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.

Role of prenatal magnetic resonance imaging in fetuses with isolated anomalies of corpus callosum: multinational study.

OBJECTIVE: To assess the performance of fetal magnetic resonance imaging (MRI) in detecting associated anomalies in fetuses diagnosed with isolated corpus callosal (CC) anomaly on multiplanar ultrasound evaluation of the fetal brain (neurosonography). METHODS: This was a multicenter, retrospective cohort study involving 14 fetal medicine centers in Italy, UK, Portugal, Canada, Austria and Spain. Inclusion criteria were fetuses with an apparently isolated CC anomaly, defined as an anomaly of the CC and no other additional central nervous system (CNS) or extra-CNS abnormality detected on expert ultrasound, including multiplanar neurosonography; normal karyotype; maternal age ≥ 18 years; and gestational age at diagnosis ≥ 18 weeks. The primary outcome was the rate of additional CNS abnormalities detected exclusively on fetal MRI within 2 weeks following neurosonography. The secondary outcomes were the rate of additional abnormalities according to the type of CC abnormality (complete (cACC) or partial (pACC) agenesis of the CC) and the rate of additional anomalies detected only on postnatal imaging or at postmortem examination. RESULTS: A total of 269 fetuses with a sonographic prenatal diagnosis of apparently isolated CC anomalies (207 with cACC and 62 with pACC) were included in the analysis. Additional structural anomalies of the CNS were detected exclusively on prenatal MRI in 11.2% (30/269) of cases, with malformations of cortical development representing the most common type of anomaly. When stratifying the analysis according to the type of CC anomaly, the rate of associated anomalies detected exclusively on MRI was 11.6% (24/207) in cACC cases and 9.7% (6/62) in pACC cases. On multivariate logistic regression analysis, only maternal body mass index was associated independently with the likelihood of detecting associated anomalies on MRI (odds ratio, 1.07 (95% CI, 1.01-1.14); P = 0.03). Associated anomalies were detected exclusively after delivery and were missed on both types of prenatal imaging in 3.9% (8/205) of fetuses with prenatal diagnosis of isolated anomaly of the CC. CONCLUSION: In fetuses with isolated anomaly of the CC diagnosed on antenatal neurosonography, MRI can identify a small proportion of additional anomalies, mainly malformations of cortical development, which are not detected on ultrasound. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

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.

Heterogeneity in defining fetal corpus callosal pathology: systematic review.

OBJECTIVE: Fetal anomalies of the corpus callosum (CC) have been reported in the prenatal imaging literature since 1985, and, especially when isolated, pose challenges for both the patient and fetal medicine specialist. The purpose of this study was to review systematically the literature on prenatally diagnosed abnormalities of the CC, focusing on the terminology used to describe abnormalities other than complete agenesis of the CC, and to assess the heterogeneity of the nomenclature and definitions used. METHODS: This study was conducted in accordance with the PRISMA statement for reporting systematic reviews. A literature search was performed to identify prospective or retrospective case series or cohort studies, published in English, French, Italian, German or Spanish, reporting fetal imaging findings and describing anomalies of the CC. Quality and risk of bias of the studies were evaluated using the Newcastle-Ottawa scale and a modification of the scale developed by Conde-Agudelo et al. for other fetal imaging studies. The data extracted included the number of patients, the number of different anomalies identified, the descriptive names of the anomalies, and, where applicable, the definitions of the anomalies, the number of cases of each type of anomaly and the biometric charts used. Secondary tests used to confirm the diagnosis, as well as the postnatal or post-termination tests used to ascertain the diagnosis, were also recorded. RESULTS: The search identified 998 records, and, after review of titles and abstracts and full review of 45 papers, 27 studies were included initially in the review, of which 24 were included in the final analysis. These 24 studies had a broad range of quality and risk of bias and represented 1135 cases of CC anomalies, of which 49% were complete agenesis and the remainder were described using the term partial agenesis or nine other terms, of which five had more than one definition. CONCLUSIONS: In comparison to the postnatal literature, in the prenatal literature there is much greater heterogeneity in the nomenclature and definition of CC anomalies other than complete agenesis. This heterogeneity and lack of standard definitions in the prenatal literature make it difficult to develop large multicenter pooled cohorts of patients who can be followed in order to develop a better understanding of the genetic associations and neurodevelopmental and psychological outcomes of patients with CC anomalies. As this information is important to improve counseling of these patients, a good first step towards this goal would be to develop a simpler categorization of prenatal CC anomalies that matches better the postnatal literature. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

A novel technique to assess fetal corpus callosum by two-dimensional axial plane.

