Cerebral biometry in fetal magnetic resonance imaging: new reference data

Analysis of MRI brain biometrics in fetuses monitored for intra uterine growth restriction and their prognostic value: Results of a prospective multicenter study

OBJECTIVE

Show a prognostic value of brain changes in fetuses with intra uterine growth restriction (IUGR) on early neonatal outcome.

STUDY DESIGN

We prospectively recruited pregnant women whose fetuses presented fetal weight < 5th centile. A brain MRI was performed between 28 and 32 weeks of gestation (WG). Several brain biometrics were measured (as fronto-occipital diameter (FOD) and transverse cerebellar diameter (TCD)). Neonatal prognosis was evaluated according to a composite criterion.

RESULTS

Of the 78 patients included, 62 had a fetal brain MRI. The mean centile value of FOD was lower in the unfavorable outcome group (n = 9) compared to the favorable outcome group (n = 53) (24.5 ± 16.8 vs. 8.6 ± 13.2, p = 0.004). The ROC curve for predicting risk of unfavorable neonatal outcome based on FOD presented an area under the curve of 0.81 (95 % CI, [0.63---0.99]) and a threshold determined at the 3rd centile was associated with sensitivity of 0.78 and a specificity of 0.89. In multivariate analysis, a FOD less than the 3rd centile was significantly associated with an unfavorable neonatal risk. There also was a reduction in TCD (25.5 ± 21.5 vs. 10.4 ± 10.4, p = 0.03) in the unfavorable neonatal outcome group.

CONCLUSION

We found an association between a reduction in FOD and TCD in fetal MRIs conducted between 28 and 32 WG in fetuses monitored for IUGR with an unfavorable neonatal outcome. Our results suggest that these biometric changes could constitute markers of poor neonatal prognosis.

Outcome of partial agenesis of corpus callosum

BACKGROUND

The diagnosis of corpus callosum anomalies by prenatal ultrasound has improved over the last decade because of improved imaging techniques, scanning skills, and the routine implementation of transvaginal neurosonography.

OBJECTIVE

Our aim was to investigate all cases of incomplete agenesis of the corpus callosum and to report the sonographic characteristics, the associated anomalies, and the perinatal outcomes.

STUDY DESIGN

We performed a retrospective analysis of cases from January 2007 to December 2017 with corpus callosum anomalies, either referred for a second opinion or derived from the prenatal ultrasound screening program in a single tertiary referral center. Cases with complete agenesis were excluded from the analysis. Standardized investigation included a detailed fetal ultrasound including neurosonogram, fetal karyotyping (standard karyotype or array comparative genomic hybridization) and fetal magnetic resonance imaging. The pregnancy outcome was collected, and pathologic investigation in case of termination of the pregnancy or fetal or neonatal loss was compared with the prenatal findings. The pregnancy and fetal or neonatal outcomes were reported. The neurologic assessment was conducted by a pediatric neurologist using the Bayley Scales of Infant Development-II and the standardized Child Development Inventory when the Bayley investigation was unavailable.

RESULTS

Corpus callosum anomalies were diagnosed in 148 cases during the study period, 62 (41.9%) of which were excluded because of complete agenesis, and 86 fetuses had partial agenesis (58.1%). In 20 cases, partial agenesis (23.2%) was isolated, whereas 66 (76.7%) presented with different malformations among which 29 cases (43.9%) were only central nervous system lesions, 21 cases (31.8%) were non-central nervous system lesions, and 16 cases (24.3%) had a combination of central nervous system and non-central nervous system lesions. The mean gestational age at diagnosis for isolated and non-isolated cases was comparable (24.29 [standard deviation, 5.05] weeks and 24.71 [standard deviation, 5.35] weeks, respectively). Of the 86 pregnancies with partial agenesis, 46 patients opted for termination of the pregnancy. Neurologic follow-up data were available for 35 children. The overall neurologic outcome was normal in 21 of 35 children (60%); 3 of 35 (8.6%) showed mild impairment and 6 of 35 (17.1%) showed moderate impairment. The remaining 5 of 35 (14.3%) had severe impairment. The median duration of follow-up for the isolated form was 45.6 months (range, 36-52 months) and 73.3 months (range, 2-138 months) for the nonisolated form.

CONCLUSION

Partial corpus callosum agenesis should be accurately investigated by neurosonography and fetal magnetic resonance imaging to describe its morphology and the associated anomalies. Genetic anomalies are frequently present in nonisolated cases. Efforts must be taken to improve ultrasound diagnosis of partial agenesis and to confirm its isolated nature to enhance parental counseling. Although 60% of children with prenatal diagnosis of isolated agenesis have a favorable prognosis later in life, they often have mild to severe disabilities including speech disorders at school age and behavior and motor deficit disorders that can emerge at a later age.

Assessment of fetal corpus callosum biometry by 3D super-resolution reconstructed T2-weighted magnetic resonance imaging

Objective

To assess the accuracy of corpus callosum (CC) biometry, including sub-segments, using 3D super-resolution fetal brain MRI (SR) compared to 2D or 3D ultrasound (US) and clinical low-resolution T2-weighted MRI (T2WS).

Method

Fetal brain biometry was conducted by two observers on 57 subjects [21-35 weeks of gestational age (GA)], including 11 cases of partial CC agenesis. Measures were performed by a junior observer (obs1) on US, T2WS and SR and by a senior neuroradiologist (obs2) on T2WS and SR. CC biometric regression with GA was established. Statistical analysis assessed agreement within and between modalities and observers.

Results

This study shows robust SR to US concordance across gestation, surpassing T2WS. In obs1, SR aligns with US, except for genu and CC length (CCL), enhancing splenium visibility. In obs2, SR closely corresponds to US, differing in rostrum and CCL. The anterior CC (rostrum and genu) exhibits higher variability. SR's regression aligns better with literature (US) for CCL, splenium and body than T2WS. SR is the method with the least missing values.

Conclusion

SR yields CC biometry akin to US (excluding anterior CC). Thanks to superior 3D visualization and better through plane spatial resolution, SR allows to perform CC biometry more frequently than T2WS.

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.

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.

Fetal brain volumes and neurodevelopmental outcome of intrauterine growth restricted fetuses

OBJECTIVE

This study aims to investigate the correlation of MRI measured fetal brain volumetrics with long-term neurodevelopmental outcome, among intrauterine growth restricted (IUGR) and apparently healthy fetuses.

STUDY DESIGN

A historical cohort study at a single tertiary referral medical center during 6 years period, of fetuses diagnosed with IUGR due to placental insufficiency, and apparently healthy fetuses, who had fetal brain MRI scan. The volumes of the supratentorial brain region, both hemispheres and the cerebellum were measured by 3D MRI semi-automated volume measurements. The cerebellar to supratentorial ratio (CER/ST) was calculated. Volumes were plotted on normal growth curves. 17 IUGR fetuses, and 53 apparently healthy fetuses adhered to participate in the VABS-II questionnaire, evaluating neurodevelopmental outcome.

RESULTS

70 patients (mean age at conducting VABS-II questionnaire 4.4 ± 2.1 years, 38 males) were evaluated. Among fetuses born in a gestational age of 36 weeks or later, IUGR fetuses demonstrated a significantly larger number of abnormal results in the VABS-II communication domain (p =.049). No significant differences were found in other domains or in overall neurodevelopmental outcome. The CER/ST ratio correlated with the overall neurodevelopmental outcome of the total study population (r = 0.40, p <.001), and of the IUGR group separately (ρ = 0.58, p =.02).

CONCLUSION

CER/ST ratio measured using fetal brain MRI was found to be correlated with long term neurodevelopmental outcome. This result may aid in clinical interpretation of biometric data obtained by fetal brain MRI, linking it with long term neurodevelopmental outcome.

Automatic biometry of fetal brain MRIs using deep and machine learning techniques

Linear biometric measurements on magnetic resonance images are important for the assessment of fetal brain development, which is expert knowledge dependent and laborious. This study aims to construct a segmentation-based method for automatic two-dimensional biometric measurements of fetal brain on magnetic resonance images that provides a fast and accurate measurement of fetal brain. A total of 268 volumes (5360 images) magnetic resonance images of normal fetuses were included. The automatic method involves two steps. First, the fetal brain was segmented into four parts with a deep segmentation network: cerebrum, cerebellum, and left and right lateral ventricles. Second, the measurement plane was determined, and the corresponding biometric parameters were calculated according to clinical guidelines, including cerebral biparietal diameter (CBPD), transverse cerebellar diameter (TCD), left and right atrial diameter (LAD/RAD). Pearson correlation coefficient and Bland-Altman plots were used to assess the correlation and agreement between computer-predicted values and manual measurements. Mean differences were used to evaluate the errors quantitatively. Analysis of fetal cerebral growth based on the automatic measurements was also displayed. The experiment results show that correlation coefficients for CBPD, TCD, LAD and RAD were as follows: 0.977, 0.990, 0.817, 0.719, mean differences were - 2.405 mm, - 0.008 mm, - 0.33 mm, - 0.213 mm, respectively. The correlation between the errors and gestational age was not statistically significant (p values were 0.2595, 0.0510, 0.1995, and 0.0609, respectively). The proposed automatic method for linear measurements on fetal brain MRI achieves excellent performance, which is expected to be applied in clinical practice and be helpful for prenatal diagnosis and clinical work efficiency improvement.

