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

Pituitary Gland Duplication Syndrome: An International Imaging Analysis

BACKGROUND AND PURPOSE

Duplication of the pituitary gland is a rare developmental anomaly. Multiple associated craniofacial malformations have previously been reported with the largest series to date consisting of 5 patients. In this multi-institutional series of 10 patients, we present a detailed review of the imaging features and discuss a possible overarching pathogenesis that would explain most of the detected malformations.

MATERIALS AND METHODS

Inclusion criteria for this retrospective imaging review were the presence of a pituitary stalk and gland duplication and the characteristic appearance of the hypothalamic ventral midline. In addition to the clinical presentation, we recorded the imaging findings of 10 patients (9 girls) through onsite and online reviews. Genetic analysis was available for 6 patients.

RESULTS

The duplicated pituitary stalk and gland showed normal imaging appearances in all patients. Mammillary bodies were clearly identified lateral to the characteristic prominence of the hypothalamic ventral midline. Strands of tissue extending to the anterior dura ("limited ventral myeloschisis") were noted at the medulla oblongata in 10, and at the cervical spinal cord in 7 patients. The medulla oblongata showed a "butterfly" appearance on axial images in 9 patients. Ten patients had cervical segmentation anomalies ("zipperlike"), 9 had anterior-posterior brainstem patterning defects (small pons, elongated medulla), and corpus callosum measurements were abnormal in all patients. Three patients each presented with diencephalic-mesencephalic junction abnormalities and 4 with an anterior mesencephalic "cap." An oropharyngeal teratoma was present in 4 patients. Genetics was normal in 3 of the 6 patients studied; the remainder were found to have mutations in EFNB1 and a gene variant of GIT1, 2 copies of 7 and 8 exon of SMN1 gene, and 2.126 megabase duplication at bands q11.1 and q11.2 of 1 chromosome 15, respectively.

CONCLUSIONS

Duplication of the pituitary gland presents as well-defined craniofacial and cervical spine malformation phenotype. Axial mesoderm duplication generating an excess of Sonic Hedgehog may be the primary embryologic driver leading to this condition.

Parental magnetic resonance imaging for the evaluation of fetuses with brain anomalies

AIM

To evaluate the role of parental magnetic resonance imaging (MRI) in assessing fetuses with suspected brain anomalies and its use in prenatal counselling.

METHOD

A retrospective, multicentre chart review was conducted on fetuses who underwent brain MRI because of suspected brain abnormalities between January 2008 and December 2022, with one or both parents who underwent brain MRI (MRI-Trio) as part of prenatal counselling. Clinical and demographic data were collected, including fetal and parental MRI findings, prenatal counselling outcomes, genetic testing results, family and previous pregnancy history, neurological examinations of the born children up to 24 months of age, and autopsy reports of fetuses from terminated pregnancies. MRI-Trio concordance was defined as at least one abnormal brain feature identified with similarity in the fetus and the parents. The live-born children were assessed postnatally through either neurodevelopmental evaluations or telephone interviews.

RESULTS

Sixty pregnancies were included (41.7% with concordant and 58.3% with discordant MRI-Trio). Forty-two children were born (70%) and 17 pregnancies were terminated (28.3%). One case of in utero fetal death (1.7%) was reported. The most common brain findings were multiple anomalies (n = 26, 43.3%), isolated disorders of the corpus callosum (n = 17, 28.3%), atypical periventricular pseudocysts (n = 6, 10%), and anomalies of the anterior complex (n = 4, 6.7%). MRI-Trio enabled better prognostication. When MRI-Trio was concordant, counselling was more favourable (n = 22, 36.6%) and the majority of live-born children exhibited typical development (p < 0.001).

INTERPRETATION

MRI-Trio is a valuable tool for identifying dominantly inherited brain anomalies that may not hold developmental significance or are associated with favourable outcomes, acknowledging the potential for variable penetrance, which may result in more severe presentations. Concordant MRI-Trio findings can enhance the accuracy of prenatal counselling, potentially reducing the incidence of termination of pregnancy.

