Abnormal shape of the cavum septi pellucidi: an indirect sign of partial agenesis of the corpus callosum

Partial agenesis of the corpus callosum: Prenatal ultrasound characteristics, associations, and outcome

INTRODUCTION

To investigate prenatal ultrasound characteristics, associated abnormalities, and outcomes of partial agenesis of the corpus callosum (pACC).

MATERIAL AND METHODS

A total of 118 fetuses with pACC diagnosed using prenatal ultrasound were studied, and their prenatal ultrasound characteristics, associated abnormalities, genetics, and outcomes were collected. The fetuses were categorized into three groups according to gestational age: <24 weeks, 24-28 weeks, and >28 weeks, and the brain transverse plane ultrasound signs were compared among the three groups.

RESULTS

Prenatal ultrasound revealed the presence of abnormal cavum septi pellucidi (CSP), distention of the interhemispheric fissure (IF), dilated and elevated third ventricle (TV), and ventriculomegaly in 102 (86.4%), 91 (77.1%), 56 (47.4%), and 42 (35.6%) cases, respectively, in the transverse plane of the brain. Among the cases with dilatation and elevation of the TV, 38 (67.8%) showed posterior displacement, manifested by a cystic mass in the midline that communicated with the TV. There were statistically significant differences in the incidence of ventriculomegaly and abnormal CSP among the three groups at <24 weeks, 24-28 weeks, and >28 weeks. However, there were no statistically significant differences in the distention of the IF and TV among the three groups. Moreover, our cohort studies demonstrated that 32.2% (38/118), 18.6% (22/118), and 17.8% (21/118) of the cases were associated with intracranial, extracranial, and intra-extracranial anomalies, respectively. The most common intracranial and extracranial anomalies were cerebral cortical dysplasia and cardiovascular anomalies. Genetic analysis demonstrated that 37.8% (17/41) of patients had genetic abnormalities. 25% (4/16) and 52% (13/25) of isolated and non-isolated pACC cases showed genetic abnormalities. Eight isolated cases were born, with an average age of 28 months, and their neurological development was normal.

CONCLUSIONS

Abnormal CSP was the most common indirect sign of pACC. A cystic mass in the midline communicating with the TV can be another indirect sign of a pACC. pACC is likely to be accompanied by intracranial and extracranial abnormalities. The detection rate of genetic abnormalities was higher in non-isolated pACC cases than in isolated cases. Isolated pACC has a good prognosis but requires long-term follow-up of neurological development.

Can cavum septum pellucidum width and length measurements also be reliable indicators of corpus callosum measurements in normal fetuses?

OBJECTIVE

To examine the association between cavum septum pellucidum (CSP) and corpus callosum (CC) length and width measurements in mid-trimester sonographic screening in normal fetuses.

METHODS

This prospective cohort study examined 152 pregnant women who underwent mid-trimester sonographic fetal anomaly screening. CSP and CC lengths and their anterior, middle, and posterior width measurements were examined sonographically. The association between length and width measurements of both structures, gestational week and CSP ratio (length/width) were evaluated.

RESULTS

The mean CSP length was 7.96 ± 1.09 mm, and the mean middle width was 3.43 ± 0.82 mm. The mean CC length was 20 ± 3.76 mm, and the mean middle width was 3.43 ± 0.82 mm. There was a positive correlation between CSP and CC lengths (r = 0.691, p < 0.001). There was also a significant correlation between CSP and CC anterior, middle and posterior widths (anterior (r = 0.366, p < 0.001), middle (r = 0.305, p < 0.001), and posterior (r = 0.233, p = 0.004)). All CSP and CC measurements were correlated with gestational age, biparietal diameter (BPD), and head circumference (HC) (p < 0.001, for all). The CSP ratio was not related to CC dimensions (p > 0.05, for all) and also decreased with the increase in BPD and HC dimensions (r = -0.186, p = 0.022, and r = -0.174, p = 0.032; respectively).

CONCLUSION

In normal fetuses, the length and width of the CC and CSP structures developed in relation to each other, as well as to the gestational week, BPD, and HC dimensions. In addition, while the CSP ratio was not found to be associated with CC dimensions, it decreased due to the increase in BPD and HC sizes.