Corpus callosum in children with neurodevelopmental delay: MRI standard qualitative assessment versus automatic quantitative analysis

BACKGROUND

The corpus callosum (CC) is a key brain structure. In children with neurodevelopmental delay, we compared standard qualitative radiological assessments with an automatic quantitative tool.

METHODS

We prospectively enrolled 73 children (46 males, 63.0%) with neurodevelopmental delay at single university hospital between September 2020 and September 2022. All of them underwent 1.5-T brain magnetic resonance imaging (MRI) including a magnetization-prepared 2 rapid acquisition gradient echoes - MP2RAGE sequence. Two radiologists blindly reviewed the images to classify qualitatively the CC into normal, hypoplasic, hyperplasic, and/or dysgenetic classes. An automatic tool (QuantiFIRE) was used to provide brain volumetry and T1 relaxometry automatically as well as deviations of those parameters compared with a healthy age-matched cohort. The MRI reference standard for CC volumetry was based on the Garel et al. study. Cohen κ statistics was used for interrater agreement. The radiologists and QuantiFIRE's diagnostic accuracy were compared with the reference standard using the Delong test.

RESULTS

The CC was normal in 42 cases (57.5%), hypoplastic in 20 cases (27.4%), and hypertrophic in 11 cases (15.1%). T1 relaxometry values were abnormal in 26 children (35.6%); either abnormally high (18 cases, 24.6%) or low (8 cases, 11.0%). The interrater Cohen κ coefficient was 0.91. The diagnostic accuracy of the QuantiFIRE prototype was higher than that of the radiologists for hypoplastic and normal CC (p = 0.003 for both subgroups, Delong test).

CONCLUSIONS

An automated volumetric and relaxometric assessment can assist the evaluation of brain structure such as the CC, particularly in the case of subtle abnormalities.

RELEVANCE STATEMENT

Automated brain MRI segmentation combined with statistical comparison to normal volume and T1 relaxometry values can be a useful diagnostic support tool for radiologists.

KEY POINTS

• Corpus callosum abnormality detection is challenging but clinically relevant. • Automated quantitative volumetric analysis had a higher diagnostic accuracy than that of visual appreciation of radiologists. • Quantitative T1 relaxometric analysis might help characterizing corpus callosum better.

Effect of magnet strength on fetal brain biometry - a single-center retrospective MRI-based cohort study

PURPOSE

Abnormal fetal brain measurements might affect clinical management and parental counseling. The effect of between-field-strength differences was not evaluated in quantitative fetal brain imaging until now. Our study aimed to compare fetal brain biometry measurements in 3.0 T with 1.5 T scanners.

METHODS

A retrospective cohort of 1150 low-risk fetuses scanned between 2012 and 2021, with apparently normal brain anatomy, were retrospectively evaluated for biometric measurements. The cohort included 1.5 T (442 fetuses) and 3.0 T scans (708 fetuses) of populations with comparable characteristics in the same tertiary medical center. Manually measured biometry included bi-parietal, fronto-occipital and trans-cerebellar diameters, length of the corpus-callosum, vermis height, and width. Measurements were then converted to centiles based on previously reported biometric reference charts. The 1.5 T centiles were compared with the 3.0 T centiles.

RESULTS

No significant differences between centiles of bi-parietal diameter, trans-cerebellar diameter, or length of the corpus callosum between 1.5 T and 3.0 T scanners were found. Small absolute differences were found in the vermis height, with higher centiles in the 3.0 T, compared to the 1.5 T scanner (54.6th-centile, vs. 39.0th-centile, p < 0.001); less significant differences were found in vermis width centiles (46.9th-centile vs. 37.5th-centile, p = 0.03). Fronto-occipital diameter was higher in 1.5 T than in the 3.0 T scanner (66.0th-centile vs. 61.8th-centile, p = 0.02).

CONCLUSIONS

The increasing use of 3.0 T MRI for fetal imaging poses a potential bias when using 1.5 T-based charts. We elucidate those biometric measurements are comparable, with relatively small between-field-strength differences, when using manual biometric measurements. Small inter-magnet differences can be related to higher spatial resolution with 3 T scanners and may be substantial when evaluating small brain structures, such as the vermis.

Biometric magnetic resonance imaging analysis of fetal brain development in Down syndrome

OBJECTIVES

To assess brain development in living fetuses with Down syndrome (DS) by biometric measurements on fetal brain magnetic resonance images (MRI).

METHODS

We scanned 10 MRIs of fetuses with confirmed trisomy 21 at birth and 12 control fetal MRIs without any detected anomalies. Fetal brain MRIs were analyzed using 14 fetal brain and skull biometric parameters. We compared measures between DS and controls in both raw MRIs and motion-corrected and anterior-posterior commissure-aligned images.

RESULTS

In the reconstructed images, the measured values of the height of the cerebellar vermis (HV) and anteroposterior diameter of the cerebellar vermis (APDV) were significantly smaller, and the anteroposterior diameter of the fourth ventricle (APDF) was significantly larger in fetuses with DS than controls. In the raw MRIs, the measured values of the right lateral ventricle were significantly larger in fetuses with DS than in controls. Logistic regression analyses revealed that a new parameter, the cerebellar-to-fourth-ventricle ratio (i.e., (APDV * Height of the vermis)/APDF), was significantly smaller in fetuses with DS than controls and was the most predictive to distinguish between fetuses with DS and controls.

CONCLUSIONS

The study revealed that fetuses with DS have smaller cerebellums and larger fourth ventricles compared to the controls.

Onset of Chiari type 1 malformation: insights from a small series of intrauterine MR imaging cases

PURPOSE

Morphometric studies on idiopathic Chiari malformation type 1 (CM1) pathogenesis have been mainly based on post-natal neuroimaging. Prenatal clues related to CM1 development are lacking. We present pre- and post-natal imaging time course in idiopathic CM1 and assess fetal skull and brain biometry to establish if clues about CM1 development are present at fetal age.

METHODS

Multicenter databases were screened to retrieve intrauterine magnetic resonance (iuMR) of children presenting CM1 features at post-natal scan. Syndromes interfering with skull-brain growth were excluded. Twenty-two morphometric parameters were measured at fetal (average 24.4 weeks; range 21 to 32) and post-natal (average 15.4 months; range 1 to 45) age; matched controls were included.

RESULTS

Among 7000 iuMR cases, post-natal scans were available for 925, with postnatal CM1 features reported in seven. None of the fetuses presented CM1 features. Tonsillar descent was clear at a later post-natal scan in all seven cases. Six fetal parameters resulted to be statistically different between CM1 and controls: basal angle (p = 0.006), clivo-supraoccipital angle (p = 0.044), clivus' length (p = 0.043), posterior cranial fossa (PCF) width (p = 0.009), PCF height (p = 0.045), and PCFw/BPDb (p = 0.013). Postnatally, only the clivus' length was significant between CM1 cases and controls.

CONCLUSION

Pre- and post-natal CM1 cases did not share striking common features, making qualitative prenatal assessment not predictive; however, our preliminary results support the view that some of the pathogenetic basis of CM1 may be embedded to some extent already in intrauterine life.

Corpus callosal reference ranges: systematic review of methodology of biometric chart construction and measurements obtained

OBJECTIVE

Adequate reference ranges of size of the corpus callosum (CC) are necessary to improve characterization of CC abnormalities and parental counseling. The objective of this study was to evaluate the methodology used in studies developing references charts for CC biometry.

METHODS

We conducted a systematic review of studies on fetal CC biometry using a set of predefined quality criteria of study design, statistical analysis and reporting methods. We included observational studies whose primary aim was to create ultrasound or magnetic resonance imaging charts for CC size in a normal population of fetuses. Studies were scored against a predefined set of independently agreed methodological criteria, and an overall quality score was given for each study.

RESULTS

Twelve studies met the inclusion criteria. Quality scores ranged between 17.4% and 95.7%. The greatest potential for bias was noted for the following items: sample selection and sample-size calculation, as only 17% of the studies were population-based and had consecutive or random recruitment of patients and with a justification of the sample size; number of measurements obtained for CC biometry, as only 17% of the studies performed more than one measurement per fetus and per scan; and description of characteristics of the study population, as only 8% of the studies clearly reported a minimum dataset of demographic characteristics.

CONCLUSIONS

Our review demonstrates substantial heterogeneity in methods and final biometric values of the fetal CC across the evaluated studies. The use of uniform methodology of the highest quality is essential in order to define a 'short' CC and provide appropriate parental counseling. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Abnormalities of the corpus callosum. Can prenatal imaging predict the genetic status? Correlations between imaging phenotype and genotype

OBJECTIVE

Recent studies have evaluated prenatal exome sequencing (pES) for abnormalities of the corpus callosum (CC). The objective of this study was to compare imaging phenotype and genotype findings.

