Prenatal diagnosis of microcephaly with simplified gyral pattern: series of eight cases.

Microcephaly with simplified gyral pattern (MSG) is an intrinsic genetic central nervous system disorder, characterized by microcephaly (a reduction of brain volume) and a simplified gyral pattern (a reduced number of gyri and shallow sulci associated with normal cortical thickness and neuroanatomical architecture), related to a reduced number of neuronal progenitors in the germinal matrix. We report the first prenatal series of MSG and define the prenatal imaging pattern, which should inform diagnosis and guide prenatal counseling in cases of fetal microcephaly. In this single-center retrospective study of fetuses with MSG, we assessed features on ultrasound and magnetic resonance imaging (MRI), as well as genetic and neuropathological/postnatal data. We included eight patients who had been referred following observation of microcephaly. Ultrasound examination confirmed microcephaly, with a mean growth delay in head circumference of 3.4 weeks, associated with both a lack of gyration and a lack of opercularization of the Sylvian fissure and without any extracephalic anomaly. Fetal brain MRI confirmed lack of gyration with normal cortical thickness and normal intensity of the white matter in all cases. These MRI features led to exclusion of migration/corticogenesis disorders (lissencephaly/polymicrogyria), instead suggesting MSG. The posterior fossa was normal in seven of the eight cases. The corpus callosum was thin in four cases, hypoplastic in two and dysgenetic in two. In four cases, the pregnancy was terminated. The diagnosis of MSG was confirmed from neuropathological and postnatal MRI data. MSG was associated with a genetic diagnosis of RTTN (n = 1) and ASPM (n = 2) biallelic variants in three of the six cases in which genetic work-up was performed. Mild or moderate intellectual deficit with speech delay was present in the three surviving children who were at least 5 years of age at their last examination, without seizures. In conclusion, in the presence of isolated fetal microcephaly with lack of gyration on ultrasound, fetal cerebral MRI is key to diagnosing MSG, which, in the majority of cases, affects the supratentorial space exclusively, and to ruling out other cortical malformations that show a similar sonographic pattern. In addition to imaging, genetic assessment may guide prenatal counseling, since the prenatal prognosis of MSG is different from that of both diffuse polymicrogyria and lissencephaly. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Prenatal evaluation of genetic variants in fetuses with small head circumference: A single-center retrospective study.

OBJECTIVES: To comprehensively evaluate the contributions of numerical chromosomal abnormality, copy number variant (CNV), and sequence variant (SV) to fetuses with small head circumference in a Chinese cohort using chromosome microarray analysis and whole exome sequencing. METHODS: A total of 157 fetuses with small heads defined as head circumference < - 2 standard deviation (SD) were recruited between October 2014 and March 2023. We used the ultrasonic measurement parameter Z-score to define small head as possible microcephaly (3 < Z ≤ -2), microcephaly (-5 < Z ≤ -3), or pathologic microcephaly (Z ≤ -5). Ultrasound findings and genetic results were analyzed. RESULTS: The overall diagnostic yield of chromosomal abnormalities by microarray analysis was 13 %. Whole exome sequencing revealed eight novel variants and two interesting candidate genes and provided a 25.4 % incremental yield compared with microarray analysis. Of the detected SVs, 56 % were de novo and the most common inheritance pattern was autosomal dominant inheritance presented in 11/16 fetuses. Compared with isolated small heads, non-isolated small heads had a significantly higher detection rate of chromosomal abnormalities (16 % vs. 3.0 %, P = 0.049) but not SVs (24 % vs. 5.5 %, P = 0.126). Subgroup analysis showed that intracranial anomalies had a similar high detection rate of SVs in fetuses with all small heads subgroups while no chromosomal abnormalities and causative SVs were found in fetuses with isolated possible microcephaly. CONCLUSIONS: Ultrasound findings of small fetal head circumference < 3 SD below the mean, especially those with intracranial structural abnormalities, indicate the need for genetic counseling. Genetic variants, mainly copy number variants and SV, may be responsible for the substantial proportion of small fetal head circumference, while most are de novo. Whole exome sequencing and microarray analysis are effective diagnostic approaches for this population.

