Fetal cerebral imaging - ultrasound vs. MRI: an update

PDFF-CNN: An attention-guided dynamic multi-orientation feature fusion method for gestational age prediction on imbalanced fetal brain MRI dataset

BACKGROUND

Fetal brain magnetic resonance imaging (MRI)-based gestational age prediction has been widely used to characterize normal fetal brain development and diagnose congenital brain malformations.

PURPOSE

The uncertainty of fetal position and external interference leads to variable localization and direction of the fetal brain. In addition, pregnant women typically concentrate on receiving MRI scans during the fetal anomaly scanning week, leading to an imbalanced distribution of fetal brain MRI data. The above-mentioned problems pose great challenges for deep learning-based fetal brain MRI gestational age prediction.

METHODS

In this study, a pyramid squeeze attention (PSA)-guided dynamic feature fusion CNN (PDFF-CNN) is proposed to robustly predict gestational ages from fetal brain MRI images on an imbalanced dataset. PDFF-CNN contains four components: transformation module, feature extraction module, dynamic feature fusion module, and balanced mean square error (MSE) loss. The transformation and feature extraction modules are employed by using the PSA to learn multiscale and multi-orientation feature representations in a parallel weight-sharing Siamese network. The dynamic feature fusion module automatically learns the weights of feature vectors generated in the feature extraction module to dynamically fuse multiscale and multi-orientation brain sulci and gyri features. Considering the fact of the imbalanced dataset, the balanced MSE loss is used to mitigate the negative impact of imbalanced data distribution on gestational age prediction performance.

RESULTS

Evaluated on an imbalanced fetal brain MRI dataset of 1327 routine clinical T2-weighted MRI images from 157 subjects, PDFF-CNN achieved promising gestational age prediction performance with an overall mean absolute error of 0.848 weeks and anR 2 $R^2$ of 0.904. Furthermore, the attention activation maps of PDFF-CNN were derived, which revealed regional features that contributed to gestational age prediction at each gestational stage.

CONCLUSIONS

These results suggest that the proposed PDFF-CNN might have broad clinical applicability in guiding treatment interventions and delivery planning, which has the potential to be helpful with prenatal diagnosis.

Agreement between Fetal Brain Ultrasonography and Magnetic Resonance Imaging in the Measurements of the Corpus Callosum and Transverse Cerebellar Diameter

As the use of magnetic resonance imaging of the fetal brain has evolved, the need to understand its efficiency in the biometry of the fetal brain has broadened. This study aimed to assess the level of agreement and correlation between the two cardinal imaging methods of fetal neuroimaging, ultrasonography (US) and magnetic resonance imaging (MRI), by measuring the corpus callosum (CC) and transverse cerebellar diameter (TCD) in terms of length and percentile. Measurements of CC and TCD length and percentile were documented over a 7-year span in a tertiary referral medical center. All US and MRI examinations were performed in the customary planes and subcategorized by valid reference charts. Exclusion and inclusion criteria were set before the collection and processing of the data. A total of 156 fetuses out of 483 were included in the study. A positive, strong correlation and agreement were found (r = 0.78; ICC = 0.76) between US and MRI in TCD measurements. For CC length measurement, a moderate correlation and moderate agreement (r = 0.51; ICC = 0.49) between US and MRI was observed. TCD and CC percentiles had lower levels of correlation and agreement compared with the length variables. Our study indicates good agreement between MRI and US in the assessment of TCD measurement as a part of antenatal neuroimaging. Furthermore, while the two techniques are not always compatible, they are complementary methods.

Transcranial Doppler Ultrasonography detection on cerebral infarction and blood vessels to evaluate hypoxic ischemic encephalopathy modeling

BACKGROUND

This study aimed to observe changes of rats' brain infarction and blood vessels during neonatal hypoxic ischemic encephalopathy (NHIE) modeling by Transcranial Doppler Ultrasonography (TCD) so as to assess the feasibility of TCD in evaluating NHIE modeling.

METHODS

Postnatal 7-days (d)-old Sprague Dawley (SD) rats were divided into the Sham group, hypoxic-ischemic (HI) group, and hypoxia (H) group. Rats in the HI group and H group were subjected to hypoxia-1 hour (h), 1.5 h and 2.5 h, respectively. Evaluation on brain lesion was made based on Zea-Longa scores, hematoxylin-eosin (HE) staining and Nissl staining. The brain infarction and blood vessels of rats were monitored and analyzed under TCD. Correlation analysis was applied to reveal the connection between hypoxic duration and infarct size detected by TCD or Nissl staining.

RESULTS

In H and HI modeling, longer duration of hypoxia was associated with higher Zea-Longa scores and more severe nerve damage. On the 1 d after modeling, necrosis was found in SD rats' brain indicated by HE and Nissl staining, which was aggravated as hypoxic duration prolonged. Alteration of brain structures and blood vessels of SD rats was displayed in Sham, HI and H rats under TCD. TCD images for coronal section revealed that brain infarct was detected at the cortex and there was marked cerebrovascular back-flow of HI rats regardless of hypoxic duration. On the 7 d after modeling, similar infarct was detected under TCD at the cortex of HI rats in hypoxia-1 h, 1.5 h and 2.5 h groups, whereas the morphological changes were deteriorated with longer hypoxic time. Correlation analysis revealed positive correlation of hypoxic duration with infarct size detected by histological detection and TCD.

CONCLUSIONS

TCD dynamically monitored cerebral infarction after NHIE modeling, which will be potentially served as a useful auxiliary method for future animal experimental modeling evaluation in the case of less animal sacrifice.

Prenatal diagnosis of pontocerebellar hypoplasia with postnatal follow-up

OBJECTIVE

To describe the MR features enabling prenatal diagnosis of pontocerebellar hypoplasia (PCH).

METHOD

This was a retrospective single monocentre study. The inclusion criteria were decreased cerebellar biometry on dedicated neurosonography and available fetal Magnetic Resonance Imaging (MRI) with PCH diagnosis later confirmed either genetically or clinically on post-natal MRI or by autopsy. The exclusion criteria were non-available MRI and sonographic features suggestive of a known genetic or other pathologic diagnosis. The collected data were biometric or morphological imaging parameters, clinical outcome, termination of pregnancy (TOP), pathological findings and genetic analysis (karyotyping, chromosomal microarray, DNA sequencing targeted or exome). PCH was classified as classic, non-classic, chromosomal, or unknown type.

