Imaging of fetal cerebral ventriculomegaly: a guide to management and outcome

Antenatal imaging: A pictorial review

Today, in parallel with the use of imaging modalities increases in all fields, the use of imaging methods in pregnant women is increasing. Imaging has become an integral component of routine pregnancy follow-up. Imaging provides parents with an early opportunity to learn about the current situation, including prenatal detection of anomalies or diseases, etiology, prognosis, and the availability of prenatal or postnatal treatments. Various imaging modalities, especially ultrasonography, are frequently used for imaging both maternal and fetal imaging. The goal of this review was to address imaging modalities in terms of usefulness and safety, as well as to provide demonstrative examples for disorders. And this review provides current information on selecting a safe imaging modality to evaluate the pregnant and the fetus, the safety of contrast medium use, and summarizes major pathological situations with demonstrative sonographic images to assist radiologists and obstetricians in everyday practice.

Prenatal Ventriculomegaly - Diagnosis, Prognostication and Management

Fetal ventriculomegaly (VM) refers to the abnormal enlargement of one or more ventricles of the brain in-utero. The enlargement may or may not be related to ventricular obstruction and increased intracranial pressure; therefore, the term "hydrocephalus" is not used. VM is diagnosed usually in the mid-trimester when the atrial diameter (AD) of the lateral ventricle is more than 10 mm on one or both sides. A thorough workup is then required to identify the cause as the etiology is diverse. Fetal magnetic resonance imaging (MRI) may yield additional information. Serial ultrasound follow-up would be required to assess its progression with advancing gestation. The prognosis and long-term outcomes greatly depend upon the etiology, the severity at diagnosis, progression, and associations. This article reviews the definitions, diagnosis, and workup of fetal VM, discusses follow-up protocols and prognosis, and examines the role of fetal therapy, including fetoscopic surgery in its prenatal management.

Prenatal ventriculomegaly: natural course, survival, and neurodevelopmental status

OBJECTIVE

Prenatal ventriculomegaly is classified as mild, moderate, or severe based on the atrium diameter. The natural course and intrauterine progression of mild and moderate ventriculomegaly associated with the neurodevelopmental status of these children has been widely reported.

METHODS

One hundred twenty-two pregnancies with mild and moderate ventriculomegaly referred to the pediatric neurosurgery clinic of Children's Medical Center between 2010 and 2018 were retrospectively studied. The authors collected demographic and first and sequential ultrasonographic information, associated abnormalities, information about pregnancy outcomes, and the latest developmental status of these children according to Centers for Disease Control and Prevention criteria by calling parents at least 1 year after birth.

RESULTS

The mean gestational age at the time of diagnosis was 29.1 weeks, and 53% of fetuses were female. The width of the atrium was registered precisely in 106 cases, in which 61% had mild and 39% had moderate ventriculomegaly. Information on serial ultrasound scans was collected in 84 cases in which ventriculomegaly regressed in 5, remained stable in 67, and progressed in 12 patients. Fourteen cases (29.7%) in the mild ventriculomegaly group and 6 cases (16.2%) in the moderate group had associated abnormalities, with corpus callosum agenesis as the most frequent abnormality. The survival rate was 80% in mild and 89.4% in moderate ventriculomegaly. Considering survival to live birth and progression of the ventriculomegaly, the survival rate was 100% in regressed, 97% in stable, and 41.6% in progressed ventricular width groups (p < 0.001). Neurodevelopmental status was evaluated in 73 cases and found to be normal in 69.8% of the cases; 16.4% of children had mild delay, and 5.4% and 8.2% of cases were diagnosed with moderate and severe delays, respectively.

CONCLUSIONS

In spite of a high rate of missed data in our retrospective study, most patients with mild or moderate ventriculomegaly had a stable or regressed course. Most cases had near-normal developmental status. Prospective studies with a larger sample size and detailed developmental evaluation tests are needed to answer the questions related to the natural course, survival, and prognosis of prenatal ventriculomegaly.

