The brain has four fluid filled spaces that
communicate with each other called ventricles. There are two "lateral" ventricles and two midline (the third and fourth) ventricles. Fluid
(cerebrospinal fluid) produced within the brain circulates through the ventricles of
the brain and around the spinal cord.
Enlargement of the lateral ventricles to between 10 mm and 15 mm in width is
called ventriculomegaly [1,3]. Ventriculomegaly has been reported in 0.07%
to 0.7% of fetuses examined by prenatal ultrasound [4,5].
What Causes Ventriculomegaly ?
The lateral ventricles may become enlarged if the outflow of cerebrospinal fluid
from the lateral ventricles is blocked at the interventricular foramen( foramen of Monro). The
interventricular foramen may be congenitally malformed, or may have become
obstructed by infection, hemorrhage , or a tumor [6-9].
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Lippincott Williams & Wilkins. All rights reserved.
Ventriculomegaly may be associated with other malformations
such as agenesis of the corpus callosum, spina bifida, and heart defects .
Fetuses with ventriculomegaly and additional abnormal ultrasound findings are at greater risk
for having a chromosomal abnormality (usually Down
syndrome) [2, 3, 10].
Other investigations that may be
considered [ 5, 10-12 ]:
- Amniocentesis for chromosome analysis
- Maternal blood IgM and IgG for toxoplasmosis, cytomegalovirus, and
- Fetal echocardiography
- Magnetic resonance imaging (MRI) of the fetal nervous
Will The Condition Get Better?
Isolated mild ventriculomegaly may be expected to remain unchanged in 60
percent of cases and to resolve in one-third of cases. The ventricles can
be expected to enlarge in approximately 8 percent of fetuses.
Isolated ventriculomegaly greater than or equal to 12 mm is associated with
normal neurodevelopment in approximately 77% of cases. Whereas isolated ventriculomegaly of less than 12 mm is associated with
normal neurodevelopment in 97% of cases .
1. 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.
2. 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
3. Pilu G, Falco P, Gabrielli S, Perolo A, Sandri F, Bovicelli L. The clinical significance of fetal isolated cerebral borderline ventriculomegaly: report of 31 cases and review of the literature.Ultrasound Obstet Gynecol 1999;5;320-6
4. Kinzler WL, Smulian JC, McLean DA, et al. Outcome of
prenatally diagnosed mild unilateral cerebral ventriculomegaly. J Ultrasound
5. Vergani P, Locatelli A, Strobelt N, et al. Clinical
outcome of mild fetal ventriculomegaly.Am J Obstet Gynecol.1998;178:218-222.
6. Senat MV, Bernard JP, Schwarzler P, et al. Prenatal diagnosis and follow-up of 14 cases of
unilateral ventriculomegaly. Ultrasound Obstet Gynecol 1999;14:327-332.
7. Patten RM, Mack LA, Finberg HJ. Unilateral hydrocephalus: prenatal sonographic diagnosis. AJR Am J Roentgenol.1991;156: 359-363.
8. Wilberger JE Jr, Vertosick FT Jr, Vries JK. Unilateral hydrocephalus secondary to congenital atresia of the foramen of
Monro. Case report. J Neurosurg. 1983;59:889-901.
9. Oi S, Yamada H, Sasaki K, et al. Atresia of the foramen of Monro resulting in severe unilateral hydrocephalus with
subfascial herniation and infratentorial diverticulum. Neurosurgery.1985;16: 103-106.
10. Achiron R, Schimmel M, Achiron A, et al. Fetal mild
idiopathic lateral ventriculomegaly: is there a correlation with fetal trisomy?
Ultrasound Obstet Gynecol. 1993;4:89-92.
11. Levine D, Barnes PD, Madsen JR, et al. Central nervous system abnormalities assessed with prenatal magnetic resonance imaging.
12. Fetal serum interferon-alpha suggests viral infection as the aetiology of unexplained lateral cerebral ventriculomegaly.