RESULTS

Forty-two fetuses were diagnosed with PCH, of which 27 were referred for decreased transverse cerebellar diameter at screening ultrasound. Neurosonography and fetal MRI were performed at a mean gestational age of 29 + 4 and 31 + 0 weeks, respectively. Termination of pregnancy occurred. Pregnancy was terminated in 24 cases. Neuropathological examination confirmed the diagnosis in 24 cases and genetic testing identified abnormalities in 29 cases (28 families, 14 chromosomal anomaly). Classic PCH is associated with pontine atrophy and small MR measurements decreasing with advancing gestation.

CONCLUSION

This is the first large series of prenatally diagnosed PCHs. Our study shows the essential contribution of fetal MRI to the prenatal diagnosis of PCH. Classic PCHs are particularly severe and are associated with certain MR features.

Toxoplasma gondii Infection in Pregnancy - Recommendations of the Working Group on Obstetrics and Prenatal Medicine (AGG - Section on Maternal Disorders)

Aim The AGG (Working Group for Obstetrics and Prenatal Diagnostics, Section Maternal Diseases) has issued these recommendations to improve the detection and management of Toxoplasma gondii infection in pregnancy. Methods Members of the Task Force developed the recommendations and statements presented here using recently published literature. The recommendations were adopted after a consensus process by members of the working group. Recommendations This article focuses on the epidemiology and pathophysiology of Toxoplasma gondii infection in pregnancy and includes recommendations for maternal and fetal diagnosis, transmission prophylaxis, therapy, prevention, screening, and peripartum management.

Spectrum of brain malformations in fetuses with mild tubulinopathy

OBJECTIVE

To report on a large cohort of fetuses with mild forms of tubulinopathy and to define prenatal ultrasound and magnetic resonance imaging (MRI) features that can facilitate prenatal diagnosis.

METHODS

This was a retrospective multicenter study of fetuses diagnosed between January 2007 and February 2022 with a mild tubulinopathy (without lissencephaly or microlissencephaly). We collected and reviewed brain imaging and genetic data, and defined major criteria as findings observed in ≥ 70% of the patients and minor criteria as those observed in ≥ 50% but < 70% of the patients.

RESULTS

Our cohort included 34 fetuses. The mean gestational age at ultrasound screening, when suspicion of a central nervous system anomaly was first raised, was 24.2 (range, 17-33) weeks. Callosal anomalies (n = 19 (56%)) and abnormal ventricles (n = 18 (53%)) were the main reasons for referral. The mean gestational age at neurosonography was 28.3 (range, 23-34) weeks and that at MRI was 30.2 (range, 24-35) weeks. Major ultrasound criteria were midline distortion, ventricular asymmetry, dysmorphic and/or dilated frontal horn(s) and abnormal sulcation. Minor ultrasound criteria were distortion of the cavum septi pellucidi, abnormal corpus callosum, absent or asymmetric olfactory sulci, ventriculomegaly and basal ganglia dysmorphism. Major MRI criteria were midline distortion, distortion of the cavum septi pellucidi, ventricular asymmetry, dilatation (generally unilateral) and/or distortion, dysmorphic and/or dilated frontal horn(s) and abnormal sulcation (mainly dysgyria). Minor MRI criteria were absent or asymmetric olfactory sulci, abnormal bulge of the pons, anteroposterior diameter of the pons ≤ 5th centile and brainstem asymmetry. A mutation was found in TUBB3 (44.1% of cases), TUBB (23.5%), TUBB2B (14.7%) or TUBA1A (17.6%). The mutation was inherited from a parent in 18/34 cases. The pregnancy was terminated in 23/34 cases.

CONCLUSIONS

Prenatal diagnosis of mild forms of tubulinopathy is possible but challenging. We have defined, in this large series of fetuses, major and minor criteria that can help identify this entity in utero. Most findings can be visualized on ultrasound. This evaluation is also important for prenatal counseling. Once a prenatal diagnosis of mild tubulinopathy is suspected, the family members should be referred for exome sequencing and MRI. © 2022 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Effective Approaches to Fetal Brain Segmentation in MRI and Gestational Age Estimation by Utilizing a Multiview Deep Inception Residual Network and Radiomics

To completely comprehend neurodevelopment in healthy and congenitally abnormal fetuses, quantitative analysis of the human fetal brain is essential. This analysis requires the use of automatic multi-tissue fetal brain segmentation techniques. This paper proposes an end-to-end automatic yet effective method for a multi-tissue fetal brain segmentation model called IRMMNET. It includes a inception residual encoder block (EB) and a dense spatial attention (DSAM) block, which facilitate the extraction of multi-scale fetal-brain-tissue-relevant information from multi-view MRI images, enhance the feature reuse, and substantially reduce the number of parameters of the segmentation model. Additionally, we propose three methods for predicting gestational age (GA)-GA prediction by using a 3D autoencoder, GA prediction using radiomics features, and GA prediction using the IRMMNET segmentation model's encoder. Our experiments were performed on a dataset of 80 pathological and non-pathological magnetic resonance fetal brain volume reconstructions across a range of gestational ages (20 to 33 weeks) that were manually segmented into seven different tissue categories. The results showed that the proposed fetal brain segmentation model achieved a Dice score of 0.791±0.18, outperforming the state-of-the-art methods. The radiomics-based GA prediction methods achieved the best results (RMSE: 1.42). We also demonstrated the generalization capabilities of the proposed methods for tasks such as head and neck tumor segmentation and the prediction of patients' survival days.

Fetal MRI Neuroradiology: Indications

Fetal MRI is a safe, noninvasive examination of the fetus and placenta, a complement to ultrasonography. MRI provides detailed CNS evaluation, including depicting parenchymal architecture and posterior fossa morphology, and is key in prenatal assessment of spinal dysraphism, neck masses, and ventriculomegaly. Fetal MRI is typically performed after 22 weeks gestation, and ultrafast T1 and T2-weighted MRI sequences are the core of the exam, with advanced sequences such as diffusion weighted imaging used for specific questions. The fetal brain grows and develops rapidly, and familiarity with gestational age specific norms is essential to MRI interpretation.

Contribution of fetal magnetic resonance imaging in the evaluation of neurosonographically detected cases of isolated mild and moderate cerebral ventriculomegaly

AIM

This study aimed to present the contribution of prenatal magnetic resonance imaging (MRI) in the diagnosis of fetuses that were previously identified as isolated mild and moderate cerebral ventriculomegaly (VM) by ultrasound (US).

METHODS

The data between February 2013 and August 2020 were collected for women who were diagnosed with isolated mild or moderate fetal VM by US and subsequently underwent a fetal MRI.

