Cobblestone lissencephaly: neuropathological subtypes and correlations with genes of dystroglycanopathies

Fetal imaging of posterior fossa malformations

Posterior fossa anomalies are less common in prenatal diagnosis than midline anomalies or ventricular dilatations. However, they constitute an important entity, combining neurological disorders as well as normal variants that should be recognized in prenatal diagnosis because of the genetic implications and neurodevelopmental outcome of some of these conditions. Here we present some of the main imaging features enabling prenatal diagnosis of posterior fossa anomalies in a context of constantly evolving classifications, resulting from advances in genetics and neuroimaging.

Cobblestone lissencephaly (Type II), clinical, and neuroimaging: A case report and literature review

Cobblestone lissencephaly (C-LIS) (TYPE II) is a rare and severe neuronal migration disorder characterized by a smooth brain surface with overmigrated neurons and abnormal formation of cerebral convolutions or gyri during fetal development, resulting in a cobblestone appearance. C-LIS is associated with eye anomalies and muscular dystrophy. This case report presents a detailed clinical and neuroimaging analysis of a patient diagnosed with cobblestone lissencephaly (Type II). It reviews pertinent literature to enhance our understanding of this complex condition. We report a case of a 6-year-old female child with cobblestone lissencephaly (C-LIS) (Type II) severe developmental delays, hypotonia, and recurrent intractable seizures. Magnetic resonance imaging (MRI) revealed a characteristic cobblestone appearance on the brain surface, indicative of abnormal neuronal migration. In addition to the classic findings of Type II Cobblestone lissencephaly, the patient displayed ventriculomegaly and cerebellar hypoplasia, contributing to the overall neurological impairment observed. The literature review highlights the genetic basis of cobblestone lissencephaly, emphasizing the involvement of genes associated with glycosylation processes and basement membrane integrity. Neuroimaging findings, including MRI and computed tomography scans, are crucial for accurate diagnosis and prognostication. Early identification of cobblestone lissencephaly allows for appropriate counseling and management strategies. However, the prognosis remains guarded, and interventions primarily focus on supportive care and seizure management. This case report contributes to the knowledge of cobblestone lissencephaly, shedding light on the clinical spectrum and neuroimaging features associated with this rare disorder. To clarify the underlying genetic mechanisms and possible therapeutic pathways for better patient outcomes, more investigation is necessary.

Malformations of Cortical Development: Updated Imaging Review

Malformations of cortical development (MCD) are structural anomalies that disrupt the normal process of cortical development. Patients with these anomalies frequently present with seizures, developmental delay, neurologic deficits, and cognitive impairment, resulting in a wide spectrum of neurologic outcomes. The severity and type of malformation, in addition to the genetic pathways of brain development involved, contribute to the observed variability. While neuroimaging plays a central role in identifying congenital anomalies in vivo, the precise definition and classification of cortical developmental defects have undergone significant transformations in recent years due to advances in molecular and genetic knowledge. The authors provide a concise overview of embryologic brain development, recently standardized nomenclature, and the categorization system for abnormalities in cortical development, offering valuable insights into the interpretation of their neuroradiologic patterns. ©RSNA, 2024 Supplemental material is available for this article. The slide presentation from the RSNA Annual Meeting is available for this article.

Polymicrogyria, Cobblestone Malformations, and Tubulin Mutation (Overmigration beyond Pial Limiting Membrane): Diagnosis, Treatment, and Rehabilitation Approach

Polymicrogyria, cobblestone malformations, and tubulinopathies constitute a group of neuronal migration abnormalities beyond the pial limiting membrane. Their etiopathogenesis remains unclear, with proposed environmental and genetic factors, including copy number variations and single-gene disorders, recently categorized.

Polymicrogyria features numerous small circumvolutions separated by large, shallow grooves, often affecting the perisylvian cortex with various presentations. Clinical manifestations vary depending on lesion degree, extent, and location, commonly including epilepsy, encephalopathies, spastic tetraparesis, mental retardation, and cortical function deficits.

Cobblestone malformations exhibit a Roman-like pavement cortex, affecting both hemispheres symmetrically due to disruption of the glia limitans, frequently linked to glycosyltransferase gene mutations. Classified separately from lissencephaly type II, they are associated with congenital muscular dystrophy syndromes such as Fukuyama congenital muscular dystrophy, Walker–Warburg syndrome, and muscle–eye–brain disease.

Tubulinopathies encompass diverse cerebral malformations resulting from α-tubulin isotype gene variants, exhibiting a wide clinical spectrum including motor/cognitive impairment, facial diplegia, strabismus, and epilepsy.

Diagnosis relies on magnetic resonance imaging (MRI) with age-specific protocols, highlighting the gray–white junction as a polymicrogyria marker, though neonatal diagnosis may be challenging due to technical and brain maturity issues.

To date, no effective treatments are available and management include physiotherapy, speech and language therapy, and vision training program for oculomotor disabilities; antiepileptic drugs are commonly necessary, and most severe forms usually require specific nutritional support.

Lissencephaly, Pachygyrias, Band Heterotopias, RELN Pathway, and ARX Mutations (Incomplete Neuron Migration)

Lissencephaly (LIS) is a group of malformations of cortical development consisting of a defective neuronal migration that results in lack of formation of the normal cerebral convolutions. It includes a spectrum of defect with varying degrees of severity, from agyria and pachygyria to subcortical band heterotopia. The etiopathogenesis of LIS includes both genetic and environmental factors. Although nongenetic forms of LIS have been reported, genetic causes are certainly more frequent and to date 19 LIS-SBH-associated genes have been identified. Most common mutations involve LIS1, DCX, ARX, and RELN genes. Clinically affected individuals present with early hypotonia, which can progress to limb spasticity, seizures, and psychomotor retardation. Convulsive episodes usually appear early (first months of life) and include infantile spasms, akinetic or myoclonic seizures, up to the development of complex epileptic syndromes, including atypical absences, myoclonia, and partial or tonic–clonic seizures. Several clinical entities are associated with classical LIS, including the following: isolated lissencephaly sequence (ILS); Miller–Dieker syndrome (MDS; OMIM 247200); subcortical band heterotopia (OMIM 300067); X-linked LIS with abnormal genitalia; and LIS with cerebellar hypoplasia. Diagnosis primarily depends on genetic and neuroimaging. Magnetic resonance imaging (MRI) is the gold standard, and it detects the presence of thick cortical cortex, its location, and the layers' architecture. Based on neuroimaging, it is possible to distinguish six subtypes of gyral malformations. Clinical and therapeutic management of these patients is challenging, considering the necessity to face drug-resistant epilepsy, intellectual disability, spasticity, and dysphagia and feeding problems. At the present moment, no gene-specific treatment for LIS is available.

Prenatal Imaging of Supratentorial Fetal Brain Malformation

This review article provides a comprehensive overview of fetal MR imaging in supratentorial cerebral malformations. It emphasizes the importance of fetal MR imaging as an adjunct diagnostic tool used alongside ultrasound, improving the detection and characterization of prenatal brain abnormalities. This article reviews a spectrum of cerebral malformations, their MR imaging features, and the clinical implications of these findings. Additionally, it outlines the growing importance of fetal MR imaging in the context of perinatal care.