METHOD

This multicenter retrospective study included fetuses with abnormalities of the CC between 2018 and 2020 by ultrasound and/or MRI and for which pES was performed. Abnormalities of the CC were classified as complete (cACC) or partial (pACC) agenesis of the CC, short CC (sCC), callosal dysgenesis (CD), interhemispheric cyst (IHC), or pericallosal lipoma (PL), isolated or not. Only pathogenic (class 5) or likely pathogenic (class 4) (P/LP) variants were considered.

RESULTS

113 fetuses were included. pES identified P/LP variants for 3/29 isolated cACC, 3/19 isolated pACC, 0/10 isolated sCC, 5/10 isolated CD, 5/13 non-isolated cACC, 3/6 non-isolated pACC, 8/11 non-isolated CD and 0/12 isolated IHC and PL. Associated cerebellar abnormalities were significantly associated with P/LP variants (OR = 7.312, p = 0.027). No correlation was found between phenotype and genotype, except for fetuses with a tubulinopathy and an MTOR pathogenic variant.

CONCLUSIONS

P/LP variants were more frequent in CD and in non-isolated abnormalities of the CC. No such variants were detected for fetuses with isolated sCC, IHC and PL.

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.

MRI Findings in Third-Trimester Opioid-Exposed Fetuses, With Focus on Brain Measurements: A Prospective Multicenter Case-Control Study

BACKGROUND. The opioid epidemic has profoundly affected infants born in the United States, as in utero opioid exposure increases the risk of cognitive and behavioral problems in childhood. Scarce literature has evaluated prenatal brain development in fetuses with opioid exposure in utero (hereafter opioid-exposed fetuses). OBJECTIVE. The purpose of this study is to compare opioid-exposed fetuses and fetuses without opioid exposure (hereafter unexposed fetuses) in terms of 2D biometric measurements of the brain and additional pregnancy-related assessments on fetal MRI. METHODS. This prospective case-control study included patients in the third trimester of pregnancy who underwent investigational fetal MRI at one of three U.S. academic medical centers from July 1, 2020, through December 31, 2021. Fetuses were classified as opioid exposed or unexposed in utero. Fourteen 2D biometric measurements of the fetal brain were manually assessed and used to derive four indexes. Measurements and indexes were compared between the two groups by use of multivariable linear regression models, which were adjusted for gestational age (GA), fetal sex, and nicotine exposure. Additional pregnancy-related findings on MRI were evaluated. RESULTS. The study included 65 women (mean age, 29.0 ± 5.5 [SD] years). A total of 28 fetuses (mean GA at the time of MRI, 32.2 ± 2.5 weeks) were opioid-exposed, and 37 fetuses (mean GA at the time of MRI, 31.9 ± 2.7 weeks) were unexposed. In the adjusted models, seven measurements were smaller (p < .05) in opioid-exposed fetuses than in unexposed fetuses: cerebral frontooccipital diameter (93.8 ± 7.4 vs 95.0 ± 8.6 mm), bone biparietal diameter (79.0 ± 6.0 vs 80.3 ± 7.1 mm), brain biparietal diameter (72.9 ± 7.7 vs 74.1 ± 8.6 mm), corpus callosum length (37.7 ± 4.0 vs 39.4 ± 3.7 mm), vermis height (18.2 ± 2.7 vs 18.8 ± 2.6 mm), anteroposterior pons measurement (11.6 ± 1.4 vs 12.1 ± 1.4 mm), and transverse cerebellar diameter (40.4 ± 5.1 vs 41.4 ± 6.0 mm). In addition, in the adjusted model, the frontoocccipital index was larger (p = .02) in opioid-exposed fetuses (0.04 ± 0.02) than in unexposed fetuses (0.04 ± 0.02). Remaining measures and indexes were not significantly different between the two groups (p > .05). Fetal motion, cervical length, and deepest vertical pocket of amniotic fluid were not significantly different (p > .05) between groups. Opioid-exposed fetuses, compared with unexposed fetuses, showed higher frequencies of both breech position (21% vs 3%, p = .03) and increased amniotic fluid volume (29% vs 8%, p = .04). CONCLUSION. Fetuses with opioid exposure in utero had a smaller brain size and altered fetal physiology. CLINICAL IMPACT. The findings provide insight into the impact of prenatal opioid exposure on fetal brain development.

Complete agenesis of corpus callosum and unilateral cortical formation anomalies detected on fetal MR imaging: a phenotype strongly associated with the male fetuses

INTRODUCTION

In a previous study of classifying fetuses with cortical formation abnormalities (CFA) with fetal MR, we noticed a cluster of cases with unilateral CFA and complete agenesis of the corpus callosum (ACC). In this study, we provide a detailed morphological analysis of such fetuses using fetal MR to determine if there are indicators (such as the gender of the fetus) that could be used to delineate a genetic substrate of the phenotype in order to inform future studies.

METHODS

We have studied 45 fetuses with the unilateral CFA/ACC phenotype and analysed through an expert consensus panel the location and fine detail of the CFA and the associated findings such as associated anomalies, head size, and sex of the fetus.

RESULTS

The frontal lobe was significantly more frequently involved by CFA when compared with other lobes (p < 0.001) but no preference for the left or right hemisphere. CFA most often consisted of excessive/dysmorphic sulcation. The CFA/ACC phenotype was overwhelmingly more frequent in male fetuses (M:F 4.5:1-p < 0.0001). The most frequent associated findings were: ventriculomegaly (16/45 fetuses) and interhemispheric cysts (12/45 cases).

CONCLUSIONS

This report highlights the specific phenotype of unilateral CFA/ACC that is much more common in male fetuses. This finding provides a starting point to study possible sex-linked genetic abnormalities that underpin the unilateral CFA/ACC phenotype.

KEY POINTS

• We collected fetuses with unilateral cortical formation abnormality and callosal agenesis. • That distinctive neuroimaging phenotype has a strong male gender prevalence (over 80%). • This observation forms the basis of studies about outcomes and genetic substrates.

Reference Ranges for Corpus Callosum and Cavum Septi Pellucidi Biometry on Prenatal Ultrasound: Systematic Review and Meta-Analysis

We conducted a systematic review and meta-analysis of published nomograms for fetal corpus callosum and cavum septi pellucid biometry. A structured literature search was conducted to identify studies that reported normal measurements of the fetal corpus callosum and cavum septi pellucidi. Random effects metaanalysis was used to calculate normal ranges, and reference curves are provided. The quality assessment demonstrated that there was generally poor reporting regarding maternal characteristics and neonatal outcomes. Our findings emphasize that standardization of research protocols and publishing criteria for normal biometric ranges is needed.

Fetal Brain Anatomy

"Fetal brain development has been well studied, allowing for an ample knowledge of the normal changes that occur during gestation. Imaging modalities used to evaluate the fetal central nervous system (CNS) include ultrasound and MRI. MRI is the most accurate imaging modality for parenchymal evaluation and depiction of developmental CNS anomalies. The depiction of CNS abnormalities in a fetus can only be accurately made when there is an understanding of its normal development. This article reviews the expected normal fetal brain anatomy and development during gestation. Additional anatomic structures seen on brain imaging sequences are also reviewed."

Quantitative Evaluation of a Cross-Sectional Area of the Fetal Straight Sinus by Magnetic Resonance Imaging and Its Clinical Value

Objective

The intracranial venous system plays an important role in ensuring blood circulation and a stable blood supply to the fetal brain. In the present study, a cross-sectional area of the fetal straight sinus was quantitatively evaluated by fetal magnetic resonance imaging (MRI) to explore the method's clinical value.

Methods

The clinical and MRI data of 126 normal fetuses in mid-to-late stage pregnancies were retrospectively analyzed. The “dominant” sequence of the fetal straight sinus was selected, and the cross-sectional area of the lumen was measured at each gestational age to obtain the normal range at different ages and to analyze the developmental pattern and characteristics of the fetal straight sinus.

Results

There were statistically significant differences in the cross-sectional area of the fetal straight sinus among different gestational ages (P &lt; 0.05). The cross-sectional area of the fetal straight sinus was positively correlated with gestational age (coefficient of determination = 0.6892, P &lt; 0.05). That is, the cross-sectional area of the fetal straight sinus grew with increasing gestational age, and the regression equation was y = 0.27 x – 2.14 (P &lt; 0.05). Additionally, there were five fetuses with cerebral venous abnormalities, including four with heart failure and one with venous sinus thrombosis.

Conclusion

Quantitative measurement of a cross-sectional area of the fetal straight sinus by MRI enhanced understanding of the anatomical features and developmental pattern of fetal cerebral veins and provided a reference for the clinical diagnosis of related diseases and investigation concerning pathogenesis.

