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

Perinatal and neurodevelopmental outcome with isolated fetal ventriculomegaly: A systematic review

OBJECTIVE

To establish the perinatal and neurodevelopmental outcomes of fetuses diagnosed with isolated ventriculomegaly (IVM).

METHODS

A systematic review of cohort, case/control studies, case series and case reports of IVM (unilateral or bilateral enlargement of the lateral ventricle, >or=10 mm, with no additional diagnosis at the time of the initial ultrasound), identified by searching, without language restrictions, The Cochrane Library, MEDLINE and Embase databases in June 2004.

RESULTS

No cohort study was retrieved but 577 cases were identified in one case/control study and 29 case series/case reports. Of 207 cases with follow-up and known gestational age at diagnosis, normal developmental outcomes were found in 82%, mild impairments in 9% and moderate/severe impairments in 10%. Prenatal diagnosis could possibly have reduced the risk of moderate/severe impairments to 7%. In 137 cases followed to at least 20 months of age, 79% had normal neurodevelopment, 10% were mildly delayed and 11% had moderate/severe developmental delays.

CONCLUSIONS

Outcome was favorable in 85% of IVM cases, decreasing to 79% when cases were followed to at least 20 months of age. We recommend prospective cohort studies with new diagnostic modalities to better identify the underlying conditions relating to moderate/severe impairments in the remaining cases.

The significance of fetal ventriculomegaly: etiology, short- and long-term outcomes

Fetal cerebral ventriculomegaly (VM) is diagnosed when the width of one or both ventricles, measured at the level of the glomus of the choroid plexus (atrium), is > or = 10 mm. VM can result from different processes: abnormal turnover of the cerebrospinal fluid (CSF), neuronal migration disorders, and destructive processes. In a high percentage of cases, it is associated with structural malformations of the central nervous system (CNS), but also of other organs and systems. The rate of associated malformations is higher (> or =60%) in severe VM (>15 mm) and lower (10-50%) in cases of borderline VM (10-15 mm). When malformations are not present, aneuploidies are found in 3-15% of borderline VM; the percentage is lower in severe VM. The neurodevelopmental outcome of isolated VM is normal in > 90% of cases if the measurement of ventricular width is between 10 and 12 mm; it is less favorable when the measurement is > 12 mm.

Normal sonographic development of the central nervous system from the second trimester onwards using 2D, 3D and transvaginal sonography

The developmental changes of the fetal central nervous system (CNS) during the second and third trimesters, specifically the brain, relate mostly to changes in size. However, other changes do occur in the fetal brain during the second and third trimester such as: the union of the cerebellar hemispheres, development of the corpus callosum (CC), and increasing complexity of the cerebral cortex. These changes follow a well-defined developmental timeline recognizable by sonography. The fetal neuroscan can be divided into a 'basic scan' which is performed transabdominally and a 'targeted Exam or neurosonogram' which uses a multiplanar approach, which preferably should be performed transvaginally. During the 'basic scan', several brain structures are imaged in addition to obtaining important biometric measurements. The 'neurosonogram' is a more extensive or detailed fetal study during which the emphasis is on the addition of coronal and sagittal planes. The easiest way to obtain these planes, if the fetus is in a cephalic presentation, is the transvaginal route. Three-dimensional (3D) sonography should, if possible, be performed transvaginally using the multiplanar approach. An added benefit of 3D sonography is the ability to display and render the volume in a variety of ways which may enhance the detection of pathology.

Prenatal mild ventriculomegaly predicts abnormal development of the neonatal brain

BACKGROUND

Many psychiatric and neurodevelopmental disorders are associated with mild enlargement of the lateral ventricles thought to have origins in prenatal brain development. Little is known about development of the lateral ventricles and the relationship of prenatal lateral ventricle enlargement with postnatal brain development.

METHODS

We performed neonatal magnetic resonance imaging on 34 children with isolated mild ventriculomegaly (MVM; width of the atrium of the lateral ventricle >/= 1.0 cm) on prenatal ultrasound and 34 age- and sex-matched control subjects with normal prenatal ventricle size. Lateral ventricle and cortical gray and white matter volumes were assessed. Fractional anisotropy (FA) and mean diffusivity (MD) in corpus callosum and corticospinal white matter tracts were determined obtained using quantitative tractography.

RESULTS

Neonates with prenatal MVM had significantly larger lateral ventricle volumes than matched control subjects (286.4%; p < .0001). Neonates with MVM also had significantly larger intracranial volumes (ICV; 7.1%, p = .0063) and cortical gray matter volumes (10.9%, p = .0004) compared with control subjects. Diffusion tensor imaging tractography revealed a significantly greater MD in the corpus callosum and corticospinal tracts, whereas FA was significantly smaller in several white matter tract regions.

CONCLUSIONS

Prenatal enlargement of the lateral ventricle is associated with enlargement of the lateral ventricles after birth, as well as greater gray matter volumes and delayed or abnormal maturation of white matter. It is suggested that prenatal ventricle volume is an early structural marker of altered development of the cerebral cortex and may be a marker of risk for neuropsychiatric disorders associated with ventricle enlargement.