Diagnostic work-up in malformations of cortical development

Malformations of cortical development (MCDs) represent a heterogeneous spectrum of disorders characterized by atypical development of the cerebral cortex. MCDs are most often diagnosed on the basis of imaging, although subtle lesions, such as focal cortical dysplasia, may only be revealed on neuropathology. Different subtypes have been defined, including lissencephaly, heterotopia, cobblestone malformation, polymicrogyria, and dysgyria. Many MCDs are of genetic origin, although acquired factors, such as congenital cytomegalovirus infections and twinning sequence, can lead to similar phenotypes. In this narrative review, we provide an overview of the diagnostic approach to MCDs, which is illustrated with clinical vignettes, on diagnostic pitfalls such as somatic mosaicism and consanguinity, and recognizable phenotypes on imaging, such as tubulinopathies, the lissencephaly spectrum, tuberous sclerosis complex, and FLNA-related periventricular nodular heterotopia.

Protein O-mannosylation: one sugar, several pathways, many functions

Recent research has unveiled numerous important functions of protein glycosylation in development, homeostasis, and diseases. A type of glycosylation taking the center stage is protein O-mannosylation, a posttranslational modification conserved in a wide range of organisms, from yeast to humans. In animals, protein O-mannosylation plays a crucial role in the nervous system, whereas protein O-mannosylation defects cause severe neurological abnormalities and congenital muscular dystrophies. However, the molecular and cellular mechanisms underlying protein O-mannosylation functions and biosynthesis remain not well understood. This review outlines recent studies on protein O-mannosylation while focusing on the functions in the nervous system, summarizes the current knowledge about protein O-mannosylation biosynthesis, and discusses the pathologies associated with protein O-mannosylation defects. The evolutionary perspective revealed by studies in the Drosophila model system are also highlighted. Finally, the review touches upon important knowledge gaps in the field and discusses critical questions for future research on the molecular and cellular mechanisms associated with protein O-mannosylation functions.

An adhesion signaling axis involving Dystroglycan, β1-Integrin, and Cas adaptor proteins regulates the establishment of the cortical glial scaffold

The mature mammalian cortex is composed of 6 architecturally and functionally distinct layers. Two key steps in the assembly of this layered structure are the initial establishment of the glial scaffold and the subsequent migration of postmitotic neurons to their final position. These processes involve the precise and timely regulation of adhesion and detachment of neural cells from their substrates. Although much is known about the roles of adhesive substrates during neuronal migration and the formation of the glial scaffold, less is understood about how these signals are interpreted and integrated within these neural cells. Here, we provide in vivo evidence that Cas proteins, a family of cytoplasmic adaptors, serve a functional and redundant role during cortical lamination. Cas triple conditional knock-out (Cas TcKO) mice display severe cortical phenotypes that feature cobblestone malformations. Molecular epistasis and genetic experiments suggest that Cas proteins act downstream of transmembrane Dystroglycan and β1-Integrin in a radial glial cell-autonomous manner. Overall, these data establish a new and essential role for Cas adaptor proteins during the formation of cortical circuits and reveal a signaling axis controlling cortical scaffold formation.

Metabolic Cardiomyopathies and Cardiac Defects in Inherited Disorders of Carbohydrate Metabolism: A Systematic Review

Heart failure (HF) is a progressive chronic disease that remains a primary cause of death worldwide, affecting over 64 million patients. HF can be caused by cardiomyopathies and congenital cardiac defects with monogenic etiology. The number of genes and monogenic disorders linked to development of cardiac defects is constantly growing and includes inherited metabolic disorders (IMDs). Several IMDs affecting various metabolic pathways have been reported presenting cardiomyopathies and cardiac defects. Considering the pivotal role of sugar metabolism in cardiac tissue, including energy production, nucleic acid synthesis and glycosylation, it is not surprising that an increasing number of IMDs linked to carbohydrate metabolism are described with cardiac manifestations. In this systematic review, we offer a comprehensive overview of IMDs linked to carbohydrate metabolism presenting that present with cardiomyopathies, arrhythmogenic disorders and/or structural cardiac defects. We identified 58 IMDs presenting with cardiac complications: 3 defects of sugar/sugar-linked transporters (GLUT3, GLUT10, THTR1); 2 disorders of the pentose phosphate pathway (G6PDH, TALDO); 9 diseases of glycogen metabolism (GAA, GBE1, GDE, GYG1, GYS1, LAMP2, RBCK1, PRKAG2, G6PT1); 29 congenital disorders of glycosylation (ALG3, ALG6, ALG9, ALG12, ATP6V1A, ATP6V1E1, B3GALTL, B3GAT3, COG1, COG7, DOLK, DPM3, FKRP, FKTN, GMPPB, MPDU1, NPL, PGM1, PIGA, PIGL, PIGN, PIGO, PIGT, PIGV, PMM2, POMT1, POMT2, SRD5A3, XYLT2); 15 carbohydrate-linked lysosomal storage diseases (CTSA, GBA1, GLA, GLB1, HEXB, IDUA, IDS, SGSH, NAGLU, HGSNAT, GNS, GALNS, ARSB, GUSB, ARSK). With this systematic review we aim to raise awareness about the cardiac presentations in carbohydrate-linked IMDs and draw attention to carbohydrate-linked pathogenic mechanisms that may underlie cardiac complications.

Malformation of cortical development with abnormal cortex: early ultrasound diagnosis between 14 and 24 weeks of gestation

OBJECTIVE

To describe neurosonographic findings diagnostic or highly suggestive of the presence of malformations of cortical development involving the cortex that may be identified before 24 weeks of gestation.

METHODS

This was a retrospective single-center study of fetuses referred for neurosonography, during 2012-2019, with an abnormal cortical or sulcation pattern diagnosed early in the mid trimester. Stored files were analyzed for demographic data, abnormal brain findings, non-central nervous system abnormalities, final diagnosis and postnatal outcome.

RESULTS

The study cohort included 20 fetuses, with a mean gestational age at diagnosis of 18.7 (range, 14.4-23.6) weeks, in 11 of which the diagnosis was made before 20 weeks of gestation. Reasons for referral were: midline anomaly (n = 7), ventriculomegaly (n = 4), infratentorial findings (n = 3), suspected malformation of cortical development (n = 3), 'abnormal brain' (n = 2) and skeletal dysplasia (n = 1). On neurosonography, both the sulcation pattern and the cortical layer were abnormal in four cases, only the sulcation pattern was considered abnormal in seven and only the cortical layer was abnormal in nine. Nineteen fetuses presented with associated central nervous system anomalies and six also had non-central nervous system malformations. One case was recurrent. Eighteen parents opted for termination of pregnancy, including one selective termination in a twin pregnancy, and two fetuses were liveborn.