Imaging diagnosis of ventriculomegaly: fetal, neonatal, and pediatric

Ventriculomegaly is the term used to describe abnormal enlargement of ventricles in the brain. Neuroimaging, whether it is by ultrasound, computed tomography, or magnetic resonance imaging, is the key to its identification and can help to diagnose its cause and guide management in many cases. The implementation of the imaging modalities and potential differential considerations varies from the fetus, infant, and pediatric patient. Here we discuss how the imaging modalities can be used in these patient populations and review some of the differential considerations.

Intracisternal BioGlue injection in the fetal lamb: a novel model for creation of obstructive congenital hydrocephalus without additional chemically induced neuroinflammation

OBJECTIVE

The authors hypothesized that new agents such as BioGlue would be as efficacious as kaolin in the induction of hydrocephalus in fetal sheep.

METHODS

This study was performed in 34 fetal lambs randomly divided into 2 studies. In the first study, fetuses received kaolin, BioGlue (2.0 mL), or Onyx injected into the cisterna magna, or no injection (control group) between E85 and E90. In the second study, fetuses received 2.0-mL or 2.5-mL injections of BioGlue into the cisterna magna between E85 and E90. Fetuses were monitored using ultrasound to assess lateral ventricle size and progression of hydrocephalus. The fetuses were delivered (E120-E125) and euthanized for histological analysis. Selected brain sections were stained for ionized calcium binding adaptor 1 (Iba1) and glial fibrillary acidic protein (GFAP) to assess the presence and activation of microglia and astroglia, respectively. Statistical comparisons were performed with Student's t-test for 2 determinations and ANOVA 1-way and 2-way repeated measures for multiple determinations.

RESULTS

At 30 days after injection, the lateral ventricles were larger in all 3 groups that had undergone injection than in controls (mean diameter in controls 3.76 ± 0.05 mm, n = 5). However, dilatation was greater in the fetuses injected with 2 mL of BioGlue (11.34 ± 4.76 mm, n = 11) than in those injected with kaolin (6.4 ± 0.98 mm, n = 7) or Onyx (5.7 ± 0.31 mm, n = 6) (ANOVA, *p ≤ 0.0001). Fetuses injected with 2.0 mL or 2.5 mL of BioGlue showed the same ventricle dilatation but it appeared earlier (at 10 days postinjection) in those injected with 2.5 mL. The critical threshold of ventricle dilatation was 0.1 for all the groups, and only the BioGlue 2.0 mL and BioGlue 2.5 mL groups exceeded this critical value (at 30 days and 18 days after injection, respectively) (ANOVA, *p ≤ 0.0001). Moderate to severe hydrocephalus with corpus callosum disruption was observed in all experimental groups. All experimental groups showed ventriculomegaly with significant microgliosis and astrogliosis in the subventricular zone around the lateral ventricles. Only kaolin resulted in significant microgliosis in the fourth ventricle area (ANOVA, *p ≤ 0.005).

CONCLUSIONS

The results of these studies demonstrate that BioGlue is more effective than Onyx or kaolin for inducing hydrocephalus in the fetal lamb and results in a volume-related response by obstructive space-occupancy without local neuroinflammatory reaction. This novel use of BioGlue generates a model with potential for new insights into hydrocephalus pathology and the development of therapeutics in obstructive hydrocephalus. In addition, this model allows for the study of acute and chronic obstructive hydrocephalus by using different BioGlue volumes for intracisternal injection.

Comparative study of intracisternal kaolin injection techniques to induce congenital hydrocephalus in fetal lamb

PURPOSE

Kaolin (aluminum silicate) has been used to generate hydrocephalus by direct cisterna magna injection in animal models. The aim of the present study is to compare which method of Kaolin injection into fetal cisterna magna is feasible, safer, and more effective to induce hydrocephalus in fetal lambs.