Comparison of Cavum Septum Pellucidum Size in Euploid and Aneuploid Fetuses

OBJECTIVE

 The aim of the present study is to compare the cavum septum pellucidi (CSP) z-score in euploid and aneuploid fetuses and to investigate the performance of the CSP width/length and CSP width/biparietal diameter (BPD) ratios as a diagnostic marker in aneuploidy.

METHODS

 A total of 54 patients, 20 aneuploid and 35 euploid fetuses, between 18 and 37 weeks of gestation, were included in this retrospective study. The CSP width z-score was compared between the two groups. Receiver operating characteristic (ROC) curves were calculated for the CSP width/length and CSP width/BPD ratios to predict aneuploidy.

RESULTS

 The median CSP width was 4.8 mm (range, 1.8 to 8.5 mm) in the euploid group, and 5.4 mm (range 3.1 to 8.4 mm) in the aneuploid group. Cavum septum pellucidi width z-score, CSP width/length ratio, and CSP width/BPD ratio were significantly higher in fetuses with aneuploidy than in fetuses with normal karyotype (p = 0.001; p = 0.013; p = 0.028). In the ROC analysis, the CSP width/length ratio had the optimal cutoff value of 0.59, with 72.0% sensitivity and 58.0% specificity, and for the CSP width/BPD ratio, the cutoff value was 0.081 with 83.0% sensitivity and 61.0% specificity for detection of aneuploidy.

CONCLUSION

 CSP width z-score was found to be increased in aneuploid fetuses. The CSP width /BPD ratio can be used as a new marker for predicting aneuploidy.

Obliterated cavum septi pellucidi: Clinical significance and role of fetal magnetic resonance

INTRODUCTION

The objective of this study was to describe a cohort of fetuses with an ultrasound prenatal diagnosis of obliterated cavum septi pellucidi (oCSP) with the aim to explore the rate of associated malformations, the progression during pregnancy and the role of fetal magnetic resonance imaging (MRI).

MATERIAL AND METHODS

This was a retrospective multicenter international study of fetuses diagnosed with oCSP in the second trimester with available fetal MRI and subsequent ultrasound and/or fetal MRI follow-up in the third trimester. Where available, postnatal data were collected to obtain information on neurodevelopment.

RESULTS

We identified 45 fetuses with oCSP at 20.5 weeks (interquartile range 20.1-21.1). oCSP was apparently isolated at ultrasound in 89% (40/45) and fetal MRI found additional findings in 5% (2/40) of cases, including polymicrogyria and microencephaly. In the remaining 38 fetuses, fetal MRI found a variable amount of fluid in CSP in 74% (28/38) and no fluid in 26% (10/38). Ultrasound follow-up at or after 30 weeks confirmed the diagnosis of oCSP in 32% (12/38) while fluid was visible in 68% (26/38). At follow-up MRI, performed in eight pregnancies, there were periventricular cysts and delayed sulcation with persistent oCSP in one case. Among the remaining cases with normal follow-up ultrasound and fetal MRI findings, the postnatal outcome was normal in 89% of cases (33/37) and abnormal in 11% (4/37): two with isolated speech delay, and two with neurodevelopmental delay secondary to postnatal diagnosis of Noonan syndrome at 5 years in one case and microcephaly with delayed cortical maturation at 5 months in the other.

CONCLUSIONS

Apparently isolated oCSP at mid-pregnancy is a transient finding with the visualization of the fluid later in pregnancy in up to 70% of cases. At referral, associated defects can be found in around 11% of cases at ultrasound and 8% at fetal MRI indicating the need for a detailed evaluation by expert physicians when oCSP is suspected.

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.