RESULTS

Among 321 women, 21 (6.5%) had a clinically important additional finding after MRI. Twelve of 276 (4.3%) fetuses with mild VM and 9 of 45 (20%) with moderate VM had turned out to have additional central nervous system abnormalities. Additional findings were detected more in fetuses with moderate VM, mothers with an anterior-located placenta, and mothers with higher body mass indexes (BMIs) with statistical significance (p = 0.001, p = 0.013, p = 0.036, respectively). The most common additional MRI finding was grade 3 or 4 germinal matrix hemorrhage, which was detected in 11 of 21 fetuses (52.3%).

CONCLUSIONS

Considering the countries' health policies, prenatal MRI would contribute mostly to the diagnosis of fetuses with moderate VM, pregnancies with anterior-located placenta, and mothers with high BMIs. According to our data, we believe that MRI will be valuable, especially in the diagnosis of grade 3 and 4 intracranial hemorrhage group.

Quantification of Intracranial Structures Volume in Fetuses Using 3-D Volumetric MRI: Normal Values at 19 to 37 Weeks' Gestation

Objective

The purpose of this study is to establish a reference of intracranial structure volumes in normal fetuses ranging from 19 to 37 weeks' gestation (mean 27 weeks).

Materials and Methods

A retrospective analysis of 188 MRI examinations (1.5 T) of fetuses with a normal brain appearance (19–37 gestational weeks) from January 2018 to December 2021 was included in this study. Three dimensional (3-D) volumetric parameters from slice-to-volume reconstructed (SVR) images, such as total brain volume (TBV), cortical gray matter volume (GMV), subcortical brain tissue volume (SBV), intracranial cavity volume (ICV), lateral ventricles volume (VV), cerebellum volume (CBV), brainstem volume (BM), and extra-cerebrospinal fluid volume (e-CSFV), were quantified by manual segmentation from two experts. The mean, SD, minimum, maximum, median, and 25th and 75th quartiles for intracranial structures volume were calculated per gestational week. A linear regression analysis was used to determine the gestational weekly age-related change adjusted for sex. A t-test was used to compare the mean TBV and ICV values to previously reported values at each gestational week. The formulas to calculate intracranial structures volume derived from our data were created using a regression model. In addition, we compared the predicted mean TBV values derived by our formula with the expected mean TBV predicted by the previously reported Jarvis' formula at each time point. For intracranial volumes, the intraclass correlation coefficient (ICC) was calculated to convey association within and between observers.

Results

The intracranial volume data are shown in graphs and tabular summaries. The male fetuses had significantly larger VV compared with female fetuses (p = 0.01). Measured mean ICV values at 19 weeks are significantly different from those published in the literature (p &lt; 0.05). Means were compared with the expected TBV generated by the previously reported formula, showing statistically differences at 22, 26, 29, and 30 weeks' gestational age (GA) (all p &lt; 0.05). A comparison between our data-derived formula and the previously reported formula for TBV showed very similar values at every GA. The predicted TBV means derived from the previously reported formula were all within the 95% confidence interval (CI) of the predicted means of this study. Intra- and inter-observer agreement was high, with an intraclass correlation coefficient larger than 0.98.

Conclusion

We have shown that the intracranial structural volume of the fetal brain can be reliably quantified using 3-D volumetric MRI with a high degree of reproducibility and reinforces the existing data with more robust data in the earlier second and third stages of pregnancy.

Fetal brain imaging: A comparison between fetal ultrasonography and intra uterine magnetic resonance imaging (a systematic review and meta-analysis)

OBJECTIVE

The aim of this study was to compare ultrasound (US) and intra uterine MRI (IUMRI) of the brain in the diagnosis of fetal brain abnormalities.

METHODS

The present systematic review is done based on guidelines for preferred reporting items for systematic reviews and meta-analysis. All major articles comparing fetal US with IUMRI in fetuses with suspected brain abnormalities were qualified. Articles published before 2010 were excluded from the study. An I²  > 20% was considered as a sign of significant change. The statistical analysis was done using STATA -15 and Meta-Disk 1.4 applications.

RESULTS

Five articles were considered for meta-analysis. The sensitivity of US and IUMRI in diagnosing fetal abnormalities were 86% and 95%, respectively. The corresponding rates for specificity were 77% and 80%. IUMRI and US were concordant in 72.5% (95% CI: 68%-77%) of diagnoses. However, IUMRI added information in 21.7% of cases, while US added value was only 1.48.

CONCLUSION

Our results approved the good diagnostic performance of both US and IUMRI in confirming fetal brain normal development and emphasized that US is an appropriate screening technique in pregnancy. In cases of detected abnormalities in US, IUMRI is suggested as it was the most accurate imaging method and added information about the diagnosis in 22.2% of cases.

Reference biometry of foetal brain by prenatal MRI and the distribution of measurements in foetuses with ventricular septal defect

OBJECTIVE

To provide the reference biometric measurements of the normal foetal brain by prenatal MRI and describe the distribution of measurements in the foetuses with ventricular septal defect (VSD).

METHODS

This retrospective study analysed the biometric measurements of 218 foetuses between 18 - 37 gestational weeks with normal MRI findings from July 2014 to August 2019, as well as 18 foetuses with VSD. The measurements included fronto-occipital diameter (FOD), biparietal diameter (BPD), and transverse cerebellar diameter (TCD). All the prenatal MRI examinations have been taken on the same 1.5 T MR unit with a standard protocol of the foetal brain. All the linear measurements of the foetal brain were obtained on the T2-weighted imaging. The distribution of measurements in 18 foetuses with VSD was plotted on centile curves.

RESULTS

The reference data were presented in mean, standard deviation, 95% predicted confidence intervals, and the 3rd, 10th, 25th, 50th, 75th, 90th, 97th centiles at each gestational age. The value of TCD in 56% (10/18 cases) foetuses with VSD was lower than the 3rd centile, and the rate for FOD and BPD was 33% (6/18 cases) and 22% (4/18 cases) separately. On the curves, most VSD cases with measurements lower than the 3rd centile were in relatively early gestational stage (≤28 weeks).

CONCLUSIONS

We have presented reference linear biometry of the foetal brain by prenatal MRI from 18 to 37 gestational weeks, which could help us to interpret and monitor the brain development for foetuses with VSD and other congenital heart diseases.Key messages:We have presented reference linear biometry of the foetal brain by prenatal MRI from 18 to 37 gestational weeks in multiple statistical methods: mean and standard deviation; 95% predicted confidence intervals and the 3rd, 10th, 25th, 50th, 75th, 90th, 97th centiles.Our data showed that the involvement of the brain in VSD may be not globally, but regionally, and the cerebellum may be more possible to be involved.We speculated that the earlier the VSD diagnosed the worse the brain involved, which might suggest a poor outcome and necessary follow-up.

