Distal lateral ventricular atrium: reevaluation of normal range

Width of the fetal lateral ventricular atrium between 10 and 12 mm: a simple variation of the norm?

OBJECTIVES

The prognosis of borderline forms of anomalies that can be detected by ultrasound is one of the most challenging issues in prenatal diagnosis. The aim of this study was to determine the prognosis for fetuses presenting with isolated mild ventriculomegaly (MVM).

METHODS

Fetuses in which the width of the lateral ventricular atria was 10-12 mm and which had no other detectable chromosomal or morphological anomalies were followed by monthly ultrasound examinations until delivery. For the cases identified up to December 1997, postnatal information was gathered retrospectively through interviews. Children born from January 1998 onwards were included in a protocol involving planned neuropsychiatric visits at 12 and 18 months of age in which the Griffith scale was used to assess neurodevelopment.

RESULTS

Between September 1992 and January 2001, 60 fetuses with isolated MVM were identified. Ventricular dilatation diminished in 18 cases (and became normal in nine of these) and stabilized in 42 cases. Information was obtained on 38 children born up to December 1997 and their neurodevelopment was found to be completely normal. The 22 children born from January 1998 onwards showed normal development at 12 and 18 months of age.

CONCLUSIONS

When MVM is observed on prenatal ultrasound examination it can be very difficult to offer parents appropriate counseling. It is important to exclude aneuploidy or morphological abnormalities but even then there will be anxieties about long-term neurological outcome. Our data, which show normal neurodevelopment between 18 months and 10 years after birth in cases of MVM (10-12 mm), should provide a basis for reassuring counseling.

Mild fetal cerebral ventriculomegaly: diagnosis, clinical associations, and outcomes

The normal fetal lateral ventricular diameter remains stable at 10 mm over gestation. Mild ventriculomegaly, defined as a lateral ventricular diameter of >or=10 mm but <or=15 mm or a choroid-lateral ventricular separation >or=3 mm but <or=8 mm occurs bilaterally in 0.15-0.7% of fetuses and unilaterally in 0.07% of pregnancies. This finding is associated with an increased risk of fetal chromosomal abnormalities, congenital anomalies and infections, syndromes, perinatal death, and childhood developmental delays. Prenatal evaluation includes targeted sonographic examination for central nervous system and extra-central nervous system abnormalities, and diagnostic amniocentesis for chromosomal analysis and infectious disease studies. Individualized patient counseling is based on these test results. Optimal postnatal care involves appropriate pediatric neurologic and developmental specialists.

Fetal lateral ventricular width: what should be its upper limit? A prospective cohort study and reanalysis of the current and previous data

OBJECTIVE

The upper limit of the fetal atrial width in normal fetuses is debated. This was a prospective cohort evaluation of the lateral ventricular width with special regard to the upper limit of its size.

METHODS

Measurements of fetal atrial ventricular size were obtained by abdominal ultrasonography in 427 male and female fetuses between 20 and 40 weeks' gestation of normal singleton pregnancies. In addition, reanalysis of previous data (8 studies) and the current data was performed to produce a pooled mean and SD.

RESULTS

The mean ventricular width +/- SD was 6.2 +/- 1.2 mm. The ventricular width did not show significant modification throughout gestation. Reanalysis of the current and previous studies (8216 cases) yielded a pooled mean of 6.4 +/- 1.2.

CONCLUSIONS

According to the current and previous studies, the upper cutoff of fetal ventricular atrium width should be 10 mm. This cutoff represents a range of approximately 3 SDs above the pooled mean, corresponding to a 99.74% confidence interval.

Cerebral lateral ventricular atrial diameter of male and female fetuses at 20-24 weeks' gestation

OBJECTIVE

To determine if the lateral ventricular atrial diameter differs between male and female fetuses at 20-24 weeks' gestation.

DESIGN

Prospective study.

METHODS

The transverse diameter of the ventricular atrium was measured from inner wall to inner wall for a total of 202 pregnant women with 105 male fetuses and 97 female fetuses.

RESULTS

The mean diameter of the ventricular atrium for the 202 fetuses was 4.96 +/- 0.96 mm (range, 2.1-8.4 mm). The 105 males had a mean diameter of 4.95 +/- 0.98 mm and the 97 females a mean diameter of 4.97 +/- 0.94 mm. There was no statistical difference between the sexes.

CONCLUSIONS

In our population, there was no difference between ventricular atrial diameter in male and female fetuses at 20-24 weeks' gestation.

Central nervous system anomalies

Fetal central nervous system abnormalities encompass a variety of lesions. Most of the anomalies are seen in association with an increased incidence of fetal aneuploidy and an increase in other anomalies both within and outside of the central nervous system. These associated findings and the underlying lesion all have a role in the eventual prognosis for the ongoing pregnancy. The antenatal diagnosis of a central nervous system abnormality should prompt a careful search for other defects, and consideration should be given for genetic evaluation and testing.