CONCLUSIONS

Familiarity with fetal brain anatomy and its early sonographic landmarks allowed early diagnosis of malformations involving cortical development. These patients are likely to represent the most severe cases and all had associated malformations. The presence of an abnormal cortical layer and/or abnormal overdeveloped sulci appear to be early signs of malformation of cortical development. © 2022 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Fetal Presentation of Walker-Warburg Syndrome with Compound Heterozygous POMT2 Missense Mutations

Background: Walker-Warburg syndrome (WWS) (OMIM #236670) is an autosomal recessive disorder characterized by congenital muscular dystrophy, hydrocephalus, cobblestone lissencephaly, and retinal dysplasia. The main genes involved are: POMT1, POMT2, POMGNT1, FKTN, LARGE1, and FKRP. Case report: We present a fetus with WWS showing at ultrasound severe triventricular hydrocephalus. Pregnancy was legally terminated at 21 weeks +2 days of gestation. In vivo and postmortem magnetic resonance revealed corpus callosum agenesis and cerebellar hypoplasia. Cobblestone lissencephaly was observed at post-mortem. Next generation sequencing (NGS) of 193 genes, performed on fetal DNA extracted from amniocytes, detected two heterozygous mutations in the POMT2 gene. The c.1238G > C p.(Arg413Pro) mutation was paternally inherited and is known to be pathogenic. The c.553G > A p.(Gly185Arg) mutation was maternally inherited and has not been previously described. Conclusion: Compound heterozygous mutations in the POMT2 gene caused a severe cerebral fetal phenotype diagnosed prenatally at midgestation allowing therapeutic pregnancy termination.

Protein tyrosine phosphatase 69D is a substrate of protein O-mannosyltransferases 1-2 that is required for the wiring of sensory axons in Drosophila

Mutations in protein O-mannosyltransferases (POMTs) result in severe brain defects and congenital muscular dystrophies characterized by abnormal glycosylation of α-dystroglycan (α-Dg). However, neurological phenotypes of POMT mutants are not well understood, and the functional substrates of POMTs other than α-Dg remain unknown. Using a Drosophila model, here we reveal that Dg alone cannot account for the phenotypes of POMT mutants, and identify Protein tyrosine phosphatase 69D (PTP69D) as a gene interacting with POMTs in producing the abdomen rotation phenotype. Using RNAi-mediated knockdown, mutant alleles, and a dominant-negative form of PTP69D, we reveal that PTP69D is required for the wiring of larval sensory axons. We also found that PTP69D and POMT genes interact in this process, and that their interactions lead to complex synergistic or antagonistic effects on axon wiring phenotypes, depending on the mode of genetic manipulation. Using glycoproteomic approaches, we further characterized the glycosylation of the PTP69D transgenic construct expressed in genetic strains with different levels of POMT activity. We found that the PTP69D construct carries many O-linked mannose modifications when expressed in Drosophila with wild-type or ectopically upregulated expression of POMTs. These modifications were absent in POMT mutants, suggesting that PTP69D is a substrate of POMT-mediated O-mannosylation. Taken together, our results indicate that PTP69D is a novel functional substrate of POMTs that is required for axon connectivity. This mechanism of POMT-mediated regulation of receptor-type protein tyrosine phosphatase functions could potentially be conserved in mammals and may shed new light on the etiology of neurological defects in muscular dystrophies.

Analysis of the expression and distribution of protein O-linked mannose β1,2-N-acetylglucosaminyltransferase 1 in the normal adult mouse brain

Introduction

Protein O-linked mannose β1,2-N-acetylglucosaminyltransferase 1 (POMGNT1) is crucial for the elongation of O-mannosyl glycans. Mutations in POMGNT1 cause muscle-eye-brain (MEB) disease, one of the main features of which is anatomical aberrations in the brain. A growing number of studies have shown that defects in POMGNT1 affect neuronal migration and distribution, disrupt basement membranes, and misalign Cajal-Retzius cells. Several studies have examined the distribution and expression of POMGNT1 in the fetal or neonatal brain for neurodevelopmental studies in the mouse or human brain. However, little is known about the neuroanatomical distribution and expression of POMGNT1 in the normal adult mouse brain.

Methods

We analyzed the expression of POMGNT1 mRNA and protein in the brains of various neuroanatomical regions and spinal cords by western blotting and RT-qPCR. We also detected the distribution profile of POMGnT1 in normal adult mouse brains by immunohistochemistry and double-immunofluorescence.

Results

In the present study, we found that POMGNT1-positive cells were widely distributed in various regions of the brain, with high levels of expression in the cerebral cortex and hippocampus. In terms of cell type, POMGNT1 was predominantly expressed in neurons and was mainly enriched in glutamatergic neurons; to a lesser extent, it was expressed in glial cells. At the subcellular level, POMGNT1 was mainly co-localized with the Golgi apparatus, but expression in the endoplasmic reticulum and mitochondria could not be excluded.

Discussion

The present study suggests that POMGNT1, although widely expressed in various brain regions, may has some regional and cellular specificity, and the outcomes of this study provide a new laboratory basis for revealing the possible involvement of POMGNT1 in normal physiological functions of the brain from a morphological perspective.

Neurological Consequences of Congenital Disorders of Glycosylation

The chapter is devoted to neurological aspects of congenital disorders of glycosylation (CDG). At the beginning, the various types of CDG with neurological presentation of symptoms are summarized. Then, the occurrence of various neurological constellation of abnormalities (for example: epilepsy, brain anomalies on neuroimaging, ataxia, stroke-like episodes, autistic features) in different CDG types are discussed followed by data on possible biomarkers and limited treatment options.

The many roles of dystroglycan in nervous system development and function: Dystroglycan and neural circuit development: Dystroglycan and neural circuit development

The glycoprotein dystroglycan was first identified in muscle, where it functions as part of the dystrophin glycoprotein complex to connect the extracellular matrix to the actin cytoskeleton. Mutations in genes involved in the glycosylation of dystroglycan cause a form of congenital muscular dystrophy termed dystroglycanopathy. In addition to its well-defined role in regulating muscle integrity, dystroglycan is essential for proper central and peripheral nervous system development. Patients with dystroglycanopathy can present with a wide range of neurological perturbations, but unraveling the complex role of Dag1 in the nervous system has proven to be a challenge. Over the past two decades, animal models of dystroglycanopathy have been an invaluable resource that has allowed researchers to elucidate dystroglycan's many roles in neural circuit development. In this review, we summarize the pathways involved in dystroglycan's glycosylation and its known interacting proteins, and discuss how it regulates neuronal migration, axon guidance, synapse formation, and its role in non-neuronal cells.

Malformation of the Cortical Development Associated with Severe Clusters of Epileptic Seizures

Three cases of the malformation of the cortical development are described: a mixed breed dog and a Border Collie pup with a focal and diffuse cortical dysplasia, respectively, and a kitten with lissencephaly. All cases presented with intractable epilepsy and were euthanized, due to the cluster of epileptic seizures. The gross examination at necropsy revealed the morphologic alteration of the telencephalic region in two cases. Histopathologically, a disorganization of the cortical lamination with the presence of megalic neurons, was found in the focal cortical dysplasia case. An altered organization of the white and gray matter, with a loss of the normal neuronal distribution and altered neurons, characterized the diffuse cortical dysplasia case. In the lissencephalic cat, there was no recognizable organization of the brain with areas of neuroglial tissue forming nodules in the leptomeningeal space. We strongly support the hypothesis that, as in humans, as well as in the veterinary patients, malformations of the cortical development could be the cause of refractory epilepsy.