A practical approach to prenatal diagnosis of malformations of cortical development

Malformations of cortical development (MCD) can frequently be diagnosed at multi-disciplinary Fetal Neurology clinics with the aid of multiplanar neurosonography and MRI. The patients are usually referred following prenatal sonographic screening that raises the suspicion of a possible underlying MCD. These indirect findings include, but are not limited to, ventriculomegaly (lateral ventricles larger than 10 mm), asymmetric ventricles, commissural anomalies, absent cavum septum pellucidum, cerebellar vermian and/or hemispheric anomalies, abnormal head circumference (microcephaly or macrocephaly), multiple CNS malformations, and associated systemic defects. The aim of this paper is to suggest a practical approach to prenatal diagnosis of malformations of cortical development utilizing dedicated neurosonography and MRI, based on the current literature and our own experience. We suggest that an MCD should be suspected in utero when the following intracranial imaging signs are present: abnormal development of the Sylvian fissure; delayed achievement of cortical milestones, premature appearance of sulcation; irregular ventricular borders, abnormal cortical thickness (thick, thin); abnormal shape and orientation of the sulci and gyri; irregular, abnormal, asymmetric, and enlarged hemisphere; simplified cortex; non continuous cortex or cleft; and intraparenchymal echogenic nodules. Following the putative diagnosis of fetal MCD by neurosonography and MRI, when appropriate and possible (depending on gestational age), the imaging diagnosis is supplemented by genetic studies (CMA and trio whole exome sequencing). In some instances, no further studies are required during pregnancy due to the clear dire prognosis and then the genetic evaluation can be deferred after delivery or termination of pregnancy (in countries where allowed).

Prenatal Imaging Features and Postnatal Outcome of Short Corpus Callosum: A Series of 42 Cases

OBJECTIVES

Our goal was to provide a better understanding of isolated short corpus callosum (SCC) regarding prenatal diagnosis and postnatal outcome.

METHODS

We retrospectively reviewed prenatal and postnatal imaging, clinical, and biological data from 42 cases with isolated SCC.

RESULTS

Prenatal imaging showed SCC in all cases (n = 42). SCC was limited to rostrum and/or genu and/or splenium in 21 cases, involved body in 16 cases, and was more extensive in 5 cases. Indirect imaging features included typical buffalo horn ventricles (n = 14), septal dysmorphism (n = 14), parallel lateral ventricles (n = 12), and ventriculomegaly (n = 4), as well as atypical features in 5 cases. SCC was associated with interhemispheric cysts and pericallosal lipomas in 3 and 6 cases, respectively. Aneuploidy was found in 2 cases. Normal psychomotor development, mild developmental disorders, and global developmental delay were found in 70, 15, and 15% of our cases, respectively.

CONCLUSIONS

SCC should be investigated to look for pericallosal lipoma and typical versus atypical indirect features of corpus callosum agenesis (CCA). Prenatal counselling should be guided by imaging as well as clinical and genetic context. Outcome of patients with SCC was similar to the one presenting with complete CCA.

Association of gestational age with MRI-based biometrics of brain development in fetuses

Background

Reported date of last menstrual period and ultrasonography measurements are the most commonly used methods for determining gestational age in antenatal life. However, the mother cannot always determine the last menstrual period with certainty, and ultrasonography measurements are accurate only in the first trimester. We aimed to assess the ability of various biometric measurements on magnetic resonance imaging (MRI) in determining the accurate gestational age of an individual fetus in the second half of gestation.

Methods

We used MRI to scan a total of 637 fetuses ranging in age from 22 to 40 gestational weeks. We evaluated 9 standard fetal 2D biometric parameters, and regression models were fitted to assess normal fetal brain development. A stepwise linear regression model was constructed to predict gestational age, and measurement accuracy was determined in a held-out, unseen test sample (n = 49).

Results

A second-order polynomial regression model was found to be the best descriptor of biometric measures including brain bi-parietal diameter, head circumference, and fronto-occipital diameter in relation to normal fetal growth. Normal fetuses showed divergent growth patterns for the cerebrum and cerebellum, where the cerebrum undergoes rapid growth in the second trimester, while the cerebellum undergoes rapid growth in the third trimester. Moreover, a linear model based on biometrics of brain bi-parietal diameter, length of the corpus callosum, vermis area, transverse cerebellar diameter, and cerebellar area accurately predicted gestational age in the second and third trimesters (cross-validation R² = 0.822, p < 0.001).

Conclusions

These results support the use of MRI biometry charts to improve MRI evaluation of fetal growth and suggest that MRI biometry measurements offer a potential estimation model of fetal gestational age in the second half of gestation, which is vital to any assessment of pregnancy, fetal development, and neonatal care.

Magnetic resonance imaging of the fetal central nervous system: Timing and consistency between pre- and postnatal diagnoses

INTRODUCTION

It has been shown that a proper comparison of prenatal ultrasound and magnetic resonance imaging (MRI) is possible only in the case of a short interval between tests. However, it is worth noting that the reference test is a postnatal examination. The aim of our study was to evaluate the effect of time between prenatal MRI (pMRI) and postnatal examinations on the consistency of diagnoses.

MATERIAL AND METHODS

The prospective observational study was carried out between 2014 and 2017 at the Department of Obstetrics and Perinatology of Krakow University Hospital. In total, 60 patients with fetuses suspected of central nervous system (CNS) defects were included in the study group. PMRI examinations were conducted in the third trimester of pregnancy.

RESULTS

The median gestational age of pMRI was 35 weeks and median of the time interval between carrying out pre- and postnatal test was 34.5 days. In the group of nonconcordant diagnoses, the interval was longer. The analysis did not show a statistically significant relationship between consistency of diagnoses and timing of pMRI. The median time of pregnancy at which pMRI was performed was similar in both groups. A prolongation of the interval between examinations reduced the probability of consistency of diagnoses.

CONCLUSIONS

The number of inaccurate results increased with the prolongation of the interval between pre- and postnatal tests.

KEY MESSAGE

Prolongation of the interval between pre- and postnatal increases number of inaccurate results.

Ultrasound features of fetal toxoplasmosis: A contemporary multicenter survey in 88 fetuses

OBJECTIVE

To describe the lesions detected by prenatal ultrasound examination in congenital toxoplasmosis (CT).

METHODS

We retrospectively analyzed all cases of fetal infection with Toxoplasma gondii with ultrasound anomalies described by fetal medicine experts in 2009 to 2019 in 30 French centers.