Cavum septum pellucidum nomogram during the second trimester of pregnancy

This study aimed to determine cavum septum pellucidum (CSP) nomogram values between 15-28 weeks of gestation. Routine biometric measurements and CSP width were measured by transabdominal ultrasonography in 6042 structurally normal foetuses between 15-28 weeks of gestation. Distribution of CSP width by the week of pregnancy and percentile values were calculated. The mean week of gestation (GW) was 21 ± 1.7, and the mean biparietal diameter (BPD) was 50.2 ± 5.8 mm. The CSP width range was 1.6-7.7 mm at 15-28 weeks, and the mean CSP width was 4.1 ± 0.8 mm. CSP width was found to have a significant correlation between a gestational week (CSP = GW X 0.2705-1.6121; R = 0.62; p < .01) and BPD (CSP = BPD X 0.0859-0.273; R = 0.651; p 0.01). CSP width was found to differ significantly according to gestational weeks, and percentile distributions were calculated. Between 15 and 28 weeks of gestation, the 95th percentile values of CSP width were found to be 3.7-7 mm. Our study was determined that CSP width increased linearly between 15-28 weeks of gestation. For this reason, we think that it would be more appropriate to use CSP width percentile values in the examination of the foetus. Impact statementWhat is already known on this subject? The cavum septum pellucidum can be easily identified and evaluated by ultrasonography after 18 weeks of pregnancy. CSP can be associated with severe brain anomalies if it is not visualised or deformed. Moreover; large CSP may be associated with chromosomal abnormalities.What do the results of this study add? Our study showed that CSP width increased linearly between 15-28 weeks of gestation. CSP width was found to differ significantly according to gestational weeks, and between 15 and 28 weeks of gestation, the 95th percentile values of CSP width were found to be 3.7-7 mm.What are the implications of these findings for clinical practice and/or further research? We reported that it would be more appropriate to use CSP percentile values according to the gestational week in the definition of abnormal CSP.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Fetal Brain Development: Regulating Processes and Related Malformations

This paper describes the contemporary state of knowledge regarding processes that regulate normal development of the embryonic–fetal central nervous system (CNS). The processes are described according to the developmental timetable: dorsal induction, ventral induction, neurogenesis, neuronal migration, post-migration neuronal development, and cortical organization. We review the current literature on CNS malformations associated with these regulating processes. We specifically address neural tube defects, holoprosencephaly, malformations of cortical development (including microcephaly, megalencephaly, lissencephaly, cobblestone malformations, gray matter heterotopia, and polymicrogyria), disorders of the corpus callosum, and posterior fossa malformations. Fetal ventriculomegaly, which frequently accompanies these disorders, is also reviewed. Each malformation is described with reference to the etiology, genetic causes, prenatal sonographic imaging, associated anomalies, differential diagnosis, complimentary diagnostic studies, clinical interventions, neurodevelopmental outcome, and life quality.

Subcortical Segmentation of the Fetal Brain in 3D Ultrasound using Deep Learning

The quantification of subcortical volume development from 3D fetal ultrasound can provide important diagnostic information during pregnancy monitoring. However, manual segmentation of subcortical structures in ultrasound volumes is time-consuming and challenging due to low soft tissue contrast, speckle and shadowing artifacts. For this reason, we developed a convolutional neural network (CNN) for the automated segmentation of the choroid plexus (CP), lateral posterior ventricle horns (LPVH), cavum septum pellucidum et vergae (CSPV), and cerebellum (CB) from 3D ultrasound. As ground-truth labels are scarce and expensive to obtain, we applied few-shot learning, in which only a small number of manual annotations (n = 9) are used to train a CNN. We compared training a CNN with only a few individually annotated volumes versus many weakly labelled volumes obtained from atlas-based segmentations. This showed that segmentation performance close to intra-observer variability can be obtained with only a handful of manual annotations. Finally, the trained models were applied to a large number (n = 278) of ultrasound image volumes of a diverse, healthy population, obtaining novel US-specific growth curves of the respective structures during the second trimester of gestation.