Orchestrating human neocortex development across the scales; from micro to macro

How our brains have developed to perform the many complex functions that make us human has long remained a question of great interest. Over the last few decades, many scientists from a wide range of fields have tried to answer this question by aiming to uncover the mechanisms that regulate the development of the human neocortex. They have approached this on different scales, focusing microscopically on individual cells all the way up to macroscopically imaging entire brains within living patients. In this review we will summarise these key findings and how they fit together.

Congenital Malformations of Cerebellum

Advances in pre and postnatal neuroimaging techniques, and molecular genetics have increased our understanding of the congenital malformation of the brain. Correct diagnosis of these malformations in regards to embryology, and molecular neurogenetics is of paramount importance to understand the inheritance pattern and risk of recurrence. Lesions detected on prenatal imaging require confirmation either with postnatal ultrasound and/or with MR imaging. With the advent of the faster (rapid) MRI techniques, which can be conducted without sedation, MRI is commonly used in the evaluation of congenital malformation of the brain. Based on neuroimaging pattern, the congenital malformations of the posterior fossa are classified into 4 main categories: (a) predominantly cerebellar, (b) cerebellar and brainstem, (c) predominantly brainstem, and (d) predominantly midbrain malformations.

Teleost Fish and Organoids: Alternative Windows Into the Development of Healthy and Diseased Brains

The variety in the display of animals’ cognition, emotions, and behaviors, typical of humans, has its roots within the anterior-most part of the brain: the forebrain, giving rise to the neocortex in mammals. Our understanding of cellular and molecular events instructing the development of this domain and its multiple adaptations within the vertebrate lineage has progressed in the last decade. Expanding and detailing the available knowledge on regionalization, progenitors’ behavior and functional sophistication of the forebrain derivatives is also key to generating informative models to improve our characterization of heterogeneous and mechanistically unexplored cortical malformations. Classical and emerging mammalian models are irreplaceable to accurately elucidate mechanisms of stem cells expansion and impairments of cortex development. Nevertheless, alternative systems, allowing a considerable reduction of the burden associated with animal experimentation, are gaining popularity to dissect basic strategies of neural stem cells biology and morphogenesis in health and disease and to speed up preclinical drug testing. Teleost vertebrates such as zebrafish, showing conserved core programs of forebrain development, together with patients-derived in vitro 2D and 3D models, recapitulating more accurately human neurogenesis, are now accepted within translational workflows spanning from genetic analysis to functional investigation. Here, we review the current knowledge of common and divergent mechanisms shaping the forebrain in vertebrates, and causing cortical malformations in humans. We next address the utility, benefits and limitations of whole-brain/organism-based fish models or neuronal ensembles in vitro for translational research to unravel key genes and pathological mechanisms involved in neurodevelopmental diseases.

Seizures and EEG characteristics in a cohort of pediatric patients with dystroglycanopathies

PURPOSE

To delineate the seizure type, phenotype and V-EEG patterns of dystroglycanopathy (DGP) and correlate them with the neuroradiological and genetic results.

METHODS

Patients with seizures were screened from our dystroglycanopathy database from January 2010 to March 2021. Detailed clinical information, including seizure type, brain magnetic resonance imaging (MRI), EEG and genetic analysis, was collected.

RESULTS

Thirteen patients (15.1%, 13/86) had seizures. Most patients had a severe phenotype. The mean age at first seizure onset was 2 years and 8 months. The most common seizure type was generalized tonic-clonic seizure (GTCS), with 92.3% (12/13) induced by fever. Three patients were diagnosed with epilepsy. Most patients did not take any medicine. A few patients had irregular use of antiseizure medications (ASMs). Of the 13 patients, seven patients were diagnosed with MEB, four patients with POMGNT1 mutations, two with ISPD mutations, and one with POMT1 mutation. Three patients were diagnosed with FCMD with FKTN mutations. Two patients were diagnosed with CMD-MR, one patient with ISPD mutation, and one with POMT1 mutation. One patient was diagnosed with LGMD with FKRP mutation. Nine patients underwent EEG examination, and eight patients had abnormal EEG results, including abnormal background activities in three patients, abnormal background activities combined with paroxysmal discharges in three patients, pure paroxysmal discharges in one patient and positive phase sharp waves in the occipital region in one patient. For radiology, brain MRI was available for 12 patients. The brain MRI of nine patients showed type II lissencephaly. Two patients showed cerebellar hypoplasia and brainstem hypoplasia. One patient had a normal brain MRI result. Patients with type II lissencephaly usually had abnormal background activities and paroxysmal discharges.

CONCLUSION

The seizure phenotype of dystroglycanopathy (DGP) is characterized by GTCS, which was the most common seizure type, while focal seizures and epileptic spasms could also occur in DGP patients. Most seizures were induced by fever. Seizures were relatively more frequent in severe phenotypes of DGP, such as FCMD and MEB. Abnormal background activities were the most common EEG patterns, which were closely related to type II lissencephaly.

Congenital Brain Malformations: An Integrated Diagnostic Approach

Congenital brain malformations are abnormalities present at birth that can result from developmental disruptions at various embryonic or fetal stages. The clinical presentation is nonspecific and can include developmental delay, hypotonia, and/or epilepsy. An informed combination of imaging and genetic testing enables early and accurate diagnosis and management planning. In this article, we provide a streamlined approach to radiologic phenotyping and genetic evaluation of brain malformations. We will review the clinical workflow for brain imaging and genetic testing with up-to-date ontologies and literature references. The organization of this article introduces a streamlined approach for imaging-based etiologic classification into malformative, destructive, and migrational abnormalities. Specific radiologic ontologies are then discussed in detail, with correlation of key neuroimaging features to embryology and molecular pathogenesis.

Pediatric Brain Maturation and Migration Disorders

Neurodevelopmental disorders, including neuronal migration disorders, are best understood in the context of altered normal development. Neurons normally migrate from their site of origin to their (usually cortical) destination using a wide range of molecular and cellular signaling as a guide. In the case of abnormal migration neurons: (1) do not migrate and remain at their site of origin; (2) incompletely migrate and remain within the white matter; (3) migrate to the cortex but fail to organize correctly; or (4) over-migrate, beyond the cortex. In this review, we discuss normal brain development, along with the malformations that result from these different migration abnormalities.

Malformations of cerebral development and clues from the peripheral nervous system: A systematic literature review

Clinical manifestations of malformations of cortical development (MCD) are variable and can range from mild to severe intellectual disability, cerebral palsy and drug-resistant epilepsy. Besides common clinical features, non-specific or more subtle clinical symptoms may be present in association with different types of MCD. Especially in severely affected individuals, subtle but specific underlying clinical symptoms can be overlooked or overshadowed by the global clinical presentation. To facilitate the interpretation of genetic variants detailed clinical information is indispensable. Detailed (neurological) examination can be helpful in assisting with the diagnostic trajectory, both when referring for genetic work-up as well as when interpreting data from molecular genetic testing. This systematic literature review focusses on different clues derived from the neurological examination and potential further work-up triggered by these signs and symptoms in genetically defined MCDs. A concise overview of specific neurological findings and their associations with MCD subtype and genotype are presented, easily applicable in daily clinical practice. The following pathologies will be discussed: neuropathy, myopathy, muscular dystrophies and spastic paraplegia. In the discussion section, tips and pitfalls are illustrated to improve clinical outcome in the future.