[EXAMINING THE ASSOCIATION BETWEEN THE FETAL SUPRATENTORIAL BRAIN VOLUME AND THE SUBARACHNOID SPACE IN VARIOUS FETAL PATHOLOGIES USING MAGNETIC RESONANCE IMAGING].

INTRODUCTION: The subarachnoid space (SAS) is a potential space surrounding the brain where the cerebrospinal fluid (CSF) flows. Previous work demonstrated how the SAS width changes during pregnancy and measured the normal values per gestational week. OBJECTIVES: Studying the ratio between the fetal brain volume (STV) and the SAS width (SS ratio), as measured via fetal magnetic resonance imaging (MRI) in different fetal pathologies - macrocephaly and microcephaly, and studying the correlation between this ratio and the gestational week. METHODS: A retrospective study was conducted on 77 fetuses that underwent fetal MRI scans during gestational weeks 29-37, in three groups: 23 normocephaly, 27 macrocephaly, and 27 microcephaly. SAS width was measured in 10 points via fetal MRI scans, and a ratio was calculated between the width and STV. RESULTS: The SS ratio is largest in microcephaly group and smallest in normocephaly group, with the macrocephaly group between them. All comparisons were statistically significant except between the macrocephaly and normocephaly groups. There was a strong positive correlation between SS ratio and week of gestation. CONCLUSIONS: The SS ratio is statistically different between normocephalic fetuses and fetuses with macrocephaly or microcephaly. From week 29 this ratio enlarges with gestational age. DISCUSSION: The SAS affects the fetal head circumference, an important parameter of fetal growth, thus we decided to study the SS ratio in pathologies of the head circumference. Previous work demonstrated how the STV and the SAS width expand starting at a specific gestational age, thus the gestational week also affects the SS ratio. Summary: The SS ratio is affected by pathologies of the fetal head circumference and by gestational age.

A founder PPIL1 variant underlies a recognizable form of microlissencephaly with pontocerebellar hypoplasia.

Biallelic variants in PPIL1 have been recently found to cause a very rare type of pontocerebellar hypoplasia and congenital microcephaly in which simplified gyral pattern was not observed in all of the patients. Here, we describe a series of nine patients from eight unrelated Egyptian families in whom whole exome sequencing detected a previously reported homozygous missense variant (c.295G>A, p.Ala99Thr) in PPIL1. Haplotype analysis confirmed that this variant has a founder effect in our population. All our patients displayed early onset drug-resistant epilepsy, profound developmental delay, and visual impairment. Remarkably, they presented with recognizable imaging findings showing profound microcephaly, hypoplastic frontal lobe and posteriorly predominant pachygyria, agenesis of corpus callosum with colpocephaly, and pontocerebellar hypoplasia. In addition, Dandy-Walker malformation was evident in three patients. Interestingly, four of our patients exhibited hematopoietic disorder (44% of cases). We compared the phenotype of our patients with other previously reported PPIL1 patients. Our results reinforce the hypothesis that the alterative splicing of PPIL1 causes a heterogeneous phenotype. Further, we affirm that hematopoietic disorder is a common feature of the condition and underscore the role of major spliceosomes in brain development.

Feingold syndrome type 1: a rare cause of fetal microcephaly (prenatal diagnosis).

We report a case of fetal microcephaly found during the second trimester ultrasound and confirmed by further ultrasound scans and fetal MRI. The array comparative genomic hybridisation analysis of the fetus and the male parent showed a 1.5 Mb deletion overlapping the Feingold syndrome region, an autosomal dominant syndrome that can cause microcephaly, facial/hand abnormalities, mild neurodevelopmental delay and others. This case illustrates the need for a detailed investigation by a multidisciplinary team to provide prenatal counselling regarding a postnatal outcome to the parents and orient their decision towards the continuation or termination of pregnancy.

Voxel-based morphometric magnetic resonance imaging evaluation of small head fetus: A comparative study with normal developmental fetus.