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.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Neurodevelopmental Outcomes following Prenatal Diagnosis of Isolated Corpus Callosum Agenesis: A Systematic Review

Abnormalities of corpus callosum are one of the most common brain anomalies. Fetuses with isolated corpus callosum agenesis (CCA) have a better prognosis than those with additional anomalies. However, unpredictable neurodevelopmental outcomes of truly isolated CCA make prenatal counseling a challenge. The aim of this review is to evaluate neurodevelopmental outcomes in children with prenatal diagnosis of isolated CCA. Controlled clinical trials published between May 23, 2009, and May 23, 2019, using the MeSH term "agenesis of corpus callosum" were reviewed. A total of 942 articles were identified, and 8 studies were included in the systematic review depending on the inclusion criteria. These studies included 217 fetuses with isolated CCA and no other anomalies at prenatal assessment. Neurodevelopmental outcome was reported to be normal in 83 children with a prenatal diagnosis of isolated CCA confirmed at birth within 128 completed assessments. About 45 children presented borderline, moderate, or severe neurodevelopmental outcome. In this review, neurodevelopment was favorable in two-thirds of the cases, but mild disabilities emerged in older children. Despite this, disabilities can occur later beyond school age and a low risk of severe cognitive impairment exists. Our study highlights the essential early diagnosis and proper supportive therapy.

Ultrasound and Magnetic Resonance Imaging of Agenesis of the Corpus Callosum in Fetuses: Frontal Horns and Cavum Septi Pellucidi Are Clues to Earlier Diagnosis

OBJECTIVES

We hypothesized that: (1) fetal frontal horn (FH) morphology and their proximity to the cavum septi pellucidi (CSP) can assist in suspecting complete agenesis of the corpus callosum (cACC) and partial agenesis of the corpus callosum (pACC) earlier than known indirect ultrasound (US) findings; (2) FHs assist in differentiating a true CSP from a pseudocavum; and (3) magnetic resonance imaging (MRI) is useful in learning FH morphology and pseudocavum etiology.

METHODS

Thirty-two patients with cACC and 9 with pACC were identified on an Institutional Review Board-approved retrospective review. Of the 41 cases, 40 had prenatal US, and 21 had prenatal MRI; 17 had follow-up neonatal US, and 14 had follow-up neonatal MRI. Variables evaluated retrospectively were the presence of a CSP or a pseudocavum, ventricle size and shape, and FH shape (comma, trident, parallel, golf club, enlarged, or fused). Displacement between the inferior edge of the FH and the midline or cavum/pseudocavum was measured.

RESULTS

Fetal FHs had an abnormal shape in 77% ≤20 weeks' gestation, 86% ≤24 weeks, and 90% >24 weeks. Frontal horns were laterally displaced greater than 2 mm in 85% ≤20 weeks, 91% ≤24 weeks, and 95% >24 weeks. The CSP was absent in 100% of cACC cases and 78% of pACC cases, and a pseudocavum was present in 88% of cACC cases and 78% of pACC cases across gestation. Magnetic resonance imaging confirmed US pseudocavums to be focal interhemispheric fluid or an elevated/dilated third ventricle.

CONCLUSIONS

Frontal horns assist in assessing ACC ≤24 weeks and throughout gestation. Pseudocavums, often simulating CSPs, are common in ACC. Frontal horn lateral displacement and abnormal morphology, recognized by MRI correlations, are helpful in differentiating a pseudocavum from a true CSP. A normal CSP should not be cleared on screening US unless normally shaped FHs are seen directly adjacent to it.

Corpus Callosum Agenesis: An Insight into the Etiology and Spectrum of Symptoms

Brain hemispheres are connected by commissural structures, which consist of white matter fiber tracts that spread excitatory stimuli to various regions of the cortex. This allows an interaction between the two cerebral halves. The largest commissure is the corpus callosum (CC) which is located inferior to the longitudinal fissure, serving as its lower border. Sometimes this structure is not completely developed, which results in the condition known as agenesis of the corpus callosum (ACC). The aim of this paper was to review the latest discoveries related to the genetic and metabolic background of ACC, including the genotype/phenotype correlations as well as the clinical and imaging symptomatology. Due to various factors, including genetic defects and metabolic diseases, the development of CC may be impaired in many ways, which results in complete or partial ACC. This creates several clinical implications, depending on the specificity of the malformation and other defects in patients. Epilepsy, motor impairment and intellectual disability are the most prevalent. However, an asymptomatic course of the disease is even more common. ACC presents with characteristic images on ultrasound and magnetic resonance imaging (MRI).

Scoping Review of the Prenatal Diagnosis of Agenesis of the Corpus Callosum

OBJECTIVE

To map and summarize the literature related to the prenatal diagnosis of agenesis of the corpus callosum (ACC) to inform nursing practice.

