Definitions and classification of malformations of cortical development: practical guidelines

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.

Bisphenol A (BPA) and neurological disorders: An overview

The human body is commonly exposed to bisphenol A (BPA), which is widely used in consumer and industrial products. BPA is an endocrine-disrupting chemical that has adverse effects on human health. In particular, many studies have shown that BPA can cause various neurological disorders by affecting brain development and neural function during prenatal, infancy, childhood, and adulthood exposure. In this review, we discussed the correlation between BPA and neurological disorders based on molecular cell biology, neurophysiology, and behavioral studies of the effects of BPA on brain development and function. Recent studies, both animal and epidemiological, strongly indicate that BPA significantly impacts brain development and function. It hinders neural processes, such as proliferation, migration, and differentiation during development, affecting synaptic formation and activity. As a result, BPA is implicated in neurodevelopmental and neuropsychiatric disorders like autism spectrum disorder (ASD), attention-deficit hyperactivity disorder (ADHD), and schizophrenia.

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.

SEEG-RFTC in patients with refractory focal epilepsy: real-world outcomes from 121 cases

OBJECTIVE

Radiofrequency thermocoagulation (RFTC) has emerged as an effective and safe treatment method for patients with refractory focal epilepsy, when stereo-electroencephalography (SEEG) is implanted. Although real-world research results are still limited, a considerable number of patients have shown favorable outcomes with this less invasive method. This study aims to describe the outcomes and predictive factors of SEEG-RFTC in real-world research.

METHODS

A retrospective observational study was conducted on patients in the authors' epilepsy center. In total, 121 patients who underwent RFTC were included in the study. Post-RFTC outcomes were evaluated using the seizure-free rate and response rate (seizure frequency reduction more than 50%). Predictive factors influencing post-RFTC outcome were considered by comparing different variables.

RESULTS

The mean follow-up period was 18.3 months. Eighty-two patients (67.8%) were responders and 54 (44.6%) were seizure free. In 36 patients with malformation of cortical development, the seizure-free rate and the response rate were 69.44% and 83.33%, respectively. In 20 patients with hippocampal sclerosis, 19 patients were responders and 14 (70%) patients were seizure free at the last follow-up. The MRI feature and etiology of epilepsy are correlated with the outcome. MR-positive is a predictive factor for seizure freedom (p < 0.01) and responders (p < 0.01). Other factors have no predictive value for post-RFTC outcome.

INTERPRETATION

SEEG-RFTC is a safe procedure and yields favorable outcomes in numerous cases of focal DRE. The MRI feature and etiology of epilepsy are correlated with the seizure-free rate and response rate. And MRI positivity is the predictor for good RFTC outcome.

Clinical features and genotype-phenotype correlations in epilepsy patients with de novo DYNC1H1 variants

OBJECTIVE

DYNC1H1 variants are involved on a disease spectrum from neuromuscular disorders to neurodevelopmental disorders. DYNC1H1-related epilepsy has been reported in small cohorts. We dissect the electroclinical features of 34 patients harboring de novo DYNC1H1 pathogenic variants, identify subphenotypes on the DYNC1H1-related epilepsy spectrum, and compare the genotype-phenotype correlations observed in our cohort with the literature.

METHODS

Patients harboring de novo DYNC1H1 pathogenic variants were recruited through international collaborations. Clinical data were retrospectively collected. Latent class analysis was performed to identify subphenotypes. Multivariable binary logistic regression analysis was applied to investigate the association with DYNC1H1 protein domains.

RESULTS

DYNC1H1-related epilepsy presented with infantile epileptic spasms syndrome (IESS) in 17 subjects (50%), and in 25% of these individuals the epileptic phenotype evolved into Lennox-Gastaut syndrome (LGS). In 12 patients (35%), focal onset epilepsy was defined. In two patients, the epileptic phenotype consisted of generalized myoclonic epilepsy, with a progressive phenotype in one individual harboring a frameshift variant. In approximately 60% of our cohort, seizures were drug-resistant. Malformations of cortical development were noticed in 79% of our patients, mostly on the lissencephaly-pachygyria spectrum, particularly with posterior predominance in a half of them. Midline and infratentorial abnormalities were additionally reported in 45% and 27% of subjects. We have identified three main classes of subphenotypes on the DYNC1H1-related epilepsy spectrum.