Fetal Corpus Callosum Anomalies: A Review of Underlying Genetic Disorders and Prenatal Testing Options

Anomalies of the corpus callosum (CC) are amongst the most common fetal Central Nervous System (CNS) anomalies detectable on ultrasound. Underlying genetic disease plays an important part in defining prognosis. Associations with aneuploidy and submicroscopic chromosomal deletions or duplications have been well demonstrated using chromosomal microarray analysis. Next-generation sequencing techniques such as exome sequencing, have revolutionized the ability to detect monogenic disease in these fetuses. In the context of important recent publications on exome sequencing in prenatal populations, an updated review of genetic testing options in CC anomalies is presented.

New reference charts for fetal ultrasound corpus callosum length with emphasis on the third trimester

OBJECTIVES

To provide new prospective 2D ultrasound reference charts of fetal corpus callosum (CC) length on a large sample size with emphasis on the third trimester of pregnancy and to establish other standards of CC growth evaluation (external cranial occipitofrontal dimension (ECOFD) / CC length ratio and head circumference (HC) / CC length ratio) in a large population of healthy fetuses.

METHODS

A prospective observational study was conducted in a single expert center for fetal ultrasound between November 1st 2021 and June 30th 2022. CC measurement was performed in all fetuses examined between 17 weeks and 36+6 weeks. Image quality criteria for a strict mid-sagittal plane of the fetal brain and caliper position for CC measurement were defined prior to data collection and only high-quality measurements were included for analysis. Fetuses with inaccurate gestational ages and at high-risk of central nervous system anomalies were excluded.

RESULTS

Among 3591 CC measurements available, 3191 were included in this study. An accurate high-quality measurement was obtained in 92.8 % of cases. We established the third-degree polynomial model expressing the length of the corpus callosum as a function of Corpus callosum length in mm=0.00213x(GA in weeks)3 - 0.2538x(GA in weeks)2 + 10.5897xGA in weeks -108.8556 +/- SD (SD=0.0567xGA In weeks + 0.1054), with an R² adj of 0.94. ECOFD/CC and HC/CC ratios were stable throughout pregnancy at 2.7 ± 0.2 and 7.7 ± 0.6 respectively.

CONCLUSION

These new reference charts were established using a uniform methodology of the highest quality in order to assess CC growth accurately and help clinicians correctly define a "short" CC. ECOFD/CC and HC/CC ratios may be used as additional markers of normal CC development in borderline cases.

Callosal Injuries in Cytomegalovirus Fetopathy: A Neurosonographic Study

INTRODUCTION

Among the fetal brain anomalies described in cases of congenital infection, callosal insults are rarely cited in medical literature. The aim of this study was to describe the rate and pattern of callosal injury in cytomegalovirus (CMV) fetopathy.

METHODS

This retrospective study included fetuses with confirmed CMV-PCR, assessed in a single center. Demographic data including maternal seroconversion info were collected. Dedicated US including neurosonography was performed, with high frequency probes, using TV route whenever feasible. Fetal brain biometry including callosal length and the corpus callosum (CC)/OFD ratio was performed. Length below the 5th centile or morphological abnormalities were considered abnormal. Brain and body morphology were thoroughly assessed, and any abnormal finding reported.

RESULTS

Seventy-two patients were included in our cohort. In 76% infection occurred in the 1st T or periconceptional. In 12 patients, the exact time of infection was inconclusive, including two cases of secondary infection. In 34.7%, a callosal anomaly was observed and it was never isolated. CNS abnormalities included: periventricular hyperechogenicity (PVHE) 55.5%, calcifications 52%, ventriculomegaly 33%, periventricular pseudocysts 31.4%, occipital cysts 22.2%, echogenic ganglionic eminence 30.5%, lentostriatal vasculopathy 26.4%, sulcation abnormalities 22.2%, cerebellar findings 18% and HC below -2 SD 18%. In 19 cases, the CC was short with calcifications in four. In one case, the insult was severe and in another the CC was absent. The most common association with CC insult was PVHE (56%) and calcifications (52%).