PURPOSE: To explore the application value of voxel-based morphometric (VBM) in prenatal diagnosis of microcephaly. METHODS: A retrospective study of magnetic resonance imaging of fetuses with microcephaly was performed using a single-shot fast spin echo sequence; semiautomatic segmentation of grey matter (GM), white matter (WM), and cerebrospinal fluid (CSF); calculation of their volumes; and VBM analysis of their GM. Two independent samples t-test was used to statistically analyse the fetal GM volume in the microcephaly and normal control groups. Total intracranial volume (TIV), GM volume, WM volume, and CSF volume were linearly regressed against gestational age and compared between the two groups. RESULTS: In the fetus with microcephaly, GM volume of frontal lobe, temporal lobe, cuneus, anterior central gyrus, and posterior central gyrus decreased significantly (P < 0.001, corrected by family-wise error at mass level). The GM volume of microcephaly was significantly lower than that of the control group (except for 28 weeks of gestation) (P < 0.05). TIV, GM volume, WM volume, and CSF volume were all positively correlated with gestational age, and the curves in the microcephaly group were all lower than those in the control group. CONCLUSION: Compared with the normal control group, the GM volume of microcephaly fetuses decreased, and there were significant differences in many brain regions through VBM analysis.

Case Report: Prenatal Recurrent Microcephaly and Corpus Callosum Abnormalities in a Chinese Family with Novel Biallelic SASS6 Mutations.

INTRODUCTION: Primary microcephaly (MCPH) is not an uncommon disorder with multiple etiologies. There are a growing number of MCPH-related genes discovered due to the extensive application of whole-exome sequencing (WES) in clinical and research settings. Biallelic mutations in the SASS6 gene cause an extremely rare MCPH, type 14. To date, only two families with SASS6 gene-related microcephaly have been reported. CASE DESCRIPTION: We report a case of recurrent congenital microcephaly in a Chinese family. The two affected fetuses presented with microcephaly early in the second trimester with agenesis of the corpus callosum. In the first affected fetus, trio WES detected two compound heterozygous candidate variants c.1139T>C(p.L380P) and c.1223C>G (p.T408S) in the SASS6 gene. Another affected fetus also inherited both variants, while the normal child carried neither variant through Sanger sequencing analysis. Both variants were classified as a variant of uncertain significance according to the current American College of Medical Genetics and Genomics guidelines. CONCLUSION: We reported novel biallelic variants in the SASS6 gene, encoding the SAS6 centriolar assembly protein, associated with prenatal onset of autosomal recessive microcephaly. We postulate that the pathomechanism of the compound heterozygous variants in close proximity could potentiate the overall coiled instability leading to the phenotypic features of our case.

Prenatal diagnosis of SMPD4 loss - A neurodevelopmental disorder with microcephaly, arthrogryposis and structural brain anomalies.

SMPD4 loss is a rare neurodevelopmental disorder that leads to severe mental and physical disability and early death in infancy. Most cases of this genetic condition have been diagnosed postnatally. This article focuses on the prenatal findings of affected fetuses. The phenotypes can include growth restriction, arthrogryposis (clenched hands, foot deformity), as well as cerebral abnormalities (simplified gyral pattern/lissencephaly, cerebellar hypoplasia, corpus callosum deformity). SMPD4 loss is detectable via exome sequencing. Here, two fetuses displayed a homozygotic pathogen variant in the SMPD4 gene, encoding for the enzyme Sphingomyelinase-4. Both parents were heterozygous carriers of the pathogenic variant. On detection of the above mentioned signs exome sequencing is indicated, with focus on the SMPD4 gene.

Prenatal and Postnatal Zika Intrauterine Infection: Diagnostic Imaging Techniques and Placental Pathology.

Introduction: Zika virus (ZIKV) is an arbovirus (arthropod-borne virus) in the genus Flavivirus and Flaviviridae family. In November 2015, several cases of microcephaly in Northeastern of Brazil suggested ZIKV involvement. Case Report: A 33-year-old primigravida developed fever and cutaneous rash at 7th week of gestation (WGA). The ultrasound and MRI examination showed head circumference < 5th centile and enlargement of lateral ventricles. The infant was delivered at 39th WGA with microcephaly. Microscopy of the placenta showed chronic villitis and intervillitis, nodular stromal fibrosis in the stem villi, and vascular thickening. Postnatal CT showed collapsed cranium due to growth impairment of the suprathalamic brain, multiple cerebral calcifications, parenchymal atrophy, and ventricular dilatation. Now, at 6 years old, the child suffers from severe neurologic symptoms, including seizures. Conclusion: This case gathers images of prenatal and postnatal period, and placental histopathology. The long-term follow-up highlights the dramatic neurological sequelae induced by ZIKV.

