Outcome of prenatally diagnosed agenesis of the corpus callosum

Fetal agenesis of the corpus callosum: Clinical and genetic analysis in a series of 40 patients

OBJECTIVES

This study aimed to explore the genetic causes of agenesis of the corpus callosum (ACC) and assess the utility of karyotype analysis, copy number variation sequencing (CNV-seq), and whole-exome sequencing (WES) to genetically diagnose fetal ACC.

METHODS

We retrospectively examined 40 fetuses diagnosed with ACC who underwent prenatal ultrasonography or magnetic resonance imaging between January 2019 and October 2023. Genetic tests were conducted on the fetuses using karyotype analysis or CNV-seq as the first-line diagnosis. WES was performed if aneuploid and pathogenic CNVs were excluded.

RESULTS

Among the 40 fetuses, 29 (72 %) had non-isolated ACC and 11 (28 %) had isolated ACC. Cerebellar dysplasia and hydrocephalus were the most common abnormal developments in the central nervous system. Twenty-eight patients underwent karyotype analysis, with a detection rate of 14 % (4/28). Twenty-six patients underwent CNV-seq; three patients were found to have pathogenic CNVs, with a detection rate of 12 % (3/26). Thirty-three fetuses with no findings of karyotype analysis or CNV-seq were subsequently tested using WES, with a detection rate of 36 % (12/33). Overall, the total diagnostic yield was 48 % (19/40), and monogenic etiology accounted for 30 % (12/40). The genetic detection rate of fetal non-isolated ACC (62 %, 18/29) was higher than that of isolated ACC (9 %, 1/11).

CONCLUSION

Prenatal genetic analysis of fetuses with ACC is clinically significant, with monogenic disorders being the main cause. WES may enhance the detection rate of fetuses with ACC with negative karyotype analysis or CNV-seq results.

Fetal neuroimaging applications for diagnosis and counseling of brain anomalies: Current practice and future diagnostic strategies

Advances in fetal brain neuroimaging, especially fetal neurosonography and brain magnetic resonance imaging (MRI), allow safe and accurate anatomical assessments of fetal brain structures that serve as a foundation for prenatal diagnosis and counseling regarding fetal brain anomalies. Fetal neurosonography strategically assesses fetal brain anomalies suspected by screening ultrasound. Fetal brain MRI has unique technological features that overcome the anatomical limits of smaller fetal brain size and the unpredictable variable of intrauterine motion artifact. Recent studies of fetal brain MRI provide evidence of improved diagnostic and prognostic accuracy, beginning with prenatal diagnosis. Despite technological advances over the last several decades, the combined use of different qualitative structural biomarkers has limitations in providing an accurate prognosis. Quantitative analyses of fetal brain MRIs offer measurable imaging biomarkers that will more accurately associate with clinical outcomes. First-trimester ultrasound opens new opportunities for risk assessment and fetal brain anomaly diagnosis at the earliest time in pregnancy. This review includes a case vignette to illustrate how fetal brain MRI results interpreted by the fetal neurologist can improve diagnostic perspectives. The strength and limitations of conventional ultrasound and fetal brain MRI will be compared with recent research advances in quantitative methods to better correlate fetal neuroimaging biomarkers of neuropathology to predict functional childhood deficits. Discussion of these fetal sonogram and brain MRI advances will highlight the need for further interdisciplinary collaboration using complementary skills to continue improving clinical decision-making following precision medicine principles.

Inhibitory control in children with agenesis of the corpus callosum compared with typically developing children

OBJECTIVES

The developmental absence (agenesis) of the corpus callosum (AgCC) is a congenital brain malformation associated with risk for a range of neuropsychological difficulties. Inhibitory control outcomes, including interference control and response inhibition, in children with AgCC are unclear. This study examined interference control and response inhibition: 1) in children with AgCC compared with typically developing (TD) children, 2) in children with different anatomical features of AgCC (complete vs. partial, isolated vs. complex), and 3) associations with white matter volume and microstructure of the anterior (AC) and posterior commissures (PC) and any remnant corpus callosum (CC).

METHODS

Participants were 27 children with AgCC and 32 TD children 8-16 years who completed inhibitory control assessments and brain MRI to define AgCC anatomical features and measure white matter volume and microstructure.

RESULTS

The AgCC cohort had poorer performance and higher rates of below average performance on inhibitory control measures than TD children. Children with complex AgCC had poorer response inhibition performance than children with isolated AgCC. While not statistically significant, there were select medium to large effect sizes for better inhibitory control associated with greater volume and microstructure of the AC and PC, and with reduced volume and microstructure of the remnant CC in partial AgCC.

CONCLUSIONS

This study provides evidence of inhibitory control difficulties in children with AgCC. While the sample was small, the study found preliminary evidence that the AC (f2=.18) and PC (f2=.30) may play a compensatory role for inhibitory control outcomes in the absence of the CC.

Evaluation of the height of the corpus callosum body region in fetal meningomyelocele malformation

PURPOSE

To investigate height of the corpus callosum (CC) in order to describe the corpus callosum anomalies in fetuses with meningomyelocele (MMC) and compare these findings with the corpus callosum of healthy fetuses.

METHODS

In this study, fetal MRI examinations were performed on 44 fetal MMC malformation cases. As the control group, 34 fetal MRI examinations, which were anatomically normal, were evaluated retrospectively. In the study group, lateral ventricle diameter, the level and diameter of the MMC defect, and CC height were measured. In the control group, CC height and lateral ventricular diameter were measured.

RESULTS

The mean CC body height was 1.36 mm in the study group, and 2.48 mm in the control group. The height of the CC body region of the study population was inclined to be thinner compared with the control population (p<0.001).

CONCLUSIONS

The fact that the height of the CC body region was found to be thinner in fetal MRI in cases of MMC compared with normal fetuses suggests that various callosal anomalies are uncertain, investigation of additional callosal anomalies may be beneficial in the decision for the continuation of pregnancy, and termination or intrauterine surgery in cases with MMC. Further large case group studies are needed.

Social anxiety disorder in an adolescent with agenesis of the corpus callosum: a case report

BACKGROUND

The agenesis of corpus callosum (ACC) could impair the connectivity of the hemispheres of the cerebral cortex and cause cognitive impairments, social and behavioral issues, and even psychiatric disorders. Although social deficits are common in ACC patients, it is rare for a social anxiety disorder to occur.

CASE PRESENTATION

To report a 17-year-old adolescent with complete ACC associated with social anxiety disorder, depression, impulsive behavior, and other neurodevelopmental defects such as intellectual disabilities. His avoidance and fear were improved after treatment with sertraline.

CONCLUSIONS

This is the first report of social anxiety disorder in ACC patients. The possible relationship between brain structural abnormities and anxiety syndrome should be investigated in more studies.

Magnetic Resonance Imaging (MRI) Diagnosis of Fetal Corpus Callosum Abnormalities and Follow-up Analysis

OBJECTIVES

We analyzed the magnetic resonance imaging (MRI) manifestations of fetal corpus callosum abnormalities and discussed their prognosis based on the results of postnatal follow up.

