![]() ![]() The specific symptoms and severity of WWS vary greatly from case to case. Walker-Warburg syndrome (WWS) is a rare genetic multisystem disorder characterized by muscle disease and brain and eye abnormalities. ![]() (For more information on this disorder, choose “hydrocephalus” as your search term in the Rare Disease Database.) There are several different forms of hydrocephalus: communicating hydrocephalus, non-communicating hydrocephalus or obstructive hydrocephalus, internal hydrocephalus, normal pressure hydrocephalus, and benign hydrocephalus. An enlarged head in infants and increased cerebrospinal fluid pressure are frequent findings but are not necessary for the diagnosis of hydrocephalus. The cerebrospinal fluid accumulates in the skull and puts pressure on the brain tissue. Hydrocephalus is a condition in which abnormally widened (dilated) cerebral spaces in the brain (ventricles) inhibit the normal flow of cerebrospinal fluid (CSF). Comparisons may be useful for a differential diagnosis: Symptoms of the following disorders can be similar to those of Dandy-Walker malformation. Many other syndromes and chromosome abnormalities have been reported with DWM, but most of these appear to have CVH rather than typical DWM. DWM may also occur as part of a genetic syndrome that includes multiple birth defects, such as the PHACES syndrome of facial hemangioma, heart and sternal defects and DWM. In these families, the recurrence risk is higher, up to 25%. A few examples of affected siblings with isolated Dandy-Walker malformation have been reported, suggesting autosomal recessive or X-linked inheritance, but most of these are probably CVH and not typical DWM. In the remainder, it is probably due to other more complex genetic and perhaps environmental factors (teratogens) as the recurrence risk in siblings less than 5%. A few patients have chromosome abnormalities including deletion of chromosome 3q24.3 (the location of the first DWM genes, known as ZIC1 and ZIC4), 6p25 or 13q32.2-q33.2, or duplication of 9p. The uncertainty in prognosis for these three overlapping conditions is accounted for by both natural variability and difficulty in distinguishing them.ĭWM results from defects in early embryonic development of the cerebellum and surrounding structures. This has been reported as a normal variant, but emerging experience suggests that it may be associated with developmental disabilities although these are usually less severe than seen in DWM or CVH. The increased size is associated with an enlarged fluid collection beneath and often behind the cerebellum. MCM is characterized by an enlarged posterior fossa despite normal or very nearly normal size of the cerebellum. The available data regarding outcome is limited, but this is often more severe than in typical DWM. This malformation has also been called the “Dandy-Walker variant”, a potentially confusing term. CVH consists of a small vermis without the striking upward rotation of the vermis, cystic enlargement of the 4th ventricle or enlarged posterior fossa that characterize typical DWM. But emerging experience suggests that this is an oversimplification that may contribute to inaccurate information about both outcome and genetic risks. ![]() The clinical presentation and imaging features of DWM overlap with isolated cerebellar vermis hypoplasia (CVH) and mega-cisterna magna (MCM), and these have been classified together as a spectrum of anomalies known as the Dandy-Walker complex. The age at diagnosis varies depending on the onset and severity of hydrocephalus, and presence of other birth defects or medical problems. Respiratory control centers in the brainstem are sometimes affected and can lead to respiratory failure, again most likely with severe hydrocephalus. Seizures occur in 15-30% of those affected. Mental retardation occurs in fewer than half, most often in those with severe hydrocephalus, chromosome abnormalities or other birth defects. The symptoms of Dandy Walker syndrome typically include developmental delay, low tone (hypotonia) or later high tone (spasticity), poor coordination and balance (ataxia), and sometimes enlarged head circumference and increased pressure within the skull due to hydrocephalus.
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