Diagnostic ultrasound ( PDFDrive )

1530 PART V Pediatric Sonography
A B C
D
E
FIG. 45.22 Agenesis of the Corpus Callosum, Isolated Anomaly in Two Neonates. Neonate 1: (A) Small frontal horns are widely separated.
(B) Sulci radiate in sunburst pattern in parasagittal just off midline view. (C) Colpocephaly seen in parasagittal view of lateral ventricle. Neonate 2:
(D) Coronal view of the occipital horns shows enlarged right occipital horn. (E) Colpocephaly seen in parasagittal view of right lateral ventricle.
Generalized obstructive hydrocephalus occurs in up to 80%
of cases. If there is also agenesis of the corpus callosum, colpocephaly
is typically present. 7,57
Dandy-Walker Malformation:
Sonographic Findings
Enlarged fourth ventricle connects to Dandy-Walker cyst
posteriorly
Large posterior fossa
Hypoplastic cerebellar vermis
Hypoplastic cerebellar hemispheres displaced laterally by
fourth ventricle
Small brainstem
Hydrocephalus (80%)
Obstruction above and below fourth ventricle
Absent or dysgenetic corpus callosum (up to 70%)
he etiology of Dandy-Walker malformation is not deinitively
known. heories include agenesis of the foramina of Luschka
and Magendie in the irst trimester, malformation of the roof
of the fourth ventricle, and delayed opening of the foramen
of Magendie. 31 he prenatal diagnosis of Dandy-Walker malformation,
with diferentiation from Dandy-Walker variant, a
posterior fossa arachnoid cyst, and mega–cisterna magna, is
usually possible. Some severe cases may be diagnosed early, but
typically Dandy-Walker malformation is diagnosed ater 17 weeks’
gestation, when the inferior vermis has normally completely
formed. 40,58
he Dandy-Walker malformation is associated with other
CNS anomalies in up to 70% of cases. hese include partial or
complete agenesis of the corpus callosum, encephalocele, holoprosencephaly,
microcephaly, gray matter heterotopia, and gyral
malformations. Chromosomal abnormalities are described in
up to 20% to 50% of cases and include trisomy 13, 18, and 21.
Other associated anomalies include gastrointestinal, genitourinary,
cardiac, musculoskeletal, and pulmonary malformations, including
congenital diaphragmatic hernia and cystic hygroma. 57,59,60
herapy for the Dandy-Walker malformation includes ventriculoperitoneal
shunting, which will decompress the lateral
ventricles but may not decompress the posterior fossa cyst. he
cyst may require a separate shunt for decompression. Sonography
can be used to follow these procedures until the infant is
approximately 18 months of age, but this method is rarely used
ater the irst few months of life.
In the Dandy-Walker Spectrum, there is variable hypoplasia
of the posterior inferior vermis and communication between
the fourth ventricle and cisterna magna. he fourth ventricle
may be slightly to moderately enlarged. In the mildest form, the
posterior fossa is normal in size, and although the vermis is
small, the cerebellar hemispheres are normal. here is no associated
hydrocephalus. Mastoid fontanelle views should be taken
in this setting through the fourth ventricle so that the normal