Anatomical and diffusion-weighted imaging of brain abnormalities in third-trimester fetuses with cytomegalovirus infection

OBJECTIVES

In this study of cytomegalovirus (CMV)-infected fetuses with first-trimester seroconversion, we aimed to evaluate the detection of brain abnormalities using magnetic resonance imaging (MRI) and neurosonography (NSG) in the third trimester, and compare the grading systems of the two modalities. We also evaluated the feasibility of routine use of diffusion-weighted imaging (DWI) fetal MRI and compared the regional apparent diffusion coefficient (ADC) values between CMV-infected fetuses and presumed normal, non-infected fetuses in the third trimester.

METHODS

This was a retrospective review of MRI and NSG scans in fetuses with confirmed first-trimester CMV infection performed between September 2015 and August 2019. Brain abnormalities were recorded and graded using fetal MRI and NSG grading systems to compare the two modalities. To investigate feasibility of DWI, a four-point rating scale (poor, suboptimal, good, excellent) was applied to assess the quality of the images. Quantitative assessment was performed by placing a freehand drawn region of interest in the white matter of the frontal, parietal, temporal and occipital lobes and the basal ganglia, pons and cerebellum to calculate ADC values. Regional ADC measurements were obtained similarly in a control group of fetuses with negative maternal CMV serology in the first trimester, normal brain findings on fetal MRI and normal genetic testing.

RESULTS

Fifty-three MRI examinations of 46 fetuses with confirmed first-trimester CMV infection were included. NSG detected 24 of 27 temporal cysts seen on MRI scans, with a sensitivity of 78% and an accuracy of 83%. NSG did not detect abnormal gyration visible on two (4%) MRI scans. Periventricular calcifications were detected on two MRI scans compared with 10 NSG scans. While lenticulostriate vasculopathy was detected on 11 (21%) NSG scans, no fetus demonstrated this finding on MRI. MRI grading correlated significantly with NSG grading of brain abnormalities (P < 0.0001). Eight (15%) of the DWI scans in the CMV cohort were excluded from further analysis because of insufficient quality. The ADC values of CMV-infected fetuses were significantly increased in the frontal (both sides, P < 0.0001), temporal (both sides, P < 0.0001), parietal (left side, P = 0.0378 and right side, P = 0.0014) and occipital (left side, P = 0.0002 and right side, P < 0.0001) lobes and decreased in the pons (P = 0.0085) when compared with non-infected fetuses. The ADC values in the basal ganglia and the cerebellum were not significantly different in CMV-infected fetuses compared with normal controls (all P > 0.05). Temporal and frontal ADC values were higher in CMV-infected fetuses with more severe brain abnormalities compared to fetuses with mild abnormalities.

CONCLUSIONS

Ultrasound and MRI are complementary during the third trimester in the assessment of brain abnormalities in CMV-infected fetuses, with a significant correlation between the grading systems of the two modalities. On DWI in the third trimester, the ADC values in several brain regions are abnormal in CMV-infected fetuses compared with normal controls. Furthermore, they seem to correlate in the temporal area and, to a lesser extent, frontal area with the severity of brain abnormalities associated with CMV infection. Larger prospective studies are needed for further investigation of the microscopic nature of diffusion abnormalities and correlation of different imaging findings with postnatal outcome. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

Prevalence of supratentorial anomalies assessed by magnetic resonance imaging in fetuses with open spina bifida

OBJECTIVES

To determine the prevalence of brain anomalies at the time of preoperative magnetic resonance imaging (MRI) assessment in fetuses eligible for prenatal open spina bifida (OSB) repair, and to explore the relationship between brain abnormalities and features of the spinal defect.

METHODS

This was a retrospective cross-sectional study, conducted in three fetal medicine centers, of fetuses eligible for OSB fetal surgery repair between January 2009 and December 2019. MRI images obtained as part of the presurgical assessment were re-evaluated by two independent observers, blinded to perinatal results, to assess: (1) the type and area of the defect and its anatomical level; (2) the presence of any structural central nervous system (CNS) anomaly and abnormal ventricular wall; and (3) fetal head and brain biometry. Binary regression analyses were performed and data were adjusted for type of defect, upper level of the lesion (ULL), gestational age (GA) at MRI and fetal medicine center. Multiple logistic regression analysis was performed in order to identify lesion characteristics and brain anomalies associated with a higher risk of presence of abnormal corpus callosum (CC) and/or heterotopia.

RESULTS

Of 115 fetuses included, 91 had myelomeningocele and 24 had myeloschisis. Anatomical level of the lesion was thoracic in seven fetuses, L1-L2 in 13, L3-L5 in 68 and sacral in 27. Median GA at MRI was 24.7 (interquartile range, 23.0-25.7) weeks. Overall, 52.7% of cases had at least one additional brain anomaly. Specifically, abnormal CC was observed in 50.4% of cases and abnormality of the ventricular wall in 19.1%, of which 4.3% had nodular heterotopia. Factors associated independently with higher risk of abnormal CC and/or heterotopia were non-sacral ULL (odds ratio (OR), 0.51 (95% CI, 0.26-0.97); P = 0.043), larger ventricular width (per mm) (OR, 1.23 (95% CI, 1.07-1.43); P = 0.005) and presence of abnormal cavum septi pellucidi (OR, 3.76 (95% CI, 1.13-12.48); P = 0.031).

CONCLUSIONS

Half of the fetuses assessed for OSB repair had an abnormal CC and/or an abnormal ventricular wall prior to prenatal repair. The likelihood of brain abnormalities was increased in cases with a non-sacral lesion and wider lateral ventricles. These findings highlight the importance of a detailed preoperative CNS evaluation of fetuses with OSB. © 2021 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Third Trimester Structural and Diffusion Brain Imaging after Single Intrauterine Fetal Death in Monochorionic Twins: MRI-Based Cohort Study

BACKGROUND AND PURPOSE

Single intrauterine fetal death increases the risk of antenatal brain lesions in the surviving twin. We evaluated the prevalence of structural brain lesions, biometry, and diffusivity on routine third trimester MR imaging performed following single intrauterine fetal death.

MATERIALS AND METHODS

In a retrospective MR imaging-based cohort study, we compared 29 monochorionic twins complicated with single intrauterine fetal death (14 following laser ablation treatment for twin-to-twin transfusion syndrome, 8 following selective fetal reduction, and 7 spontaneous) with 2 control cohorts (49 singleton fetuses and 28 uncomplicated twin fetuses). All fetuses in the single intrauterine fetal death group underwent fetal brain MR imaging as a routine third trimester evaluation. Structural brain lesions were analyzed. Cerebral biometry and diffusivity were measured and compared.

RESULTS

Brain lesions consistent with the evolution of prior ischemic injury were found in 1 of 29 fetuses, not detected by ultrasound. No acute brain infarction, hemorrhage, or cortical abnormalities were found. Supratentorial biometric measurements in the single intrauterine fetal death group were significantly smaller than those in the singleton group, but not significantly different from those in the uncomplicated twin group. There were no significant differences in ADC values of the cerebral hemispheres, basal ganglia, and pons between the single intrauterine fetal death group and either control group.

CONCLUSIONS

Although smaller brain biometry was found, normal diffusivity in surviving twins suggests normal parenchymal microstructure. The rate of cerebral structural injury was relatively low in our cohort, arguing against the routine use of fetal brain MR imaging in twin pregnancies complicated with single intrauterine fetal death. Larger prospective studies are necessary to guide appropriate surveillance protocol and parental counseling in twin pregnancies complicated by single intrauterine fetal death.

Reference ranges for fetal brain structures using magnetic resonance imaging: systematic review

OBJECTIVE

To evaluate the methodology of studies reporting reference ranges for fetal brain structures on magnetic resonance imaging (MRI).

METHODS

MEDLINE, EMBASE, CINAHL and the Web of Science databases were searched electronically up to 31 December 2020 to identify studies investigating biometry and growth of the fetal brain and reporting reference ranges for brain structures using MRI. The primary aim was to evaluate the methodology of these studies. A list of 26 quality criteria divided into three domains, including 'study design', 'statistical and reporting methods' and 'specific aspects relevant to MRI', was developed and applied to evaluate the methodological appropriateness of each of the included studies. The overall quality score of a study, ranging between 0 and 26, was defined as the sum of scores awarded for each quality criterion and expressed as a percentage (the lower the percentage, the higher the risk of bias).

RESULTS

Fifteen studies were included in this systematic review. The overall mean quality score of the studies evaluated was 48.7%. When focusing on each domain, the mean quality score was 42.0% for 'study design', 59.4% for 'statistical and reporting methods' and 33.3% for 'specific aspects relevant to MRI'. For the 'study design' domain, sample size calculation and consecutive enrolment of women were the items found to be at the highest risk of bias. For the 'statistical and reporting methods' domain, the presence of regression equations for mean and SD for each measurement, the number of measurements taken for each variable and the presence of postnatal assessment information were the items found to be at the highest risk of bias. For the 'specific aspects relevant to MRI' domain, whole fetal brain assessment was not performed in any of the included studies and was therefore considered to be the item at the highest risk of bias.