OBJECTIVE: The definition of new normal values of the corpus callosum (CC) in axial sonographic scans and evaluation of their feasibility in diagnosing abnormal CC. METHODS: A cross-sectional study assessed CC from 20-gestational-week to full-term. CC observations across three axial planes (the largest CC length plane, trans-genu-and-splenium plane, and trans-body plane) were developed. The largest CC length, genu and splenium thickness, and body width and thickness were compared with compound scatter plots. Ultrasonographic features of normal and abnormal CC were described and the feasibility of the new approach studied. Intra-class correlation coefficient (ICC) was used for assessing the intra- and inter-observer agreements. RESULTS: Six hundred seventy normal and 42 abnormal fetuses from 20-gestational-week to full-term were studied. The mean normal and abnormal group maternal ages were 30.46 ± 4.36 years and 29.69 ± 4.49 years (p = 0.269). The success rate in obtaining satisfactory axial planes reached 100% but only 13.9% for sagittal plane in the normal group. The success rate of abnormal cases obtaining satisfactory axial planes was 100% and 59.5% by sagittal plane (p < 0.05). The compound scatter plots of abnormal and normal groups showed that the largest CC length and body width were significantly lower in normal fetuses, and the thickness of the genu and splenium with CC hypoplasia was significantly lower than normal fetuses. The intra- and inter-observer agreements were reproducible (all ICC > 0.850). CONCLUSIONS: The feasibility of incorporating an evaluation of CC into routine anatomical screening was demonstrated. Additionally, a focused examination of the craniocerebral axial planes exploring CC at the time of central nervous system scanning might facilitate CC anomaly detection. KEY POINTS: • Three axial planes with direct CC measurements can detect CC anomalies more accurately compared with indirect CC signs. Besides, this method is simpler, more convenient, and time-saving compared with the sagittal plane. • Assessing fetal CC on the axial plane helps clinicians to diagnose fetuses with abnormal CC. • A prospective single-center study showed that our new technique provides enough diagnostic confidence.

L1CAM mutations in three fetuses diagnosed by medical exome sequencing.

OBJECTIVE: The L1 cell adhesion molecule (L1CAM) gene, encodes the L1 cell adhesion molecule, is involved in the central nervous system development. Its mutations result in L1 syndrome which is associated with brain malformation and nervous developmental delay. CASE REPORT: We presented three fetuses with hydrocephalus and agenesis of the corpus callosum detected by ultrasound, followed by medical exome sequencing (MES) test with L1CAM mutations: two known missense mutation c.551G > A (p. R184Q) and c.1354G > A (p. G452R), and a novel frameshift mutation c.1322delG which causes the early termination of translation (p. G441Afs∗72). By utilizing multiple computational analysis, all the variants were scored to be likely pathogenic. CONCLUSION: Combined use of ultrasound and MES to identify the molecular etiology of fetal anomalies may contribute to expanding our knowledge of the clinical phenotype of L1 syndrome observed in the south Chinese population.

Prenatal diagnosis of mosaic trisomy 8 by amniocentesis in a fetus with ventriculomegaly and dysgenesis of the corpus callosum.

OBJECTIVE: We present prenatal diagnosis of mosaic trisomy 8 by amniocentesis in a fetus with central nervous system abnormalities. CASE REPORT: A 39-year-old woman was found to have fetal bilateral ventriculomegaly and enlargement of the third ventricle on prenatal ultrasound at 32 weeks of gestation. Fetal magnetic resonance imaging examination confirmed bilateral ventriculomegaly and dysgenesis of the corpus callosum. Amniocentesis was performed subsequently. Array comparative genomic hybridization (aCGH) analysis on the DNA extracted from uncultured amniotic cells revealed trisomy 8 mosaicism with a result of arr [GRCh37] (8) × 3[0.19], (X,Y) × 1. Conventional cytogenetic analysis on cultured amniocytes showed that among 108 cells in 12 colonies of three cultures, only one cell was abnormal with trisomy 8, trisomy 9 and monosomy 13, while the rest 107 cells had a normal karyotype. Repeat amniocentesis and cord blood sampling revealed a result of arr 8p23.3q24.3 (191,530-146,280,020) × 2.3 with a log2 ratio of 0.2 compatible with 20-30% mosaicism for trisomy 8 on the uncultured amniocytes, and a result of arr 8p23.3q24.3 (191,530-146,280,020) × 2.1 with a log2 ratio of 0.08 compatible with <10% mosaicism for trisomy 8 on the cord blood lymphocytes. Polymorphic DNA marker analysis excluded uniparental disomy 8. A malformed 2440-g dead fetus was delivered at 34 weeks of gestation with facial dysmorphism. CONCLUSION: Cytogenetic discrepancy can occur between cultured and uncultured amniocytes in mosaic trisomy 8 at amniocentesis. aCGH analysis on uncultured amniocytes is useful for confirmation of mosaic trisomy 8 at amniocentesis. Fetuses with low-level mosaicism for trisomy 8 may prenatally present ventriculomegaly and dysgenesis of the corpus callosum.