METHODS

One hundred fifty-five fetuses were diagnosed with corpus callosum abnormalities by MRI at our hospital from 2004 to 2019. Gesell Development Scales were used to evaluate the prognosis of corpus callosum abnormalities after birth.

RESULTS

Corpus callosum abnormalities were diagnosed in 149 fetuses from singleton pregnancies, and 6 pairs of twins, 1 in each pair is a corpus callosum abnormality. Twenty-seven cases (27/155) were lost to follow up, whereas 128 cases (128/155) were followed up. Of these, 101 cases were induced for labor, whereas 27 cases were born naturally. Among the 27 cases of corpus callosum abnormality after birth, 22 cases were from singleton pregnancies (22/27). Moreover, 1 twin from each of 5 pairs of twins (5/27) demonstrated corpus callosum abnormalities. The average Gesell Development Scale score was 87.1 in 19 cases of agenesis of the corpus callosum and 74.9 in 3 cases of hypoplasia of the corpus callosum. Among the 5 affected twins, 2 had severe neurodevelopmental delay, 2 had mild neurodevelopmental delay, and 1 was premature and died.

CONCLUSION

The overall prognosis of agenesis of the corpus callosum is good in singleton pregnancies. Hypoplasia of the corpus callosum is often observed with other abnormalities, and the development quotient of hypoplasia of the corpus callosum is lower compared with agenesis of the corpus callosum. Corpus callosum abnormalities may occur in one twin, in whom the risk may be increased.

Prenatal genetic testing in 19 fetuses with corpus callosum abnormality

Background

Corpus callosum abnormality (CCA) can lead to epilepsy, moderate severe neurologic or mental retardation. The prognosis of CCA is closely related to genetic etiology. However, copy number variations (CNVs) associated with fetal CCA are still limited and need to be further identified. Only a few scattered cases have been reported to diagnose CCA by whole exome sequencing (WES).

Methods

Karyotyping analysis, copy number variation sequencing (CNV‐seq), chromosomal microarray analysis (CMA) and WES were parallelly performed for prenatal diagnosis of 19 CCA cases.

Results

The total detection rate of karyotyping analysis, CMA (or CNV‐seq) and WES were 15.79% (3/19), 21.05% (4/19) and 40.00% (2/5), respectively. Two cases (case 11 and case 15) were diagnosed as aneuploidy (47, XY, + 13 and 47, XX, + 21) by karyotyping analysis and CNV‐seq. Karyotyping analysis revealed an unknown origin fragment (46,XY,add(13)(p11.2)) in case 3, which was further confirmed to originate from p13.3p11.2 of chromosome 17 by CNV‐seq. CMA revealed arr1q43q44 (238923617–246964774) × 1(8.04 Mb) in case 8 with a negative result of chromosome karyotype. WES revealed that 2 of 5 cases with negative results of karyotyping and CNV‐seq or CMA carried pathogenic genes ALDH7A1 and ARID1B.

Conclusion

Parallel genetic tests showed that CNV‐seq and CMA are able to identify additional, clinically significant cytogenetic information of CCA compared to karyotyping; WES significantly improves the detection rate of genetic etiology of CCA. For the patients with a negative results of CNV‐seq or CMA, further WES test is recommended.

Improved neurodevelopmental prognostication in isolated corpus callosal agenesis: fetal magnetic resonance imaging-based scoring system

OBJECTIVES

Corpus callosal agenesis (CCA) is one of the most common brain malformations and is generally associated with a good outcome when isolated. However, up to 25% of patients are at risk of neurodevelopmental delay, which currently available clinical and imaging parameters are inadequate to predict. The objectives of this study were to apply and validate a fetal magnetic resonance imaging (MRI) anatomical scoring system in a cohort of fetuses with isolated CCA and to evaluate the correlation with postnatal neurodevelopmental outcome.

METHODS

This was a retrospective cohort study of cases of prenatally diagnosed isolated CCA (as determined on ultrasound and MRI), with normal karyotype and with known postnatal neurodevelopmental outcome assessed by standardized testing. A fetal brain MRI anatomical scoring system based on seven categories (gyration, opercularization, temporal lobe symmetry, lamination, hippocampal position, basal ganglia and ventricular size) was developed and applied to the cohort; a total score of 0-11 points could be given, with a score of 0 representing normal anatomy. Images were scored independently by two neuroradiologists blinded to the outcome. For the purpose of assessing the correlation between fetal MRI score and neurodevelopmental outcome, neurodevelopmental test results were scored as follows: 0, 'below average' (poor outcome); 1, 'average'; and 2, 'above average' (good outcome). Spearman's rank coefficient was used to assess correlation, and inter-rater agreement in the assessment of fetal MRI score was calculated.

RESULTS

Twenty-one children (nine females (42.9%)) fulfilled the inclusion criteria. Thirty-seven fetal MRI examinations were evaluated. Mean gestational age was 28.3 ± 4.7 weeks (range, 20-38 weeks). All fetuses were delivered after 35 weeks' gestation with no perinatal complications. Fetal MRI scores ranged from 0 to 6 points, with a median of 3 points. Inter-rater agreement in fetal MRI score assessment was excellent (intraclass correlation coefficient, 0.959 (95% CI, 0.921-0.979)). Neurodevelopmental evaluation was performed on average at 2.6 ± 1.46 years (range, 0.5-5.8 years). There was a significant negative correlation between fetal MRI score and neurodevelopmental outcome score in the three areas tested: cognitive (ρ = -0.559, P < 0.0001); motor (ρ = -0.414, P = 0.012) and language (ρ = -0.565, P < 0.0001) skills. Using fetal MRI score cut-offs of ≤ 3 (good outcome) and ≥ 4 points (high risk for poor outcome), the correct prognosis could be determined in 20/21 (95.2% (95% CI, 77.3-99.2%)) cases.

CONCLUSION

By assessing structural features of the fetal brain on MRI, it may be possible to better stratify prenatally the risk of poor neurodevelopmental outcome in CCA patients. © 2020 Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Role of prenatal magnetic resonance imaging in fetuses with isolated agenesis of corpus callosum in the era of fetal neurosonography: A systematic review and meta-analysis

INTRODUCTION

Corpus callosum agenesis (ACC) is frequently diagnosed during fetal life; its prognosis depends also on additional anomalies. The additional value of fetal magnetic resonance imaging (MRI) in fetuses with "isolated" complete (cACC) and partial (pACC) agenesis of the corpus callosum on ultrasound is still debated.

MATERIAL AND METHODS

We performed a systematic literature review and meta-analysis including fetuses with a prenatal diagnosis of cACC and pACC without associated structural anomalies on ultrasound, undergoing fetal MRI. The primary outcome was the rate of additional anomalies detected at fetal MRI. Further analyses assessed the effect of type of ultrasound assessment (neurosonography vs standard axial assessment), gestational age at fetal MRI and rate of postnatally detected brain anomalies. Random-effect meta-analyses of proportions were used to analyze the data.