Protein O-mannosylation across kingdoms and related diseases: From glycobiology to glycopathology

The post-translational glycosylation of proteins by O-linked α-mannose is conserved from bacteria to humans. Due to advances in high-throughput mass spectrometry-based approaches, a variety of glycoproteins are identified to be O-mannosylated. Various proteins with O-mannosylation are involved in biological processes, providing essential necessity for proper growth and development. In this review, we summarize the process and regulation of O-mannosylation. The multi-step O-mannosylation procedures are quite dynamic and complex, especially when considering the structural and functional inspection of the involved enzymes. The widely studied O-mannosylated proteins in human include α-Dystroglycan (α-DG), cadherins, protocadherins, and plexin, and their aberrant O-mannosylation are associated with many diseases. In addition, O-mannosylation also contributes to diverse functions in lower eukaryotes and prokaryotes. Finally, we present the relationship between O-mannosylation and gut microbiota (GM), and elucidate that O-mannosylation in microbiome is of great importance in the dynamic balance of GM. Our study provides an overview of the processes of O-mannosylation in mammalian cells and other organisms, and also associated regulated enzymes and biological functions, which could contribute to the understanding of newly discovered O-mannosylated glycoproteins.

Roots of the Malformations of Cortical Development in the Cell Biology of Neural Progenitor Cells

The cerebral cortex is a structure that underlies various brain functions, including cognition and language. Mammalian cerebral cortex starts developing during the embryonic period with the neural progenitor cells generating neurons. Newborn neurons migrate along progenitors’ radial processes from the site of their origin in the germinal zones to the cortical plate, where they mature and integrate in the forming circuitry. Cell biological features of neural progenitors, such as the location and timing of their mitoses, together with their characteristic morphologies, can directly or indirectly regulate the abundance and the identity of their neuronal progeny. Alterations in the complex and delicate process of cerebral cortex development can lead to malformations of cortical development (MCDs). They include various structural abnormalities that affect the size, thickness and/or folding pattern of the developing cortex. Their clinical manifestations can entail a neurodevelopmental disorder, such as epilepsy, developmental delay, intellectual disability, or autism spectrum disorder. The recent advancements of molecular and neuroimaging techniques, along with the development of appropriate in vitro and in vivo model systems, have enabled the assessment of the genetic and environmental causes of MCDs. Here we broadly review the cell biological characteristics of neural progenitor cells and focus on those features whose perturbations have been linked to MCDs.

The Role of the Extracellular Matrix in Neural Progenitor Cell Proliferation and Cortical Folding During Human Neocortex Development

Extracellular matrix (ECM) has long been known to regulate many aspects of neural development in many different species. However, the role of the ECM in the development of the human neocortex is not yet fully understood. In this review we discuss the role of the ECM in human neocortex development and the different model systems that can be used to investigate this. In particular, we will focus on how the ECM regulates human neural stem and progenitor cell proliferation and differentiation, how the ECM regulates the architecture of the developing human neocortex and the effect of mutations in ECM and ECM-associated genes in neurodevelopmental disorders.

Intellectual disability in paediatric patients with genetic muscle diseases

The differential diagnosis of genetic muscle disease has become increasingly difficult due to the rapid progress in genetic medicine in recent years. Where classifications based on the clinical picture were attributed to one gene only a few years ago, today we know that a variety of clinical presentations can result from the same mutation and, conversely, various genes are associated with a similar phenotype. A significant consideration in assessing a patient with muscle weakness is the presence or absence of intellectual disability, thus narrowing the differential diagnostic approach in any child with an as yet undiagnosed muscle disease. Intellectual disability in neuromuscular diseases is often associated with behavioural disorders and may be correlated with abnormal brain imaging. Conversely, brain involvement can sometimes be seen without intellectual disability, but may be associated with an epilepsy risk and is helpful for the differential diagnosis. This review focuses on the three most common causes of paediatric muscle diseases with intellectual disability, dystrophinopathies, myotonic dystrophy type 1 and dystroglycanopathies. It also summarises differential diagnostic considerations when assessing a child with a genetic muscle disease and intellectual disability. The recent scientific literature on this topic is reviewed, the frequency of intellectual disability assessed, and specific clinical features are described. Where available, data on disease onset, progression and serum creatine kinase levels are presented and the pattern of muscle involvement described in an algorithm. Central nervous involvement and brain imaging analysis was reviewed and included.

Clinical and neuroimaging findings in patients with lissencephaly/subcortical band heterotopia spectrum: a magnetic resonance conventional and diffusion tensor study

PURPOSE

To clarify brain abnormalities on magnetic resonance imaging (MRI) and its clinical implications in lissencephaly/subcortical band heterotopia (LIS/SBH) spectrum patients.

METHODS

The clinical severity and classification according to Di Donato were retrospectively reviewed in 23 LIS/SBH spectrum patients. The morphological and signal abnormalities of the brainstem, corpus callosum, and basal ganglia were also assessed. The brainstem distribution pattern of the corticospinal tract (CST) was analyzed by diffusion tensor imaging (DTI) and categorized into two types: normal pattern, in which the CST and medial lemniscus (ML) are separated by the dorsal portion of the transverse pontine fiber, and the abnormal pattern, in which the CST and ML are juxtaposed on the dorsal portion of a single transverse pontine fiber. Correlations between MR grading score and potential additional malformative findings of the brain and clinical symptoms were investigated.

RESULTS

All patients with grade 3 (n = 5) showed brainstem deformities, signal abnormalities of pontine surface and had a tendency of basal ganglia deformity and callosal hypoplasia whereas those abnormalities were rarely seen in patients with grade 1 and 2 (n = 18). For DTI analysis, the patients with grade 3 LIS/SBH had typically abnormal CST, whereas the patients with grade 1 and 2 LIS/SBH had normal CST. The classification was well correlated with CST and brainstem abnormalities and clinical severity.

CONCLUSION

MR assessment including DTI analysis may be useful in assessing the clinical severity in LIS/BH spectrum and may provide insight into its developmental pathology.

TRAPPC11-related muscular dystrophy with hypoglycosylation of alpha-dystroglycan in skeletal muscle and brain

AIMS

TRAPPC11, a subunit of the transport protein particle (TRAPP) complex, is important for complex integrity and anterograde membrane transport from the endoplasmic reticulum (ER) to the ER-Golgi intermediate compartment. Several individuals with TRAPPC11 mutations have been reported with muscle weakness and other features including brain, liver, skeletal and eye involvement. A detailed analysis of brain and muscle pathology will further our understanding of the presentation and aetiology of TRAPPC11 disease.

METHODS

We describe five cases of early-onset TRAPPC11-related muscular dystrophy with a systematic review of muscle pathology in all five individuals, post-mortem brain pathology findings in one and membrane trafficking assays in another.

RESULTS

All affected individuals presented in infancy with muscle weakness, motor delay and elevated serum creatine kinase (CK). Additional features included cataracts, liver disease, intellectual disability, cardiomyopathy, movement disorder and structural brain abnormalities. Muscle pathology in all five revealed dystrophic changes, universal hypoglycosylation of alpha-dystroglycan and variably reduced dystrophin-associated complex proteins. Membrane trafficking assays showed defective Golgi trafficking in one individual. Neuropathological examination of one individual revealed cerebellar atrophy, granule cell hypoplasia, Purkinje cell (PC) loss, degeneration and dendrite dystrophy, reduced alpha-dystroglycan (IIH6) expression in PC and dentate neurones and absence of neuronal migration defects.