Prenatal diagnosis of partial monosomy 21q (21q22.1→qter) associated with intrauterine growth restriction and corpus callosum dysgenesis.

OBJECTIVE: A prenatal diagnosis of partial monosomy 21q(21q22.1→ qter) in fetus with intrauterine growth restriction and corpus callosum dysgenesis but escaped from the detection by cell free DNA testing was reported. CASE REPORT: A 31-year-old, primigravida women, presented with intrauterine growth restriction and corpus callosum dysgenesis at 23 weeks of gestational age by anatomic ultrasound screening. The interphase fluorescence in situ hybridization (FISH) analysis on amniocytes revealed monosomy 21, while the cytogenetic analysis and array comparative genomic hybridization (CGH) with CytoScan gene chip ascertained a 12.35 Mb deletion at 21q22.1q22.3. CONCLUSION: Although noninvasive prenatal testing is used extensively and can be applied to certain microdeletion diseases, the application for uncommon deletion disorders such as the present case remains limited. Prenatal examination with detailed ultra-sonography combined with different modalities of invasive prenatal testing can provide a more comprehensive information.

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.

PlexinA1 is crucial for the midline crossing of callosal axons during corpus callosum development in BALB/cAJ mice.

The corpus callosum (CC) is the biggest commissure that links cerebral hemispheres. Guidepost structures develop in the cortical midline during CC development and express axon guidance molecules that instruct neurons regarding the proper direction of axonal elongation toward and across the cortical midline. Neuropilin-1 (Npn1), a high affinity receptor for class 3 semaphorins (Sema3s) localized on cingulate pioneering axons, plays a crucial role in axon guidance to the midline through interactions with Sema3s. However, it remains unclear which type of Plexin is a component of Sema3 holoreceptors with Npn1 during the guidance of cingulate pioneering axons. To address the role of PlexinA1 in CC development, we examined with immunohistochemistry the localization of PlexinA1, Npn1, and Sema3s using embryonic brains from wild-type (WT) and PlexinA1-deficient (PlexinA1 knock-out (KO)) mice with a BALB/cAJ background. The immunohistochemistry confirmed the expression of PlexinA1 in callosal axons derived from the cingulate and neocortex of the WT mice on embryonic day 17.5 (E17.5) but not in the PlexinA1 KO mice. To examine the role of PlexinA1 in the navigation of callosal axons, the extension of callosal axons toward and across the midline was traced in brains of WT and PlexinA1 KO mice at E17.5. As a result, callosal axons in the PlexinA1 KO brains had a significantly lower incidence of midline crossing at E17.5 compared with the WT brains. To further examine the role of PlexinA1 in CC development, the CC phenotype was examined in PlexinA1 KO mice at postnatal day 0.5 (P0.5). Most of the PlexinA1 KO mice at P0.5 showed agenesis of the CC. These results indicate the crucial involvement of PlexinA1 in the midline crossing of callosal axons during CC development in BALB/cAJ mice.

Fetal brain MRI findings and neonatal outcome of common diagnosis at a tertiary care center.

