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

Quantitative fetal MRI with diffusion tensor imaging in cases with 'short' corpus callosum

OBJECTIVES

It has been suggested previously that the presence of Probst bundles (PB) in cases with a short corpus callosum (SCC) on diffusion tensor imaging (DTI) may help to differentiate between corpus callosal (CC) dysplasia and a variant of normal CC development. The objectives of this study were to compare DTI parameters between cases of SCC vs normal CC and between cases of SCC with PB (SCC-PB+) vs SCC without PB (SCC-PB-).

METHODS

This was a retrospective study of patients referred to the Necker Hospital in Paris, France, for magnetic resonance imaging (MRI) evaluation of an apparently isolated SCC detected by sonography between November 2016 and December 2022 (IRB: 00011928). MRI was performed using a 1.5-Tesla Signa system. T2-weighted axial and sagittal sequences of the fetal brain were used to measure the length and thickness of the CC. 16-direction DTI axial brain sequences were performed to identify the presence of PB and to generate quantitative imaging parameters (fractional anisotropy (FA) and apparent diffusion coefficient (ADC)) of the entire CC, genu, body and splenium. Cases in which other associated brain abnormalities were detected on MRI were excluded. Cases were matched for fetal gender and gestational age with controls in a 1:3 ratio. Control cases were normal fetuses included in the LUMIERE on the FETUS trial (NCT04142606) that underwent the same DTI evaluation of the brain. Comparisons between SCC and normal CC cases, and between SCC-PB+ and SCC-PB- cases were performed using ANOVA and adjusted for potential confounders using ANCOVA.

RESULTS

Twenty-two SCC cases were included and compared with 66 fetuses with a normal CC. In 10/22 (45.5%) cases of SCC, PB were identified. As expected, dimensions of the CC were significantly smaller in SCC compared with normal CC cases (all P < 0.01). In SCC-PB+ vs SCC-PB- cases, FA values were significantly lower in the entire CC (median, 0.21 (range, 0.19-0.24) vs 0.24 (range, 0.22-0.28); P < 0.01), genu (median, 0.21 (range, 0.15-0.29) vs 0.24 (range, 0.17-0.29); P = 0.04), body (median, 0.21 (range, 0.18-0.23) vs 0.23 (range, 0.21-0.27); P = 0.04) and splenium (median, 0.22 (range, 0.16-0.30) vs 0.25 (range, 0.20-0.29); P = 0.03). ADC values were significantly higher in the entire CC, genu and body in SCC-PB+ vs SCC-PB- cases (all P < 0.05). In SCC-PB+ cases, all FA values were significantly lower, and ADC values in the CC body were significantly higher compared with normal CC cases (all P < 0.05). In SCC-PB- cases, there was no significant difference in FA and ADC compared with normal CC cases (all P > 0.05).

CONCLUSIONS

Fetal DTI evaluation of the CC showed that FA values were significantly lower and ADC values tended to be significantly higher in SCC-PB+ compared with normal CC cases. This may highlight alterations of the white matter microstructure in SCC-PB+. In contrast, isolated SCC-PB- did not demonstrate significant changes in DTI parameters, strengthening the possibility that this is a normal CC variant. © 2023 International Society of Ultrasound in Obstetrics and Gynecology.

Retrospective analysis of the prognostic factors of fetal corpus callosum dysplasia

BACKGROUND

To analyze the genetic characteristics and long-term outcomes of fetuses with dysplasia of the corpus callosum (DCC) or partial agenesis of the corpus callosum (PACC).

METHODS

A total of 42 fetuses with DCC (n = 36) or PACC (n = 6) were retrospectively analyzed from January 2016 to December 2022 at the Peking University First Hospital. The cohort was categorized into isolated (15/42, 36%) and nonisolated groups (27/42, 64%), and differences in the genetic abnormalities and long-term outcomes between the two groups were analyzed. DCC was subdivided into short CC, thin CC, and thick CC. The outcomes of the three different types of DCC were analyzed and discussed.