CONCLUSIONS

This report suggests that recessive mutations in TRAPPC11 are linked to muscular dystrophies with hypoglycosylation of alpha-dystroglycan. The structural cerebellar involvement that we document for the first time resembles the neuropathology reported in N-linked congenital disorders of glycosylation (CDG) such as PMM2-CDG, suggesting defects in multiple glycosylation pathways in this condition.

Normal human brainstem development in vivo: a quantitative fetal MRI study

OBJECTIVES

To characterize spatiotemporal growth differences of prenatal brainstem substructures and cerebellum, using linear biometry and planimetry on fetal magnetic resonance imaging (MRI).

METHODS

In this retrospective study, we included fetuses with normal brain and a precise midsagittal T2-weighted brain MRI sequence obtained between May 2003 and April 2019. The cross-sectional area, rostrocaudal diameter and anteroposterior diameter of the midbrain, pons (basis pontis and pontine tegmentum), medulla oblongata and cerebellar vermis, as well as the transverse cerebellar diameter, were quantified by a single observer. The diameters were also assessed by a second observer to test inter-rater variability.

RESULTS

We included 161 fetuses with normal brain and a precise midsagittal MRI sequence, examined at a mean ± SD gestational age of 25.7 ± 5.4 (range, 14 + 0 to 39 + 2) weeks. All substructures of the fetal brainstem and the cerebellum could be measured consistently (mean ± SD interobserver intraclass correlation coefficient, 0.933 ± 0.065). We provide reference data for diameters and areas of the brainstem and cerebellum in the second and third trimesters. There was a significant quadratic relationship between vermian area and gestational age, and all other measured parameters showed a significant linear growth pattern within the observed period (P < 0.001). A significant change in the relative proportions of the brainstem substructures occurred between the beginning of the second trimester and the end of the third trimester, with an increase in the area of the pons (P < 0.001) and a decrease in that of the midbrain (P < 0.001), relative to the total brainstem area.

CONCLUSIONS

The substructures of the fetal brainstem follow a distinct spatiotemporal growth pattern, characterized by a relative increase in the pons and decrease in the midbrain, between 15 and 40 weeks of gestation. Caution is needed when interpreting fetal brainstem appearance during the early second trimester, as the brainstem proportions differ significantly from the adult morphology. The reference data provided herein should help to increase diagnostic accuracy in detecting disorders of defective hindbrain segmentation. © 2020 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Fetal MRI assessment of posterior fossa anomalies: A review

Prenatal ultrasound (US) is the first prenatal imaging tool for screening and evaluation of posterior fossa malformations since it is noninvasive, widely available, and safe for both mother and child. Fetal MRI is a widely used secondary technique to confirm, correct, or complement questionable US findings and plays an essential role in evaluating fetuses with suspected US findings and /or positive family history. The main sequences of fetal MRI consist of T2-weighted (T2w) ultrafast, single-shot sequences. Axial, coronal, and sagittal images are typically acquired allowing for a detailed evaluation of the posterior fossa contents. Also, various complimentary sequences, such as T1w, T2*w gradient sequences, or advanced techniques, including diffusion-weighted imaging, diffusion tensor imaging, and magnetic resonance spectroscopy, may provide additional information based on the studied malformation. Inclusion of these techniques should be done with careful risk-benefit analysis. The use of fetal MRI also aims to evaluate for associated anomalies. In addition, prenatal diagnosis of posterior fossa malformations is still a challenge but advances in knowledge in human developmental anatomy, genetic, and imaging recognition patterns have enabled us to shed some light on prognostic information that will help with the counseling of families. Finally, high-resolution late third trimester fetal MRI offers a safe alternative to early postnatal MR imaging, basically taking advantage of the uterine environment as a kind of "maternal incubator." Our goal is to discuss the spectrum of prenatal posterior fossa pathologies that can be studied by fetal MRI and their key neuroimaging features.

The Fetus with Ganglionic Eminence Abnormality: Head Size and Extracranial Sonographic Findings Predict Genetic Diagnoses and Postnatal Outcomes

BACKGROUND AND PURPOSE

Ganglionic eminence abnormalities on fetal MR imaging are associated with cerebral malformations. Their presumed genetic basis and associated postnatal outcomes remain largely unknown. We aimed to elucidate these through a multicenter study.

MATERIALS AND METHODS

Between January 2010 and June 2020, seven hospitals in 2 countries performing fetal MR imaging examinations identified fetal MR imaging studies demonstrating ganglionic eminence enlargement, cavitation, or both. Cases with no genetic diagnosis, no whole exome sequencing, or no outcome of a liveborn child were excluded. Head size was classified as large (fronto-occipital diameter > 95th centile), small (fronto-occipital diameter <5th centile), or normal.

RESULTS

Twenty-two fetuses with ganglionic eminence abnormalities were identified. Of 8 with large heads, 2 were diagnosed with MTOR mutations; 1 with PIK3CA mutation-producing megalencephaly, polymicrogyria, polydactyly, hydrocephalus (MPPH) syndrome; 3 with TSC mutations; 1 with megalencephaly capillary malformation syndrome; and 1 with hemimegalencephaly. Cardiac rhabdomyoma was present prenatally in all cases of TSC; mutation postaxial polydactyly accompanied megalencephaly capillary malformation and MPPH. Of 12 fetuses with small heads, 7 had TUBA1A mutations, 1 had a TUBB3 mutation, 2 had cobblestone lissencephaly postnatally with no genetic diagnosis, 1 had a PDHA1 mutation, and 1 had a fetal akinesia dyskinesia sequence with no pathogenic mutation on trio whole exome sequencing. One of the fetuses with a normal head size had an OPHN1 mutation with postnatal febrile seizures, and the other had peri-Sylvian polymicrogyria, seizures, and severe developmental delay but no explanatory mutation on whole exome sequencing.

CONCLUSIONS

Fetal head size and extracranial prenatal sonographic findings can refine the phenotype and facilitate genetic diagnosis when ganglionic eminence abnormality is diagnosed with MR imaging.

Intravital Imaging of Neocortical Heterotopia Reveals Aberrant Axonal Pathfinding and Myelination around Ectopic Neurons

Neocortical heterotopia consist of ectopic neuronal clusters that are frequently found in individuals with cognitive disability and epilepsy. However, their pathogenesis remains poorly understood due in part to a lack of tractable animal models. We have developed an inducible model of focal cortical heterotopia that enables their precise spatiotemporal control and high-resolution optical imaging in live mice. Here, we report that heterotopia are associated with striking patterns of circumferentially projecting axons and increased myelination around neuronal clusters. Despite their aberrant axonal patterns, in vivo calcium imaging revealed that heterotopic neurons remain functionally connected to other brain regions, highlighting their potential to influence global neural networks. These aberrant patterns only form when heterotopia are induced during a critical embryonic temporal window, but not in early postnatal development. Our model provides a new way to investigate heterotopia formation in vivo and reveals features suggesting the existence of developmentally modulated, neuron-derived axon guidance and myelination factors.