Fetal Magnetic Resonance Imaging (MRI) is increasingly used in prenatal evaluations. OBJECTIVE: Identify common brain malformations on fetal MRI and evaluate perinatal course. METHODS: Fetal consultations from 10/2016 to 12/2017 reviewed. RESULTS: Hundred consultations were requested; 94 were completed. Findings included: posterior fossa malformations (19%), agenesis/dysgenesis of corpus callosum (15%), congenital aqueductal stenosis (CAS) (14%), ventriculomegaly (11%), isolated cortical malformations (8.5%), and holoprosencephaly (6%). Posterior fossa malformations were more likely to be associated with genetic conditions and cardiac malformations. Patients with CAS all required intensive care unit admission. Overall, few patients with congenital brain malformations required feeding or respiratory support at discharge. None had seizures as neonates except two with early epileptic encephalopathy syndromes. CONCLUSIONS: Even though long term neurological prognosis is poor for many conditions including high lifetime risk of epilepsy, most are discharged with no feeding or respiratory support. Seizures are rarely seen in the neonatal period.

Cilia in hereditary cerebral anomalies.

Ciliopathies are complex genetic multi-system disorders causally related to abnormal assembly or function of motile or non-motile cilia. While most human cells possess a non-motile sensory/primary cilium (PC) during development and/or in adult tissues, motile cilia are restricted to specialised cells. As a result, PC-associated ciliopathies are characterised by high phenotypic variability with extensive clinical and genetic overlaps. In the present review, we have focused on cerebral developmental anomalies, which are commonly found in PC-associated ciliopathies and which have mostly been linked to Hedgehog signalling defects. In addition, we have reviewed emerging evidence that PC dysfunctions could be directly or indirectly involved in the mechanisms underlying malformations of cerebral cortical development including primary microcephaly.

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.

The third ventricle of the human fetal brain: Normative data and pathologic correlation. A 3D transvaginal neurosonography study.

OBJECTIVE: The objective of the study are to describe (a) the technical aspects and (b) the anatomical boundaries of the fetal third ventricle (3V) on the midsagittal sonographic view and to assess (c) different biometric parameters in normal and abnormal fetuses and (d) and their reproducibility. METHODS: This study included 67 normal and 50 CNS anomalies fetuses which include (1) obstructive severe ventriculomegaly (SVM; atrial width ≥ 15 mm), (2) moderate ventriculomegaly (10-14.9 mm), and (3) corpus callosum agenesis (ACC). All underwent transvaginal 3D neurosonography of the midsagittal view of the 3V. The following parameters were measured: area, perimeter, craniocaudal and anteroposterior (AP) diameters, interthalamic adhesion diameter (ITAD), wedge angle, and the ratio between the last 2 variables (ITAD/WA). Repeatability was also assessed. RESULTS: The ITAD and the ITAD/WA are significantly different between normal fetuses and the SVM (P ≤ .001). Interthalamic adhesion diameter of ≤7.1 mm is able to identify SVM with 98.6% accuracy (CI: 0.92-0.99). In ACC cases, the AP diameter is significantly shorter than both normal fetuses and ventriculomegaly. Intraobserver/interobserver reliability was good for most variables. CONCLUSIONS: Transvaginal neurosonography enables visualization of the normal and abnormal fetal third ventricle. An ITAD <7.1 identifies aqueductal stenosis as the likely etiology of severe ventriculomegaly with an accuracy of 98.6%.

Variability of T1-weighted signal intensity of pericallosal lipomas in the fetus.

BACKGROUND: Pericallosal lipomas are often associated with corpus callosum dysgenesis. The diagnosis of lipoma, suggested on ultrasonography, relies on the classic T1 hyperintensity on magnetic resonance imaging (MRI). However, this feature may be absent prenatally. OBJECTIVE: Our objective was to study the changes of T1 intensity in fetal lipomas with comparison to postnatal/postmortem data and to assess the factors influencing the signal variations of pericallosal lipomas on prenatal MRI. MATERIALS AND METHODS: Patients with callosum dysgenesis and interhemispheric hyperechogenicity suggestive of a pericallosal lipoma with available postnatal or postmortem data were included. Gestational age, lipoma size and pattern, corpus callosum size and changes in fetal fat T1 intensity were recorded. Comparison with postmortem neuropathology was available for one fetus. RESULTS: Eleven patients with callosum dysgenesis and pericallosal lipomas (seven curvilinear and four tubulonodular) were included. All MRI scans were performed in the third trimester. Curvilinear lipomas were thinner and six cases were associated with prenatal T1 iso-intensity. Typical T1 hyperintensity appeared on postnatal MRI only. All tubulonodular lipomas were much larger and showed prenatal T1 hyperintensity. In two patients, the lipoma increased in size on postnatal MRI. CONCLUSION: The type and size of a lipoma influence T1 prenatal intensity. Absence of T1 intensity was observed in curvilinear lipomas only. Curvilinear lipomas are much thinner. Changes in T1 intensity may also be related to fat maturation within the lipoma and, subsequently, to gestational age. In the case of callosum dysgenesis, absence of prenatal T1 pericallosal hyperintensity should not exclude the diagnosis of pericallosal lipoma.

