Diagnostic ultrasound ( PDFDrive )

CHAPTER 34 The Fetal Brain 1193
A
B
C
FIG. 34.20 Mega–Cisterna Magna. (A) Mega–
cisterna magna (*) axial view. Note the clear luid content
and the lateral Blake cyst walls (arrows) with echogenic
subarachnoid luid lateral to the walls. (B) Mega-cisterna
magna (*) sagittal three-dimensional view. Note that
the cerebellum is intact but slightly compressed. Upper
Blake cyst wall (arrow). (C) In a different fetus, mega–
cisterna magna and otherwise normal-appearing brain on
sagittal T2-weighted magnetic resonance image.
FIG. 34.21 Arachnoid Cyst. Arachnoid cyst (A) in the supratentorial,
interhemispheric position at 25 weeks.
A
circulation and require decompression. Midline cysts can
accompany dysgenesis of the corpus callosum, so when a
supratentorial cyst is seen, it is important to evaluate the entire
corpus callosum. In the suprasellar region these cysts may be
associated with pituitary dysfunction. he diferential diagnosis
depends on the location. Arachnoid cysts in the posterior
fossa can be confused with DWM, inferior vermian hypoplasia,
mega–cisterna magna, and Blake pouch cysts. he differential
diagnosis of supratentorial cysts includes cavum veli
interpositi (CVI), aneurysm of vein of Galen, hemorrhage,
and cystic tumors. Pediatric neurosurgical opinion is important
in evaluating and counseling these patients, many of
whom require no treatment. 27,65,184,185
Malformations of Cortical Development
Malformations of cortical development comprise a broad and
heterogeneous collection of conditions resulting from disturbances
in the major steps of cortical development including neuronal
proliferation in germinal zone and apoptosis, migration, and
cortical organization. Cortical changes may be focal or global