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|Classification and external resources|
Dandy–Walker syndrome (DWS), is a congenital human brain malformation involving the cerebellum and the fluid-filled spaces around it. A key feature of this syndrome is the complete absence of the part of the brain located between the two cerebellar hemispheres (cerebellar vermis). The Dandy–Walker complex is a genetically sporadic disorder that occurs one in every 30,000 live births. Prenatal diagnosis and prognosis of outcomes associated with Dandy–Walker can be difficult. It is named for Walter Dandy and Arthur Earl Walker.
The key features of this syndrome are an enlargement of the fourth ventricle; complete absence of the cerebellar vermis, the posterior midline area of cerebellar cortex responsible for coordination of the axial musculature; and cyst formation near the internal base of the skull. An increase in the size of the fluid spaces surrounding the brain as well as an increase in pressure may also be present. The syndrome can appear dramatically or develop unnoticed.
Symptoms, which often occur in early infancy, include slower motor development and progressive enlargement of the skull. In older children, symptoms of increased intracranial pressure such as irritability, vomiting, and convulsions and signs of cerebellar dysfunction such as unsteadiness and lack of muscle coordination or jerky movements of the eyes may occur. Other symptoms include increased head circumference, bulging at the back of the skull, problems with the nerves that control the eyes, face and neck, and abnormal breathing patterns.
Dandy–Walker syndrome is frequently associated with disorders of other areas of the central nervous system including absence of the corpus callosum, the bundle of axons connecting the two cerebral hemispheres, and malformations of the heart, face, limbs, fingers and toes.
Prenatal diagnosis is possible with ultrasound. Because the syndrome is associated with an increased risk for fetal karyotype abnormalities, amniocentesis can be offered after prenatal diagnosis. There is a relative contraindication of taking Warfarin during pregnancy, as it is associated with an increased risk of Dandy–Walker syndrome if taken during the first trimester.
The term Dandy–Walker represents not a single entity, but several abnormalities of brain development which coexist. There are, at present, three identified types of Dandy–Walker complexes. These represent closely associated forms of the disorder: DWS malformation, DWS mega cisterna magna and DWS variant.
The DWS malformation is the most severe presentation of the syndrome. The posterior fossa is enlarged and the tentorium is in high position. There is complete agenesis of the cerebellar vermis. There is also cystic dilation of the fourth ventricle, which fills the posterior fossa. This often involves hydrocephalus and complications due to associated genetic conditions, such as Spina Bifida.
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The third type is the variant, which is less severe than the malformation. This form (or forms) represents the most wide-ranging set of symptoms and outcomes of DWS. Many patients who do not fit into the two other categories of DWS are often labeled as variant. The fourth ventricle is only mildly enlarged and there is mild enlargement of the posterior fossa. The cerebellar vermis is hypoplastic and has a variably sized cyst space. This is caused by open communication of the posteroinferior fourth ventricle and the cisterna magna through the enlarged vallecula. Patients exhibit hydrocephalus in 25% of cases and supratentorial CNS variances are only present in 20% of cases. There is no torcular-lambdoid inversion, as usually seen in patients with the malformation. The third and lateral ventricles as well as the brain stem are normal.
Relation to other rare disorders: genetic ciliopathy
Until recently, the medical literature did not indicate a connection among many genetic disorders, both genetic syndromes and genetic diseases, that are now being found to be related. As a result of new genetic research, some of these are, in fact, highly related in their root cause (genotype) despite the widely varying set of medical characteristics (phenotype) that are clinically visible in the disorders. Dandy–Walker syndrome is one such disease, part of an emerging class of diseases called ciliopathies. The underlying cause may be a dysfunctional molecular mechanism in the primary cilia structures of the cell, organelles which are present in many cellular types throughout the human body. The cilia defects adversely affect "numerous critical developmental signaling pathways" essential to cellular development and thus offer a plausible hypothesis for the often multi-symptom nature of a large set of syndromes and diseases. Known ciliopathies include primary ciliary dyskinesia, Bardet-Biedl syndrome, polycystic kidney and liver disease, nephronophthisis, Alstrom syndrome, Meckel-Gruber syndrome and some forms of retinal degeneration.
Genetic associations of the condition are being investigated.
Relation to PHACES syndrome
Treatment for individuals with Dandy–Walker Syndrome generally consists of treating the associated problems, if needed.
Treatment may also consist of various therapies such as occupational therapy, physiotherapy, speech therapy or specialized education. Services of a vision teacher may be helpful if the eyes are affected.
- National Institute of Neurological Disorders and Stroke, "NINDS Dandy–Walker Syndrome Information Page," http://www.ninds.nih.gov/disorders/dandywalker/dandywalker.htm. Last updated September 16, 2008. Last accessed July 6, 2009.
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- synd/433 at Who Named It?
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- Badano, Jose L.; Norimasa Mitsuma; Phil L. Beales; Nicholas Katsanis (September 2006). "The Ciliopathies : An Emerging Class of Human Genetic Disorders". Annual Review of Genomics and Human Genetics 7: 125–148. doi:10.1146/annurev.genom.7.080505.115610. PMID 16722803. Retrieved 2008-06-15.
- Grinberg I, Northrup H, Ardinger H, Prasad C, Dobyns WB, Millen KJ (October 2004). "Heterozygous deletion of the linked genes ZIC1 and ZIC4 is involved in Dandy–Walker malformation". Nat. Genet. 36 (10): 1053–5. doi:10.1038/ng1420. PMID 15338008.
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- Dandy–Walker Alliance, a non-profit organization of individuals directly and indirectly affected by Dandy–Walker
- Metry Phaces article in the Journal of Pediatrics, July 2001
- E-medicine webpage definition
- Hydrocephalus Association
- Dandy–Walker Malformation article from Pan Arab Journal of Neurosurgery
- Dandy–Walker Syndrome page at Medical College of Wisconsin website
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