Prenatal diagnosis of pericallosal curvilinear lipoma: specific imaging pattern and diagnostic pitfalls.

We report the first series of cases of pericallosal curvilinear lipoma (CL) diagnosed prenatally and highlight the limitations in identifying a specific prenatal imaging pattern using ultrasound and magnetic resonance imaging (MRI). In all five of our cases, on ultrasound, the main feature leading to referral was a short corpus callosum. This subtle callosal dysgenesis was associated with a band of hyperechogenicity surrounding the corpus callosum, mimicking the pericallosal sulcus, which increased in size during the third trimester in three of the four cases in which sonographic follow-up was performed. On T2-weighted MRI, this band showed typical hypointensity in all cases; in contrast, on T1-weighted imaging, in only one case was there hyperintensity, suggestive of fat, as seen typically in the postnatal period. For appropriate prenatal counseling regarding outcome, it is important to identify or rule out CL when mild corpus callosal dysgenesis is observed. One should be aware of subtle diagnostic findings, such as a thin band of echogenicity surrounding the corpus callosum that is seen as a band of hypointensity on T2-weighted fetal MRI, and which may increase in size during gestation. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Valor de la resonancia magnética cerebral en fetos con sospecha ecográfica de agenesia del cuerpo calloso / Value of brain MRI when sonography raises suspicion of agenesis of the corpus callosum in fetuses

Objetivo. Valorar el papel de la resonancia magnética (RM) en los fetos con sospecha ecográfica de agenesia del cuerpo calloso (ACC) para confirmar el diagnóstico y detectar anomalías intracraneales asociadas. Material y métodos. Estudio observacional descriptivo y retrospectivo de las RM cerebrales realizadas a 78 fetos remitidos a nuestro centro entre enero de 2006 y diciembre de 2015 por sospecha de ACC. Dos especialistas en diagnóstico por imagen fetal revisaron las exploraciones para evaluar la presencia y la morfología del cuerpo calloso. En los casos de ACC se valoró el resto de la neuroanatomía fetal para determinar la presencia de anomalías asociadas. Se correlacionaron los hallazgos de imagen prenatales con la RM posnatal o con la necropsia, cuando estuvieron disponibles. Resultados. La RM diagnosticó de ACC 45 casos, de los que 12 fueron de tipo parcial (26,7%) y 33 completa (73,3%). Se detectaron anomalías asociadas en 28 casos (62,2%), siendo la más frecuente la ventriculomegalia (78,6%), seguida de las malformaciones corticales (53,6%) y las anomalías de la fosa posterior (25%) y de la línea media (10,7%). Conclusión. La RM fetal facilita el diagnóstico de la ACC y la detección de anomalías asociadas. Su realización es importante ante la sospecha ecográfica prenatal de ACC (AU)

Objective. To evaluate the role of magnetic resonance imaging (MRI) in fetuses with a previous sonographic suspicion of agenesis of the corpus callosum (ACC) to confirm the diagnosis and to detect associated intracranial anomalies. Material and methods. Single-center retrospective and descriptive observational study of the brain MRI performed in 78 fetuses with ACC sonographic suspicion between January 2006 and December 2015. Two experts in fetal imaging reviewed the MRI findings to evaluate the presence and morphology of the corpus callosum. When ACC was detected the whole fetal brain anatomy was thoroughly studied to determine the presence of associated anomalies. Prenatal MR imaging findings were compared to postnatal brain MRI or necropsy findings when available. Results. Fetal MRI diagnosed 45 cases of ACC, 12 were partial (26.7%) and 33 complete (73.3%). In 28 cases (62,2%) associated intracranial anomalies were identified. The most often abnormality was ventriculomegaly (78,6%), followed by cortical malformations (53,6%), posterior fossa (25%) and midline anomalies (10,7%). Conclusion. Fetal brain MRI has an important role in the diagnosis of ACC and detection of associated anomalies. To perform a fetal brain MRI is important in fetuses with sonographic suspicion of ACC (AU)

Four Steps in Diagnosing Complete Agenesis of the Corpus Callosum in Prenatal Life.