METHODS

Twenty-five well-dated pregnant ewes at gestational 85-90 days (E85-90) were used to compare three different kaolin injection puncture techniques into the fetal cisterna magna. Group 1, ultrasound guidance in a maternal percutaneous transabdominal (TA); group 2, without opening the uterus in a transuterine (TU) technique; group 3, by occipital direct access after exteriorizing fetal head (EFH); and group 4, control group, was normal fetal lambs without injection. The fetal lambs were assessed using lateral ventricle diameter ultrasonographic measurements prior the kaolin injection and on the subsequent days. We analyzed the effectivity, mortality, and fetal losses to determine the best technique to create hydrocephalus in fetal lamb.

RESULTS

After fetal intracisternal kaolin (2%, 1mL) injection, lateral ventricle diameters increased progressively in the three different interventional groups compared with the normal values of the control group (p ≤ 0.05). We observed that the transabdominal method had a 60% of fetal losses, considering failure of injection and mortality, compared with the 12.5% in the open group (EFH), and 0% for the transuterine group.

CONCLUSIONS

Based on our study, we believe that both, open uterine (EFH) and transuterine approaches are more effective and safer than the transabdominal ultrasound-guided method to induce hydrocephalus.

Lateral ventricular volume measurement by 3D MR hydrography in fetal ventriculomegaly and normal lateral ventricles

BACKGROUND

In fetuses with prenatal ventriculomegaly (VM), ventricular volume on MRI has been shown to correlate with poor postnatal outcomes and in utero death. 3D magnetic resonance hydrography (MRH) has been widely used for MR cholangiopancreatography.

PURPOSE

To investigate the reliability of 3D MRH for lateral ventricular volume measurement in fetuses with VM and normal lateral ventricles, using manual multisection planimetry (MSP) as a reference standard.

STUDY TYPE

Prospective study.

POPULATION

Thirty-five fetuses with VM at 24-37 gestational weeks (GA) and 35 fetuses with normal lateral ventricles at 24-38 GA.

FIELD STRENGTH/SEQUENCE

1.5T MRI with 3D MRH and T₂ -weighted single-shot fast-spin echo sequence.

ASSESSMENT

Left, right, and total lateral ventricle volumes in fetuses were acquired from 3D MRH and manual MSP. All image analysis was performed by a radiologist twice and another radiologist once, blindly.

STATISTICAL TESTS

Analysis of linear regression analysis, Pearson's correlation coefficient, Bland-Altman plots, intraclass correlation coefficient (ICC), and independent samples t-test were used for statistical analyses.

RESULTS

There were highly significant relationships between all 3D MRH and manual MSP measurements of lateral ventricular volumes (r_VM  = 0.92-0.98; r_N  = 0.95-0.98; all P < 0.0001; VM: VM group, N: normal group), although left, right, and total lateral ventricular volumes measured by 3D MRH tended to be slightly larger than MSP (bias_VM 0.1 ± 0.95, 0.26 ± 0.63, and 0.3 ± 0.68 mL, respectively; bias_N 0.1 ± 0.95, 0.26 ± 0.63, and 0.3 ± 0.68 mL, respectively). Interrater agreement and intrarater repeatability were also excellent for 3D MRH (ICC_VM  = 0.994-0.99, ICC_N  = 0.989-0.992; ICC_VM  = 0.975-0.987, ICC_N  = 0.958-0.971, respectively). 3D MRH showed significantly reduced measurement time (VM: 3.55 ± 0.42 vs. 11.81 ± 0.13 min; N: 3.08 ± 0.39 vs. 12.12 ± 0.11 min; all P < 0.0001).

DATA CONCLUSION

Lateral ventricular volume measurement by 3D MRH was comparable to manual MSP.