SIGNIFICANCE

We propose a classification in which pathogenic de novo DYNC1H1 variants feature drug-resistant IESS in half of cases with potential evolution to LGS (Class 1), developmental and epileptic encephalopathy other than IESS and LGS (Class 2), or less severe focal or genetic generalized epilepsy including a progressive phenotype (Class 3). We observed an association between stalk domain variants and Class 1 phenotypes. The variants p.Arg309His and p.Arg1962His were common and associated with Class 1 subphenotype in our cohort. These findings may aid genetic counseling of patients with DYNC1H1-related epilepsy.

Brain and spine malformations and neurodevelopmental disorders in a cohort of children with CAKUT

BACKGROUND

Congenital anomalies of the kidney and urinary tract (CAKUT) represent 20-30% of all birth defects and are often associated with extra-renal malformations. We investigated the frequency of brain/spine malformations and neurological features in children with CAKUT.

METHODS

We reviewed the clinico-radiological and genetic data of 199 out of 1,165 children with CAKUT evaluated from 2006 to 2023 (99 males, mean age at MRI 6.4 years) who underwent brain and/or spine MRI. Patients were grouped according to the type of CAKUT (CAKUT-K involving the kidney and CAKUT-H involving the inferior urinary tract). Group comparisons were performed using χ2 and Fisher exact tests.

RESULTS

Brain/spine malformations were observed in 101/199 subjects (50.7%), 8.6% (101/1165) of our CAKUT population, including midbrain-hindbrain anomalies (40/158, 25.3%), commissural malformations (36/158, 22.7%), malformation of cortical development (23/158, 14.5%), Chiari I anomaly (12/199, 6%), cranio-cervical junction malformations (12/199, 6%), vertebral defects (46/94, 48.9%), caudal regression syndrome (29/94, 30.8%), and other spinal dysraphisms (13/94, 13.8%). Brain/spine malformations were more frequent in the CAKUT-K group (62.4%, p < 0.001). Sixty-two subjects (62/199, 31.2%) had developmental delay/intellectual disability. Neurological examination was abnormal in 40/199 (20.1%). Seizures and/or electroencephalographic anomalies were reported in 28/199 (14%) and behavior problems in 19/199 subjects (9%). Developmental delay/intellectual disability was more frequent in kidney dysplasia (65.2%) and agenesis (40.7%) (p = 0.001).

CONCLUSIONS

We report a relative high frequency of brain/spine malformations and neurodevelopmental disorders in children with CAKUT who underwent MRI examinations in a tertiary referral center, widening the spectrum of anomalies associated with this condition.

Disproportion of Corpus Callosum in Fetuses With Malformations of Cortical Development

OBJECTIVE

To evaluate corpus callosum (CC) size in fetuses with malformations of cortical development (MCD) and to explore the diagnostic value of three CC length (CCL) ratios in identifying cortical abnormalities.

METHODS

This is a single-center retrospective study in singleton fetuses at 20-37 weeks of gestation between April 2017 and August 2022. The midsagittal plane of the fetal brain was obtained and evaluated for the following variables: length, height, area of the corpus callosum, and relevant markers, including the ratios of corpus callosum length to internal cranial occipitofrontal dimension (CCL/ICOFD), corpus callosum length to femur length (CCL/FL), and corpus callosum length to cerebellar vermian diameter (CCL/VD). Intra-class correlation coefficient (ICC) was used to evaluate measurement consistency. The accuracy of biometric measurements in prediction of MCD was assessed using the area under the receiver-operating-characteristics curves (AUC).

RESULTS

Fetuses with MCD had a significantly decreased CCL, height (genu and splenium), and area as compared with those of normal fetuses (P < .05), but there was no significant difference in body height (P = .326). The CCL/ICOFD, CCL/FL, and CCL/VD ratios were significantly decreased in fetuses with MCD when compared with controls (P < .05). The CCL/ICOFD ratio offered the highest predictive accuracy for MCD, yielding an AUC of 0.856 (95% CI: 0.774-0.938, P < .001), followed by CCL/FL ratio (AUC, 0.780 (95% CI: 0.657-0.904), P < .001), CCL/VD ratio (AUC, 0.677 (95% CI: 0.559-0.795), P < .01).

CONCLUSION

The corpus callosum biometric parameters in fetuses with MCD are reduced. The CCL/ICOFD ratio derived from sonographic measurements is considered a promising tool for the prenatal detection of cortical malformations. External validation of these findings and prospective studies are warranted.

Clinical features of unilateral multilobar and hemispheric polymicrogyria (PMG)-related epilepsy and seizure outcome with different treatment options

OBJECTIVE

To provide evidence for choosing surgical or nonsurgical treatment for epilepsy in patients with unilateral multilobar and hemispheric polymicrogyria (PMG).

