Journal of Ultrasound in Medicine, Vol 16, Issue 11 731-734, Copyright © 1997 by American Institute of Ultrasound in Medicine
Clinical significance of isolated enlargement of the cisterna magna (> 10 mm) on prenatal sonography
J. A. Haimovici, P. M. Doubilet, C. B. Benson and M. C. Frates
Department of Radiology, Brigham and Women's Hospital, Boston, MA 02115, USA.
Enlargement of the cisterna magna has been reported to be associated with
aneuploidy. In prior studies of cisterna magna enlargement, however, those
fetuses with abnormal chromosomes have had other sonographic abnormalities
in addition to a large cisterna magna. Our goal was to assess the clinical
significance of the isolated finding of a cisterna magna measuring more
than 10 mm in anteroposterior dimension on a prenatal sonogram. We
retrieved all prenatal sonograms performed at our institution between 1989
and 1996 in which an enlarged cisterna magna was the only sonographic
abnormality. Cases were included in our study if the cisterna magna
measured more than 10 mm in the appropriate plane and the fetal survey was
otherwise normal, including normal cerebellar size and morphology.
Pregnancy outcome and postnatal follow-up were obtained in each case.
Fifteen cases comprised our study population. In all 15 fetuses, the
enlarged cisterna magna was first seen in the third trimester (gestational
age range, 26 to 37 weeks). The cisterna magna ranged from 11 to 19 mm in
size (mean, 12.9 mm). All 15 pregnancies resulted in phenotypically normal
liveborn infants. All the mother and infants had short hospital stays (1 to
4 days), and the infants were normal at discharge. Longer follow-up was
available in eight cases (range, 2 to 69 months), and all eight of these
infants were normal. Our results suggest that isolated enlargement of the
cisterna magna to more than 10 mm is associated with normal pregnancy and
neonatal outcome.