DATA SOURCES

We searched MEDLINE, CINAHL, PyscINFO, and Academic Search Complete with the use of strings of curated terms to cover the broad ACC nomenclature. Documents were published in English between 2009 and June 1, 2020. We also hand searched the reference lists of included documents.

STUDY SELECTION

We screened 582 abstracts and retrieved the full texts of primary research articles, reviews, discussion papers, and peer-reviewed book chapters if the abstracts specifically mentioned ACC and the prenatal period. We excluded case reports, conference and poster abstracts, papers on broader anomalies, and animal studies. We reviewed 84 full-text documents and identified 61 for inclusion.

DATA EXTRACTION

We charted the data through an iterative process under headings for location, article type, study design, participant age, ACC type, recruitment, method, tools/assessments, results, key recommendations, gestational age at diagnosis, termination of pregnancy rate, the definition of isolated ACC, and our notes of critique of the document.

DATA SYNTHESIS

We constructed a narrative synthesis from thematically arranged data. In the included documents, ACC was diagnosed between 17 and 38 weeks gestation and was frequently described as heterogeneous because of different causes, presentations, and outcomes. Whether the ACC was isolated as the only anomaly or present with other anomalies was considered the key factor for prenatal counseling. However, the definition of isolated ACC was inconsistent.

CONCLUSION

The inconsistent nomenclature and definitions of an isolated presentation of ACC increase the ambiguity in the prenatal diagnosis and must be considered when the outcome and diagnostic efficacy studies are interpreted. There is an absence of research on parents' experiences of prenatal diagnoses of ACC to inform holistic nursing interventions and the provision of psychosocial support.

Feasibility and agreement of including anterior-posterior complexes and landmarks of the proximal hemisphere into basic examination of the fetal brain: A prospective study

OBJECTIVE

To assess the feasibility of identifying structures included in anterior complex (AC) and posterior complex (PC), as well as a series of anatomic landmarks that could help to demonstrate the integrity of the cerebral proximal hemisphere (PH).

METHODS

This was a prospective observational multicenter study of healthy pregnant women attending routine ultrasound screening at 20 + 0 to 33 + 6 weeks' gestation. Six physicians performed transabdominal (TA) ultrasound, in order to obtain the planes required to visualize the AC, PC, and PH. Blind analysis by a nonexpert and two experts in fetal neurosonography was used to assess the structures included in each plane view.

RESULTS

In the population studied (n = 747), detection of the structure rates for AC, PC, and proximal hemisphere was of 94%, 93%, and 96%, respectively, with an agreement of 97%, 94%, and 98% when comparing an expert and a nonexpert in fetal brain examiner. Detection of structures in the proximal hemisphere was significantly higher when observed through the proximal hemisphere plane rather than the transventricular plane.

CONCLUSION

Our results suggest that inclusion of AC and PC complexes visualization, as well as real-time access to the proximal hemisphere, is feasible and could improve the prenatal detection of fetal cerebral anomalies.

A new method for evaluating short fetal corpus callosum

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Utility of indirect sonographic signs (including cavum septum pellucidum ratio) in midgestational screening for partial agenesis of corpus callosum

PURPOSE

This study was undertaken to evaluate the performance of indirect sonographic signs in detecting partial agenesis of the corpus callosum (pACC) at midgestation, focusing on the cavum septum pellucidum (CSP) ratio.

METHODS

A retrospective case-controlled study of singleton pregnancies was conducted, examining fetuses diagnosed with isolated pACC and normal controls. At midgestational age, fetal head volumes were imaged with 3D US and stored for the evaluation of indirect sonographic findings in axial planes.

RESULTS

Fifteen normal and 15 abnormal fetuses (with pACC) were analyzed. Based on a CSP ratio < 1.5, detection of pACC increased from 66.7% (10/15) to 80% (12/15). All indirect signs proved highly suspicious for pACC (risk ratios > 1).

CONCLUSION

Use of indirect sonographic signs to screen for pACC at midgestation is challenging. However, a low CSP ratio may improve the detection rate, serving as a new indirect sign.