METHODS

We searched published studies until September 2022 related to unilateral multilobar and hemispheric PMG and included patients who were followed up at the Pediatric Epilepsy Centre of Peking University First Hospital in the past 10 years. We summarized the clinical characteristics and compared the long-term outcomes after surgical or nonsurgical (anti-seizure medications, ASMs) treatment.

RESULTS

A total of 70 patients (49 surgical, 21 non-surgical) with unilateral multilobar and hemispheric PMG were included. The median age at epilepsy onset was 2.5 years (1.0-4.1). The most common seizure types were focal and atypical absence seizures. In the whole cohort, 87.3% had hemiparesis and 67.1% had electrical status epilepticus during slow sleep (ESES). There were significant differences in age at epilepsy onset, extent of lesion, and EEG interictal discharges between the two groups. At the last follow-up (median 14.1 years), the rates of seizure-freedom (81.6% vs. 57.1%, p = 0.032) and ASM discontinuation (44.4% vs. 6.3%, p = 0.006) were higher in the surgical group than in the nonsurgical group. Patients in the surgical group had a higher rate of seizure-freedom with complete resection/disconnection than with subtotal resection (87.5% vs. 55.6%, p = 0.078), but with no statistically significant difference. In the nonsurgical group, more extensive lesions were associated with worse seizure outcomes. Cognition improved postoperatively in 90% of surgical patients.

SIGNIFICANCE

In patients with unilateral multilobar and hemispheric PMG, the age of seizure onset, the extent of the lesion and EEG features can help determine whether surgery should be performed early. Additionally, surgery could be more favorable for achieving seizure freedom and cognitive improvement sooner.

PLAIN LANGUAGE SUMMARY

We aim to summarize clinical characteristics and compare the long-term outcomes after surgical and nonsurgical (ASM) treatment to provide a basis for treatment decisions for patients with unilateral multilobar and hemispheric polymicrogyria (PMG)-related epilepsy. We found that patients with unilateral hemispheric and multilobar PMG had significantly higher rates of seizure freedom and ASM discontinuation with surgical treatment than with nonsurgical treatment. In the surgical group, seizure outcomes were better in patients treated with complete resection/disconnection than in those treated with subtotal resection, but the difference was not statistically significant.

Exhaustive clinical examination of etiology and initial response to first-line treatment in 577 children with infantile epileptic spasm syndrome children: A 5-year retrospective observational study

OBJECTIVE

Employing whole-exome sequencing (WES) technology to investigate the etiology of infantile epileptic spasm syndrome (IESS), and determining whether different etiologies exhibit phenotypic variations, while elucidating the potential associated factors, might improve short-term responses to first-line treatment.

METHODS

We retrospectively evaluated patients with IESS admitted for treatment between January 2018 and June 2023. Clinical phenotypic differences among etiological classifications and clinical manifestations were analyzed. Variable selection using the best subset method was performed, followed by logistic regression analysis to identify the factors influencing treatment response.

RESULTS

A total of 577 patients were included; 412 completed trio-WES. Magnetic resonance imaging abnormalities were detected in 387 patients (67.1%). Patients with etiology as structural abnormalities were likelier to have non-spasms at the initial seizure onset. A total of 532 patients completed the first-line treatment; 273 patients received it for the first time at our hospital (initial response rates: 30.1% and 42.1%, respectively). The response group had a lower proportion of early-onset seizures (≤3 months) than the no-response group (11.3% vs. 23.7%, p < 0.01 and 11.3% vs. 21.5%, p = 0.03, respectively). Logistic regression analysis indicated that earlier initiation of first-line treatment was associated with a higher likelihood of an initial response. However, the etiological classification did not have a significant impact on the initial response.

INTERPRETATION

IESS patients with structural abnormalities are more likely to present with non-spasm seizures at initial onset. Early initiation of first-line treatment is crucial; however, initial responses may be less favorable when seizures occur in early infancy.

