Diagnostic ultrasound ( PDFDrive )

1528 PART V Pediatric Sonography
A
B
C
D
FIG. 45.20 Chiari II and Absent Corpus Callosum. (A) Anterior coronal image shows widely separated frontal horns. (B) Posterior coronal
view shows the parallel orientation of the ventricles. Gyral interdigitation is best seen before shunting in this patient. (C) and (D) Anterior and
posterior coronal ultrasound scans show Chiari II malformation after ventriculoperitoneal shunting for hydrocephalus. The right lateral ventricle is
much smaller, typical of the side with the shunt. See also Video 45.4, Video 45.5, and Video 45.6.
utero or at birth to delineate associated indings that may cause
a poor prognosis and change patient management. 31,55 Isolated
agenesis of the corpus callosum may have a normal prognosis.
However, Barkovich 31 has reported that symptomatic patients
with absence of the corpus callosum typically have seizures,
microcephaly, delayed development, mental retardation, or
hypothalamic dysfunction.
he key diagnostic clues to agenesis of the corpus callosum
on sonography are the widely spaced, parallel-oriented lateral
ventricles that have extremely narrow, oten slitlike frontal horns 56
(Fig. 45.22). Coronally, the frontal horns and ventricular bodies
have sharply angled, lateral peaks. here may be relative enlargement
of the occipital horns (colpocephaly) and oten, enlarged
temporal horns. Probst bundles, longitudinal callosal ibers that
failed to decussate or cross to the other cerebral hemisphere,
bulge into the ventricles along the superomedial aspect of the
lateral ventricles. hese are best seen on coronal images as the
concave medial border to the lateral ventricles. here is no septum
pellucidum. he third ventricle is oten dilated and elevated; its
roof extends superiorly between the lateral ventricles and into
the interhemispheric issure and may be associated with a dorsal
midline cyst (Fig. 45.23). he medial cerebral sulci are typically
radially arranged, perpendicular to the expected course of the
corpus callosum, causing a “sunburst” sign on sagittal midline
images (Fig. 45.24). he pericallosal sulcus is missing, and the
cingulate sulcus is absent or present only as unconnected segments.
Because agenesis of the corpus callosum has additional
brain anomalies in more than 75% of patients, further evaluation
with postnatal MRI is indicated. Cerebellar hypoplasia, gyral
anomalies, and heterotopia are seen most oten on MRI. 28