Diagnostic ultrasound ( PDFDrive )

CHAPTER 34 The Fetal Brain 1173
FIG. 34.6 Bilateral Choroid Plexus Cysts (Arrows). Note that on the right, an oblique scan plane has been used to view the upper hemisphere
through the squamosal suture. See also Video 34.4.
*
A
B
C
FIG. 34.7 Blake Pouch Cyst. (A) Note the clear, echo-free
space (*) in the midline behind the normal cerebellum and vermis.
This is the Blake pouch cyst, which contains clear cerebrospinal
luid. It has thin, lateral cyst walls (arrows), which separate it
from the adjacent, mildly echogenic subarachnoid space of the
cisterna magna that is visible on either side. Such “cysts” are
common and with careful scanning can be found in most fetuses.
(B) and (C) Pseudo–vermis dysgenesis or hypoplasia appearance
caused by rotation of cerebellum and vermis by a Blake
pouch cyst. (B) Axial view shows apparent cleft or defect in the
vermis (arrow) that could easily be called vermian dysgenesis.
(C) Midsagittal view shows an intact, symmetrical normal-size
vermis with three issures visible. It is rotated such that its lower
part is elevated away from the brainstem (arrow). Many now
believe that this represents a normal fetus, with the Blake pouch
cyst elevating the lower part of the vermis and giving it the
appearance of a cleft.