RESULTS

Fourteen studies (798 fetuses) were included. In cases with isolated cACC, 10.9% (95% CI 4.1-20.6) and 4.3% (95% CI 1.4-8.8) additional anomalies were detected by fetal MRI and postnatally, respectively. Stratifying according to the type of ultrasound assessment, the rate of associated anomalies detected only on fetal MRI was 5.7% (95% CI 0.5-16.0) with dedicated neurosonography and 18.5% (95% CI 7.8-32.4) with a standard axial assessment. In fetuses with isolated pACC, 13.4% (95% CI 4.0-27.0) and 16.2% (95% CI 5.9-30.3) additional anomalies were detected by fetal MRI or postnatally, respectively. Stratifying according to the type of ultrasound assessment, the rate of associated anomalies detected only on fetal MRI was 11.4% (95% CI 2.7-25.0) when dedicated neurosonography was performed. Cortical and posterior fossa anomalies represented the most common anomalies missed at ultrasound with both cACC and pACC. Due to the very small number of included cases, stratification according to early (<24 weeks of gestation) and late (>24 weeks) fetal MRI could not be done for either cACC or pACC.

CONCLUSIONS

The rate of associated anomalies detected exclusively at fetal MRI in isolated ACC undergoing neurosonography is lower than previously reported. Cortical and posterior fossa anomalies are among the most common anomalies detected exclusively at MRI, thus confirming the crucial role of fetal MRI in determining the prognosis of these fetuses. However, some anomalies still go undetected prenatally and this should be stressed during parental counseling.

Natural History of Ventriculomegaly in Fetal Agenesis of the Corpus Callosum

OBJECTIVES

To assess the natural evolution of the size of the fetal lateral ventricles throughout pregnancy in fetuses with callosal anomalies.

METHODS

Cases of fetal callosal anomalies were retrospectively classified as isolated or complex based on the presence of other structural or genetic anomalies. Longitudinal ultrasound studies were reviewed, and postnatal outcomes were retrieved for isolated cases.

RESULTS

In 135 fetuses, those who first presented after 24 weeks' gestation were more likely to have ventriculomegaly (n = 58 of 68 [85%]) than those who presented before 24 weeks (n = 39 of 67 [58%]; P < .001). In 79 cases that had longitudinal follow-up, the mean increase in ventricular width was 0.6 mm/wk, without a significant difference between isolated and complex cases (mean ± SD, 0.6 ± 1.5 versus 0.6 ± 1.1 mm; P = .45).

CONCLUSIONS

Callosal anomalies are associated with progressive ventriculomegaly on prenatal ultrasound imaging, without a difference between isolated and complex anomalies. This feature should be considered part of the disease spectrum. The consequence of progressive ventriculomegaly on the long-term neurodevelopmental outcome is still unknown, and further studies should be aimed at obtaining long-term follow-up of these cases.

An analysis of 109 fetuses with prenatal diagnosis of complete agenesis of corpus callosum

BACKGROUND

Agenesis of the corpus callosum (ACC) is the most frequent commissural malformation of the brain. It continues to be an important cause of the pregnancy termination associated with the central nervous system (CNS).

OBJECTIVE

The aim of the study is to provide a comprehensive assessment of fetuses with diagnosis of complete ACC, as well as postnatal neurodevelopmental outcomes.

METHODS

The data of 75,843 fetuses were screened for evaluation of complete ACC between 2003 and 2017, and a total of 109 cases with complete ACC were included in the study. ACC was considered isolated when no additional anomalies were detected, and ACC was considered complex when additional anomalies were present.

RESULTS

The prevalence of complete ACC was 9.4 per 10,000 live births, and the incidence was ranged from 1.8 to 16.6 per 10,000 person-years. Patients with isolated ACC had a significantly higher survival when compared with patients with complex ACC (97.4%, n = 38/39 vs. 68.8%, n = 22/32, P = 0.001).The most important cause of death were congenital heart disease and/or respiratory failure during neonatal period. Developmental and intellectual disabilities were significantly higher in the complex ACC cases (P < 0.001). Postnatal neurodevelopmental outcomes were completely normal in 79.4% of cases with isolated ACC.

CONCLUSIONS

Isolated complete ACC is usually associated with a favorable outcome. The most important prognostic factors are the presence or absence of associated congenital anomalies.

Disorganized Patterns of Sulcal Position in Fetal Brains with Agenesis of Corpus Callosum

Fetuses with isolated agenesis of the corpus callosum (ACC) are associated with a broad spectrum of neurodevelopmental disability that cannot be specifically predicted in prenatal neuroimaging. We hypothesized that ACC may be associated with aberrant cortical folding. In this study, we determined altered patterning of early primary sulci development in fetuses with isolated ACC using novel quantitative sulcal pattern analysis which measures deviations of regional sulcal features (position, depth, and area) and their intersulcal relationships in 7 fetuses with isolated ACC (27.1 ± 3.8 weeks of gestation, mean ± SD) and 17 typically developing (TD) fetuses (25.7 ± 2.0 weeks) from normal templates. Fetuses with ACC showed significant alterations in absolute sulcal positions and relative intersulcal positional relationship compared to TD fetuses, which were not detected by traditional gyrification index. Our results reveal altered sulcal positional development even in isolated ACC that is present as early as the second trimester and continues throughout the fetal period. It might originate from altered white matter connections and portend functional variances in later life.

Genetic testing in fetuses with isolated agenesis of the corpus callosum

PURPOSE

The objectives of this study were to explore genetics pathogenesis of isolated agenesis of corpus callosum (ACC) and assess the utility of chromosomal microarray analysis (CMA) for genetic diagnosis of isolated ACC.

METHODS

We analyzed the genomes of 16 fetuses with isolated ACC using Afymetrix CytoScan HD arrays and conducted further bioinformatic analysis for one proband fetus with an abnormal copy number variation (CNV).

RESULTS

Of the 16 fetal samples examined, two (12.5%) had pathogenic CNVs and three (18.75%) had variants of unknown significance. Two cases, case 2 and case 9, were found to have pathogenic CNVs. Bioinformatic analyses indicated that the CNV of one fetus (case 9) contained 115 annotated coding genes, five of which (SLC6A5, BDNF, ELP4, PAX6, and SLC1A2) have been associated with neurodevelopment. Three of these genes (SLC1A2, BDNF, and PAX6) may play a key role in ACC development. GO cluster analysis of the implicated genes revealed strong representations of protein binding and metal ion binding functions. KEGG pathway analysis pointed to four pathways: longevity regulating pathway, amyotrophic lateral sclerosis, cocaine addiction, and autophagy-animal.

CONCLUSIONS

BDNF, SLC1A2, and PAX6 may be involved in the development of isolated ACC. CMA is a feasible technology for prenatal diagnosis of isolated ACC.