An investigation of the standardization of fetal cavum septi pellucidi measurements using three-dimensional volumes of the fetal head

PURPOSE

The purpose of this study was to measure the maximal width, middle width, and length of the cavum septi pellucidi (CSP) in normal fetuses, and compare these measurements obtained in the transthalamic (TT) plane with those obtained in the transventricular (TV) plane.

METHOD

A prospective study was conducted of normal singleton fetuses, ranging from 18 to 36 weeks in gestational age. In each case, a three-dimensional volume of the fetal head was obtained in the TT plane for further offline measurements, then the maximal width, middle width, and length of the CSP in both the TT and TV planes were measured. Intraobserver and interobserver reproducibility was assessed, and curve estimation was used to assess the possible relationship between these measurements of CSP and gestational age (GA).

RESULTS

A total of 267 normal fetuses were studied. The CSP width and length in TT and TV planes as a function of GA were analyzed using a quadratic regression model. Intraobserver and interobserver agreement of the CSP measurements was excellent overall (ICCs >0.9), with intraobserver and interobserver differences of less than 4%.

CONCLUSION

Measurements of CSP in the TT and TV planes are equally reproducible.

Cavum septi pellucidi (CSP) ratio: a marker for partial agenesis of the fetal corpus callosum

OBJECTIVE

While complete agenesis of the corpus callosum is often suspected on fetal ultrasound due to absence of the cavum septi pellucidi (CSP), suspicion of partial agenesis of the corpus callosum (pACC) is a challenge since the CSP is almost always present. The aim of this study was to measure the length and width of the CSP and calculate the length-to-width ratio (CSP ratio), and compare these between fetuses with pACC and normal fetuses.

METHODS

In this retrospective case-control study, the length and width of the CSP were measured in the axial plane of the fetal head, and the CSP length-to-width ratio calculated, in 323 normal fetuses and in 20 fetuses with pACC between 20 and 34 weeks' gestation. From the normal population we constructed reference ranges in relation to biparietal diameter (BPD). For all fetuses we calculated Z-scores for the CSP ratio.

RESULTS

In the normal population, the length and width of the CSP increased with increasing BPD, while the CSP ratio decreased. The CSP was short (< 5^th centile) in 85% (17/20) of fetuses with pACC and wide (> 95^th centile) in 65% (13/20). The CSP ratio was small (< 5^th centile) in 95% (19/20) of pACC fetuses, with 16/20 (80%) having a ratio below an empirical cut-off of 1.5. Analysis of Z-scores showed that fetuses with pACC had a significantly smaller CSP ratio (P < 0.0001) compared with the normal population.

CONCLUSIONS

Fetuses with a normal-sized corpus callosum have a rectangular-shaped CSP, with a CSP ratio > 1.5 in the second half of gestation. Most fetuses with pACC have an abnormally shaped, wide and short CSP, with a decreased CSP ratio. This simple ratio has the potential to identify fetuses at high risk for pACC. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

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.

Routine Screening for Callosal Dysgenesis in the Second Trimester Is Achievable With Intensive Training

OBJECTIVES

The purpose of this study was to determine whether routine direct visualization of the corpus callosum is achievable during second-trimester sonography when performed by a large group of sonographers in a general second-trimester sonographic screening program. The secondary aim was to determine the time taken to obtain a sagittal corpus callosum image.

METHODS

We conducted a retrospective cohort study of visualization of the corpus callosum before and after intensive training. Images from 150 consecutive second-trimester scans were reviewed before and after training to evaluate the image quality of the corpus callosum.

RESULTS

A total of 300 cases were evaluated before and after training. There was a significant increase in the rate of complete visualization of the corpus callosum after intensive training (P < .0001). Before training 35 of 150 cases (23%) had complete visualization of the corpus callosum versus 107 of 150 (71%) after training. The mean time to perform the corpus callosum views was 53.4 seconds before training compared to 56.2 seconds after training.

CONCLUSIONS

Assessing the corpus callosum in the sagittal view is difficult and requires appropriate training and patience; however, this view is feasible without adding substantial time to the examination and provides additional information during a routine second-trimester morphologic scan.