Cobblestone Malformation in LAMA2 Congenital Muscular Dystrophy (MDC1A)

Congenital muscular dystrophy type 1A (MDC1A) is caused by recessive variants in laminin α2 (LAMA2). Patients have been found to have white matter signal abnormalities on magnetic resonance imaging (MRI) but rarely structural brain abnormalities. We describe the autopsy neuropathology in a 17-year-old with white matter signal abnormalities on brain MRI. Dystrophic pathology was observed in skeletal muscle, and the sural nerve manifested a mild degree of segmental demyelination and remyelination. A diffuse, bilateral cobblestone appearance, and numerous points of fusion between adjacent gyri were apparent on gross examination of the cerebrum. Brain histopathology included focal disruptions of the glia limitans associated with abnormal cerebral cortical lamination or arrested cerebellar granule cell migration. Subcortical nodular heterotopia was present within the cerebellar hemispheres. Sampling of the centrum semiovale revealed no light microscopic evidence of leukoencephalopathy. Three additional MDC1A patients were diagnosed with cobblestone malformation on brain MRI. Unlike the autopsied patient whose brain had a symmetric distribution of cobblestone pathology, the latter patients had asymmetric involvement, most severe in the occipital lobes. These cases demonstrate that cobblestone malformation may be an important manifestation of the brain pathology in MDC1A and can be present even when patients have a structurally normal brain MRI.

Neuropathology of genetically defined malformations of cortical development-A systematic literature review

AIMS

Malformations of cortical development (MCD) include a heterogeneous spectrum of clinical, imaging, molecular and histopathological entities. While the understanding of genetic causes of MCD has improved with the availability of next-generation sequencing modalities, genotype-histopathological correlations remain limited. This is the first systematic review of molecular and neuropathological findings in patients with MCD to provide a comprehensive overview of the literature.

METHODS

A systematic review was performed between November 2019 and February 2020. A MEDLINE search was conducted for 132 genes previously linked to MCD in order to identify studies reporting macroscopic and/or microscopic findings in patients with a confirmed genetic cause.

RESULTS

Eighty-one studies were included in this review reporting neuropathological features associated with pathogenic variants in 46 genes (46/132 genes, 34.8%). Four groups emerged, consisting of (1) 13 genes with well-defined histological-genotype correlations, (2) 27 genes for which neuropathological reports were limited, (3) 5 genes with conflicting neuropathological features, and (4) 87 genes for which no histological data were available. Lissencephaly and polymicrogyria were reported most frequently. Associated brain malformations were variably present, with abnormalities of the corpus callosum as most common associated feature.

CONCLUSIONS

Neuropathological data in patients with MCD with a defined genetic cause are available only for a small number of genes. As each genetic cause might lead to unique histopathological features of MCD, standardised thorough neuropathological assessment and reporting should be encouraged. Histological features can help improve the understanding of the pathogenesis of MCD and generate hypotheses with impact on further research directions.

Diagnostic Approach to Cerebellar Hypoplasia

Cerebellar hypoplasia (CH) refers to a cerebellum of reduced volume with preserved shape. CH is associated with a broad heterogeneity in neuroradiologic features, etiologies, clinical characteristics, and neurodevelopmental outcomes, challenging physicians evaluating children with CH. Traditionally, neuroimaging has been a key tool to categorize CH based on the pattern of cerebellar involvement (e.g., hypoplasia of cerebellar vermis only vs. hypoplasia of both the vermis and cerebellar hemispheres) and the presence of associated brainstem and cerebral anomalies. With the advances in genetic technologies of the recent decade, many novel CH genes have been identified, and consequently, a constant updating of the literature and revision of the classification of cerebellar malformations are needed. Here, we review the current literature on CH. We propose a systematic approach to recognize specific neuroimaging patterns associated with CH, based on whether the CH is isolated or associated with posterior cerebrospinal fluid anomalies, specific brainstem or cerebellar malformations, brainstem hypoplasia with or without cortical migration anomalies, or dysplasia. The CH radiologic pattern and clinical assessment will allow the clinician to guide his investigations and genetic testing, give a more precise diagnosis, screen for associated comorbidities, and improve prognostication of associated neurodevelopmental outcomes.

Congenital Disorders of Glycosylation from a Neurological Perspective

Most plasma proteins, cell membrane proteins and other proteins are glycoproteins with sugar chains attached to the polypeptide-glycans. Glycosylation is the main element of the post-translational transformation of most human proteins. Since glycosylation processes are necessary for many different biological processes, patients present a diverse spectrum of phenotypes and severity of symptoms. The most frequently observed neurological symptoms in congenital disorders of glycosylation (CDG) are: epilepsy, intellectual disability, myopathies, neuropathies and stroke-like episodes. Epilepsy is seen in many CDG subtypes and particularly present in the case of mutations in the following genes: ALG13, DOLK, DPAGT1, SLC35A2, ST3GAL3, PIGA, PIGW, ST3GAL5. On brain neuroimaging, atrophic changes of the cerebellum and cerebrum are frequently seen. Brain malformations particularly in the group of dystroglycanopathies are reported. Despite the growing number of CDG patients in the world and often neurological symptoms dominating in the clinical picture, the number of performed screening tests eg transferrin isoforms is systematically decreasing as broadened genetic testing is recently more favored. The aim of the review is the summary of selected neurological symptoms in CDG described in the literature in one paper. It is especially important for pediatric neurologists not experienced in the field of metabolic medicine. It may help to facilitate the diagnosis of this expanding group of disorders. Biochemically, this paper focuses on protein glycosylation abnormalities.

Fetal magnetic resonance imaging: supratentorial brain malformations

Fetal MRI is the modality of choice to study supratentorial brain malformations. To accurately interpret the MRI, the radiologist needs to understand the normal sequence of events that occurs during prenatal brain development; this includes familiarity with the processes of hemispheric cleavage, formation of interhemispheric commissures, neuro-glial proliferation and migration, and cortical folding. Disruption of these processes results in malformations observed on fetal MRI including holoprosencephaly, callosal agenesis, heterotopic gray matter, lissencephaly and other malformations of cortical development (focal cortical dysplasia, polymicrogyria). The radiologist should also be familiar with findings that have high association with specific conditions affecting the central nervous system or other organ systems. This review summarizes and illustrates common patterns of supratentorial brain malformations and emphasizes aspects that are important to patient care.

Imaging phenotype correlation with molecular and molecular pathway defects in malformations of cortical development

The increase in understanding of molecular biology and recent advances in genetic testing have caused rapid growth in knowledge of genetic causes of malformations of cortical development. Imaging diagnosis of malformations of cortical development can be made prenatally in a large subset of fetuses based on the presence of specific deviations from the normal pattern of development, characteristic imaging features, and associated non-central-nervous-system (CNS) abnormalities. In this review the authors discuss the role of four key cell molecules/molecular pathways in corticogenesis that are frequently implicated in complex prenatally diagnosed malformations of cortical development. The authors also list the currently described genes causing defects in these molecules/molecular pathways when mutated, and the constellation of imaging findings resultant of such defects.