Homozygous SLC20A2 mutations cause congenital CMV infection-like phenotype.

BACKGROUND: Idiopathic basal ganglia calcification, also known as Fahr's disease, it is a neurological disease characterized by intracranial calcification caused by heterozygous SLC20A2 mutations. Patients with calcifications can either be asymptomatic or show a wide spectrum of neuropsychiatric symptoms, including parkinsonism, tremor, dystonia, ataxia, and seizures. OBJECTIVES: The aim of this study was to investigating the clinical implications of the SLCA20A2 gene and identifying a new phenotype through a family. METHODS: Two siblings with growth retardation, bilateral cataracts, microcephaly, and convulsion were included in the study. The MRI showed cerebral atrophy, corpus callosum hypoplasia, microcalcifications. Chromosomal microarray analysis was performed to identify the existence of copy number variation. The whole exome sequencing analysis of the individual IV-I was performed, and Sanger sequencing was performed for segregation. RESULTS: Whole exome sequencing revealed a homozygous NM_006749.5:c.1794 + 1G > A of the SLC20A2 gene. The Sanger sequencing confirmed the affected siblings were homozygous and the parents were heterozygous. CONCLUSIONS: SLC20A2 gene heterozygous mutations were associated with the adult-onset phenotype, while homozygous SLC20A2 mutations in the two affected siblings we reported in our study resulted in a severe clinic including growth retardation, bilateral cataracts, microcephaly, and convulsion. We showed that biallelic mutations in the SLC20A2 gene that cause the Fahr's disease lead to more severe phenotypes contrary to what is known. The two siblings, showing similar phonotypic and genotypic characteristics, would be the youngest cases in the pediatric age group published in the literature.

Mild phenotypes of phosphoglycerate dehydrogenase deficiency by a novel mutation of PHGDH gene: Case report and literature review.

Phosphoglycerate dehydrogenase (PHGDH) deficiency is a rare autosomal recessive genetic disease of serine biosynthesis. Its typical features are congenital microcephaly, epileptic seizures, and psychomotor developmental delay. Here, we reported the first Chinese familial cases with genetically confirmed PHGDH deficiency and reviewed several previous reports. Two siblings in this family presented with microcephaly, psychomotor retardation, and epilepsy in early juvenile. Brain magnetic resonance imaging (MRI) showed only a slight change of enlarged ventricle. Biochemical investigations revealed low serum serine and glycine concentrations. The whole-exome sequencing (WES) results identified a missense variant in the PHGDH gene (NM_006623.4: exon11: c.1211T>A, p. Val404Asp). Although two patients in this Chinese family carried the same pathogenic mutation in the PHGDH, their symptoms and responses to treatment were not exactly the same. We found a novel variant in the PHGDH gene and expanded the genotypic and phenotypic spectrum of serine biosynthesis disorders.

Mouse Brain MRI: Including In Vivo, Ex Vivo, and fcMRI for the Study of Microcephaly.

With its sensitivity to soft tissue, MRI is a powerful tool for the study of the neuroanatomical manifestations of a variety of conditions, such as microcephaly-related morbidities that are not easily visualized by other imaging techniques, such as CT. In addition to structural imaging, more recently, researchers have found changes in brain function in a wide range of neurological conditions-highlighting the utility of MRI for the study of microcephaly.In this methods chapter, basic mouse preparation and the acquisition of data for in vivo anatomical MRI will be discussed. Additionally, we will provide our protocol for the perfusion and fixation of brain tissue with gadolinium contrast agent. Following that, the process of optimization of system parameters will be shown for anatomical imaging of in vivo and ex vivo brain tissue. Lastly, the chapter will detail a protocol for fcMRI along with a discussion of considerations specific to functional imaging.

A novel homozygous CHMP1A variant arising from segmental uniparental disomy causes pontocerebellar hypoplasia type 8.