PURPOSE: Among congenital brain anomalies, complete agenesis of the corpus callosum (cACC) including cases of callosal hypoplasia has a prevalence of 1.8 per 10 000 in the general population. It is also one of the most challenging brain anomalies to detect during the mid-trimester ultrasound scan. Standard axial planes do not provide enough information to make the definitive diagnosis of cACC. MATERIALS AND METHODS: From our library of images and ultrasound reports, we reviewed our most recent cases of complete agenesis of the corpus callosum in the fetus at the mid-trimester scan. In our analysis we included only cases that were confirmed postnatally or by autopsy. Exams were performed between January 2010 and June 2012. All of the patients were scanned transabdominally by means of 2 D and static 3 D. From the 2 D and 3 D images we identified 4 anatomical views that consistently gave us enough information to identify cACC: axial biparietal transthalamic view (AX1); axial biparietal falx view (AX2); coronal transthalamic view (COR); mid-sagittal view (SAG). RESULTS: From our library 30 cases were selected with confirmed cACC postnatally or in autopsy findings. The mean gestational age at the time of referral to our center was 20.7 weeks (range 19 - 23 weeks). In all analyzed cases sufficient 2 D images were found and in 93.3 % of them informative 3 D volumes were also available for off-line review. We identified the following patterns of cACC at the mid-trimester scan: A- normal size of 3 rd ventricle + normal size of the lateral ventricles or mild ventriculomegaly; B1- dilated 3 rd ventricle + normal size of the lateral ventricles; B2- dilated 3 rd ventricle + mild or moderate ventriculomegaly; C- dilated 3 rd ventricle + severe ventriculomegaly; D- gross dilatation of 3 rd ventricle with the appearance of interhemispheric cyst. The AX1 view revealed: absence of the cavum septum pellucidi in all cases; dilatation of the third ventricle in 86.6 % of cases; separation of frontal horns in 83.3 % of cases; ventriculomegaly in 73.3 % of cases, including 13.6 % with severe forms. The AX2 view showed separation of the interhemispheric fissure (IHF) in 90 % of cases and upward displacement of the 3 rd ventricle in 80 % of cases. The COR view confirmed separation of the interhemispheric fissure in 90 % of cases including gross separation in 7.4 % of cases; absence of CC fibers at this level and descent of the falx towards the roof of the 3 rd ventricle in all cases, and upward displacement of the 3 rd ventricle in 80 % of cases. The SAG view revealed the absence of the CSP-CC complex in all cases and dilatation of the 3 rd ventricle in 86.6 % of cases. CONCLUSION: 1. We suggest a stepwise ultrasound diagnostic approach for cACC and variations of this condition. 2. We suggest a classification of characteristic patterns found in fetuses with proven cACC based on findings presented in axial views.

Detection of Fetal Corpus Callosum Abnormalities by Means of 3D Ultrasound.

PURPOSE: The objective of this study was to prenatally detect corpus callosum pathologies such as agenesis, partial agenesis, hypo- and hyperplasia and enhanced echogenicity. MATERIALS AND METHODS: Between 2009 and 2013 detailed 3D ultrasound examinations of the fetal corpus callosum were carried out as part of a level III examination for fetal anomalies. All scans were performed using Voluson E8 equipment (GE, Zipf, Austria) with a 5 - 8 MHz 3D transabdominal and 5 - 9 MHz 3D transvaginal transducer. All cases were evaluated for the following variables: inner, outer and curved length of the corpus callosum, height of the different segments of the corpus callosum and the corpus callosum area. All parameters were compared with normal growth charts. In all cases of suspected corpus callosum anomaly direct and indirect signs for corpus callosum agenesis and associated malformations were observed. RESULTS: 31 fetuses with pathological corpus callosum were diagnosed with 3D ultrasound. Gestational age at the time of diagnosis ranged from 20 to 38 weeks. 12 cases showed agenesis, 11 cases partial agenesis, 5 cases hypoplasia, 2 cases a combination of partial hyper- and hypoplasia and one case a lipoma of the corpus callosum. In corpus callosum underdevelopment, the more affected parts were the body and splenium. Associated anomalies were present in 25 of the 31 cases (80.6%) of corpus callosum pathologies. CONCLUSION: 3D neurosonography serves as an excellent tool to precisely demonstrate the pathological development of the fetal corpus callosum. By correlating the measures with the function of each affected corpus callosum segment, we can try to get a vague prediction of the neurological prognosis.