Prenatal presentation of Walker–Warburg syndrome with a POMT2 mutation: an extended fetal phenotype

Background

Walker–Warburg syndrome (WWS) is a rare, lethal, genetically, and clinically heterogeneous congenital muscular dystrophy resulting from defective glycosylation of α-dystroglycan (α-DG) and is associated with both cranial and ocular malformations. Prenatal detection of posterior fossa anomalies in association with hydrocephalus are nonspecific, however, an additional finding of eye anomalies are typical for WWS. The purpose of this report is to elucidate the pattern of associated malformations in a fetus with WWS born to 3rd degree consanguineously married couple. Additionally, the fetal ultrasonography revealed congenital heart disease, clenched hands, and talipes equinovarus; these findings have not been previously reported and represent an expansion of prenatal spectrum associated with WWS.

Case presentation

We report on a specific sonographic pattern of congenital anomalies including hydrocephalus, agenesis of corpus callosum, and Dandy–Walker malformation. Ocular abnormalities include microphthalmia, cataract, and an echoic structure suggestive of persistent primary vitreous. Other features include congenital heart disease, unilateral multicystic kidney, and previously unreported findings of bilateral clenched hands and talipes equinovarus. The molecular analysis detected a homozygous splicing mutation, c.924-2A>C, in the POMT2 gene; this variant segregated with the phenotype.

Conclusion

WWS syndrome has characteristic prenatal ultrasound findings which can improve the prenatal identification of this condition and help in guiding the molecular diagnosis and counseling. The detection of bilateral clenched hands and talipes equinovarus is a novel finding that further expands the phenotypic spectrum of WWS.

Insight into developmental mechanisms of global and focal migration disorders of cortical development

Cortical development involves neurogenesis followed by migration, maturation, and myelination of immature neurons. Disruptions in these processes can cause malformations of cortical development (MCD). Radial glia (RG) are the stem cells of the brain, both generating neurons and providing the scaffold upon which immature neurons radially migrate. Germline mutations in genes required for cell migration, or cell-cell contact, often lead to global MCDs. Somatic mutations in RG in genes involved in homeostatic function, like mTOR signaling, often lead to focal MCDs. Two different mutations occurring in the same patient can combine in ways we are just beginning to understand. Our growing knowledge about MCD suggests mTOR inhibitors may have expanded utility in treatment-resistant epilepsy, while imaging techniques can better delineate the type and extent of these lesions.

Definitions and classification of malformations of cortical development: practical guidelines

Malformations of cortical development are a group of rare disorders commonly manifesting with developmental delay, cerebral palsy or seizures. The neurological outcome is extremely variable depending on the type, extent and severity of the malformation and the involved genetic pathways of brain development. Neuroimaging plays an essential role in the diagnosis of these malformations, but several issues regarding malformations of cortical development definitions and classification remain unclear. The purpose of this consensus statement is to provide standardized malformations of cortical development terminology and classification for neuroradiological pattern interpretation. A committee of international experts in paediatric neuroradiology prepared systematic literature reviews and formulated neuroimaging recommendations in collaboration with geneticists, paediatric neurologists and pathologists during consensus meetings in the context of the European Network Neuro-MIG initiative on Brain Malformations (https://www.neuro-mig.org/). Malformations of cortical development neuroimaging features and practical recommendations are provided to aid both expert and non-expert radiologists and neurologists who may encounter patients with malformations of cortical development in their practice, with the aim of improving malformations of cortical development diagnosis and imaging interpretation worldwide.

Further evidence for POMK as candidate gene for WWS with meningoencephalocele

Background

Walker-Warburg syndrome (WWS) is a rare form of alpha-dystroglycanopathy characterized by muscular dystrophy and severe malformations of the CNS and eyes. Bi-allelic pathogenic variants in POMK are the cause of a broad spectrum of alpha-dystroglycanopathies. POMK encodes protein-O-mannose kinase, which is required for proper glycosylation and function of the dystroglycan complex and is crucial for extracellular matrix composition.

Results

Here, we report on male monozygotic twins with severe CNS malformations (hydrocephalus, cortical malformation, hypoplastic cerebellum, and most prominently occipital meningocele), eye malformations and highly elevated creatine kinase, indicating the clinical diagnosis of a congenital muscular dystrophy (alpha-dystroglycanopathy). Both twins were found to harbor a homozygous nonsense mutation c.640C>T, p.214* in POMK, confirming the clinical diagnosis and supporting the concept that POMK mutations can be causative of WWS.

Conclusion

Our combined data suggest a more important role for POMK in the pathogenesis of meningoencephalocele. Only eight different pathogenic POMK variants have been published so far, detected in eight families; only five showed the severe WWS phenotype, suggesting that POMK-associated WWS is an extremely rare disease. We expand the phenotypic and mutational spectrum of POMK-associated WWS and provide evidence of the broad phenotypic variability of POMK-associated disease.

International consensus recommendations on the diagnostic work-up for malformations of cortical development

Malformations of cortical development (MCDs) are neurodevelopmental disorders that result from abnormal development of the cerebral cortex in utero. MCDs place a substantial burden on affected individuals, their families and societies worldwide, as these individuals can experience lifelong drug-resistant epilepsy, cerebral palsy, feeding difficulties, intellectual disability and other neurological and behavioural anomalies. The diagnostic pathway for MCDs is complex owing to wide variations in presentation and aetiology, thereby hampering timely and adequate management. In this article, the international MCD network Neuro-MIG provides consensus recommendations to aid both expert and non-expert clinicians in the diagnostic work-up of MCDs with the aim of improving patient management worldwide. We reviewed the literature on clinical presentation, aetiology and diagnostic approaches for the main MCD subtypes and collected data on current practices and recommendations from clinicians and diagnostic laboratories within Neuro-MIG. We reached consensus by 42 professionals from 20 countries, using expert discussions and a Delphi consensus process. We present a diagnostic workflow that can be applied to any individual with MCD and a comprehensive list of MCD-related genes with their associated phenotypes. The workflow is designed to maximize the diagnostic yield and increase the number of patients receiving personalized care and counselling on prognosis and recurrence risk.

Dystroglycan Mediates Clustering of Essential GABAergic Components in Cerebellar Purkinje Cells

Muscle dystrophin–glycoprotein complex (DGC) links the intracellular cytoskeleton to the extracellular matrix. In neurons, dystroglycan and dystrophin, two major components of the DGC, localize in a subset of GABAergic synapses, where their function is unclear. Here we used mouse models to analyze the specific role of the DGC in the organization and function of inhibitory synapses. Loss of full-length dystrophin in mdx mice resulted in a selective depletion of the transmembrane β-dystroglycan isoform from inhibitory post-synaptic sites in cerebellar Purkinje cells. Remarkably, there were no differences in the synaptic distribution of the extracellular α-dystroglycan subunit, of GABA_A receptors and neuroligin 2. In contrast, conditional deletion of the dystroglycan gene from Purkinje cells caused a disruption of the DGC and severely impaired post-synaptic clustering of neuroligin 2, GABA_A receptors and scaffolding proteins. Accordingly, whole-cell patch-clamp analysis revealed a significant reduction in the frequency and amplitude of spontaneous IPSCs recorded from Purkinje cells. In the long-term, deletion of dystroglycan resulted in a significant decrease of GABAergic innervation of Purkinje cells and caused an impairment of motor learning functions. These results show that dystroglycan is an essential synaptic organizer at GABAergic synapses in Purkinje cells.