Pontocerebellar hypoplasia (PCH) is currently classified into 16 subgroups. Using mostly next-generation sequencing, pathogenic variants have been identified in as many as 24 PCH-associated genes. PCH type 8 (PCH8) is a rare heterogeneous disorder. Its clinical presentation includes severe development delay, increased muscle tone, microcephaly, and magnetic resonance imaging (MRI) abnormalities such as reduced cerebral white matter, a thin corpus callosum, and brainstem and cerebellar hypoplasia. To date, only two variants in the CHMP1A gene (MIM: 164010), NM_002768.5: c.88 C > T (p.Glu30*) and c.28-13 G > A, have been identified homozygously in seven patients with PCH8 from four families (MIM: 614961). CHMP1A is a subunit of the endosomal sorting complex required for transport III (ESCRT-III), which regulates the formation and release of extracellular vesicles. Biallelic CHMP1A loss of function impairs the ESCRT-III-mediated release of extracellular vesicles, which causes impaired progenitor proliferation in the developing brain. Herein, we report a patient with PCH8 who had a homozygous CHMP1A variant, c.122delA (p.Asn41Metfs*2), which arose from segmental uniparental disomy. Although our patient had similar MRI findings to those of previously reported patients, with no progression, we report some novel neurological and developmental findings that expand our knowledge of the clinical consequences associated with CHMP1A variants.

Characteristics associated with drug resistant epilepsy in children up to 36 months old with Congenital Zika Syndrome.

OBJECTIVES: To verify characteristics associated with drug resistant epilepsy in children up to 36 months of age with Congenital Zika Syndrome (CZS). METHODS: This is a prospective cohort study with children aged up to 36 months diagnosed with CZS. Obstetric, demographic, phenotype and other clinical signs, cranial tomography, growth and motor development of the children were collected. RESULTS: Of a total of 109 children diagnosed with CZS, 100 (91.7%) had epilepsy and 68 (68%) with drug resistant seizures. The types of seizures associated with drug resistant epilepsy were focal seizures from the occipital lobe, generalized tonic and generalized tonic-clonic seizures. There was an association between drug resistant epilepsy and microcephaly at birth, severe microcephaly at birth, excess nuchal skin, ventriculomegaly, reduced brain parenchyma volume, and hypoplasia or malformation of the cerebellum. Difficulty sleeping, irritability, continuous crying, dysphagia and gross motor function were clinical signs associated with drug resistant epilepsy, as were the presence of ocular abnormalities, low head circumference in the first year of life and low weight in the first six months. CONCLUSIONS: The prevalence of drug resistant epilepsy in children up to 36 months with CZS was 62.4% and was associated with the severity of the child's neurological damage, with emphasis on the reduction of brain parenchyma volume and damage to the cerebellum.

Imaging of Microcephaly.

One of the most common definitions of microcephaly cited is that of an occipitofrontal circumference (OFC) of the head that is less than two standard deviations below the average for age (or gestational age, if identified prenatally) and sex. Similarly, severe microcephaly is defined as an OFC that is less than three standard deviations below the average. Microcephaly is not a diagnosis, but rather, a finding that is secondary to a multitude of etiologies that can be categorized as prenatal versus postnatal, genetic versus environmental, and congenital versus acquired.

A homozygous loss-of-function variant in BICD2 is associated with lissencephaly and cerebellar hypoplasia.

Developmental brain malformations are rare but are increasingly reported features of BICD2-related disorders. Here, we report a 2-year old boy with microcephaly, profound delay and partial seizures. His brain MRI showed lissencephaly, hypogenesis of corpus callosum, dysplastic hipocampus and cerebellar hypoplasia. Whole-exome sequencing identified a novel homozygous likely pathogenic variant in the BICD2 gene, c.229 C > T p.(Gln77Ter). This is the first report of lissencephaly and cerebellar hypoplasia seen in a patient with homozygous loss-of-function variant in BICD2 that recapitulated the animal model. Our report supports that BICD2 should be considered in the differential diagnosis for patients with lissencephaly and cerebellar hypoplasia Additional clinical features of BICD2 are likely to emerge with the identification of additional patients.

Zika-Related Microcephaly and Its Repercussions for the Urinary Tract: Clinical, Urodynamic, Scintigraphic and Radiological Aspects.

