Prenatal Imaging of
Congenital Malformations of the Brain
Beth M. Kline-Fath, MD, and Maria A. Calvo-Garcia, MD
This article represents an overview of ultrasound (US) and magnetic resonance imaging
(MRI) of the normal fetal brain during the second and third trimesters, followed by the
description of congenital pathologic conditions. Fetal imaging of the brain requires an
understanding of embryology that deﬁnes the normal anatomy of the brain at each gesta-
tional age. Without knowledge of the normal developmental milestones, it is impossible to
accurately diagnose prenatal central nervous system (CNS) disorders. In the ﬁrst section,
a brief review of the normal anatomy and milestones by using US and fetal MRI will be
described. The second part will provide a summary of congenital malformations with
respect to embryologic event and their typical imaging patterns on prenatal US and MRI.
Semin Ultrasound CT MRI 32:167-188 © 2011 Elsevier Inc. All rights reserved.
Prenatal screening for neurologic abnormalities is usually
based on US performed either routinely or after abnormal
maternal alpha-fetoprotein (AFP) screening. Fetal karyotyp-
ing and, in some instances, search for in utero infection
markers or teratogen exposure might also be required.
The basic US examination is performed via transabdomi-
nal sonography by using 3 standard axial sections through
the fetal brain. When an anomaly is suggested, additional
sagittal and coronal planes should be attained.
If the fetus is
cephalic, transvaginal imaging might improve imaging.
When the fetus is breech, increased resolution with high-
frequency probes in the maternal umbilicus might be help-
In addition, imaging can be enhanced with improve-
ments in US technology including 2- or 3-dimensional or
Professional guidelines require assessment of the cerebel-
lum, cisterna magna (CM), lateral cerebral ventricles, choroid
plexus, midline falx, and cavum septum pellucidum to im-
prove the accuracy of prenatal diagnosis. These structures
can be documented in 3 axial levels of imaging: transven-
tricular, transthalamic, and transcerebellar.
It is from these
standard views that the routine cranial fetal biometry is ob-
tained. These levels comprise the minimum planes that will
satisfy prenatal brain imaging guidelines.
US Anatomic Details
Ventricular size and conﬁguration are best depicted on the
standard transventricular image (Fig. 1), with landmarks an-
terior to posterior: cavum septi pellucidum between anterior
horn of the lateral ventricles to the posterior horn of the
lateral ventricles containing hyperechoic choroid. Ventricu-
lar walls should be echogenic, thin, and smooth, clearly de-
marcated by cerebrospinal ﬂuid (CSF) within the ventricle.
At the widest part of the lateral ventricles and glomus of the
choroid plexus, also known as the atria, calipers should be
placed along the inner aspect of the wall. A measurement up
to 10 mm is considered normal.
The cavum septum pellucidum (CSP) is a thin plate
consisting of 2 laminae. Under normal conditions it
should be easily detected beyond approximately 18-20
weeks. It is seen anterior and superior to the third ventri-
cle during the routine measurement of the biparietal di-
ameter. Its identiﬁcation virtually excludes complete
agenesis of the corpus callosum (ACC).
nonvisualization of the CSP might be associated with a
variety of abnormalities, including agenesis of the corpus
callosum (ACC), septo-optic dysplasia, holoprosenceph-
aly, schizencephaly, porencephaly/hydranencephaly, basi-
lar encephaloceles, and severe hydrocephalus.
The germinal matrix itself is not well-delineated with US.
However, because the walls of the lateral ventricles normally
are smooth (Fig. 1), focal nodularity along the ventricular
surface can suggest gray matter heterotopia, related to abnor-
mality of the germinal matrix.
Department of Radiology, Fetal Care Center of Cincinnati, Cincinnati Chil-
dren’s Hospital Medical Center, Cincinnati, OH.
Address reprint requests to Beth M. Kline-Fath, MD, Department of Radiol-
ogy, MLC 5031, Cincinnati Children’s Hospital Medical Center, 3333
Burnet Ave, Cincinnati, OH 45229. E-mail: firstname.lastname@example.org
0887-2171/$-see front matter © 2011 Elsevier Inc. All rights reserved.