RESULTS

Eighty-eight cases of CT were included. Forty-five (51.1%) had one or more cerebral signs only, 35 (39.8%) had cerebral plus extracerebral signs and 8 (9.1%) had extracerebral signs only. The main cerebral signs were intracranial hyperechogenic nodular foci (n = 60) of which 20 were isolated, ventriculomegalies (n = 44) which generally increased during follow-up, and periventricular abscesses (n = 12). The main extracerebral signs were hepatomegaly and/or splenomegaly (n = 14), small for gestational age (n = 14), ascites (n = 14, including 2 with hydrops), and hyperechogenic bowel (n = 11). Maternal infection occurred mostly in the first or second trimester (81 cases), periconceptionally in one and in the third trimester in six cases. The first ultrasound signs were detected after a median of 7 weeks (range: 1.4; 24.0) following maternal toxoplasmosis seroconversion.

CONCLUSION

While no sign was specific of CT, there were typical associations of cerebral signs with or without extracerebral signs. Detailed ultrasound examination could improve prognostic evaluation, as well as diagnosis of CT in settings lacking serological screening.

Antenatal diagnosis of absence of septum pellucidum

The absence of septum pellucidum (ASP) is a rare disease, which affects the structure of the brain. It is either isolated or associated with various congenital brain malformations. The diagnosis of ASP can be performed by second-trimester ultrasound. When the ASP is isolated, prenatal counseling is optimistic regarding neurological outcome, but there is a 20% risk of septo-optic dysplasia in the neonate.

The prevalence and the adding value of fetal MRI imaging in midline cerebral anomalies

Background

Foetal MR imaging is widely accepted as an adjunct to foetal ultrasonography; however, there are many controversies regarding its importance and indications. Therefore, this study aimed to evaluate foetuses with different midline cerebral abnormalities, to determine the prevalence of these anomalies, to define the role of foetal MRI, and to compare MRI and ultrasound (US) result with postnatal MRI findings. Seventy-eight pregnant women who had foetuses with CNS abnormalities detected by sonogram were included. Foetuses with midline anomalies were selected and evaluated by anomaly scan foetal US, pre- and postnatal MRI.

Results

Midline brain anomalies were found in 47.4% of foetuses with brain anomalies. Holoprosencephaly was found in 24.3% of midline anomaly foetuses, corpus callosum abnormalities (ACC) were detected in 40.5%, midline intracranial mass lesions in 2.7%, and midline posterior fossa anomalies in 32.4%. An agreement between MRI and US in the main diagnosis was in 56.76% of cases; MRI added information to US findings in 43.2% of cases, and US added information to MRI findings in 8.1% of cases.

Conclusion

In evaluating midline cerebral anomalies, US and MRI are complementary techniques. US is the primary survey, and MRI can add additional information and/or change the main diagnosis.

"He looks gorgeous" - iuMR images and the transforming of foetal and parental identities

The MERIDIAN study examined whether in-utero MRI (iuMRI) improves the accuracy of diagnosis of foetal brain abnormalities, when used as an adjunct to ultrasound anomaly scanning. A diagnostic iuMRI differs from routine ultrasound screening because of its infrequent use and scanning procedure. Nested within this trial, this sociological study explored the acceptability of iuMRI as a technology and its contribution to parental decision-making. Our sociological interpretation of the role of iuMR images in prenatal diagnosis draws on narrative interviews with women (and some partners) who underwent MRI imaging at three different centres. Overall, participants found iuMRI helpful in decision-making because it either confirmed or disconfirmed previous results, or provided additional information. Expectant couples experienced the iuMR imaging process as informative, but also as having emotive and practical value. Our paper extends the existing sociological literature on antenatal testing and visualising the foetus, by using iuMR diagnostic imaging to further explore the concept of the unborn entity. Our data suggest that alongside the iuMR images, the 'parental gaze' and accompanying commentary are used by parents to construct and transform foetal and parental identities despite ongoing uncertainties about, and shifting social contexts to their pregnancy.

MRI for Fetal Developmental Brain Abnormalities: Perspectives From the Pregnant Patient

Ultrasound is routinely used as a prenatal screening and diagnostic tool but has limitations. Some anomalies in the developing fetal brain can be difficult to detect, and in utero magnetic resonance imaging (iuMRI) is increasingly used as an adjunct to ultrasound. However, understandings of patient perspectives of iuMRI technology are still developing. Our qualitative study of 41 mothers who experienced iuMRI was embedded in a diagnostic accuracy trial and aimed to inform policy recommendations that might stem from the clinical findings. Our analysis suggests that iuMRI is seen as useful, offering valuable additional information and helping women make decisions about care options at a difficult time. However, patients' experiences demonstrated the uncertainty and anxiety associated with the prenatal diagnosis (PND) process relating to brain anomalies including the challenges of their embodied contributions. Our findings suggest more could be done to reduce the impact on pregnant women during an already difficult, anxious period.

Prenatal imaging findings in fetal Zika virus infection

PURPOSE OF REVIEW

The aim of this review is to report the most recent observations concerning intrauterine Zika virus (ZIKV) infection and associated neuroimaging.

RECENT FINDINGS

ZIKV outbreak in Brazil in 2015 was associated with an impressive registration of cases of congenital microcephaly in women with symptoms suggestive of ZIKV infection. Clinical and laboratory testing for ZIKV and hypothetic etiopathogenetic mechanisms are described. Diagnostic tests on blood, urine and amniotic fluid should be performed in all mothers with symptoms suggestive of intrauterine ZIKV infection. ZIKV causes multiple teratogenic malformations, mainly affecting the developing brain.

SUMMARY

Neuroimaging investigation contributes to the prenatal detection of microcephaly and other brain abnormalities in cases of intrauterine ZIKV infection. Neuroimaging is based antenatally on two-dimensional and three-dimensional ultrasound and fetal MRI, whereas computed tomography scan is performed postnatally. Although neuropathology associated with intrauterine ZIKV infection is characterized by nonspecific findings of brain disorder, reduced cortical gyration and white-matter hypomyelination or dysmyelination and cerebellar hypoplasia have been consistently observed in the majority of fetuses and newborns. Prenatal or postnatal genetic workup should be carried out to exclude cases of primary microcephaly. Follow-up should rely upon MRI and computed tomography scan as well as neuropediatrician to better define developmental outcome in survivors.

MRI and US in the evaluation of fetal anomalies: The need to work together

PURPOSE

Real-time virtual sonography (RVS) is a new technique that synchronizes real-time ultrasonography (US) and multiplanar reconstructed magnetic resonance imaging (MRI). The purpose of this study was to evaluate the feasibility and ability of RVS to assess the main pathologies in fetuses with suspected US anomalies.