CONCLUSION

Although not referred as a classic brain structure affected by CMV infection, the CC was injured in one-third of our patients, including cases of late infection. The mechanism of disease and the prenatal patterns of callosal involvement in these cases appear to be different from the postnatal patterns and are not reversible. The presence of a callosal injury would imply a worse prognosis and significant increment to the risk of neurodevelopmental impairment.

Loss-of-function variants in ZEB1 cause dominant anomalies of the corpus callosum with favourable cognitive prognosis

BACKGROUND

The neurodevelopmental prognosis of anomalies of the corpus callosum (ACC), one of the most frequent brain malformations, varies extremely, ranging from normal development to profound intellectual disability (ID). Numerous genes are known to cause syndromic ACC with ID, whereas the genetics of ACC without ID remains poorly deciphered.

METHODS

Through a collaborative work, we describe here ZEB1, a gene previously involved in an ophthalmological condition called type 3 posterior polymorphous corneal dystrophy, as a new dominant gene of ACC. We report a series of nine individuals with ACC (including three fetuses terminated due to ACC) carrying a ZEB1 heterozygous loss-of-function (LoF) variant, identified by exome sequencing.

RESULTS

In five cases, the variant was inherited from a parent with a normal corpus callosum, which illustrates the incomplete penetrance of ACC in individuals with an LoF in ZEB1. All patients reported normal schooling and none of them had ID. Neuropsychological assessment in six patients showed either normal functioning or heterogeneous cognition. Moreover, two patients had a bicornuate uterus, three had a cardiovascular anomaly and four had macrocephaly at birth, which suggests a larger spectrum of malformations related to ZEB1.

CONCLUSION

This study shows ZEB1 LoF variants cause dominantly inherited ACC without ID and extends the extraocular phenotype related to this gene.

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.

Does diabetes mellitus affect the development of fetal brain structures and spaces including corpus callosum, subarachnoid space, insula, and parieto-occipital fissure?

PURPOSE

We investigated the impact of pregestational and gestational diabetes mellitus (PGDM and GDM) on the development of fetal intracranial structures and spaces.

METHODS

This prospective cross-sectional study involved singleton pregnancies between 20 and 32 weeks of gestation. The study comprised a control group (n = 65) of healthy pregnant women without diabetes mellitus (DM); a PGDM group (n = 43) of pregnant women having type 2 DM in a controlled diabetic state; and a GDM group (n = 26) of pregnant women with GDM diagnosed with 2-h 75-g oral glucose tolerance test and received intervention to reduce the diabetic impact on fetus. During neurosonographic evaluation, the simultaneous measurements of corpus callosum (CC) width and depth in the midsagittal image; and lateral craniocortical and posterior craniocortical widths of the subarachnoid space and insular and parieto-occipital fissure depths in the axial image were performed. Before statistical analysis, these values were carefully adjusted for the occipitofrontal diameter.

RESULTS

The DM groups displayed substantially higher frequencies of family history of DM and obstetric history of GDM compared to the control group (p < 0.05). Regarding the neurosonographic parameters, the CC length and insular and parieto-occipital fissure depths were significantly increased in the GDM group but not in the PGDM group (p < 0.05). No significant difference was found among the study groups regarding other neurosonographic parameters (p > 0.05).

CONCLUSION

The results of neurosonographical evaluation of fetal brain structures and spaces reveal that diabetic impact may not be seen in the presence of PGDM, especially in pregnant women receiving prenatal interventions to reduce or avoid diabetic adverse effects on fetal brain development. The effect of GDM on neurosonographically assessed fetal brain development should be evaluated in further studies with subjects matched for gestational weeks and antenatal care conditions.