CONCLUSIONS

Most of the previously published studies reporting fetal brain reference ranges on MRI are highly heterogeneous and have low-to-moderate quality in terms of methodology, which is similar to the findings reported for ultrasound studies. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Prenatal diagnosis of rhombencephalosynapsis: neuroimaging features and severity of vermian anomaly

OBJECTIVES

To describe the prenatal neuroimaging spectrum of rhombencephalosynapsis (RES) and criteria for its classification according to the severity of vermian anomaly.

METHODS

In this multicenter retrospective study of fetuses with RES between 2002 and 2020, the medical records and brain ultrasound and magnetic resonance images were evaluated comprehensively to determine the severity of the vermian anomaly and the presence of associated brain findings. RES was classified, according to the pattern of vermian agenesis and the extent of the fusion of the hemispheres, as complete RES (complete absence of the vermis) or partial RES (further classified according to the part of the vermis that was missing and, consequently, the region of hemispheric fusion, as anterior, posterior, severe or mixed RES). Findings were compared between cases with complete and those with partial RES.

RESULTS

Included in the study were 62 fetuses with a gestational age ranging between 12 and 37 weeks. Most had complete absence of the vermis (complete RES, 77.4% of cases), a 'round-shaped' cerebellum on axial views (72.6%) and a transverse cerebellar diameter (TCD) < 3^rd centile (87.1%). Among the 22.6% of cases with partial RES, 6.5% were classified as severe partial, 6.5% as partial anterior, 8.1% as partial mixed and 1.6% as partial posterior. Half of these cases presented with normal or nearly normal cerebellar morphology and 28.5% had a TCD within the normal limits. Infratentorially, the fourth ventricle was abnormal in 88.7% of cases overall, and anomalies of the midbrain and pons were frequent (93.5% and 77.4%, respectively). Ventriculomegaly was observed in 80.6% of all cases, being more severe in cases with complete RES than in those with partial RES, with high rates of parenchymal and septal disruption.

CONCLUSIONS

This study provides prenatal neuroimaging criteria for the diagnosis and classification of RES, and identification of related features, using ultrasound and magnetic resonance imaging. According to our findings, a diagnosis of RES should be considered in fetuses with a small TCD (severe cerebellar hypoplasia) and/or a round-shaped cerebellum on axial views, during the second or third trimester, especially when associated with ventriculomegaly. Partial RES is more common than previously thought, but presents an extreme diagnostic challenge, especially in cases with normal or nearly-normal cerebellar morphobiometric features. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

The Myelic Limited Dorsal Malformation: Prenatal Ultrasonographic Characteristics of an Intermediate Form of Dysraphism

OBJECTIVES

The aim of the study was to report a subtype of dysraphism designated as myelic limited dorsal malformation (MyeLDM) and to describe its characteristics at prenatal ultrasound (US).

METHODS

It was a retrospective study from 2014 to 2020 based on second-line US evaluation of patients referred to our institution for myelomeningocele (MMC). Magnetic resonance imaging and acetylcholine esterase evaluation in the amniotic fluid were also offered. Major and minor criteria for open and closed dysraphism were defined and recorded for each patient. Patients were included as MyeLDM when both criteria of closed and open dysraphism were observed in the same fetus. Correlations were obtained with the postpartum data.

RESULTS

Twenty patients fulfilled the inclusion criteria, some of them being very close to MMC, others very close to limited dorsal myeloschisis (LDM), and others lying in between. There were 13 live-born neonates and 7 terminations of pregnancy. Correlations between prenatal and postpartum data were overall very good.

CONCLUSION

Our series describe the ultrasonographic characteristics of an intermediate type of dysraphism and suggest that there is a continuum between MMC and LDM with numerous possibilities of hybrid forms (MyeLDM) sharing characteristics of both open and closed dysraphisms.

Correlation between 2D and 3D Fetal Brain MRI Biometry and Neurodevelopmental Outcomes in Fetuses with Suspected Microcephaly and Macrocephaly

BACKGROUND AND PURPOSE

Definitions of fetal microcephaly and macrocephaly are debatable. A better understanding of their long-term prognoses would help guide parental education and counseling. This study aimed to explore the correlation between 2D and 3D fetal brain MR imaging biometry results and the long-term neurodevelopmental outcomes.

MATERIALS AND METHODS

This analysis is a historical cohort study. Fetal brain biometry was measured on 2D and 3D MR imaging using a volumetric MR imaging semiautomated algorithm. We measured and assessed the following brain structures: the supratentorial brain volume and cerebellar volume and cerebellar volume/supratentorial brain volume ratio, in addition to commonly used 2D brain MR imaging biometric variables, including occipitofrontal diameter, biparietal diameter, and transcerebellar diameter. Microcephaly was defined as ≤ 3rd percentile; and macrocephaly, as ≥ 97th percentile, corresponding to -2 SDs and +2 SDs. The neurodevelopmental outcome of this study cohort was evaluated using the Vineland-II Adaptive Behavior Scales, and the measurements were correlated to the Vineland standard scores.

RESULTS

A total of 70 fetuses were included. No significant correlation was observed between the Vineland scores and either the supratentorial brain volume, cerebellar volume, or supratentorial brain volume/cerebellar volume ratio in 3D or 2D MR imaging measurements, after correction for multiple comparisons. No differences were found among fetuses with macrocephaly, normocephaly, or microcephaly regarding the median Vineland standard scores.

CONCLUSIONS

Provided there is normal brain structure on MR imaging, the developmental milestone achievements in early years are unrelated to 2D and 3D fetal brain MR imaging biometry, in the range of measurements depicted in this study.

L1CAM variants cause two distinct imaging phenotypes on fetal MRI

Data on fetal MRI in L1 syndrome are scarce with relevant implications for parental counseling and surgical planning. We identified two fetal MR imaging patterns in 10 fetuses harboring L1CAM mutations: the first, observed in 9 fetuses was characterized by callosal anomalies, diencephalosynapsis, and a distinct brainstem malformation with diencephalic–mesencephalic junction dysplasia and brainstem kinking. Cerebellar vermis hypoplasia, aqueductal stenosis, obstructive hydrocephalus, and pontine hypoplasia were variably associated. The second pattern observed in one fetus was characterized by callosal dysgenesis, reduced white matter, and pontine hypoplasia. The identification of these features should alert clinicians to offer a prenatal L1CAM testing.

Alterations of brain metrics in fetuses of women with polycystic ovary syndrome : a retrospective study based on fetal magnetic resonance imaging

Background

Maternal polycystic ovary syndrome (PCOS) has potential detrimental effects on the neurodevelopment of offspring. This study aimed to evaluate the brain metrics in fetuses of women with PCOS based on fetal magnetic resonance imaging (MRI).

Methods

This retrospective study included 60 pregnant women with PCOS (PCOS group) and 120 pregnant non-PCOS women (control group). Fetal MRI was performed followed an ultrasound and for numerous clinical indications including known or suspected fetal pathology, history of fetal abnormality in previous pregnancy or in a family member. Fetal brain biometry and apparent diffusion coefficient (ADC) value were analysed.

Results

After adjusting for potential confounders, fetuses in the PCOS group showed the following characteristics compared to fetuses in the control group: (1) smaller cerebral fronto-occipital diameter (FOD), vermian height (VH) and anteroposterior diameter of the pons (APDP) (evident before 32 weeks; P = 0.042, P = 0.002 and P = 0.016, respectively); (2) larger left and right biparietal index (evident before 32 weeks; P = 0.048 and P = 0.025, respectively); (3) smaller left lateral ventricle (LV) (evident after 32 weeks; P = 0.005); (4) larger anteroposterior diameter of the vermis (APDV) and hippocampal infolding angle (HIA) (evident after 32 weeks; P = 0.003 and P < 0.001, respectively); (5) higher ADC value in frontal white matter (FWM) and in basal ganglia (BG) (evident before and after 32 weeks; all P < 0.05).

Conclusions

There exist a different pattern of brain metrics in PCOS offspring in utero.

Normal human brainstem development in vivo: a quantitative fetal MRI study

OBJECTIVES

To characterize spatiotemporal growth differences of prenatal brainstem substructures and cerebellum, using linear biometry and planimetry on fetal magnetic resonance imaging (MRI).

METHODS

In this retrospective study, we included fetuses with normal brain and a precise midsagittal T2-weighted brain MRI sequence obtained between May 2003 and April 2019. The cross-sectional area, rostrocaudal diameter and anteroposterior diameter of the midbrain, pons (basis pontis and pontine tegmentum), medulla oblongata and cerebellar vermis, as well as the transverse cerebellar diameter, were quantified by a single observer. The diameters were also assessed by a second observer to test inter-rater variability.