METHOD AND MATERIALS

Real-time virtual sonography (Hitachi, HI VISION Ascendus) was offered to 30 patients who had undergone fetal MRI. The acquired MRI image dataset was loaded into the fusion system and displayed together with the real-time US image. The ability of RVS to assess the main anatomical sites and fetal anomalies was evaluated.

RESULTS

Real-time virtual sonography was technically possible in all cases. From a total of 30 patients, RVS helped the diagnosis in 10 cases. In 15 cases of encephalic pathology, fusion imaging improved the accuracy of the diagnosis; in the other 5 cases, MRI was superior to US even when using the RVS.

CONCLUSION

This is a study on the feasibility and practical use of RVS. Thanks to information from both US and MRI, RVS allowed better identification of the fetal pathologies and improved the performance of the ultrasound examination. In our experience, it was really helpful in pathologies that would benefit from US follow-up.

Contemporary Modalities to Image the Fetal Brain

Fetal brain ultrasound remains as the mainstay for screening fetal intracranial anatomy. One of its main advantages is the availability of 3 dimensional and other ultrasound modalities for a better understanding of fetal neurodevelopment. Neurosonography is performed when findings, suggestive of an abnormality, are present on a screening ultrasound or if a high-risk situation of brain injury is present. This technique offers the use of complementary imaging planes, axial, coronal and sagittal, and the ability to image intracranial anatomy from the transabdominal and transvaginal approaches. Fetal brain magnetic resonance imaging is more sensitive than ultrasound. As an adjunctive imaging modality, magnetic resonance imaging offers additional sequences to complete the information on neurodevelopment from different perspectives, such as brain metabolism, microstructure, and connectivity.

Texture analysis of the developing human brain using customization of a knowledge-based system

Background: Pattern recognition software originally designed for geospatial and other technical applications could be trained by physicians and used as texture-analysis tools for evidence-based practice, in order to improve diagnostic imaging examination during pregnancy.Methods: Various machine-learning techniques and customized datasets were assessed for training of an integrable knowledge-based system (KBS), to determine a hypothetical methodology for texture classification of closely-related anatomical structures in fetal brain magnetic resonance (MR) images. Samples were manually categorized according to the magnetic field of the MRI scanner (i.e. 1.5-tesla (1.5T), 3-tesla (3T)), rotational planes (i.e. coronal, sagittal and axial), and signal weighting (i.e. spin-lattice, spin-spin, relaxation, proton density). In the machine-learning sessions, the operator manually selected relevant regions of interest (ROI) in 1.5/3T MR images. Semi-automatic procedures in MaZda/B11 were performed to determine optimal parameter sets for ROI classification. Four classes were defined: ventricles, thalamus, grey matter, and white matter. Various textures analysis methods were tested. The KBS performed automatic data pre-processing and semi-automatic classification of ROIs.Results: After testing 3456 ROIs, statistical binary classification revealed that combination of reduction techniques with linear discriminant algorithms (LDA) or nonlinear discriminant algorithms (NDA) yielded the best scoring in terms of sensitivity (both 100%, 95% CI: 99.79-100), specificity (both 100%, 95% CI: 99.79-100) and Fisher coefficient (≈E+4, ≈E+5, respectively). Conclusions: LDA and NDA in MaZda can be useful data mining tools for screening a population of interest subjected to a clinical test.

Prenatal Diagnosis of Subependymal Hemorrhage

Fetal intracranial hemorrhage is a rare sonographic finding. Due to the subtle and variable nature of hemorrhage on sonography, prenatal diagnosis of intracranial hemorrhage is difficult. Subependymal hemorrhage of the germinal matrix is the least severe form of intracranial hemorrhage. Knowledge of the sonographic appearances of intracranial hemorrhage can make prenatal diagnosis possible and is essential to protecting the neurodevelopmental outcome of the fetus.

Volumetric MRI study of the intrauterine growth restriction fetal brain

OBJECTIVES

Intrauterine growth restriction (IUGR) is a pathologic fetal condition known to affect the fetal brain regionally and associated with future neurodevelopmental abnormalities. This study employed MRI to assess in utero regional brain volume changes in IUGR fetuses compared to controls.

METHODS

Retrospectively, using MRI images of fetuses at 30-34 weeks gestational age, a total of 8 brain regions-supratentorial brain and cavity, cerebral hemispheres, temporal lobes and cerebellum-were measured for volume in 13 fetuses with IUGR due to placental insufficiency and in 21 controls. Volumes and their ratios were assessed for difference using regression models. Reliability was assessed by intraclass correlation coefficients (ICC) between two observers.

RESULTS

In both groups, all structures increase in absolute volume during that gestation period, and the rate of cerebellar growth is higher compared to that of supratentorial structures. All structures' absolute volumes were significantly smaller for the IUGR group. Cerebellar to supratentorial ratios were found to be significantly smaller (P < 0.05) for IUGR compared to controls. No other significant ratio differences were found. ICC showed excellent agreement.

CONCLUSIONS

The cerebellar to supratentorial volume ratio is affected in IUGR fetuses. Additional research is needed to assess this as a radiologic marker in relation to long-term outcome.

KEY POINTS

• IUGR is a pathologic fetal condition affecting the brain • IUGR is associated with long-term neurodevelopmental abnormalities; fetal characterization is needed • This study aimed to evaluate regional brain volume differences in IUGR • Cerebellar to supratentorial volume ratios were smaller in IUGR fetuses • This finding may play a role in long-term development of IUGR fetuses.

Malformations of Cortical Development: From Postnatal to Fetal Imaging

Abnormal fetal corticogenesis results in malformations of cortical development (MCD). Abnormal cell proliferation leads to microcephaly or megalencephaly, incomplete neuronal migration results in heterotopia and lissencephaly, neuronal overmigration manifests as cobblestone malformations, and anomalous postmigrational cortical organization is responsible for polymicrogyria and focal cortical dysplasias. MCD comprises various congenital brain disorders, caused by different genetic, infectious, or vascular etiologies and is associated with significant neurological morbidity. Although MCD are rarely diagnosed prenatally, both dedicated multiplanar neurosonography and magnetic resonance imaging enable good demonstration of fetal cortical development. The imaging signs of fetal MCD are: delayed or absent cerebral sulcation; premature abnormal sulci; thin and irregular hemispheric parenchyma; wide abnormal overdeveloped gyri; wide opening of isolated sulci; nodular bulging into the lateral ventricles; cortical clefts; intraparenchymal echogenic nodules; and cortical thickening. The postnatal and prenatal imaging features of four main malformations of cortical development—lissencephaly, cobblestone malformations, periventricular nodular heterotopia, and polymicrogyria—are described.