LEVEL OF EVIDENCE

1 Technical Efficacy Stage 1 J. Magn. Reson. Imaging 2017.

Post-mortem magnetic resonance (PMMR) imaging of the brain in fetuses and children with histopathological correlation

Post-mortem magnetic resonance (PMMR) imaging is rapidly emerging as an alternative, "less invasive", and more widely accepted investigative approach for perinatal deaths in the UK. PMMR has a high diagnostic accuracy for congenital and acquired fetal neuropathological anomalies compared to conventional autopsy, and is particularly useful when autopsy is non-diagnostic. The main objectives of this review are to describe and illustrate the range of common normal and abnormal central nervous system (CNS) findings encountered during PMMR investigation. This article covers the standard PMMR sequences used at our institution, normal physiological post-mortem findings, and a range of abnormal developmental and acquired conditions. The abnormal findings include diseases ranging from neural tube defects, posterior fossa malformations, those of forebrain and commissural development as well as neoplastic, haemorrhagic, and infectious aetiologies. Neuropathological findings at conventional autopsy accompany many of the conditions we describe, allowing readers to better understand the underlying disease processes and imaging appearances.

Fetal Brain Anomalies Associated with Ventriculomegaly or Asymmetry: An MRI-Based Study

BACKGROUND AND PURPOSE

Fetal lateral ventriculomegaly is a relatively common finding with much debate over its clinical significance. The purpose of this study was to examine the association between ventriculomegaly and asymmetry and concomitant CNS findings as seen in fetal brain MR imaging.

MATERIALS AND METHODS

Fetal brain MR imaging performed for various indications, including ventriculomegaly, with or without additional ultrasound findings, was assessed for possible inclusion. Two hundred seventy-eight cases found to have at least 1 lateral ventricle with a width of ≥10 mm were included in the study. Ventriculomegaly was considered mild if the measurement was 10-11.9 mm; moderate if, 12-14.9 mm; and severe if, ≥15 mm. Asymmetry was defined as a difference of ≥2 mm between the 2 lateral ventricles. Fetal brain MR imaging findings were classified according to severity by predefined categories.

RESULTS

The risk of CNS findings appears to be strongly related to the width of the ventricle (OR, 1.38; 95% CI, 1.08-1.76; P = .009). The prevalence of associated CNS abnormalities was significantly higher (P = .005) in symmetric ventriculomegaly compared with asymmetric ventriculomegaly (38.8% versus 24.2%, respectively, for all CNS abnormalities and 20% versus 7.1%, respectively, for major CNS abnormalities).

CONCLUSIONS

In this study, we demonstrate that the rate of minor and major findings increased with each millimeter increase in ventricle width and that the presence of symmetric ventricles in mild and moderate ventriculomegaly was a prognostic indicator for CNS abnormalities.

Choroid plexus separation in fetuses without ventriculomegaly: Natural course and postnatal outcome

PURPOSE

To evaluate fetuses with choroid plexus separation without ventriculomegaly in terms of fetal malformations, behavior of the separation during follow-up, and postnatal outcome.

METHODS

In total, 172 fetuses with choroid plexus separation without ventriculomegaly were included in this prospective study. Fetal sonography was performed at 2- to 4-week intervals, and detailed physical and neurologic examinations were performed after their delivery. Fetuses were categorized into normal and abnormal subgroups according to the outcome.

RESULTS

Sixteen fetuses (9.3%) were included in the abnormal-outcome group and 156 fetuses (90.7%) were included in the normal-outcome group. Both the initial mean lateral ventricular diameter (9.3 mm versus 8.6 mm) and the initial mean choroid plexus separation (4.8 mm versus 3.3 mm) were greater in the abnormal group than in the normal group (p < 0.001 for both comparisons). We found that 4.0 mm was the best cutoff point of choroid plexus separation to detect a major anomaly, with 87.5% sensitivity and 93.6% specificity.

CONCLUSIONS

Choroid plexus separation without ventriculomegaly often resolves within the third trimester and does not affect postnatal outcome. It can be associated with various fetal malformations; however, with a comprehensive examination, all fetal malformations can be detected prenatally. Follow-up sonography studies would be useful, especially in the case of suspected corpus callosum agenesis.

Patterns of increases in interleukin-6 and C-reactive protein as predictors for white matter injury in preterm infants

BACKGROUND

The aim of this study was to determine whether patterns of increases in serum interleukin-6 (IL-6) and C-reactive protein (CRP) levels at birth were associated with the development of white matter injury (WMI) in preterm infants with a fetal inflammatory response (FIR).