RESULTS

(1) Thirty-nine of the 42 cases underwent CMA (chromosomal microarray analysis) and CMA + WES (whole exome sequencing), with 13/15 cases in isolated group and 26/27 cases in nonisolated group. Only pathogenic or likely pathogenic (P/LP) variants were considered, identifying P/LP variants in 2/13 cases in isolated group and 12/26 cases in nonisolated group. There was no significant difference between the two groups (χ² = 3.566, P = 0.05897). (2) In the isolated group, 8 cases were terminated, and 7 cases were delivered. Postnatal follow-up detected 1 case of gross motor development delay one year after birth; no obvious abnormalities were found in the other six cases. In the nonisolated group, 21 cases were terminated, and 6 cases were delivered. Postnatal follow-up detected 4 cases of children with different degrees of language, motor and intelligence abnormalities; 1 case died 10 days after birth. No obvious abnormalities were observed in one case. Six cases (86%, 6/7) in the isolated group showed normal development, compared with 1 case (17%, 1/6) in the nonisolated group, with a significant difference (χ² = 6.198, P = 0.01279). (3) In DCC, the delivery rates of short CCs (18 cases), thin CCs (13 cases), and thick CCs (5 cases) were 17% (3/18), 54% (7/13), and 20% (1/5), respectively, with good outcomes observed in 0% (0/3), 71% (5/7), and 0% (0/1), respectively. P/LP variants were found in 6/17 cases of short CC, 3/12 cases of thin CC, and 2/5 cases of thick CC.

CONCLUSIONS

Fetuses with DCC or PACC combined with other structural abnormalities had a poor long-term prognosis compared with the isolated group. Patients with thin CCs had a higher probability of a good prognosis than those with short or thick CCs.

Spectrum of brain malformations in fetuses with mild tubulinopathy

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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

OBJECTIVE

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

METHOD

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

RESULTS

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

CONCLUSIONS

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

Early Fetal Corpus Callosum: Demonstrating Normal Growth and Detecting Pathologies in Early Pregnancy

BACKGROUND AND PURPOSE

A malformed corpus callosum carries a risk for abnormal neurodevelopment. The advent of high-frequency transducers offers the opportunity to assess corpus callosum development in early pregnancy. The aim of the study was to construct a reference chart of the fetal corpus callosum length on ultrasound between 13 and 19 weeks of gestation and to prospectively examine growth patterns in pathologic cases.

MATERIALS AND METHODS

We performed a prospective cross-sectional study between 2020 and 2022 in well-dated, low-risk, singleton pregnancies between 13 and 19 weeks of gestation. A standardized image was obtained in the midsagittal plane. Imaging criteria were used as a confirmation of the early corpus callosum. Measurements were taken by 4 trained sonographers. Intra- and interobserver variability was assessed. Corpus callosum length in centiles were calculated for each gestational week.

RESULTS

One hundred eighty-seven fetuses were included in the study. All cases met inclusion criteria. At 13 weeks of gestation, the margins of the early corpus callosum were sufficiently clear to be measured in 80% (20/25) of fetuses. A cubic polynomial regression model best described the correlation between corpus length and gestational age. The correlation coefficient (r 2) was 0.929 (P < .001). Intra- and interobserver variability had high interclass correlation coefficients (>0.99). Presented is the earliest published case of agenesis of corpus callosum and a case of dysgenetic corpus callosum in Rubinstein-Taybi syndrome.

CONCLUSIONS

Provided is a nomogram of the early fetal corpus callosum. Applying imaging criteria helped to identify a case of complete agenesis of the corpus callosum as early as 14 weeks.

Fetal corpus callosum abnormalities: Ultrasound and magnetic resonance imaging role

The corpus callosum (CC) is the major interhemispheric commissure and its abnormalities include agenesis, hypoplasia, and hyperplasia. The CC anomalies are typically related to other central nervous system (CNS) or extra-CNS malformations. The antenatal diagnosis of complete CC agenesis is easy after mid-trimester by ultrasound (US) even in the axial plane. The non-visualization of cavum septum pellucidum and colpocephaly are critical signs in the axial view. More subtle findings (i.e., hypoplasia and partial agenesis) might also be recognized antenatally. In this review, the focus was given on the prenatal diagnosis of CC abnormalities in US and magnetic resonance imaging.