Utilization of neurosonography for evaluation of the corpus callosum malformations in the era of fetal magnetic resonance imaging

AIM

We evaluated the ability of fetal neurosonography and magnetic resonance imaging (MRI) to asses callosal anomalies (CA) and associated cranial malformations. We also aimed to determine the long-term prognosis of the cases.

METHODS

Thirty-six cases of CA diagnosed combined with neurosonography and MRI between January 2012 and October 2017 were retrospectively reviewed.

RESULTS

Seventeen of 36 fetuses were diagnosed complete agenesis of corpus callosum (CACC) (47.2%), 9 had partial agenesis of corpus callosum (PACC) (25%) and 10 was dysgenesis of the corpus callosum (DCC) (27.2%) at ultrasonography (US) examination. Fetal MRI reported 16 of cases as CACC (44.4%), 11 PACC (30.5%) and nine (25%) DCC. The overall consistency between neurosonography and MRI in the definition of CA were 91% of cases. Sulcation anomalies were present in 9 cases in the US (25%) and 11 cases in MRI (30.4%). Seven of cases showed posterior fossa abnormalities in the US (19.4%) and eight cases in MRI (22.1%). Neonatal MRI added new findings to fetal MRI and neurosonography including grade-1 intraventricular hemorrhage and periventricular leukomalacia in two cases (12.5%). Eighteen cases were terminated (50%), 17 cases were followed up and mean follow up interval was 39 ± 5.1 months. The neurologic outcome was abnormal in seven (41.7%) patients. Presence of associated brain anomalies worsened the prognosis.

CONCLUSION

Fetal neurosonography has a comparable performance with MRI in the diagnosis of CA and associated anomalies. It should be used in collaboration with MRI to achieve accurate diagnosis which is crucial for counseling.

Clinical outcomes following prenatal diagnosis of asymmetric ventriculomegaly, interhemispheric cyst, and callosal dysgenesis (AVID)

OBJECTIVES

When identified prenatally, the imaging triad of asymmetric ventriculomegaly, interhemispheric cyst, and dysgenesis of the corpus callosum (AVID) can indicate a more serious congenital brain anomaly. In this follow-up series of 15 fetuses, we present the neurodevelopmental outcomes of a single institution cohort of children diagnosed prenatally with AVID.

METHODS

Our fetal ultrasound database was queried for cases of AVID between 2000 and 2016. All available fetal MR imaging studies were reviewed for the presence of (a) interhemispheric cysts or ventricular diverticula and (b) dysgenesis or agenesis of the corpus callosum. Clinical records were reviewed for perinatal management, postnatal surgical management, and neurodevelopmental outcomes.

RESULTS

Fifteen prenatal cases of AVID were identified. Twelve were live-born and three pregnancies were terminated. Of the 12 patients, 11 underwent neurosurgical intervention. Of the eight patients surviving past infancy, seven of eight have moderate to severe neurodevelopmental delays or disabilities, encompassing both motor and language skills, and all have variable visual abnormalities.

CONCLUSION

In our cohort of 15 prenatally diagnosed fetuses with AVID, eight survived past infancy and all have neurodevelopmental disabilities, including motor and language deficits, a wide range of visual defects, craniofacial abnormalities, and medical comorbidities.

Outcome of isolated agenesis of the corpus callosum: A population-based prospective study

OBJECTIVES

Neurodevelopmental outcome of apparently isolated agenesis of the corpus callosum (ACC) remains a major concern with uncertain prognosis. Despite "normal" IQ reported in a majority of patients, the rates of learning disabilities and severe outcome (ranging from 0% to 20%) are not clearly established.

METHODS

A large population-based series was investigated based on a longitudinal follow-up until school age, using Wechsler Intelligence scales at 3, 5, and 7 years.

RESULTS

Fifty women were referred to a tertiary referral unit for an "apparently" isolated ACC confirmed by ultrasound, foetal MRI, and karyotyping or array CGH. Twelve pregnancies were terminated, one foetus died in utero, one pregnancy outcome was unknown, and 36 babies were born. Two were lost to follow-up. Thirty-four children could be classified into three groups. Group 1 comprised two children (6%) with severe intellectual disability (one Mowat-Wilson syndrome and one ASD). Group 2 comprised 10 children (29%) who had learning disabilities and borderline intellectual functioning (VIQ and/or PIQ scores >70 and <85); three patients had hypopituitarism with additional MRI anomalies revealed after birth. Group 3 comprised 22 children (65%) who had both VIQ and PIQ >85 (-1 SD) with a normal school level. Longitudinal follow-up revealed weaker PIQ in younger children which improved with age.

CONCLUSION

Our data indicate that intellectual ability is normal (IQ > 85) in approximately two thirds and borderline in just over a quarter of patients. However, a low risk of severe cognitive impairment exists, and this information should be shared with couples during prenatal counselling.

Agenesis of the corpus callosum, developmental delay, autism spectrum disorder, facial dysmorphism, and posterior polymorphous corneal dystrophy associated with ZEB1 gene deletion

We report on a girl diagnosed prenatally with agenesis of the corpus callosum (ACC) on fetal ultrasound and MRI. On postnatal follow-up she was noted to have developmental delay, facial dysmorphism, autism spectrum disorder, and posterior polymorphous corneal dystrophy (PPD). Array-comparative genomic hybridization analysis (Array-CGH) showed a 2.05 Mb de novo interstitial deletion at 10p11.23p11.22. The deleted region overlaps 1 OMIM Morbid Map gene, ZEB1 (the zinc finger E-box binding homeobox transcription factor 1), previously associated with posterior polymorphous corneal dystrophy type 3 (PPCD3). To our best knowledge this is the first reported case with a deletion of the ZEB1 gene in an individual with ACC and PPD, showing that the haploinsufficiency of the ZEB1 is likely the cause of our patient's phenotype.

Prenatal and postnatal presentations of corpus callosum agenesis with polymicrogyria caused by EGP5 mutation

EPG5-related Vici syndrome is a rare multisystem autosomal recessive disorder characterized by corpus callosum agenesis (ACC), hypopigmentation, cataracts, acquired microcephaly, failure to thrive, cardiomyopathy and profound developmental delay, and immunodeficiency. We report here the first case of prenatally diagnosed Vici syndrome with delayed gyration associated with ACC. Trio based exome sequencing allowed the identification of a compound heterozygous mutation in the EPG5 gene. Our patient subsequently demonstrated severe developmental delay, hypopigmentation, progressive microcephaly, and failure to thrive which led to suspicion of the diagnosis. Her MRI demonstrated ACC with frontoparietal polymicrogyria, severe hypomyelination, and pontocerebellar atrophy. This prenatal presentation of malformations of cortical development in combination with ACC expands the EPG5-related phenotypic spectrum. Our report supports the idea that EPG5-related Vici syndrome is both a neurodevelopmental and neurodegenerative disorder. © 2017 Wiley Periodicals, Inc.