RESULTS

We included 161 fetuses with normal brain and a precise midsagittal MRI sequence, examined at a mean ± SD gestational age of 25.7 ± 5.4 (range, 14 + 0 to 39 + 2) weeks. All substructures of the fetal brainstem and the cerebellum could be measured consistently (mean ± SD interobserver intraclass correlation coefficient, 0.933 ± 0.065). We provide reference data for diameters and areas of the brainstem and cerebellum in the second and third trimesters. There was a significant quadratic relationship between vermian area and gestational age, and all other measured parameters showed a significant linear growth pattern within the observed period (P < 0.001). A significant change in the relative proportions of the brainstem substructures occurred between the beginning of the second trimester and the end of the third trimester, with an increase in the area of the pons (P < 0.001) and a decrease in that of the midbrain (P < 0.001), relative to the total brainstem area.

CONCLUSIONS

The substructures of the fetal brainstem follow a distinct spatiotemporal growth pattern, characterized by a relative increase in the pons and decrease in the midbrain, between 15 and 40 weeks of gestation. Caution is needed when interpreting fetal brainstem appearance during the early second trimester, as the brainstem proportions differ significantly from the adult morphology. The reference data provided herein should help to increase diagnostic accuracy in detecting disorders of defective hindbrain segmentation. © 2020 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Age-specific structural fetal brain atlases construction and cortical development quantification for chinese population

In magnetic resonance imaging (MRI) studies of fetal brain development, structural brain atlases usually serve as essential references for the fetal population. Individual images are usually normalized into a common or standard space for analysis. However, the existing fetal brain atlases are mostly based on MR images obtained from Caucasian populations and thus are not ideal for the characterization of the fetal Chinese population due to neuroanatomical differences related to genetic factors. In this paper, we use an unbiased template construction algorithm to create a set of age-specific Chinese fetal atlases between 21-35 weeks of gestation from 115 normal fetal brains. Based on the 4D spatiotemporal atlas, the morphological development patterns, e.g., cortical thickness, cortical surface area, sulcal and gyral patterns, were quantified. The fetal brain abnormalities were detected when referencing the age-specific template. Additionally, a direct comparison of the Chinese fetal atlases and Caucasian fetal atlases reveals dramatic anatomical differences, mainly in the medial frontal and temporal regions. After applying the Chinese and Caucasian fetal atlases separately to an independent Chinese fetal brain dataset, we find that the Chinese fetal atlases result in significantly higher accuracy than the Caucasian fetal atlases in guiding brain tissue segmentation. These results suggest that the Chinese fetal brain atlases are necessary for quantitative analysis of the typical and atypical development of the Chinese fetal population in the future. The atlases with their parcellations are now publicly available at https://github.com/DeepBMI/FBA-Chinese.

Evaluation of Posterior Fossa Biometric Measurements on Fetal MRI in the Evaluation of Dandy-Walker Continuum

BACKGROUND AND PURPOSE

Dandy-Walker malformation, vermian hypoplasia, and Blake pouch remnant represent a continuum of anomalies and are common reasons for referral for fetal MR imaging. This study aimed to determine biometric measurements that quantitatively delineate these 3 posterior fossa phenotypes.

MATERIALS AND METHODS

Our single-center institutional review board approved a retrospective analysis of all fetal MRIs for posterior fossa malformations, including Dandy-Walker malformation, vermian hypoplasia, and Blake pouch remnant. Measurements included the anterior-to-posterior pons, craniocaudal and anterior-to-posterior vermis, lateral ventricle size, and tegmentovermian and posterior fossa angles. Measurements were compared with normal biometry and also between each subgroup.

RESULTS

Thirty-three fetuses met the criteria and were included in the study. Seven were designated as having Dandy-Walker malformation; 16, vermian hypoplasia; and 10, Blake pouch remnant. No significant group interactions with adjusted mean gestational age for tegmentovermian and posterior fossa angles were observed. The tegmentovermian angle was significantly higher in Dandy-Walker malformation (109.5° [SD, 20.2°]) compared with vermian hypoplasia (52.13° [SD, 18.8°]) and Blake pouch remnant (32.1° [SD, 17.9°]), regardless of gestational age. Lateral ventricle sizes were significantly higher in Dandy-Walker malformation at a mean of ≥23.1 weeks' gestational age compared with vermian hypoplasia and Blake pouch remnant. The anterior-to-posterior and craniocaudal vermes were significantly smaller in Dandy-Walker malformation compared with vermian hypoplasia and Blake pouch remnant at mean of ≥23.1 weeks' gestational age.

CONCLUSIONS

Dandy-Walker malformation can be described in relation to vermian hypoplasia and Blake pouch remnant by an increased tegmentovermian angle; however, other potential qualifying biometric measurements are more helpful at ≥23.1 weeks' gestational age. Because they fall along the same spectrum of abnormalities, the difficulty in distinguishing these entities from one another makes precise morphologic and biometric descriptions important.

Automatic linear measurements of the fetal brain on MRI with deep neural networks

PURPOSE

Timely, accurate and reliable assessment of fetal brain development is essential to reduce short and long-term risks to fetus and mother. Fetal MRI is increasingly used for fetal brain assessment. Three key biometric linear measurements important for fetal brain evaluation are cerebral biparietal diameter (CBD), bone biparietal diameter (BBD), and trans-cerebellum diameter (TCD), obtained manually by expert radiologists on reference slices, which is time consuming and prone to human error. The aim of this study was to develop a fully automatic method computing the CBD, BBD and TCD measurements from fetal brain MRI.

METHODS

The input is fetal brain MRI volumes which may include the fetal body and the mother's abdomen. The outputs are the measurement values and reference slices on which the measurements were computed. The method, which follows the manual measurements principle, consists of five stages: (1) computation of a region of interest that includes the fetal brain with an anisotropic 3D U-Net classifier; (2) reference slice selection with a convolutional neural network; (3) slice-wise fetal brain structures segmentation with a multi-class U-Net classifier; (4) computation of the fetal brain midsagittal line and fetal brain orientation, and; (5) computation of the measurements.

RESULTS

Experimental results on 214 volumes for CBD, BBD and TCD measurements yielded a mean [Formula: see text] difference of 1.55 mm, 1.45 mm and 1.23 mm, respectively, and a Bland-Altman 95% confidence interval ([Formula: see text] of 3.92 mm, 3.98 mm and 2.25 mm, respectively. These results are similar to the manual inter-observer variability, and are consistent across gestational ages and brain conditions.

CONCLUSIONS

The proposed automatic method for computing biometric linear measurements of the fetal brain from MR imaging achieves human-level performance. It has the potential of being a useful method for the assessment of fetal brain biometry in normal and pathological cases, and of improving routine clinical practice.

The Role of Fetal MRI for Suspected Anomalies of the Posterior Fossa

BACKGROUND

Posterior fossa anomalies can be diagnostic dilemmas during the fetal period. The prognosis for different diagnoses of the posterior fossa varies widely. We investigated whether fetal magnetic resonance imaging (MRI) and prenatal neurology consultation led to an alternate prognosis for fetuses referred due to concern for a fetal posterior fossa anomaly and concordance between pre- and postnatal diagnoses.

METHODS

This is a retrospective study of cases referred to the Prenatal Pediatrics Institute at Children's National Hospital from January 2012 to June 2018 due to concern for posterior fossa anomaly. Each encounter was scored for change in prognosis based upon clinical and fetal MRI report. Postnatal imaging was compared with prenatal imaging when available.

RESULTS

In total, 180 cases were referred for fetal posterior fossa anomalies based on outside obstetric ultrasound and had both fetal MRI and a neurology consultation. Fetal MRI and neurology consultation resulted in a change in fetal prognosis in 70% of cases. The most common referral diagnosis in our cohort was Dandy-Walker continuum, but it was not often confirmed by fetal MRI. In complex cases, posterior fossa diagnosis and prognosis determined by fetal MRI impacted choices regarding pregnancy management. Postnatal imaging was obtained in 57 (47%) live-born infants. Fetal and postnatal prognoses were similar in 60%.

CONCLUSIONS

Fetal diagnosis affects pregnancy management decisions. The fetal-postnatal imaging agreement of 60% highlights the conundrum of balancing the timing of fetal MRI to provide the most accurate diagnosis of the posterior fossa abnormalities in time to make pregnancy management decisions.

Ganglionic Eminence Anomalies and Coexisting Cerebral Developmental Anomalies on Fetal MR Imaging: Multicenter-Based Review of 60 Cases

BACKGROUND AND PURPOSE

The ganglionic eminences are transient fetal brain structures that produce a range of neuron types. Ganglionic eminence anomalies have been recognized on fetal MR imaging and anecdotally found in association with a number of neurodevelopmental anomalies. The aim of this exploratory study was to describe and analyze the associations between ganglionic eminence anomalies and coexisting neurodevelopmental anomalies.

MATERIALS AND METHODS

This retrospective study includes cases of ganglionic eminence anomalies diagnosed on fetal MR imaging during a 20-year period from 7 centers in Italy and England. Inclusion criteria were cavitation or increased volume of ganglionic eminences on fetal MR imaging. The studies were analyzed for associated cerebral developmental anomalies: abnormal head size and ventriculomegaly, reduced opercularization or gyration, and abnormal transient layering of the developing brain mantle. The results were analyzed using χ² and Fisher exact tests.