METHODS

One hundred infants who were born at <32 weeks gestation and had funisitis, as determined by histological evidence of FIR, were studied. Infants were divided into four groups according to IL-6 and CRP levels at birth, with cut-off values of 200 pg/mL and 0.4 mg/dL, respectively. We compared the incidence of WMI, determined by MRI at term-equivalent age, among these groups.

RESULTS

The number of infants in each group was 12, 43, 0, and 45 in the high IL-6 and high CRP (HH) group, high IL-6 and low CRP (HL) group, low IL-6 and high CRP (LH) group, and low IL-6 and low CRP (LL) group, respectively. The incidence of WMI was significantly higher in the HH group than in the HL group and LL group (83%, 40%, and 34%, respectively). Multiple logistic regression analysis revealed that a combined elevation in IL-6 and CRP levels was an independent predictor for the development of WMI (odds ratio, 8.3).

CONCLUSION

A combined elevation in serum IL-6 and CRP levels at birth was associated with the development of WMI in preterm infants with FIR.

Perinatal characteristics of fetuses with borderline ventriculomegaly detected by routine ultrasonographic screening of low-risk populations

AIM

Fetal borderline ventriculomegaly represents a frequent dilemma in perinatal management. The present study aimed to evaluate the clinical significance of fetal borderline ventriculomegaly in a low-risk Japanese population and to identify the risk factors for associated anomalies.

METHODS

Data of cases of fetal borderline ventriculomegaly detected at 26-28 weeks of gestation by routine ultrasonographic screening of low-risk singleton pregnancies between 2006 and 2012 were retrospectively collected. Ventricular width, in utero progression, associated anomalies, chromosomal abnormalities, and perinatal and postnatal outcomes were assessed. The ventricular width, in utero progression and other perinatal characteristics were compared between the isolated and non-isolated groups.

RESULTS

Among the total 6020 singleton low-risk pregnancies, we noted that 42 had borderline ventriculomegaly. Six (14%) of these cases had other defects by subsequent detailed examination. Ventriculomegaly resolved or regressed in 35 (83%) and progressed in four (10%) cases, of which three were associated with other anomalies. The median ventricular width was 12.8 mm (range, 10.0-14.7) in the six non-isolated cases and 10.5 mm (range, 10.0-13.3) in the 36 isolated cases; the differences were statistically significant. A ventricular width of 12 mm or more and in utero progression were more frequently observed in non-isolated cases than in isolated cases.

CONCLUSION

Fetal borderline ventriculomegaly frequently resolves in utero. A ventricular diameter of more than 12 mm and in utero progression are risk factors for additional anomalies. After the initial diagnosis of borderline ventriculomegaly, the pregnancy should be carefully followed up to determine whether the ventricle size is resolved, remains stable or increases.

MRI: is there a role in obstetrics?

Magnetic resonance imaging has a complementary role in obstetrical imaging to ultrasound (US). Although US has advantages as an initial imaging technique, there are significant numbers of patients who cannot be adequately evaluated for a variety of reasons including calvarial calcification, oligoanhydramnios, or simply obesity. MR can provide additional information that cannot be obtained by US and is invaluable in central nervous system anomaly evaluation, airway management, and planning for postnatal intervention. Newer techniques established in the postnatal population such as spectroscopy, diffusion-weighted imaging, and functional imaging have future applications in the fetus.

Ultrafast MRI of the fetus: an increasingly important tool in prenatal diagnosis of congenital anomalies

OBJECTIVE

To demonstrate the additional utility of ultrafast magnetic resonance imaging (MRI) of the fetus in the evaluation of sonographically detected or equivocal fetal congenital anomalies.

MATERIAL AND METHODS

Twenty five pregnant women with ultrasound detected fetal congenital anomalies underwent ultrafast fetal MRI.

