Diagnostic ultrasound ( PDFDrive )

1174 PART IV Obstetric and Fetal Sonography
A
B
C
D
FIG. 34.8 Cavum Veli Interpositi (CVI). (A) CVI on axial view at 19 weeks (arrow). csp, Cavum septi pellucidi. CVIs of this size are frequent
but are commonly overlooked. (B) CVI on coronal view (arrow). BS, Brainstem. (C) CVI on color Doppler sagittal view (arrow) lying just below the
splenium of the corpus callosum (cc). BS, Brainstem. There is no low on color Doppler. (D) T2-weighted magnetic resonance image of 21-week
fetus showing CVI (arrow).
Fetuses with suspected CVI cysts should undergo detailed
neurosonography and anatomic scan including Doppler to exclude
vein of Galen aneurysm. If there are any atypical features or
associated indings, then MRI can be helpful in further investigation.
We no longer monitor incidentally discovered small (<8 mm)
isolated cysts but perform follow-up scans if the cysts are especially
conspicuous or if there is parental concern.
VENTRICULOMEGALY AND
HYDROCEPHALUS
he term ventriculomegaly (VM) describes ventricles 10 mm
or larger at the atrium. Care should be taken to measure the
ventricles in the appropriate plane; an oblique plane will lead to
an apparently enlarged ventricle if the trigone is measured. he
head itself may be normal, large, or even smaller than expected
for menstrual age. “Hydrocephalus” refers to enlarged ventricles
associated with increased intracranial pressure and thus is typically
associated with head enlargement. 66 Ventricular abnormality,
especially enlargement, is the most commonly encountered cranial
abnormality at prenatal ultrasound, with prenatal incidence of
10 to 80 per 10,000 pregnancies. It is oten the key inding in
the initial detection of CNS abnormalities and is found in about
88% of fetuses with cerebral abnormalities 39,43,67,68 (Fig. 34.9).
Ventricle measurement technique is important and details
should be remembered. With the head in a true axial view,
measurements are generally taken only of the distal ventricle
since the near ventricle is obscured by skull bone artifact and
ventricles are presumed to be symmetrical. Calipers are placed