RESULTS

Sixty fetuses met the inclusion criteria (21 females, 24 males, 15 sex unknown). Thirty-four had ganglionic eminence cavitations (29 bilateral and 5 unilateral), and 26 had increased volume of the ganglionic eminences (19 bilateral, 7 unilateral). Bilateral ganglionic eminence cavitations were associated with microcephaly (P = .01), reduced opercularization, (P < .001), reduced gyration (P < .001), and cerebellar anomalies (P = .01). Unilateral ganglionic eminence cavitations were not significantly associated with any particular feature. Bilateral increased volume of the ganglionic eminences showed an association with macrocephaly (P = .03). Unilateral increased volume was associated with macrocephaly (P = .002), abnormal transient layering (P = .001), unilateral polymicrogyria (P = .001), and hemimegalencephaly (P < .001).

CONCLUSIONS

Ganglionic eminence anomalies are associated with specific neurodevelopmental anomalies with ganglionic eminence cavitations and increased ganglionic eminence volume apparently having different associated abnormalities.

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.

Fetal Brain Biometric Measurements on 3D Super-Resolution Reconstructed T2-Weighted MRI: An Intra- and Inter-observer Agreement Study

We present the comparison of two-dimensional (2D) fetal brain biometry on magnetic resonance (MR) images using orthogonal 2D T2-weighted sequences (T2WSs) vs. one 3D super-resolution (SR) reconstructed volume and evaluation of the level of confidence and concordance between an experienced pediatric radiologist (obs1) and a junior radiologist (obs2). Twenty-five normal fetal brain MRI scans (18-34 weeks of gestation) including orthogonal 3-mm-thick T2WSs were analyzed retrospectively. One 3D SR volume was reconstructed per subject based on multiple series of T2WSs. The two observers performed 11 2D biometric measurements (specifying their level of confidence) on T2WS and SR volumes. Measurements were compared using the paired Wilcoxon rank sum test between observers for each dataset (T2WS and SR) and between T2WS and SR for each observer. Bland-Altman plots were used to assess the agreement between each pair of measurements. Measurements were made with low confidence in three subjects by obs1 and in 11 subjects by obs2 (mostly concerning the length of the corpus callosum on T2WS). Inter-rater intra-dataset comparisons showed no significant difference (p > 0.05), except for brain axial biparietal diameter (BIP) on T2WS and for brain and skull coronal BIP and coronal transverse cerebellar diameter (DTC) on SR. None of them remained significant after correction for multiple comparisons. Inter-dataset intra-rater comparisons showed statistical differences in brain axial and coronal BIP for both observers, skull coronal BIP for obs1, and axial and coronal DTC for obs2. After correction for multiple comparisons, only axial brain BIP remained significantly different, but differences were small (2.95 ± 1.73 mm). SR allows similar fetal brain biometry as compared to using the conventional T2WS while improving the level of confidence in the measurements and using a single reconstructed volume.

Biometric assessments of the posterior fossa by fetal MRI: A systematic review

BACKGROUND

Posterior fossa abnormalities (PFAs) are commonly identified within routine screening and are a frequent indication for fetal magnetic resonance imaging (MRI). Although biometric measurements of the posterior fossa (PF) are established on fetal ultrasound and MRI, qualitative visual assessments are predominantly used to differentiate PFAs.

OBJECTIVES

This systematic review aimed to assess 2-dimensional (2D) biometric measurements currently in use for assessing the PF on fetal MRI to delineate different PFAs.

METHODS

The protocol was registered (PROSPERO ID CRD42019142162). Eligible studies included T2-weighted MRI PF measurements in fetuses with and without PFAs, including measurements of the PF, or other brain areas relevant to PFAs.

RESULTS

59 studies were included - 6859 fetuses had 62 2D PF and related measurements. These included linear, area and angular measurements, representing measures of PF size, cerebellum/vermis, brainstem, and supratentorial measurements. 11 measurements were used in 10 or more studies and at least 1200 fetuses. These dimensions were used to characterise normal for gestational age, diagnose a range of pathologies, and predict outcome.

CONCLUSION

A selection of validated 2D biometric measurements of the PF on fetal MRI may be useful for identification of PFA in different clinical settings. Consistent use of these measures, both clinically and for research, is recommended.

The normal fetal Cavum Septum Pellucidum in MR imaging - New biometric data

BACKGROUND AND PURPOSE

The cavum septum pellucidum (CSP) is an important landmark in the evaluation of the fetal neural axis. A deviation from the ultrasonic normal values may be associated with unfavorable outcomes, and a normal CSP provides reassurance of normal central forebrain development. Today, there is biometric data regarding the normal values for the width of the CSP in fetal ultrasound, but there is no such data for fetal MRI. The aim of this study was to determine the normal values for the measurements of the fetal CSP on MRI.

MATERIALS AND METHODS

We retrospectively examined 307 MRI scans of fetuses between 25 and 41 weeks gestation. Data was collected from the electronic charts of patients who underwent fetal MR imaging at a single tertiary Medical Center. The width and length of the CSP were measured in the axial plane, and the width and height were measured in the coronal plane.

RESULTS

The width and height of the CSP in fetuses tend to decrease starting from the 27th week of gestation onwards. High levels of intraobserver and interobserver agreements were calculated. The sex of the fetus does not appear to influence the biometry of the CSP.

CONCLUSION

This study provides MRI reference values for the dimensions of the CSP starting from the 25th week of gestation. Knowing the normal values for MRI could provide valuable information for researchers and in the decision-making process in patient's consultations.

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.

Fetal brain biometry in isolated mega cisterna magna: MRI and US study

OBJECTIVE

To characterize the biometric parameters in ultrasound and brain MRI of fetuses with isolated mega cisterna magna (MCM).

METHODS

Cross-sectional historical cohort study conducted at a single tertiary medical center between 2011 and 2018. All fetuses underwent US and brain MRI scans. Matching analysis was performed according to gender and gestational age.

RESULTS

The study included a total of 103 fetuses; 44 fetuses with isolated MCM in the study group, and a control group of 59 fetuses with normal CNS. The study group had larger biparietal diameter (BPD) (86 vs. 79.8 mm, p = .001) and head circumference (HC) (318 vs. 292 mm, p < .001) on ultrasound. On MRI, study group had larger occipitofrontal diameter (OFD) (99 vs. 92 mm, p < .001) and BPD (77 vs. 72 mm, p < .001). Male fetuses' prevalence was higher in the study group (77.3% vs. 47.5%). After matching 20 fetuses from each group, the study group had larger HC (310.1 versus 300.7 mm, p = .029) and OFD (113.4 versus 108.3 mm, p = .009) on ultrasound, and larger OFD (97.4 versus 94.6, p = .013) on brain MRI.

CONCLUSIONS

Isolated MCM may be related to other large fetal CNS biometric measurements in both ultrasound and MRI and might be influenced by fetal gender.

Fetal Brain Biometry: Is there an Agreement among Ultrasound, MRI and the Measurements at Birth?

PURPOSE

Measurement of the fetal brain can be achieved by different modalities, we aimed to assess the agreement between these methods and the head circumference at birth.

METHODS

A retrospective study conducted between 2011-2018 at a tertiary referral medical center. Sonographic head circumference (HC), 2D MRI bi-parietal diameter (BPD) and occipito-frontal diameter (OFD), 3D MRI supra-tentorial volume (STV), and head circumference (HC) at birth were measured and converted into centiles according to gestational age. Spearman's rank correlation coefficient was used to assess the correlation between the modalities.

RESULTS

A total of 88 fetuses were included. Mean gestational age at the time of fetal US and brain MRI acquisition were 34.4 ± 2.8 and 34.6 ± 2.6 weeks, respectively. A correlation was found between prenatal sonographic HC and the 3D MRI STV centiles (Rs = 0.859, p < 0.001), the BPD in 2D MRI (Rs = 0.813, p < 0.001), and the OFD in 2D MRI (Rs = 0.840, p < 0.001). Sonographic HC, OFD on 2D MRI, and STV on 3D MRI were all found to be correlated with the HC at birth (Rs = 0.865, p < 0.001; Rs 0.816, p < 0.001; Rs = 0.825, p < 0.001, respectively).

CONCLUSIONS

There is a statistically significant agreement among the different prenatal clinically used modalities for measuring fetal brain and the head circumference at birth, however, this correlation is not perfect. Further study is needed to investigate the long-term prognosis of these fetuses.

Cortical formation abnormalities on foetal MR imaging: a proposed classification system trialled on 356 cases from Italian and UK centres

OBJECTIVE

To formulate a classification system for foetal cortical formation abnormalities (CFAs) based on in utero magnetic resonance (iuMR) appearances and trial it in 356 cases.

METHODS

This retrospective study included all cases of foetal CFA diagnosed between 2000 and 2017 from seven centres in Italy and UK. All of the studies were reviewed by a panel of paediatric neuroradiologists experienced in iuMR with the aid of an algorithm designed to categorise the abnormalities.