RESULTS

MRI findings altered the diagnosis of two cases of giant arachnoid cyst and sizable interhemispheric cyst associated with agenesis of the corpus callosum. MRI added additional findings of occult spinal diastematomyelia in two out of four cases of Chiari/meningocele malformation. MRI revealed impaired sulcation and unilateral cleft palate in suspected case of Walker-Warburg syndrome. In the remaining 18 cases MRI confirmed the diagnosis of Meckel-Gruber syndrome in three cases, hydronephrosis in six cases, cerebral ventriculomegaly in five cases, isolated omphalocele in three cases and findings suggestive of aneuploidy in the last case.

CONCLUSION

Ultrasound is the screening method of choice for evaluation of the fetus. Ultrafast MRI is a complementary adjunctive modality with excellent tissue contrast that can image the fetus in multiple planes and add information in sonographically detected or equivocal congenital anomalies that may be significant to establish definitive accurate diagnosis and hence adequate management and counseling.

Central nervous system congenital malformations in a developing country: issues and challenges against their prevention

BACKGROUND

Little efforts are geared towards prevention of CNS anomalies in the developing countries.

METHODS

A 1-year prospective cross-sectional analysis of the cases of CNS congenital anomalies seen in a Nigerian neurosurgical unit. This included both the children's and parents' sociodemographics, the profiles of the CNS anomalies, and the maternal obstetric health behaviors toward primary and/or secondary prevention of the anomalies. Statistical analysis was done with the Pearson's chi-square (or Fishers' exact) test. Level of significance set at P < 0.05.

RESULTS

There were 54 cases of cranial and spinal gross CNS anomalies, including 32 neural tube defects; two thirds of the parents were low-income earners, and half had only basic education. Thirty percent of the pregnancies were unbooked; the mean gestational age (GA) at booking and commencement of obstetric micronutrient supplementation was 4.6 months. No case had periconceptional folic acid supplementation. Obstetric ultrasonography was performed late in pregnancy (mean GA 6 months), made positive diagnosis of CNS anomaly in only 14%, and was performed mainly in unsupervised private clinic settings in 98%.

CONCLUSIONS

Little or no attention is currently paid to the prevention of CNS congenital anomalies in much of the low- and middle-income countries of the world. There is a great need to regulate the practice of obstetric ultrasonography in Nigeria. There is even a much greater, more fiercely urgent need to ensure periconceptional folic acid supplementation for all women of childbearing age through appropriate food fortification in these societies.

A prospective study of fetuses with isolated ventriculomegaly investigated by antenatal sonography and in utero MR imaging

BACKGROUND AND PURPOSE

Fetal ventriculomegaly (VM) is important because of its high prevalence and high risk of association with other brain abnormalities. The purpose of this article was to investigate the hypotheses that including in utero MR imaging (iuMR) in the diagnostic pathway for fetuses with isolated VM on antenatal imaging will show other brain abnormalities in a high proportion of cases and that these will have a significant effect on clinical management.

MATERIALS AND METHODS

One hundred forty-seven pregnant women were recruited prospectively from 8 fetomaternal centers in Britain. All of the fetuses had VM diagnosed on sonography but no other abnormality. iuMR was performed, and the results of the examinations were compared with those of sonography. Two fetomaternal experts made independent assessments of the effects of any new diagnoses on clinical management.

RESULTS

Categoric assessments of ventricular size were the same in approximately 90% of fetuses. Other abnormalities were shown in 17% of fetuses. The most frequent additional brain abnormality shown on iuMR was agenesis of the corpus callosum. Severe VM was associated with an approximately 10-fold increase in the risk of another brain abnormality being present when compared with fetuses with mild VM. The most profound effects on clinical management, however, were found in cases of mild VM.

CONCLUSIONS

This work supports our hypotheses by showing a high detection rate of other brain pathology when iuMR was used to supplement antenatal sonography (17%). In a high proportion of cases, the detection of the extra pathology would have led to significant changes in clinical management.

Correlation between ventriculomegaly on prenatal magnetic resonance imaging and the need for postnatal ventricular shunt placement

OBJECT

Pediatric neurosurgeons are increasingly called on to provide prognostic data regarding the antenatal diagnosis of ventriculomegaly. This study was designed to determine if there is a correlation between prenatal MR imaging results and the need for ventricular shunt placement during the neonatal period.

