In 1954, Benda introduced the term Dandy-Walker syn- drome to indicate the association of (1) ventriculomegaly of variable degree, (2) a large cisterna magna, and (3) a defect in the cerebellar vermis through which the cyst communicates with the fourth ventricle. Currently, the following findings are included in the Dandy-Walker syndrome or malformation:
(4) cystic dilatation of the fourth ventricle, (5) dysgenesis of the cerebellar vermis, and (6) a high position of the tentorium. The Dandy-Walker malformation has prevalence of about 1 in 30,000 live births and found in 4–12% of infantile hydrocephalus.
GENETICS/BASIC DEFECTS
1. Heterogeneous etiology a. Isolated
b. A part of a Mendelian disorder c. A part of a chromosome disorder
i. Trisomy 18 ii. Triploidy iii. Trisomy 13 d. Environmental factors
2. Uncertain significance of Dandy-Walker variant and mega-cisterna magna
CLINICAL FEATURES
1. Maternal polyhydramnios/oligohydramnios 2. Fetal anomalies
a. Echogenic bowel b. Effusions/hydrops c. Single umbilical artery d. Growth restriction e. Abundant nuchal folds
f. Cystic hygroma 3. Neuropathologic triad
a. Cystic dilatation of the fourth ventricle b. Hypoplasia of the cerebellar vermis c. Hydrocephalus
4. Associated intracranial anomalies (70% of cases) a. An enlarged posterior fossa
b. Ventriculomegaly
c. Atresia of the foramina of Magendie and Luschka d. Midline anomalies
i. Agenesis of the corpus callosum ii. Holoprosencephaly
iii. Occipital meningocele and encephalocele e. Porencephalic cyst
f. Migrational disorder g. Gyral abnormalities h. Microcephaly
5. Non-CNS associated malformations a. Facial clefting
b. Cardiovascular defects
c. Diaphragmatic hernia d. Omphalocele
e. Polycystic kidneys f. Spinal defects g. Limb defects
i. Polydactyly ii. Syndactyly
6. Common presenting signs and symptoms a. Macrocrania
b. Bulging fontanel c. Upward gaze palsy d. Hypertelorism e. Strabismus
f. Hypotonia
g. Headache and vomiting h. Seizures
i. Hemiparesis j. Facial palsy k. Palpebral ptosis
l. Pyramidal signs m. Cerebellar dysfunction
n. Motor dysfunction
o. Mental retardation: subnormal intelligence reported in 40–70% of cases
7. Prognosis
a. Grim but not uniformly fatal
b. Worst prognosis when there are associated anomalies and chromosome abnormalities
c. Better chance of normal outcome for isolated Dandy- Walker variant
DIAGNOSTIC INVESTIGATIONS
1. Sonography
a. Sonographic diagnosis of classic Dandy-Walker mal- formation: straightforward from mid-gestation b. Detection of Dandy-Walker malformation as early as
14 weeks using vaginal sonography c. In the transcerebellar view
i. An enlarged cisterna magna connected to the area of the fourth ventricle through a defect in the cerebellar vermis
ii. Presence of borderline-to-overt ventriculomegaly iii. Frequent association of other neural and extra-
neural malformation 2. CT and MRI of the brain
a. Large median posterior fossa cyst widely communi- cating with the fourth ventricle
b. Cystic enlargement of the fourth ventricle c. Cerebellar vermis dysgenesis
d. An upwardly displaced tentorium e. Hydrocecphalus
f. Atresia of the foramina of Magendie and Luschka
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g. Frequently associated CNS anomalies i. Agenesis of corpus callosum ii. Occipital encephalocele iii. Porencephalic cyst
iv. Holoprosencephaly v. Others
GENETIC COUNSELING
1. Recurrence risk
a. Patient’s sib: a low recurrence risk in the order of 1–5% unless the Dandy-Walker malformation is a part of a mendelian disorder or associated with chro- mosome anomaly
b. Patient’s offspring: not surviving to reproductive age because of severe neurologic deficits associated with major malformations
2. Prenatal diagnosis
a. Ultrasonography for detecting unique previously described CNS malformations
b. MRI of the fetal CNS
c. Prenatal amniocentesis for fetal karyotyping 3. Management
a. Ventriculoperitoneal shunt b. Cyst-peritoneal shunt
c. Ventriculocystoperitoneal shunt
d. Posterior fossa craniectomy with cyst fenestration
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Fig. 1. An 8-month-old patient with Dandy-Walker malformation associated with multiple congenital anomalies including facial dys- morphism, skin tags (pseudotails) on the cheek, and limb anomalies.
Fig. 2. MRI of the brain of the patient in Fig. 1 shows Dandy-Walker malformation with a large posterior fossa cyst which communicates with dilated 4th ventricle. In addition, this patient also has agenesis of corpus callosum, hydrocephalus, and vermis dysgenesis.