FETAL NEUROIMAGING

Imaging technologies have been remarkably improved and contribute to prenatal evaluation of fetal central nervous system (CNS) development and assessment of CNS abnormalities in utero.

Postnatal clinical and imaging follow-up of infants with prenatal isolated mild ventriculomegaly: a series of 101 cases

BACKGROUND

Postnatal imaging and clinical outcome of fetuses with isolated mild ventriculomegaly (IMV) have never been systematically analysed.

OBJECTIVE

To evaluate the postnatal clinical outcomes of a large cohort of fetuses with IMV and to correlate them with pre- and postnatal imaging.

MATERIALS AND METHODS

We report a prospective study of 101 fetuses with IMV (10-15 mm ventriculomegaly with otherwise normal US, MRI, karyotype and TORCH screening). IMV was divided into minor (10-11.9 mm) and moderate (12-15 mm) ventriculomegaly. Ventriculomegaly was considered uni- or bilateral, stable, progressive, regressive or resolved according to the prenatal US follow-up. Clinical follow-up was performed by a neuropaediatrician. Postnatal imaging included cranial US (n = 71) and MRI (n = 76).

RESULTS

The outcome of minor and moderate IMV was excellent in 94% and 85% of infants, respectively. It was not different between uni- and bilateral IMV, and between stable, regressive and resolved IMV, and was independent of gestational age at diagnosis and gender. Fixed neurological abnormalities were observed in nine infants. Postnatal MRI showed white-matter abnormalities in 14 infants, including 6 of the 9 infants with a poor outcome.

CONCLUSION

The prognosis was slightly better in minor IMV than in moderate IMV. Postnatal MRI showed white-matter abnormalities in two-thirds of the infants with a poor outcome.

Obstetric and neonatal outcomes in severe fetal ventriculomegaly

OBJECTIVE

To determine the early outcome and the incidence of associated structural anomalies in pregnancies complicated by severe fetal ventriculomegaly (VM).

METHODS

A review of cases of severe fetal VM (posterior horn of lateral ventricle > 15 mm at referral or during prenatal follow-up) referred to a fetal medicine centre in Eastern England over 4 years from 2001 was made. Results of specialist prenatal investigations including ultrasound (US), karyotype, antiplatelet antibodies and congenital infection screen were noted. Neonatal clinical and cranial US findings, autopsy findings and neurodevelopmental follow-up at 4 months were obtained.

RESULTS

Twenty cases of severe VM were identified, including 3 with spina bifida. Median gestation at diagnosis was 28 weeks (range 16-36 weeks). Twelve cases had additional intra-cranial abnormalities and two had abnormalities outside the central nervous system. One case was complicated by toxoplasmosis. There was one case of trisomy 21. Ten pregnancies were terminated. Ten babies were live born, all of whom had VM confirmed, and two of these babies died within 4 months. Of the remaining eight, seven have abnormal neurodevelopment.

CONCLUSIONS

Severe VM is often diagnosed after the threshold of viability. Termination of pregnancy was requested in about half the cases owing to the risk of long-term neurodisability, and in all cases diagnosed before 24 weeks. In those live born, there was abnormal outcome in all but one.

Fetal Ventriculomegaly

The causes of fetal ventriculomegaly vary. Ventriculomegaly can be caused by not only obstruction of cerebrospinal flow tract but also brain maldevelopment or other reasons. Recent advanced imaging technology and approaching technique of transvaginal sonography have contributed to an accurate prenatal diagnosis and clearly revealed fetal intracranial condition. However, management of the condition and counseling of parents are still difficult, because the initial cause, absolute risk, and degree of resulting neurological deficit cannot be determined with confidence. Ventriculomegaly is evaluated according to atrial width > 10 mm and mild ventriculomegaly is defined as an atrial width of 10 to 15 mm. In ventriculomegaly cases, accurate detection of intracranial structure and additional abnormalities is required. Furthermore, ventriculomegaly may resolve spontaneously or progress during pregnancy. Therefore, detailed neuroscan by advanced imaging technology, detailed extra-CNS scan, longitudinal serial scan during pregnancy are mandatory for proper counseling and management. Longitudinal observation study of not only short-term but also long-term neurological prognosis will be required.

Prenatal isolated mild ventriculomegaly: outcome in 167 cases

OBJECTIVE

To define the contribution of prenatal investigation and evaluate the prognosis of isolated mild ventriculomegaly (IMV).

DESIGN

Retrospective study.

SETTING

University hospital between January 1992 and December 2002.

POPULATION

One hundred and sixty-seven cases of prenatal unilateral or bilateral IMV without any associated anomaly at the time of initial diagnosis.

METHODS

Complementary investigations were performed: amniocentesis with karyotyping, screening for viruses and acetylcholinesterase electrophoresis, magnetic resonance imaging (MRI), and ultrasonography every 3-4 weeks.

MAIN OUTCOME MEASURES

Results of prenatal investigations, pregnancy outcome, and postnatal psychomotor development.