Prenatal brain MRI of fetuses with Zika virus infection

BACKGROUND

An outbreak of Zika virus was observed in French Polynesia in 2013-2014. Maternal Zika virus infection has been associated with fetal microcephaly and severe cerebral damage.

OBJECTIVE

To analyze the MRI cerebral findings in fetuses with intrauterine Zika virus infection.

MATERIALS AND METHODS

We retrospectively analyzed prospectively collected data. Inclusion criteria comprised cases with (1) estimated conception date between June 2013 and May 2014, (2) available US and MRI scans revealing severe fetal brain lesions and (3) positive polymerase chain reaction for Zika virus in the amniotic fluid. We recorded pregnancy history of Zika virus infection and analyzed US and MRI scans.

RESULTS

Three out of 12 cases of severe cerebral lesions fulfilled all inclusion criteria. History of maternal Zika virus infection had been documented in two cases. Calcifications and ventriculomegaly were present at US in all cases. MRI showed micrencephaly (n = 3), low cerebellar biometry (n = 2), occipital subependymal pseudocysts (n = 2), polymicrogyria with laminar necrosis and opercular dysplasia (n = 3), absent (n = 1) or hypoplastic (n = 1) corpus callosum and hypoplastic brainstem (n = 1).

CONCLUSION

Severe cerebral damage was observed in our series, with indirect findings suggesting that the germinal matrix is the principal target for Zika virus. The lesions are very similar to severe forms of congenital cytomegalovirus and lymphocytic choriomeningitis virus infections.

Region-specific reductions in brain apparent diffusion coefficient in cytomegalovirus-infected fetuses

OBJECTIVE

To evaluate the effects of cytomegalovirus (CMV) infection on apparent diffusion coefficient (ADC) values of the fetal brain in utero.

METHODS

In this retrospective analysis we compared 58 fetal head magnetic resonance imaging (fhMRI) scans of PCR-verified CMV-infected fetuses, obtained in 2008-2012, with those of a normal control group of 36 gestational age (GA)-matched uninfected fetuses scanned between 2006 and 2012. Estimated GA at infection ranged from 1 to 32 weeks, and fhMRI was performed at 24 to 38 weeks. The frontal, parietal, temporal and occipital lobes (mainly white matter), basal ganglia, thalamus, pons and cerebellum were analyzed by assessing ADC values. Two pregnancies were terminated and postmortem confirmation was available in these cases.

RESULTS

ADC values of CMV-infected fetuses correlated significantly and negatively with GA in all brain regions except the basal ganglia. The cerebellum had the greatest reduction (r = -0.52, P < 0.0001). Maternal age correlated positively with ADC in the frontal lobe (P < 0.05). GA at infection and overt pathological changes did not affect ADC significantly. Compared with non-infected fetuses, ADC values of affected fetuses were significantly reduced in the frontal (P < 0.0001), parietal (P < 0.0001), occipital (P = 0.0005) and temporal (P = 0.001) lobes and thalamus (P = 0.006).

CONCLUSION

CMV infection of the fetal brain results in a highly significant, region-dependent reduction of ADC values in the frontal, parietal, occipital and temporal lobes and thalamus, probably reflecting hypercellularity and inclusion bodies in damaged areas. Further studies are needed to determine if reduction in ADC values may serve as a prognostic factor in CMV-infected fetuses. Copyright © 2014 ISUOG. Published by John Wiley & Sons Ltd.

Overcoming foetal motion using interactive real-time magnetic resonance imaging

OBJECTIVE

Foetal MRI has become an established image modality in the prenatal diagnosis of CNS anomalies, but image quality can be severely affected by foetal movements. The objective was to overcome these inherent motion problems by applying interactive real-time MRI and to evaluate the diagnostic usefulness of the applied real-time MRI sequence in relation to standard protocols.

METHODS

Ten healthy foetuses (gestation week 21·3 ± 0·5) were scanned using a system, which allowed visual feedback and interactive slice positioning in real time. The data were compared to a control group of 14 healthy foetuses (gestation week 21·0 ± 0·8) who had previously been scanned using standard MRI. Comparisons were carried out by two radiologists with regard to cerebral anthropometric sizes, presence of important brain structures, degree of movement, clinical image value, image quality and ability to obtain correct slice planes.

RESULTS

Two out of eight anthropometric sizes were statistically different between the two groups. Representation of cerebral structures was found in 70-100% in the real-time group. No statistically differences were found in clinical image value and image quality. The mean ability to obtain optimal slice planes was higher in the real-time group, but it was not significant.

CONCLUSION

Imaging of the foetal brain using the proposed interactive real-time MRI system is a promising alternative to traditional foetal MRI for anthropometrics or as a supplement for the representation of foetal brain structures in cases in which foetal motion causes challenges in relation to obtaining optimal slice planes using conventional MRI techniques.

Ultrasound diagnosis of bilateral cataracts in a fetus with possible cerebro-ocular congential muscular dystrophy during the routine second trimester anomaly scan

The finding of bilateral congenital cataracts in the fetus is rare. We report bilateral congenital cataracts detected during the routine second trimester anomaly scan, which subsequently were found to be associated with other congenital anomalies and the parents opted for a termination of pregnancy. At post-mortem, Muscle-Eye Brain disease or Walker-Warburg Syndrome was considered likely, which are autosomal recessive congenital muscular dystrophy disorders associated with cerebral, cerebellar, muscle and eye anomalies. On ultrasound, bilateral cataracts appear as echogenic, solid areas within the fetal orbits. The examination of the fetal face and orbits plays an important role in confirming fetal well-being antenatally. We propose that it should become a routine part of the structural survey of fetal anatomy during the obstetric anomaly scan. This is especially important in pregnancies previously affected by fetal cataracts or pregnancies at risk of rare genetic syndromes.

Normal fetal posterior fossa in MR imaging: new biometric data and possible clinical significance

BACKGROUND AND PURPOSE

Posterior fossa malformations are a common finding in prenatal diagnosis. The objectives of this study are to re-evaluate existing normal MR imaging biometric data of the fetal posterior fossa, suggest and evaluate new parameters, and demonstrate the possible clinical applications of these data.

MATERIALS AND METHODS

This was a retrospective review of 215 fetal MR imaging examinations with normal findings and 5 examinations of fetuses with a suspected pathologic posterior fossa. Six previously reported parameters and 8 new parameters were measured. Three new parameter ratios were calculated. Interobserver agreement was calculated by using the intraclass correlation coefficient.