Role of fetal MRI in the evaluation of isolated and non-isolated corpus callosum dysgenesis: results of a cross-sectional study

PURPOSE

The aims of this study were to characterize isolated and non-isolated forms of corpus callosum dysgenesis (CCD) at fetal magnetic resonance imaging (MRI) and to identify early predictors of associated anomalies.

METHODS

We retrospectively analyzed 104 fetuses with CCD undergoing MRI between 2006 and 2016. Corpus callosum, cavum septi pellucidi, biometry, presence of ventriculomegaly, gyration anomalies, cranio-encephalic abnormalities and body malformations were evaluated. Results of genetic tests were also recorded.

RESULTS

At MRI, isolated CCD was 26.9%, the rest being associated to other abnormalities. In the isolated group, median gestational age at MRI was lower in complete agenesis than in hypoplasia (22 vs 28 weeks). In the group with additional findings, cortical dysplasia was the most frequently associated feature (P = 0.008), with a more frequent occurrence in complete agenesis (70%) versus other forms; mesial frontal lobes were more often involved than other cortical regions (P = 0.006), with polymicrogyria as the most frequent cortical malformation (40%). Multivariate analysis confirmed the association between complete agenesis and cortical dysplasia (odds ratio = 7.29, 95% confidence interval 1.51-35.21).

CONCLUSIONS

CCD is often complicated by other intra-cranial and extra-cranial findings (cortical dysplasias as the most prevalent) that significantly affect the postnatal prognosis. The present study showed CCD with associated anomalies as more frequent than isolated (73.1%). In isolated forms, severe ventriculomegaly was a reliable herald of future appearance of associated features. © 2016 John Wiley & Sons, Ltd.

Outcomes Associated With Isolated Agenesis of the Corpus Callosum: A Meta-analysis

CONTEXT

Antenatal counseling in cases of agenesis of the corpus callosum (ACC) is challenging.

OBJECTIVES

To ascertain the outcome in fetuses with isolated complete ACC and partial ACC.

DATA SOURCES

Medline, Embase, CINAHL, and Cochrane databases.

STUDY SELECTION

Studies reporting a prenatal diagnosis of ACC. The outcomes observed were: chromosomal abnormalities at standard karyotype and chromosomal microarray (CMA) analysis, additional anomalies detected only at prenatal MRI and at postnatal imaging or clinical evaluation, concordance between prenatal and postnatal diagnosis and neurodevelopmental outcome.

DATA EXTRACTION

Meta-analyses of proportions were used to combine data.

RESULTS

Twenty-seven studies were included. In cACC, chromosomal anomalies occurred in 4.81% (95% confidence interval [CI], 2.2-8.4) of the cases. Gross and fine motor control were abnormal in 4.40% (95% CI, 0.6-11.3) and 10.98% (95% CI, 4.1-20.6) of the cases, respectively, whereas 6.80% (95% CI, 1.7-14.9) presented with epilepsy. Abnormal cognitive status occurred in 15.16% (95% CI, 6.9-25.9) of cases. In partial ACC, the rate of chromosomal anomalies was 7.45% (95% CI, 2.0-15.9). Fine motor control was affected in 11.74% (95% CI, 0.9-32.1) of the cases, and 16.11% (95% CI, 2.5-38.2) presented with epilepsy. Cognitive status was affected in 17.25% (95% CI, 3.0-39.7) of cases.

LIMITATIONS

Different neurodevelopmental tools and time of follow-up of the included studies.

CONCLUSIONS

Children wih a prenatal diagnosis of isolated ACC show several degrees of impairment in motor control, coordination, language, and cognitive status. However, in view of the large heterogeneity in outcomes measures, time at follow-up, and neurodevelopmental tools used, large prospective studies are needed to ascertain the actual occurrence of neuropsychological morbidity of children with isolated ACC.

Antenatal diagnosis of agenesis of the corpus callosum

AIM

To estimate the diagnostic performance of ultrasound in detecting agenesis of the corpus callosum (ACC).

MATERIALS AND METHODS

A retrospective review was performed of 1722 in utero MRI examinations. All cases were identified in which the fetus had been referred from ultrasonography with a diagnosis of ACC and those in which ACC was given as a diagnosis on the in utero MRI study. The MRI was assumed to provide the correct diagnosis of ACC and descriptive statistics of diagnostic accuracy for ultrasound were calculated.

RESULTS

Of the 1722 ultrasound examinations performed, 121 had a diagnosis of ACC and approximately 50% were confirmed at MRI. Forty-two fetuses with ACC not suspected at ultrasonography were also identified at MRI. Ultrasonography had a positive predictive value of 47% (95% CI: 38-56%) and a negative predictive value of 97% (95% CI: 96-98%) for detecting ACC.

CONCLUSION

Ultrasound is poor in diagnosing ACC and in utero MRI should be performed if there is any suspicion on antenatal ultrasonography.

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.

Ethics of prenatal ultrasound

Prenatal ultrasound has opened new opportunities to examine, diagnose and treat the fetus, but these advances bring with them ethical dilemmas. In this chapter, I address the ethical principles that need to be considered when treating both mother and fetus as patients, and how these can be applied in practice. In particular, ultrasound practitioners have an ethical duty to maintain their theoretical knowledge and practical skills to ensure they advise parents correctly. I also discuss the ethical issues in carrying out intrauterine therapy, ultrasound-related research, and termination of pregnancy for fetal abnormality.

Agenesis of the corpus callosum: classifying functional manifestations with the ICF-CY

PURPOSE

Agenesis of the corpus callosum (ACC) is a congenital condition in which the corpus callosum fails to develop fully. In the literature, ACC has been broadly conceptualized and inconsistently described. This article demonstrates how the universal language of the International Classification of Functioning, Disability and Health-Children and Youth can increase the specificity with which researchers and clinicians describe the variable manifestations of ACC.

METHODS

The database for this article was based on a review of 83 studies on developmental and neuropsychological manifestations of congenital ACC in children and adolescents. First, the extent to which the findings on ACC could be documented using the taxonomic codes in the ICF-CY was examined. Next, the findings from each study were mapped onto the ICF-CY to summarize the distribution of clinical features reported in the literature.

RESULTS

There was a high degree of correspondence between the reported findings and the taxonomic codes of the ICF-CY. The distribution of clinical features was discussed.

CONCLUSIONS

This taxonomic application advances the ICF-CY as a common language for researchers and clinicians who work with children who have ACC. Implications for Rehabilitation Agenesis of the corpus callosum (ACC) is a condition that has been broadly conceptualized and inconsistently described in research and practice. The variable clinical manifestations of children with ACC can be most effectively described using the ICF-CY. The application of the ICF-CY to conditions with highly variable clinical manifestations, like ACC, positively impacts research and practice.

Non-visualisation of cavum septi pellucidi: implication in prenatal diagnosis?

OBJECTIVE

This manuscript reviews congenital anomalies and imaging findings associated with non-visualisation of the cavum septi pellucidi (CSP) found on prenatal sonogram.