Second trimester markers of aneuploidy

The risks of aneuploidy associated with identification of a sonographic marker in the low risk population is controversial. Prior risk estimates have been derived usually from high risk populations. Screening programmes in the first trimester, second trimester and combined first and second trimester will undoubtedly alter the second trimester scan as a screening tool for aneuploidy. This chapter reviews the current sonographic markers and the difficulties in their application to the general population.

Cerebral mantle thickness: a measurement useful in anatomic diagnosis of fetal ventriculomegaly

The ultrasonographic diagnosis of cerebral ventriculomegaly carries grave implications, in that affected fetuses may suffer abnormal postnatal development or therapeutic abortion. It is important for pathologists to corroborate the clinical diagnosis, but because diagnostic methodologies and criteria differ so radically, this can be problematic. The clinical diagnosis is made primarily by serial ultrasound examinations of the cerebral ventricles, spaces that can be altered postmortem, particularly when the brain is autolysed or deformed artifactually. We therefore sought to learn if examination of tissue, rather than spaces, can identify accurately those fetuses diagnosed with cerebral ventriculomegaly by prenatal ultrasound. The thickness of the cerebral mantle was obtained in 100 control fetuses aged 14 to 26 postmenstrual weeks. Statistical analysis revealed significant correlation of cerebral mantle thickness with crown-rump length, foot length, and head circumference. Twenty fetuses diagnosed with ventriculomegaly showed mantle thicknesses that were less than the control mean. In a few cases, mantle thickness fell between the mean and -1 SD; in several others, thickness was diminished by -1 SD to -2 SD; in one-half of cases, mantle thickness was 2 SDs or more below the expected mean. Head circumference was within 2 SDs of the control mean in most cases, and increased beyond 2 SDs in only two cases. Head circumference is an unreliable indicator of ventriculomegaly in the midgestational fetus. By contrast, cerebral mantle thickness is a simple and useful way of corroborating ultrasonographic diagnoses at autopsy and may also prove useful in clinical settings.

The fetal head: borderlines

After more than 20 years of using ultrasound to examine the fetal head, there are still areas of controversy. The size of the ventricular atrium or the anteroposterior measurement of the posterior fossa have been shown to be relatively stable throughout pregnancy. However, there are instances in which intracranial malformations occur with normal ventricular atrial measurements. Although there are more obvious posterior fossa defects such as Dandy-Walker malformation, there are other abnormalities such as Dandy-Walker variant that are difficult to detect. Another area of controversy surrounds dealing with the fetus with a choroid plexus cyst. Review and understanding of the current literature are needed to best manage these fetuses with choroid plexus cysts. Knowledge of central nervous system embryology and of technical pitfalls of sonography, and understanding the overlap between normal and abnormal anatomy are needed to obtain a more precise central nervous system diagnosis. This article will review some of the borderlines in examination of the fetal brain.

Clinical outcome of mild fetal ventriculomegaly

OBJECTIVE

Our purpose was to evaluate the outcome of fetuses with mild cerebral ventriculomegaly.

STUDY DESIGN

We prospectively collected all cases of mild cerebral ventriculomegaly (transverse diameter of the atrium of the cerebral lateral ventricles between 10 and 15 mm) diagnosed antenatally between January 1990 and December 1996. Associated ultrasonographic abnormalities including markers of aneuploidy, presence of chromosomal anomalies, structural malformations detected at birth, and neurologic outcome were recorded. Outcome information was available on all cases. In addition, published series of cases of fetal mild cerebral ventriculomegaly were reviewed to identify prognostic indicators.

RESULTS

Eighty-two cases fulfilled the inclusion criteria: 48 were isolated and 34 were associated with other ultrasonographic markers or anomalies. Among the 45 surviving euploid isolated cases, neurologic follow-up was normal at a mean age of 28 months (range 3 to 72 months). Male fetuses and those with a transverse atrial size <12 mm had a good prognosis. Ventricular atria > or =12 mm were more often associated with other anomalies (56% vs 6%) and, when isolated, with abnormal postnatal neurodevelopment (23% vs 3%). Aneuploidy was present in two cases of isolated mild cerebral ventriculomegaly, both of which were associated with advanced maternal age, and in seven cases associated with other anomalies.

CONCLUSIONS

Mild cerebral ventriculomegaly should prompt targeted ultrasonographic examination, inclusive of markers of aneuploidies, visualization of the corpus callosum, and echocardiogram as well as serologic evaluation for congenital infections. In isolated mild cerebral ventriculomegaly genetic counseling should take into account clinical, laboratory, and ultrasonographic findings. A review of the published series suggests that cognitive or motor delay is predominantly mild and that it occurs in about 9% of cases of isolated mild cerebral ventriculomegaly.