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DANDY-WALKER MALFORMATION
DEFINITION:
A congenital anomaly of the cerebellum and 4th ventricle characterized by hydrocephalus due to a cystic expansion of the 4th ventricle in the posterior fossa.
EPIDEMIOLOGY:
 incidence: ?
 age of onset:
 infancy
 risk factors:
 familial - autosomal recessive
 chrom.#: ?
 gene: ?
 exposure to isotretinoin in 1st trimester
 chromosomal malformations
 3q+, 5p+, 6p+, 8p+, 8q+, 9p+, 17q+, triploidy
 associated anomalies:
1. Neural
 agenesis of the posterior cerebellar vermis & corpus callo-sum, aqueductal stenosis, infundibular harmartomas, posterior fossa lymphomas, syringomyelia
 agyria, microgyria, grey matter heterotopias
2. Non-Neural
 abnormal lumbar vertebrae, polydactyly, syndactyly
 cleft palate, polycystic kidneys
 cataracts, retinal dysgenesis, choroid coloboma
PATHOGENESIS:
1. Background
 a developmental cerebellar defect occurring before the embryo-logic differentiation of the 4th ventricle foramina results in the blockage or atresia of these foramina plus the foramen of Magendie and foramen of Luschka. This, in turn, results in the cystic transformation of the roof of the 4th ventricle and in an obstructive (noncommunicating) hydrocephalus, the cyst arising from the compromised absorption of CSF
CLINICAL FEATURES:
1. Obstructive Hydrocephalus (90%)
 rapid increase in head size
 prominent occiput
 positive transillumination of the skull
2. Others
 long-tract signs - spasticity
 cerebellar signs - ataxia, nystagmus
 apnea, infantile hypotonia, seizures, titubation, developmental delay, mental retardation
INVESTIGATIONS:
1. Imaging Studies
1. Skull X-Rays
 enlargened posterior fossa with superior displacement of torcular herophil and lateral sinus grooves
2. CT/MRI
 the 4th ventricle is grossly misshapen and is a large, ependymal-lined cyst that may extend into the spinal canal - cerebellar hemispheres are hypoplastic and displaced superiorly
 hypoplastic or absent posterior vermis
 ventriculomegaly with enlarged aqueduct of Sylvius, 3rd and lateral ventricles
MANAGEMENT:
1. Surgical
 shunt
2. Supportive
 treat complications i.e., anticonvulsants, physiotherapy
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