METHODS

The authors retrospectively reviewed the prenatal MR imaging data of 38 consecutive patients who had been referred for neurosurgical consultation following the diagnosis of ventriculomegaly. The outcome measure was placement of a ventricular shunt. Assessed parameters included prenatal atrial diameter (AD), gestational age at MR imaging, time between imaging studies, presence of concomitant CNS anomalies, laterality of ventriculomegaly, fetal sex, and temporal evolution of ventriculomegaly. Logistic regression analysis was completed with the calculation of appropriate ORs and 95% CIs.

RESULTS

Six patients (16%) required shunt placement, all with an AD > or = 20 mm (mean 23.8 mm) at the time of imaging. Eight patients had presented with an AD > or = 20 mm. Atrial diameter was the only presenting feature that correlated with shunt placement (OR 1.58, 95% CI 1.10-2.25, p = 0.01). Logistic regression analysis revealed no statistical correlation between the need for ventricular shunting and gestational age at MR imaging, time between imaging studies, fetal sex, presence of additional CNS anomalies, and laterality of the ventriculomegaly.

CONCLUSIONS

When assessed using MR imaging, an AD > or = 20 mm at any gestational age is highly associated with the need for postnatal shunting. Patients with concomitant CNS anomalies did not require shunts at a greater rate than those with isolated ventriculomegaly. Further studies are required to assess the long-term outcome of this patient population.

Foetal brain imaging: ultrasound or MRI. A comparison between magnetic resonance imaging and a dedicated multidisciplinary neurosonographic opinion

OBJECTIVES

(i) To compare original foetal brain ultrasound findings with a multidisciplinary expert opinion; (ii) to compare the multidisciplinary expert ultrasound opinion with foetal magnetic resonance imaging (MRI) findings and (iii) to determine in which circumstances foetal MRI gives additional information, and in how many cases management is changed by having information from MRI.

STUDY DESIGN

Ultrasound scans of 51 consecutive foetuses where foetal brain MR had been performed were retrospectively reviewed by a panel consisting of maternal-foetal-medicine (MFM) consultants, a geneticist, neonatologists and MFM subspecialty trainees. The original ultrasound opinion was compared with the multidisciplinary opinion, which was then compared with MRI findings. In the cases where MRI gave additional information, an assessment was made as to whether this changed management.

RESULTS

The multidisciplinary ultrasound opinion differed from the original opinion in 9 of 51 (17%) cases. In 19 patients (37%), the MRI gave additional information to the original ultrasound, in 7 (13%) cases, management, and in 7 (13%) cases, counselling was altered by additional information gained from MRI. The multidisciplinary ultrasound and MRI diagnoses were similar in 36 cases (71%).

CONCLUSION

Multidisciplinary review of an apparently abnormal foetal brain ultrasound can provide additional diagnostic information. When compared with this level of ultrasound expertise, MRI gave additional information in 29% of cases, but only resulted in change in management in about 13%.

Reference ranges for fetal ventricular width: a non-normal approach

OBJECTIVES

Normal ranges for fetal cerebral ventricular width are usually based on parametric methods, which define cut-off values based on means and standard deviations. We aimed to construct reference charts based on a large sample and using a method that better fits with skewed measurements.

METHODS

In November 2001-December 2005, a single operator, who was unaware of the subsequent analysis, performed prospectively and routinely fetal cerebral ventricular width measurements. We used the LMS method (which summarizes the changing distribution of a variable of interest according to a covariate (gestational age) using three curves representing the median (M), the coefficient of variation (S) and skewness (L)) to describe the distribution of measurements with gestational age. The LMS method provides a general method for fitting smooth centile curves to reference data. It utilizes the power transformation family of Box and Cox to allow the skewness of the measurement distribution, as well as the median and variability, to vary with age. The theoretical proportion of fetal ventricular widths > or = 10 mm based on the LMS method and on methods based on the assumption of normality were compared with the actual proportion using binomial tests. The influence on ventricular size of gestational age and fetal gender and presentation was assessed using robust regression methods.