RESULTS

IMV was diagnosed around 26.5 weeks. Amniocentesis revealed four chromosomal anomalies and two cytomegalovirus infections. MRI diagnosed brain-associated anomalies in 15 cases and ultrasonographic monitoring highlighted malformations not initially diagnosed in 28 cases. Termination of pregnancy (TOP) was considered in 21 pregnancies (12.6%). Indications were aneuploidy, fetal infectious disease or associated malformations. In women for whom a TOP was considered, consanguinity, fetus of female sex and frontal horn enlargement were statistically more frequent, ventriculomegaly was more often bilateral and asymmetrical, atrial width, and the rate of progressive ventricular enlargement were significantly higher. One hundred and one children with prenatal IMV were assessed between 19 and 127 months (mean age 54.68 +/- 2.87 months). Twelve children had neurological disease or psychomotor delay and 89 children had a normal psychomotor development. Poor neurological outcome was more often associated with atrial width greater than or equal to 12 mm, asymmetrical bilateral enlargement, and progression of the ventriculomegaly.

CONCLUSION

The detection of IMV raises the question of the child's psychomotor development and justifies meticulous prenatal investigation. In addition to associated anomalies, three criteria are often associated with an unfavourable outcome: atrial width greater than 12 mm, progression of the enlargement, and asymmetrical and bilateral ventriculomegaly.

Ultrasound and fetal diagnosis

PURPOSE OF REVIEW

The purpose of this review is to highlight publications from the last year that have advanced the use of ultrasound in obstetrics.

RECENT FINDINGS

Anatomic examination of the fetus in the first trimester has been emphasized because it allows for early diagnosis of many conditions. The prevalence of absent nasal bone, a marker for trisomy 21, in euploid fetuses depends on ethnicity. Nasal bone hypoplasia is another marker for Down syndrome. Studies on genetic screening in the first trimester have involved various serum analytes, adjustments in timing and calculations, use in multiple gestations, and the association of extreme measurements with adverse outcomes. A first-trimester integrated screening approach, which incorporates nuchal translucency, nasal bone, crown-rump length, pregnancy-associated plasma protein-A, and free beta-human chorionic gonadotropin, has the potential to maximize detection rates of Down syndrome and trisomy 18 and minimizes the screen-positive rate. The value of combining first and second-trimester results in sequential, contingent, or integrated screening protocols has been assessed. Isolated mild ventriculomegaly (10-12 mm) may prove to be a normal variant, and the role of 'soft' ultrasound markers in genetic counseling continues to be debated. Anomaly or high-risk status detection in the second trimester has been enhanced by the use of Doppler, 3D/4D ultrasound, and magnetic resonance imaging.

SUMMARY

Imaging techniques have been critical in the development of screening methods for Down syndrome or trisomy 18 and for euploid fetuses at high risk for adverse outcomes.

Obstetric and neonatal outcomes in apparently isolated mild fetal ventriculomegaly

AIMS AND METHODS

To determine obstetrical and neonatal outcomes in referrals of apparently isolated mild ventriculomegaly following routine ultrasound scan, over the period 2001-2003. Specialist ultrasound and other investigations were performed. Neonatal examination and postnatal ultrasound findings were collected and local neurodevelopmental follow-up was obtained.

RESULTS

30 cases of suspected isolated mild ventriculomegaly (posterior horn of lateral ventricle 10-15 mm at diagnosis) were identified. There were two abnormal karyotypes, no abnormal TORCH screens, and only one false-positive alloimmune thrombocytopenia screen. In 21 cases, isolated ventriculomegaly was confirmed following specialist investigation. In 11 of 21 cases, ventriculomegaly resolved during antenatal follow-up, and in one case it progressed. Six of 21 had ventriculomegaly confirmed on postnatal ultrasound and lissencephaly was diagnosed in one following postnatal MRI. Of the 11 infants with antenatal resolution of ventriculomegaly, 2 have delayed development. The infant with progressive ventriculomegaly has severe developmental problems.

Fetal cerebral ventriculomegaly: outcome in 176 cases

OBJECTIVE

To evaluate the outcome of fetuses affected by different degrees of ventriculomegaly.

METHODS

We studied 176 fetuses with ventriculomegaly and evaluated the pregnancy outcome and the neurodevelopmental outcome at age > or = 24 months. The population was divided into three groups according to ventricular width: A (mild ventriculomegaly, 10 to 12 mm); B (moderate, 12.1 to 14.9 mm) and C (severe, > or = 15 mm).

RESULTS

Ventriculomegaly was more often an isolated finding in Group A (44/75; 58.7%) than in Group B (10/41; 24.4%) and Group C (24/60; 40%). When the ventriculomegaly was an isolated finding, 97.7% of fetuses with mild, 80% with moderate and 33.3% of those with severe dilatation were alive at > or = 24 months. The neurodevelopmental outcome was normal in 93% of Group A, 75% of Group B and 62.5% of Group C.

CONCLUSIONS

Our results suggest that the definition of borderline ventriculomegaly should be limited to ventricular width below 12 mm. Cases with measurements above this value are more often associated with malformations and have a normal neurodevelopmental outcome less frequently.