Diagnostic ultrasound ( PDFDrive )

CHAPTER 45 Neonatal and Infant Brain Imaging 1531
A
B
C
FIG. 45.23 Agenesis of Corpus Callosum (ACC) With Elevation of Third Ventricle and Continuation Into a Large Dorsal Cyst. (A) Coronal
sonogram and (B) and (C) computed tomography scans show widely separated frontal horns (F), a large third ventricle that extends superiorly as
a dorsal cyst (3) between the lateral ventricles in a newborn who also had Dandy-Walker malformation.
foramen of Magendie and vallecula, which may be enlarged with
hydrocephalus, are not mistaken for a Dandy-Walker anomaly 25
(see Fig. 45.9C). he Dandy-Walker spectrum varies greatly with
vermian hypoplasia, an enlarged fourth ventricle, a large aqueduct,
and a large third ventricle. 14 Chromosomal abnormalities occur
in up to 30% of these infants. Associated CNS or extra-CNS
anomalies may afect the outcome of the infant more than the
Dandy-Walker spectrum. 31,57
Two diferential diagnoses of posterior fossa cystic lesions
mimic Dandy-Walker syndrome. A mega–cisterna magna is
described as the mildest form of this spectrum and includes no
mass efect, no hydrocephalus, and a normal cerebellar vermis,
fourth ventricle, and cerebellar hemisphere (Fig. 45.27). A
posterior fossa subarachnoid cyst can be diferentiated from
Dandy-Walker malformation or spectrum by the lack of communication
of the cyst with the fourth ventricle. he normal
fourth ventricle, vermis, and cerebellum are displaced by the
arachnoid cyst. 58,59
Posterior Fossa Cystic Lesions
Dandy-Walker Malformation
Hypoplastic vermis with rotation
Blake pouch cyst
Mega–cisterna magna
Posterior fossa subarachnoid cyst