BACKGROUND

Observation of a normal cavum septi pellucidi (CSP) is an important landmark in the second and third trimester prenatal ultrasound evaluation of the fetal brain, and its visualisation provides reassurance of normal central forebrain development. Non-visualisation of the CSP is a prenatal sonographic finding, which in most cases is associated with neuroanatomical anomalies that include agenesis of the corpus callosum, schizencephaly, septo-optic dysplasia, holoprosencephaly, chronic hydrocephalus and acquired fetal brain injury. Isolated septal deficiency, a rare but controversial entity, is considered a variant of normal. Common pitfalls in the sonographic evaluation of CSP include columns of the fornix that mimic CSP, and prominent cavum vergae that can simulate non-visualisation of the CSP. When non-visualisation of the CSP is suspected, magnetic resonance imaging (MRI) of the fetal brain can confirm and evaluate associated anomalies.

CONCLUSION

Visualisation of the CSP is an integral component of the prenatal ultrasound and its non-visualisation is associated with other malformations, diagnosis of which is aided by MRI.

TEACHING POINTS

• Cavum septi pellucidi (CSP) is an important landmark in the prenatal ultrasound evaluation of the fetal brain, and is a marker for normal central forebrain development. • Non-visualisation of the CSP is most commonly associated with other neuroanatomical abnormalities. • Examination of the fetal brain by MRI can confirm the sonographic findings and evaluate for associated anomalies.

Diagnosis, treatment, and long-term outcomes of fetal hydrocephalus

This study analyzed 156 cases of fetal hydrocephalus treated at Osaka National Hospital from 1992 to 2011 to review current methods for diagnosing and treating fetal hydrocephalus, and for estimating its clinical outcome. This was a retrospective study of a single institute (Osaka National Hospital). Of 156 cases in total, 37% were diagnosed as isolated ventriculomegaly, 50% as another type of malformation (36 cases of myelomeningocele, six of holoprosencephaly, three of Dandy-Walker syndrome, one case of Joubert syndrome, 12 of arachnoid cyst, nine of encephalocele, three of atresia of Monro and eight of corpus callosum agenesis, and 13% as secondary hydrocephalus. Diagnoses were made between 13 and 40 weeks of gestation (average 27 weeks). Diagnosis was made before 21 weeks of gestation in 24% of cases, from the first day of 22 weeks to the sixth day of 27 weeks in 27%, and after the first day of 28 weeks in 49%. With the exclusion of 17 aborted cases and 40 cases in which the patients were too young to evaluate or lost during follow-up, the final outcome was analyzed for 90 cases. Of these, 17% of the patients died, 21% showed severe retardation, 13% moderate retardation, 26% mild retardation, and 23% showed a good outcome. The long-term outcome was mostly influenced by the basic disease and accompanying anomaly. The time of diagnosis showed no correlation with outcome. Hydrocephalus associated with arachnoid cyst, atresia of Monro, and corpus callosum agenesis, and hydrocephalus due to fetal intracranial hemorrhage, resulted in good outcomes. By contrast, holoprosencephaly, hydrocephalus associated with encephalocele, syndromic hydrocephalus, and hydrocephalus due to fetal virus infection led to poor outcomes. For accurate diagnosis and proper counseling, established protocols are important for the diagnosis and treatment of fetal hydrocephalus, including not only fetal sonography, fetal magnetic resonance imaging, and TORCH (toxoplasma, rubella, cytomegalovirus, herpes simplex) screening test, but also chromosomal and gene testing.

Asymmetric ventriculomegaly, interhemispheric cyst, and dysgenesis of the corpus callosum (AVID): an imaging triad

A series of 20 cases from 2 academic institutions is presented with a characteristic imaging triad of asymmetric ventriculomegaly, a large interhemispheric cyst, and partial or complete agenesis of the corpus callosum. Most cases were initially referred as aqueduct stenosis and hydrocephalus or focal porencephaly. We describe the imaging findings that identify an abnormal or absent corpus callosum associated with a type 1 interhemispheric cyst in fetuses initially thought to have hydrocephalus attributable to aqueductal stenosis. We suggest that the acronym AVID (asymmetric ventriculomegaly, interhemispheric cyst, and dysgenesis of the corpus callosum) may be useful in recognition of these cases. All cases presented with markedly asymmetric ventriculomegaly on initial sonography, with progressive hydrocephalus throughout gestation. Fetal magnetic resonance imaging was performed in 15 of 20 cases. Thirteen of 20 cases were identified in male fetuses. Associated fetal and postnatal abnormalities are also reported. Technological improvements in sonography and fetal magnetic resonance imaging allow improved characterization of associated intracranial anomalies in the setting of hydrocephalus. Accurate diagnosis can aid parental counseling, especially because isolated aqueductal stenosis suggests a better prognosis than hydrocephalus with anomalies. Markedly asymmetric ventriculomegaly in this series was the key to excluding isolated aqueductal stenosis and was associated with callosal malformation with a type 1a interhemispheric cyst.

Counseling in fetal medicine: agenesis of the corpus callosum

In this Review, we aim to provide up-to-date and evidence-based answers to common questions regarding the diagnosis and prognosis of prenatally detected agenesis of the corpus callosum (ACC). A systematic literature search was performed to identify all reports of ACC and reference lists of articles were identified. ACC involves partial or complete absence of the main commissural pathway that connects the two cerebral hemispheres, and can be isolated (with no other abnormalities) or complex (coexisting with other abnormalities). It is a rare finding and the prevalence is difficult to estimate because of selection bias in reported series. The corpus callosum (CC) can be assessed on ultrasound by direct visualization, but indirect features, such as ventriculomegaly, absence of the cavum septi pellucidi or widening of interhemispheric fissure, are often the reason for detection in a screening population. Careful imaging in a center with a high level of expertise is required to make a full assessment and to exclude coexisting abnormalities, which occur in about 46% of fetuses. When available, magnetic resonance imaging appears to be an important adjunct as it allows direct visualization. It can reduce false-positive rates on ultrasound and can confirm ACC, it can assess whether this is complete or partial and it can help in detecting coexisting brain abnormalities not seen on ultrasound. The overall rate of chromosomal abnormality in fetuses with ACC is 18%, but this high rate includes both isolated and complex ACC; more recent studies suggest that chromosomal abnormalities are rare in isolated cases. Nevertheless, postnatal follow-up studies suggest that about 15% of cases thought to be isolated prenatally were found to have associated abnormalities after birth. Neurodevelopmental outcome in isolated ACC was recently reported in a systematic review and suggested normal outcome in about 65-75% of cases. Findings need to be considered in light of the several limitations of existing studies, in terms of study design, selection bias, varying definitions and imaging protocols, ascertainment bias and lack of control groups. These uncertainties mean that antenatal counseling is difficult and further large prospective studies are needed.

