Mild ventriculomegaly is defined as being present when the width of the
lateral ventricle, measured at the atrium, is greater than or equal to 10
mm (1-3). Sonographic technique is important when evaluating the
ventricles. Care must be taken not to measure from the midline, but rather
to use the medial aspect of the ventricle. Oblique planes should not be
used to measure the ventricle.
Identification of a fetus with mild ventriculomegaly should prompt a
diligent search for associated central nervous system (CNS) and extra-CNS
anomalies, as many fetuses with ventriculomegaly have additional
abnormalities. Fetuses with concurrent anomalies are at greater risk for an
underlying chromosomal abnormality (4-6). Among cases of truly isolated
mild ventriculomegaly, for which chromosome analysis was performed,
approximately 2% (4,7) had a chromosomal abnormality. It should be noted
that this data has been ascertained from populations of patients already at
an increased risk for a fetal anomaly because of previous abnormal
ultrasound findings, size and date discrepancy, abnormal maternal serum
screen, twin gestation, placenta previa, advanced maternal age, and preterm
labor; therefore, it is unclear how these risk figures apply to low-risk
Given the finding of fetal ventriculomegaly, we recommend offering genetic
counseling, fetal echocardiography, amniocentesis, as well as follow-up
ultrasound examination to search for additional anomalies and assess any
progression of ventriculomegaly. A fetal MRI research protocol is currently
ongoing at BIDMC and may be useful in identifying anomalies not readily
visualized by sonography, such as agenesis of the corpus callosum, commonly
associated with ventriculomegaly. The referring clinician should be
notified at the time of the original scan to discuss these issues.
Cardoza, JD, Goldstein, RB, Filly, RA. Exclusion of fetal
ventriculomegaly with a single measurement: the width of the lateral
ventricular atrium. Radiology 1988; 169:711-714.
Heiserman J, Filly RA, Goldstein, RB. Effect of measurement errors on
sonographic evaluation of ventriculomegaly. J Ultrasound Med 1991; 10:
Siedler DE, Filly RA. Relative growth of the higher fetal brain
structures. J Ultrasound Med 1987; 6:573-576.
Nicolaides, KH, Berry, S, Snijders, RJM, Thrope-Beeston, JG, and
Godsen, C. Fetal lateral cerebral ventriculomegaly: associated
malformations and chromosomal defects. Fetal Diagn Ther 1990;5:5-14.
Bromely, B, Frigoletto, FD, and Benacerraf, Beryl. Mild fetal lateral
cerebral ventriculomegaly: clinical course and outcome. Am J Obstet
Gynecol March 1991 863-867.
Goldstein, RB, La Pidus, AS, Filly, RA, and Cardoza, J. Mild lateral
cerebral ventricular dilatation in utero: clinical significance and
prognosis. Radiology 1990;176:237-242.
Patel, MD, Filly, AL, Hersch, DR, and Goldstein, RB. Isolated mild
fetal cerebral ventriculomegaly: clinical course and outcome. Radiology