RESULTS

For measuring each structure, 151-211 MR imaging examinations were selected, resulting in a normal biometry curve according to gestational age for each parameter. Analysis of the ratio parameters showed that vermian lobe ratio and cerebellar hemisphere ratio remain constant with gestational age and that the vermis-to-cisterna magna ratio varies with gestational age. Measurements of the 5 pathologic fetuses are presented on the normal curves. Interobserver agreement was excellent, with the intraclass correlation coefficients of most parameters above 0.9 and only 2 parameters below 0.8.

CONCLUSIONS

The biometry curves derived from new and existing biometric data and presented in this study may expand and deepen the biometry we use today, while keeping it simple and repeatable. By applying these extensive biometric data on suspected abnormal cases, diagnoses may be confirmed, better classified, or completely altered.

Role of magnetic resonance imaging in the prenatal diagnosis of gastrointestinal fetal anomalies

PURPOSE

This study was done to evaluate the role of fetal magnetic resonance imaging (MRI) in the study of gastrointestinal malformations in comparison to prenatal ultrasound (US).

MATERIALS AND METHODS

A prospective (2010-2012) study of 38 fetal MRI scans was performed on 38 fetuses between 24 and 38 weeks of gestation. All the fetuses had a US diagnosis of gastrointestinal anomalies. T2-weighted HASTE, T1-weighted fast gradient echo, TrueFISP and diffusion-weighted images of the fetal abdomen were obtained on a 1.5-Tesla magnet. All fetal MRI diagnoses were compared with postnatal US findings, autopsy or surgical reports.

RESULTS

Fetal MRI was able to confirm the sonographic findings in nine of 38 fetuses (23.7%), to provide additional information in 23 of 38 fetuses (60.6%), to exclude the US diagnosis in five cases (5.2%) and to change it in two cases (5.2%). It was not able to characterize a case of gastric duplication and a case of abdominal cystic lymphangioma (5.2%).

CONCLUSIONS

Fetal MRI can be used as a complementary imaging modality to US in prenatal evaluation of gastrointestinal anomalies and can be considered a valuable tool not only for confirming or excluding but also for providing additional information to fetal ultrasonographic findings.

The Gini coefficient: a methodological pilot study to assess fetal brain development employing postmortem diffusion MRI

BACKGROUND

Diffusion-weighted imaging (DWI) is important in the assessment of fetal brain development. However, it is clinically challenging and time-consuming to prepare neuromorphological examinations to assess real brain age and to detect abnormalities.

OBJECTIVE

To demonstrate that the Gini coefficient can be a simple, intuitive parameter for modelling fetal brain development.

MATERIALS AND METHODS

Postmortem fetal specimens(n = 28) were evaluated by diffusion-weighted imaging (DWI) on a 3-T MRI scanner using 60 directions, 0.7-mm isotropic voxels and b-values of 0, 150, 1,600 s/mm(2). Constrained spherical deconvolution (CSD) was used as the local diffusion model. Fractional anisotropy (FA), apparent diffusion coefficient (ADC) and complexity (CX) maps were generated. CX was defined as a novel diffusion metric. On the basis of those three parameters, the Gini coefficient was calculated.

RESULTS

Study of fetal brain development in postmortem specimens was feasible using DWI. The Gini coefficient could be calculated for the combination of the three diffusion parameters. This multidimensional Gini coefficient correlated well with age (Adjusted R(2) = 0.59) between the ages of 17 and 26 gestational weeks.

CONCLUSIONS

We propose a new method that uses an economics concept, the Gini coefficient, to describe the whole brain with one simple and intuitive measure, which can be used to assess the brain's developmental state.

The Reliability of Fetal MRI in the Assessment of Brain Malformations

Objectives: To assess the inter- and intraobserver reliability of different fetal MRI measurements in cases of fetal brain malformations and to examine the concordance between ultrasonography (US) and MRI findings. Methods: Fetal brain MRIs and US findings of 56 pregnant women were retrieved from the institutional database. Standardized fetal brain MRI measurements were performed by 4 observers, and the inter- and intraobserver reliability was determined. Additionally, US and MRI findings were retrospectively compared. Results: The interobserver intraclass correlation coefficient (ICC) was above 0.9 for the cerebellum and posterior horn of the lateral ventricle. The measurements regarding the third ventricle (0.50), the fourth ventricle (0.58), and the corpus callosum (0.63) showed poor reliability. Overall, the intraobserver reliability was greater than the interobserver reliability. US and MRI findings were discordant in 29% of the cases with MRI rendering an extended diagnosis in 18%, a change of diagnosis in 3.6%, and excluding pathological findings suspected on US in 7.1%. Conclusions: Fetal MRI is a valuable complement to US in the investigation of fetal brain malformations. The reliability of most parameters was high, except for the measurements of the third and fourth ventricles and the corpus callosum.

Main congenital cerebral anomalies: how prenatal imaging aids counseling

The purpose of this article is to discuss some common cerebral lesions that may be detected during prenatal screening: corpus callosum dysgenesis, absent septum pellucidum, localized parenchymal ischemic-hemorrhagic lesions, megacisterna magna, Blake's pouch cyst, posterior fossa arachnoid cyst and Dandy-Walker malformation. For each cerebral defect, the main imaging findings are reminded, certain differential diagnoses are discussed and prenatal diagnostic accuracy is analyzed with emphasis on uncertainties encountered during analysis of ultrasound or magnetic resonance images. Detecting cerebral lesions in fetuses requires rapid counseling by neuropediatricians. Keeping in mind that the prenatal diagnostic accuracy is not 100%, the neuropediatricians have to answer the parents' questions regarding the outcome of the unborn child as well as the risk of recurrence for future pregnancies. This article is based on the authors' large experience in both prenatal imaging and neurocounseling. The frequently asked questions are set up. Answers are provided, underscoring the importance of an appropriate description of the cerebral defect, and therefore the pivotal role of prenatal imaging. However, prenatal neurocounseling remains challenging and the parents must be aware of uncertainties regarding both diagnostic accuracy and prognostic evaluation.

[Fetal MRI and ultrasound of congenital CNS anomalies]

In the last decade the newest technologies, fetal magnetic resonance imaging (MRI) and 3D ultrasound, have given an insight into the minute structures of the fetal brain. However, without knowledge of the basic developmental processes the imaging is futile. Knowledge of fetal neuroanatomy corresponding to the gestational week is necessary in order to recognize pathological structures. Furthermore, a modern neuroradiologist should be acquainted with the three steps in the formation of the cerebral cortex: proliferation, migration and differentiation of neurons in order to be in a position to suspect that there is a pathology and start recognizing and discovering the abnormalities. The fetal MRI has become an important complementary method to ultrasound especially in cortical malformations when confirmation of the prenatal diagnosis is needed and additional pathologies need to be diagnosed. In this manner these two methods help in parental counseling and treatment planning.