Long-term outcome of antenatally diagnosed agenesis of corpus callosum and cerebellar malformations

Recent advancements in fetal imaging and antenatal care have enabled identification of numerous anomalies including agenesis of corpus callosum and posterior fossa abnormalities. One of the important determinants of long-term prognosis in these conditions is the presence of central nervous system (CNS) and extra-CNS anomalies. The difficulty in confirming the isolated nature of these conditions antenatally and the lack of clear information regarding long-term prognoses makes it difficult for the clinician to provide accurate information to the parents antenatally. Caring for these families would require input from a multidisciplinary team involving obstetricians, geneticists, neurologists, radiologists and neonatologists.

Prenatal neurologic anomalies: sonographic diagnosis and treatment

The low prevalence of fetal CNS anomalies results in a restricted level of exposure to, and limited experience for most obstetricians involved in, prenatal ultrasound. Sonographic guidelines for screening the fetal brain in a systematic way may increase the detection rate of fetal CNS anomalies, thus promoting correct referral to tertiary care centers offering patients a multidisciplinary approach to the condition. The aim of this review is to elaborate on the prenatal sonographic diagnosis and outcome of various CNS malformations. Detailed neurosonographic investigation has become available through high-resolution vaginal ultrasound probes and the development of a variety of 3-dimensional (3D) ultrasound modalities, such as ultrasound tomographic imaging. In addition, fetal magnetic resonance imaging is particularly helpful in the detection of gyration and neurulation anomalies, and disorders of the gray and white matter. Isolated mild ventriculomegaly is a rather common finding with good overall outcome. With an increasing diameter of the atria, however, and especially with the presence of associated malformations, long-term neurodevelopmental and behavioral outcome is disturbed in about 15% or more of cases. In view of recent developments in fetal therapy for neural tube defects, there is a clear need for a high level of ultrasound screening, work-up and counseling in tertiary care centers to identify those cases that might benefit from in utero intervention. The failure of prosencephalic midline induction and development results in midline defects ranging from alobar holoprosencephaly to isolated corpus callosum defects. The detection of callosal abnormaties is enhanced by 3D ultrasound, but counseling on neurodevelopmental outcome remains challenging. The Dandy-Walker spectrum includes isolated megacisterna magna, Blake's pouch cyst, hypoplasia of the vermis and Dandy-Walker malformation. Except for complete agenesis of the vermis associated with fourth ventricle cyst formation, data on long-term outcomes for the various conditions is largely lacking. Congenital cytomegalovirus (CMV) results in the highest incidence of children born with, or developing, long-term neurologic conditions. If proof of fetal infection has been delivered, microcephaly, cortical malformations, and intraparenchymal cysts show a strong correlation with poor outcome. Fetuses with CMV-related ultrasound abnormalities might benefit from maternal transplacental treatment. The aneurysm of the vein of Galen, a vascular malformation of the brain, often results in high cardiac output failure. After neonatal arterial embolization, survival is about 50% with normal neurologic development in 36% of cases. Over 50% of intracranial tumors are teratomata, presenting as fast-growing heterogeneous solid-cystic masses with calcifications. Most intracranial hemorrhages are related to the ventricular system, and prognosis is often poor, particularly in cases involving parenchymal and subdural bleeding. Proliferation disorders of the brain are often characterized by microcephaly. Their etiology is heterogeneous and prenatal diagnosis is often made late in gestation.

Neurodevelopment after prenatal diagnosis of isolated agenesis of the corpus callosum: an integrative review

OBJECTIVE

To systematically review published data on the neurodevelopment of children that were diagnosed prenatally with isolated agenesis of the corpus callosum.

STUDY DESIGN

Medline and Scopus searches (1960-July 2011); cross-referencing of retrieved articles.

RESULTS

Sixteen reports (132 cases of apparently isolated agenesis of the corpus callosum) were included in the analysis. The rates of normal outcome, borderline or moderate disability and severe disability were 94/132 (71.2%; 95% confidence interval [CI], 63.0-78.3), 18/132 (13.6%; 95% CI, 8.8-20.5), and 22/132 (15.2%; 95% CI, 10.0-22.2), respectively. Magnetic resonance imaging detected additional cerebral abnormalities in 22.5% (95% CI, 12.3-37.5) of apparently isolated agenesis of the corpus callosum cases. In truly isolated agenesis of the corpus callosum (confirmed by magnetic resonance imaging), the rates of normal neurodevelopment and severe disability were 52/69 (75.4%; 95% CI, 64.0-84.0) and 8/69 (11.6%; 95% CI, 6.0-21.2), respectively.

CONCLUSION

Prenatally diagnosed, isolated agenesis of the corpus callosum is usually associated with a favorable outcome. Larger, prospective series are required, as current data are limited, inconsistent, and prevent subgroup analyses (eg, complete vs partial agenesis of the corpus callosum).

Reference values for the length and area of the fetal corpus callosum on 3-dimensional sonography using the transfrontal view

OBJECTIVES

The purpose of this study was to determine reference values for the length and area of the fetal corpus callosum between 20 and 33 weeks' gestation using 3-dimensional sonography.

METHODS

A cross-sectional study was performed in 293 healthy pregnant women between 20 and 33 weeks' gestation. The length and area of the corpus callosum were obtained via the transfontal view with the metopic suture as an acoustic window using 3-dimensional sonographic aquisitions. Linear and weighted polynomial regression models were used, which were adjusted by residual analysis and the R(2) determination coefficient. Intraobserver and interobserver reproducibilities were analyzed by an intraclass correlation coefficient.

RESULTS

The mean corpus callosum length ± SD varied from 19.52 ± 2.24 to 40.36 ± 2.87 mm, whereas the mean area varied from 0.44 ± 0.11 to 1.47 ± 0.21 cm(2) at 20 and 33 weeks, respectively. The length and area were highly correlated with gestational age: corpus callosum length = -52.41 + 4.71 × gestational age - 0.06 × gestational age(2) (R(2) = 0.868); and corpus callosum area = -2.47 + 0.16 × gestational age - 0.000037 × gestational age(2) (R(2) = 0.765). The intraobserver and interobserver reproducibilities were excellent, with intraclass correlation coefficients of 0.98 and 0.94 for the length and 0.99 and 0.90 for the area, respectively.

CONCLUSIONS

Reference values for the length and the area of the fetal corpus callosum between 20 and 33 weeks' gestation were determined with high reproducibility.

Neurodevelopmental outcome following prenatal diagnosis of an isolated anomaly of the corpus callosum

OBJECTIVES

To assess the ability of prenatal ultrasound and magnetic resonance imaging (MRI) to diagnose isolated anomalies of the corpus callosum (ACC) and to further document the long-term prognosis following diagnosis.

METHODS

This was a prospective case-control study carried out between 1999 and 2004. Diagnosis was made by a combination of ultrasound and MRI. All infants were examined by a neuropediatrician and parents consented to answer questionnaires (CDI, Ireton's Child Developmental Inventory) in 22 cases, which were matched with 44 control infants. The CDI was used to assess neurodevelopmental outcome in cases and controls. Mean DQ-CDI (development quotient calculated from CDI) values and frequencies of abnormal results were compared between groups, and a meta-analysis of previous studies was performed.