AIMS: Describing the urodynamic parameters of children aged 3 to 5 years with microcephaly related to congenital Zika syndrome and verifying the association with clinical, imaging and neurological characteristics. METHODS: From October 2018 to March 2020, children with Zika-related microcephaly underwent urological, ultrasonographic and urodynamic evaluation. In selected cases, complementary exams such as urethrocystography and scintigraphy were performed. The children also underwent a complete neurological evaluation. To compare frequency between groups, we used Pearson's chi-squared test or Fisher's exact test. RESULTS: This study evaluated 40 children, of whom 85% were 4 years old, and all had abnormalities on the urodynamic study, with low bladder capacity (92.5%) and detrusor overactivity (77.5%) as the most frequent findings. Only three children had ultrasound abnormalities, but no child had cystographic or scintigraphic abnormalities, and the postvoid residual volume was normal in 80% of cases. In spite of a frequency of 67.5% of intestinal constipation, there was no record of febrile urinary tract infection after the first year of life. All children presented severe microcephaly and at least one neurological abnormality in addition to microcephaly. The homogeneity of the children in relation to microcephaly severity and neurological abnormalities limited the study of the association with the urodynamic parameters. CONCLUSIONS: Urodynamic abnormalities in children aged 3 to 5 years with Zika-related microcephaly do not seem to characterize a neurogenic bladder with immediate risks for the upper urinary tract. The satisfactory bladder emptying suggests that the voiding pattern is reflex.

A rare cause of microcephaly, thin corpus callosum and refractory epilepsy due to a novel SLC1A4 gene mutation.

L-serine is an important amino acid that ensures neuronal differentiation and development. The SLC1A4 gene encodes proteins that transport amino acids such as serine, alanine, threonine and glutamate into neurons. Pathogenic variants in SLC1A4 gene interneuron transport of L-serine impaired and a severe global developmental delay occurs, characterized by microcephaly and refractory seizures. In this article, we would like to describe the demographic, clinical, electroencephalography (EEG) and magnetic resonance imaging (MRI) features of a patient with a novel pathogenic variant in the 6th exon of the SLC1A4 gene (p.Gly374Arg) detected by whole-exome sequencing, which is extremely rare (there have been twenty patients reported in the literature). It is emphasized that SLC1A4 gene variants should be kept in mind if the patients have microcephaly, global developmental delay, refractory seizures, and there are no abnormalities in basal metabolic investigations, and the thin corpus callosum and myelination delay is seen on the MRI.

A novel de novo missense mutation in EFTUD2 identified by whole-exome sequencing in mandibulofacial dysostosis with microcephaly.

BACKGROUND: Mandibulofacial dysostosis with microcephaly (MFDM) is a rare multiple malformation syndrome characterized by malar and mandibular hypoplasia and congenital- or postnatal-onset microcephaly induced by haploinsufficiency of (elongation factor Tu GTP-binding domain-containing 2) EFTUD2. METHODS: We report the case of a 16-month-old boy with MFDM symptoms, including malar and mandibular hypoplasia, microcephaly, micrognathia, midline cleft palate, microtia, auditory canal atresia, severe sensorineural hearing loss, and developmental delay. Whole-exome sequencing (WES) analysis of the patient's family was performed to identify the genetic etiology responsible for this phenotype. RESULTS: We identified a novel de novo missense mutation (c.671G>T, p.Gly224Val) in the EFTUD2. According to the American College of Medical Genetics and Genomics (ACMG) 2015 guidelines, the c.671G>T mutation was classified as likely pathogenic (PS2, PM1, PM2, and PP3). Based on our findings, prenatal diagnosis was performed on the second baby of the proband's parents to exclude the mutation and it was confirmed that the baby did not have the MFDM phenotype after 14 months of follow-up. Furthermore, the zebrafish model confirmed that the EFTUD2 c.671G>T mutation caused a loss of gene function in EFTUD2, and the pathogenicity of the EFTUD2 c.671G>T mutation was classified as pathogenic (PS2, PS3, PM1, and PM2). CONCLUSION: Our results indicate that WES is a useful tool for identifying potentially pathogenic mutations, particularly in rare disorders, and is advantageous for genetic counseling and subsequent prenatal diagnosis. Moreover, the importance of functional assays cannot be underestimated, which could further confirm the pathogenicity of the genetic variants.