DWM are those associated with hydrocephalus in the postnatal period. Hydrocephalus occurs in an estimated 80% of patients with classic DWM. This usually presents within the first year of life (85% of the time), most often within the first 3 months. Signs of hydrocephalus in infants include increasing head size, vomiting, excessive sleepiness, irritability, downward deviation of the eyes (known as "sunsetting eyes") and seizures. In contrast to classic DWM, only around 30% of those with<unk><unk><unk>  variant (DWV), in which the posterior fossa is not enlarged, have hydrocephalus. Neurological Despite the hypoplastic cerebellar vermis, just over half of individuals with DWM (between 27% and 84%) do not appear to have significant intellectual disability or developmental delay. However, many of the genetic conditions associated with DWM can present with developmental delay and other brain anomalies. Agenesis of the corpus callosum has been found in between 5% and 17% of those with DWM. This does not seem to result in intellectual disability on its own, however. Other brain abnormalities known to be sometimes associated with DWM include grey matter heterotopia, pachygyria (fewer ridges in the brain), lissencephaly (shallower ridges), polymicrogyria, holoprosencephaly and schizencephaly. Individuals with these features tend to have developmental delay or seizures. Those without any other central nervous system abnormalities tend to have normal or close-to-normal intellectual development. A 2003 review found that moderate-to-severe intellectual disability and non-DWM brain abnormalities were only present in those with the most severe cerebellar vermis<unk> s (less than two fissures/three lobules in the vermis), and these comprised 16% of their sample. Hydrocephalus also affected all of these patients. In<unk><unk><unk>  variant (DWV) and mega cisterna magna specifically, which are less severe<unk> s, there appears to be an increased rate of psychotic spectrum disorders such as schizophrenia, bipolar disorder, mania or catatonia. Associated anomalies A 2017 review found the following associations in patients with DWS (usually from an associated genetic condition or abnormality): * 27% of patients had a congenital heart defect. These included patent ductus arteriosus, coarctation of the aorta, ventricular septal defect and atrial septal defect. In 2.7% of patients, heart failure was reported. * 24% of patients had at least one ocular abnormality. These included cataracts, small eyes (microphthalmia), chorioretinal dysplasia/atrophy, optic nerve dysplasia/atrophy, a small cornea (microcornea) or corneal opacity (leukoma), short-sightedness (myopia) and coloboma (a hole in an eye structure). * 16% of patients were diagnosed with a mental or behavioural disorder, with 6.4% also having a learning disability. 5.3% had either bipolar disorder or a psychotic spectrum disorder, and 2.1% had ADHD. Slightly more of these were found in<unk><unk><unk>  variant (DWV) than in classic DWM, despite DWV being less common, at only around 20% of DWS diagnoses. * Around 12% of patients had cancers or tumours arising from congenital genetic abnormalities. The most common were neurocutaneous melanosis (5.9%), hemangiomas (4.8%, including those with PHACE syndrome) and Wilms' tumour (4.4%). 3.2% of patients had congenital melanocytic nevi, and 2.1% had tongue hamartoma. 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<unk> . 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.
Dandy–Walker malformation
Glial tumor
Subdural hygroma
Schizencephaly
Chiari malformation
Hemimegalencephaly
Subependymoma
Hydranencephaly