RESULTS

Included in the study were 4769 ventricular measurements, 42 (0.88%) of which were > or = 10 mm. The LMS method allowed us to fit the skewness of the measurements and identified slight changes throughout gestation. The actual proportion of measurements > or = 10 mm was not different from that expected according to the LMS method (0.88% vs. 1%, P = 0.25), whereas it was significantly different from that based on the classical normal approximation (0.88% vs. 0.4%, P < 0.0001). There was a significant difference with gender (males: + 0.29 +/- 0.042 mm as compared to females, P < 0.0001), but there was no difference with fetal presentation (P = 0.4).

CONCLUSION

We present new reference values for fetal ventricular width based on the LMS method. A fixed cut-off value of 10 mm identifies around 1% of the population throughout gestation, which is more than that calculated in previous studies.

Fetal magnetic resonance imaging: a review

PURPOSE OF REVIEW

To describe advances in magnetic resonance technology and the current indications and advantages of magnetic resonance imaging that have led to increased utilization in fetal medicine.

RECENT FINDINGS

The article covers the most common uses of magnetic resonance imaging in fetal medicine. The advantages of magnetic resonance imaging for the diagnosis of fetal malformations are described, in particular the advantages of magnetic resonance imaging in central nervous system malformations not optimally diagnosed by ultrasound are described. These cases include malformations of migration, malformations of development, such as agenesis of the corpus callosum, and destructive lesions. Noncentral nervous system lesions include chest abnormalities, abdominal wall defects, gastrointestinal and genitourinary abnormalities and fetal neoplasms. Abnormalities of placentation and other maternal factors affecting pregnancy are shown.

SUMMARY

Recent studies have shown that magnetic resonance imaging can add significantly to the prenatal diagnosis and management of congenital abnormalities. In addition, placental abnormalities have been diagnosed with greater accuracy.

Third-trimester fetal MRI in isolated 10- to 12-mm ventriculomegaly: is it worth it?

OBJECTIVE

The justification for magnetic resonance imaging (MRI) in isolated mild ventriculomegaly remains controversial. This study was undertaken to evaluate the contribution of third-trimester MRI in isolated 10- to 12-mm fetal ventriculomegaly.

DESIGN

Observational prospective cohort study.

SETTING

Universitary prenatal reference centre.

POPULATION

From February 2000 to May 2005, we prospectively collected data concerning fetuses referred to us for cerebral MRI following detection of ventriculomegaly by ultrasound scan (n= 310).

METHODS

Among these, we identified and analysed those cases in which ventriculomegaly was isolated and did not exceed 12 mm in ultrasound examinations prior to MRI scan (n= 185).

MAIN OUTCOME MEASURE

Cases in which MRI provided additional information that was likely to have an impact on prenatal management were detailed.

RESULTS

During the study period, 310 MRI were performed because of fetal ventriculomegaly. Hundred and eighty-five were suspected to be isolated 10- to 12-mm ventriculomegalies in ultrasound scan and formed our database. MRI confirmed the 10- to 12-mm isolated fetal ventriculomegaly in 106 cases (57.3%) and found other abnormalities in 5 (4.7%) of these 106 cases. MRI found ventricular measurement to be less than 10 mm in 43 cases (23.3%) and more than 12 mm in 36 cases (19.4%). Among these 36 fetuses with ventricle size more than 12 mm, 6 (16.7%) had other abnormalities, whereas MRI did not find other abnormalities in the 43 cases with ventricle size below 10 mm.

CONCLUSION

Before advantages of MRI to ultrasound examination can be demonstrated, it seems reasonable that MRI should remain an investigational tool, restricted to selected clinical situations in which the results are expected to modify case management. Where ultrasound scan suspects isolated ventriculomegaly of 10 to 12 mm, our data suggest that when the finding is confirmed with MRI this could be expected in around 5% of cases. Therefore, the policy of routine MRI in such cases should depend on prenatal centres' priorities.