RESULTS

The diagnosis of ACC was made prenatally and confirmed postnatally in 175 cases. The diagnosis was thought to be isolated ACC in 88/175 (50%) cases. Sixty of these 88 cases (68%) underwent termination of pregnancy and one died in utero. Twenty-seven were liveborn, of which 26 were followed up for a median of 50 (range, 30-74) months. Additional anomalies were diagnosed postnatally in four (15%) of these 26 neonates. The control group was significantly better (P < 0.05) compared with the cases diagnosed prenatally with isolated ACC with respect to gross motor, fine motor, language comprehension, numbers and general development, and it was marginally better for letters (P = 0.066). Seven of 26 (27%) (95% CI, 13-46%) infants with ACC over the age of 30 months had neurodevelopmental delay, compared with only one case with borderline developmental delay among the 44 controls (P = 0.006).

CONCLUSION

Prenatal diagnosis of ACC by a combination of ultrasound and MRI is reliable. However, the isolated nature of the anomaly could only be assessed in 85% of our cases. Since counseling is provided at the time of prenatal diagnosis, our population of isolated ACC included the cases that were missed prenatally as being ACC with associated anomalies. A meta-analysis of nine studies suggests that the development of children diagnosed prenatally with isolated ACC is normal in up to 70% (CI 95%, 56-83%) of cases. This means that the prospective risk of neurodevelopmental delay for a fetus with ACC described as isolated prenatally is 27%, compared with 15% for an infant whose diagnosis of isolated ACC is confirmed postnatally.

Corpus callosum length by gestational age as evaluated by fetal MR imaging

Although suspected corpus callosum abnormality is a common indication for fetal MR imaging, biometric data specific to MR imaging are sparse. We sought to characterize growth in corpus callosum length by EGA with fetal MR imaging. Corpus callosum segments were assessed and overall corpus callosum length was measured and plotted against the EGA for 68 anatomically normal fetal brains ranging in EGA from 18.5 to 37.7 weeks, and linear and polynomial regression models were calculated. The body of the corpus callosum was identified in all fetuses, followed in frequency by the splenium (91.2%), genu (85.3%), and rostrum (32.4%). Measurements of corpus callosum length by MR imaging were in agreement with values established by sonography. A second-degree polynomial function was the best fit for callosal length by EGA. Understanding this normal growth pattern may enhance detection of subtle growth abnormalities.

A systematic technique using 3-dimensional ultrasound provides a simple and reproducible mode to evaluate the corpus callosum

OBJECTIVE

The aim of this study was to evaluate a rapid 3-dimensional ultrasound-assisted technique for evaluation of the corpus callosum as an integral part of the anatomic survey.

STUDY DESIGN

Transabdominal 3-dimensioal gray scale and power Doppler volumes of the fetal brain were acquired in 102 consecutive healthy fetuses at 20-23 postmenstrual weeks. Offline analysis was performed by 2 of the authors using a systematic approach of "volume manipulation." Diagnostic-quality visualization of the corpus callosum and the pericallosal arteries on the median plane was recorded by the 2 examiners independently.

RESULTS

The median plane was easily obtained in all cases. Diagnostic-quality images of the corpus callosum were recorded in 93.1% and 99.0% and of the pericallosal arteries in 94.4% and 95.5% of the cases, by the 2 examiners, respectively.

CONCLUSION

Three-dimensional ultrasound enables a rapid and easy evaluation of the corpus callosum that may facilitate its inclusion as an integral part of the routine anatomic survey.

Prenatal diagnosis and outcome of partial agenesis and hypoplasia of the corpus callosum

OBJECTIVE

To present antenatal sonographic findings and outcome of fetuses with hypoplasia or partial agenesis of the corpus callosum.

METHODS

The database of our ultrasound laboratory was searched retrospectively for cases of hypoplasia or partial agenesis of the corpus callosum suspected at antenatal neurosonography between 1998 and 2008 and confirmed by pathology or postnatal neuroimaging. In surviving infants, clinical follow-up had been arranged to assess neurodevelopmental outcome.

RESULTS

Nineteen fetuses with callosal underdevelopment were identified at a median gestational age of 22 (range, 21-33) weeks and confirmed at follow-up, including 14 with partial agenesis and five with hypoplasia. Among the 14 fetuses with partial agenesis, there were additional brain findings in 10, including two with absent cavum septi pellucidi, four with mild isolated ventriculomegaly and four with cerebellar abnormalities, two of which also had ventriculomegaly. Pregnancy was terminated electively in seven of the cases with partial agenesis and there was one neonatal death. Among the six surviving infants, neurodevelopmental outcome was appropriate for age in three at follow up, including two cases with isolated partial agenesis of the corpus callosum. Among the five fetuses with prenatally diagnosed callosal hypoplasia, additional anomalies were present in four. Two cases were terminated electively and three were alive at the time of writing, with a median age of 3 years. Among them, apparently normal neurological development was observed in only one case.

CONCLUSIONS

An antenatal diagnosis of callosal underdevelopment is possible by expert sonography. There is often association with other major anomalies. However, even in fetuses with apparently isolated findings, the prognosis is uncertain.

Fetal magnetic resonance imaging of acquired and developmental brain anomalies

During the last decade, increasing interest in magnetic resonance imaging has emerged for the evaluation of fetal abnormalities detected on ultrasound. The advent of single-shot rapid acquisition sequences has greatly facilitated our ability to obtain detailed imaging information of the fetal brain. To date, fetal magnetic resonance imaging has shown to have an important role in the investigation of cerebral abnormalities suspected by sonography, and in the detection of subtle brain anomalies associated with high-risk pregnancies. Magnetic resonance imaging has proved to be a useful adjunct to sonography during the prenatal period of development, especially for the detection of acquired disorders.

Disorders of prosencephalic development

Abnormal ventral induction may result in disorders of formation, cleavage, and midline development of prosencephalic structures. Holoprosencephaly is a developmental field defect of impaired cleavage of prosencephalon. The most widely accepted classification of holoprosencephaly recognizes three major varieties: the alobar, semilobar and lobar types, according to the severity of the malformation. The brain malformations, characterized by the fusion of the cerebral hemisphere along the midline are commonly associated with facial anomalies. Corpus callosum agenesis and septo-optic dysplasia are disorders of prosencephalic midline development, and usually have less severe presentations but still, affected subjects may suffer from neurodevelopmental retardation, and/or endocrinologic and visual disorders. In this article we report an up-to-date of pathogenesis, prenatal sonographic findings, differential diagnosis and prognosis of the aforementioned anomalies.

Effects of failed commissuration on the septum pellucidum and fornix: implications for fetal imaging

In the previous article, we considered the normal appearances of the midline stuctures of the brain as they appear on high-resolution magnetic resonance imaging. In this article, we discuss the effects of failed commissuration on the midline structures. We highlight some of the misconceptions of this process that may lead to misdiagnosis of agenesis of the corpus callosum in utero.