RESULTS

Consensus expert review confirmed 356 foetuses with CFA and the first level of classification distinguished bilateral CFA (229/356-64%) from unilateral CFA (127/356-36%) cases with sub-classification of the bilateral cases into asymmetric (65/356-18%) and symmetric (164/356-46%) involvement. There was a statistically significant excess of foetuses with small head size, e.g. 17% of the cohort had a bi-parietal diameter < 3rd centile. There was a small but statistically significant excess of males in the cohort. Further categorisation was made on fine anatomical structure.

CONCLUSIONS

It is often not possible to classify foetal CFA using the principles and nomenclature used in paediatric neuroradiology. We have created a classification system for foetal CFA based on the analysis of 356 cases and believe that this will assist future research designed to correlate ante-natal and post-natal imaging features and understand the clinical sequelae of CFA described in utero.

KEY POINTS

• We describe a morphological classification system of foetal brain cortical formation abnormalities that can be used in clinical practice. • This classification system can be used in future research studies to evaluate the long-term imaging and clinical outcomes of foetal brain cortical formation abnormalities in 17- to 38-week gestational age range. • The practical value of the work is in providing a framework and language to look for imaging clues that may differentiate between different CFA in further studies.

Evaluation of the development of the posterior fossa in normal Chinese fetuses by using magnetic resonance imaging

The posterior fossa is an important brain structure containing the cerebellum, cerebral ventricle, and cistern. Early evaluation of the cerebellar structure and function may be valuable for early detection of fetal deformities. At present, no normal value for the fetal posterior fossa has been established yet. This study is aimed to investigate the development of the posterior fossa in normal Chinese fetuses by using magnetic resonance imaging (MRI).Pregnant women who need MRI scan were enrolled in our Hospital between January 2012 and December 2014. The fetal supero-inferior diameter (SID), anterio-posterior diameter (APD), cerebellar vermis area, cerebellar width (CW), cerebellar volume (CV), superior cerebellar cistern width, and cerebellomedullary cistern width were measured using MRI. Pearson's correlation analysis was used to detect the relationship between those parameters and gestational age. A regression analysis was performed for all parameters.A total of 92 participants were retrospectively enrolled finally. The results indicated SID, APD, cerebellar vermis area, CW, and CV were positively associated with gestational age, while no significant correlation was found between the superior cerebellar cistern width and cerebellomedullary cistern width and gestational age. Each equation was established.Our study demonstrated that MRI has the advantages over ultrasound imaging for prenatal evaluation of the fetal posterior fossa with multiple views. Normal value of the posterior fossa of Chinese fetuses was established in this study.

What does the normal fetal face look like? MR imaging of the developing mandible and nasal cavity

PURPOSE

Analyze fetal facial structures using MR imaging scans in an aim to establish normal biometrical measures of fetal nasal and mandibular structures for multiple gestational weeks, comprise nomograms and compare female and male fetuses.

METHODS

A Historic cohort study of 255 fetal facial MR imaging scans was performed at a tertiary medical center during a 4-year period. Clinical data was collected from electronic medical charts. Length of septal height (SH), septal length (SL), Interocular Distance(IOD), maximal nasal length(MNL), mandibular vertebral length(MVL), antero-posterior diameter(APD), inferior facial angle(IFA) and biparietal diameter(BPD) were measured and compared with gender and gestational age (GA). Interrater and intrarater reliability was investigated.

RESULTS

Normal measures were established for each gestational age. We found that all parameters but IFA correlated with GA. Males had a longer SL, BPD and MNL while females had a wider IFA.

CONCLUSIONS

Novel facial biometric parameters that correlate with GA hold cardinal information for the prenatal evaluation of facial development and thus surface the need for additional research in order to asses these findings as radiologic markers for facial structural pathologies.

Prenatal diagnosis of congenital head, face, and neck malformations-Is complementary fetal MRI of value?

OBJECTIVES

The aim of this study was to evaluate the role of fetal magnetic resonance imaging (MRI) as a complement to ultrasound (US) in the prenatal diagnosis of craniofacial anomalies.

METHODS

A historical cohort study including all pregnant women who were referred for fetal MRI because of antenatal diagnosis of craniofacial anomalies on screening US. Prenatal diagnostic US, MRI, and postnatal diagnosis were compared for consistencies and discrepancies.

RESULTS

Forty-five pregnant women with 73 suspected fetal craniofacial anomalies diagnosed by US underwent MRI. In 40 out of 73 anomalies (54.8%), US and MRI findings were in complete agreement with postnatal diagnoses. MRI correctly ruled out the diagnosis of 24 anomalies suspected on US and diagnosed four additional pathologies that were not demonstrated by US. Out of the 85 anomalies (suspected by imaging or confirmed postnatally), confident diagnosis could be made by MRI in 68 anomalies (80%), not diagnosed in 10 (11.8%), and over-diagnosed in seven (8.2%). By US, confident diagnosis could be made in 44 anomalies (51.8%), not diagnosed in 11 (12.9%), and over-diagnosed in 30 (35.3%).

CONCLUSION

MRI is valuable in the antenatal evaluation of fetal craniofacial anomalies and may be useful as an adjunct to US in the prenatal work-up of craniofacial anomalies.

A new method for evaluating short fetal corpus callosum

OBJECTIVE

Sonographic diagnosis of short corpus callosum (SCC) is based on measurement of a short for gestational age antero-posterior length of the corpus callosum (CC) in the midsagittal plane. We suggest a new method for evaluating SCC without referring to biometry tables.

METHODS

We measured the ratio between the CC length and the internal cranial occipitofrontal dimension (ICOFD) in the midsagittal plane in 399 normal fetuses at 20 + 6 to 35 + 3 weeks of gestation and in 31 fetuses with a diagnosis of a SCC and compared the mean ratio between two groups. The impact of cephalic biometric parameters, fetal presentation, and gender was assessed.

RESULTS

The ICOFD/CC length for normal pregnancies was constant throughout the pregnancy (2.35 ± 0.11). There was no correlation between the ICOFD/CC length and cephalic index, Biparietal Diameter (BPD), head circumference, fetal sex, or fetal presentation. The ratio of pregnancies with SCC was significantly higher: 3.20 ± 0.84 (P < .0001).

CONCLUSION

The ICOFD/CC length practically does not change throughout a normal pregnancy. The ratio was significantly higher in pregnancies with SCC. Measuring this ratio during fetal anatomical scan may enable rapid evaluation of the CC without the need to refer to biometry tables.

Determining gestational age using genome methylation profile: A novel approach for fetal medicine

Gestational age determination by traditional tools (last menstrual period, ultrasonography measurements and Ballard Maturational Assessment in newborns) has major limitations and therefore there is a need to find different approaches. In this study, we looked for a molecular marker that can be used to determine the accurate gestational age of the newborn. To this end, we performed reduced representation bisulfite sequencing (RRBS) on 41 cord blood and matching placenta samples from women between 25 and 40 weeks of gestation and generated an epigenetic clock based on the methylation level at different loci in the genome. We identified a set of 332 differentially methylated regions (DMRs) that undergo demethylation in late gestational age in cord blood cells and can predict the gestational age (r = -.7, P = 2E-05). Once the set of 411 DMRs that undergo de novo methylation in late gestational age was used in combination with the first set, it generated a more accurate clock (R = .77, P = 1.87E-05). We have compared gestational age determined by Ballard score assessment with our epigenetic clock and found high concordance. Taken together, this study demonstrates that DNA methylation can accurately predict gestational age and thus may serve as a good clinical predictor.

Normative volume measurements of the fetal intra-cranial compartments using 3D volume in utero MR imaging

PURPOSE

To describe the normal linear measurements of the skull (bi-parietal diameter and occipito-frontal diameter) and intracranial volumes (ventricular volume, brain parenchymal volume, extra-axial volume and total intra-cranial volume) in normal fetuses.

MATERIALS AND METHODS

We recruited pregnant women from low-risk pregnancies whose fetuses had normal ultrasound and in utero MR studies. All volunteers had in utero MR imaging on the same 1.5T MR scanner with a protocol consisting of routine and 3D steady-state volume imaging of the fetal brain. Linear measurements of the skull were made using the volume imaging. The 3D volume imaging also was manually segmented to delineate the intracranial compartments described above to determine quantitative values for each.

RESULTS

Two hundred normal fetuses were studied with gestational ages between 18 and 37 weeks. The linear skull measurements made on in utero MR imaging closely correlate with published data from ultrasonography. The intracranial volume data is presented as graphs and as tabular summaries of 3rd, 10th, 50th, 90th and 97th centiles.

CONCLUSION

It is now possible to measure the volumes of the intracranial compartments in individual fetuses using ultrafast in utero MR techniques.

KEY POINTS

• There are limitations in using the skull size of the fetus to comment on the state of the fetal brain. • Volumes for the intracranial compartments are presented, based on in utero MR imaging of the fetal brain between 18 and 37 weeks gestational age. • Those normative values can be used to assess fetuses with known or suspected structural brain abnormalities and may assist the differential diagnosis provided by visual assessment of routine iuMR studies.