Early developmental changes in a rat model of malformations of cortical development: Abnormal neuronal migration and altered response to NMDA-induced excitotoxic injury

Malformations of cortical development (MCDs) are caused by abnormal neuronal migration processes during the fetal period and are a major cause of intractable epilepsy in infancy. However, the timing of hyperexcitability or epileptogenesis in MCDs remains unclear. To identify the early developmental changes in the brain of the MCD rat model, which exhibits increased seizure susceptibility during infancy (P12-15), we analyzed the pathological changes in the brains of MCD model rats during the neonatal period and tested NMDA-induced seizure susceptibility. Pregnant rats were injected with two doses of methylazoxymethanol acetate (MAM, 15 mg/kg, i.p.) to induce MCD, while controls were administered normal saline. The cortical development of the offspring was measured by performing magnetic resonance imaging (MRI) on postnatal days (P) 1, 5, and 8. At P8, some rats were sacrificed for immunofluorescence, Golgi staining, and Western analysis. In another set of rats, the number and latency to onset of spasms were monitored for 90 min after the NMDA (5 mg/kg i.p.) injection at P8. In MCD rats, in vivo MR imaging showed smaller brain volume and thinner cortex from day 1 after birth (p < 0.001). Golgi staining and immunofluorescence revealed abnormal neuronal migration, with a reduced number of neuronal cell populations and less dendritic arborization at P8. Furthermore, MCD rats exhibited a significant reduction in the expression of NMDA receptors and AMPAR4, along with an increase in AMPAR3 expression (p < 0.05). Although there was no difference in the latency to seizure onset between MCD rats and controls, the MCD rats survived significantly longer than the controls. These results provide insights into the early developmental changes in the cortex of a MCD rat model and suggest that delayed and abnormal neuronal development in the immature brain is associated with a blunted response to NMDA-induced excitotoxic injury. These developmental changes may be involved in the sudden onset of epilepsy in patients with MCD or prenatal brain injury.

Phenotypic Variability in Novel Doublecortin Gene Variants Associated with Subcortical Band Heterotopia

Doublecortin, encoded by the DCX gene, plays a crucial role in the neuronal migration process during brain development. Pathogenic variants of the DCX gene are the major causes of the "lissencephaly (LIS) spectrum", which comprehends a milder phenotype like Subcortical Band Heterotopia (SBH) in heterozygous female subjects. We performed targeted sequencing in three unrelated female cases with SBH. We identified three DCX-related variants: a novel missense (c.601A>G: p.Lys201Glu), a novel nonsense (c.210C>G: p.Tyr70*), and a previously identified nonsense (c.907C>T: p.Arg303*) variant. The novel c.601A>G: p.Lys201Glu variant shows a mother-daughter transmission pattern across four generations. The proband exhibits focal epilepsy and achieved seizure freedom with a combination of oxcarbazepine and levetiracetam. All other affected members have no history of epileptic seizures. Brain MRIs of the affected members shows predominant fronto-central SBH with mixed pachygyria on the overlying cortex. The two nonsense variants were identified in two unrelated probands with SBH, severe drug-resistant epilepsy and intellectual disability. These novel DCX variants further expand the genotypic-phenotypic correlations of lissencephaly spectrum disorders. Our documented phenotypic descriptions of three unrelated families provide valuable insights and stimulate further discussions on DCX-SBH cases.

Novel LAMC3 pathogenic variant enriched in Finnish population causes malformations of cortical development and severe epilepsy

OBJECTIVE

Recessive LAMC3 mutations are recognized to cause epilepsy with cortical malformations characterized by polymicrogyria and pachygyria. The objective of this study was to describe the clinical picture and epilepsy phenotype of four patients with a previously undescribed LAMC3 variant.

METHODS

All epilepsy patients treated in Kuopio Epilepsy Center (located in Kuopio, Finland) are offered the possibility to participate in a scientific study investigating biomarkers in epilepsy (Epibiomarker study). We have collected a comprehensive database of the study population, and are currently re-evaluating our database regarding the patients with developmental and/or epileptic encephalopathy (DEE). If the etiology of epilepsy remains unknown in the clinical setting, we are performing whole exome sequencing to recognize the genetic causes.

RESULTS

Among our study population of 323 DEE patients we recognized three patients with similar homozygous LAMC3 c.1866del (p.(Phe623Serfs*10)) frameshift variant and one patient with a compound heterozygous mutation where the same frameshift variant was combined with an intronic LAMC3 c.4231-12C>G variant on another allele. All these patients have severe epilepsy and either bilateral agyria-pachygyria or bilateral polymicrogyria in their clinical MRI scanning. Cortical malformations involve the occipital lobes in all our patients. Epilepsy phenotype is variable as two of our patients have DEE with epileptic spasms progressing to Lennox-Gastaut syndrome and intellectual disability. The other two patients have focal epilepsy without marked cognitive deficit. The four patients are unrelated. LAMC3 c.1866del p.(Phe623Serfs*10) frameshift variant is enriched in the Finnish population.

SIGNIFICANCE

Only a few patients with epilepsy caused by LAMC3 homozygous or compound heterozygous mutations have been described in the literature. To our knowledge, the variants discovered in our patients have not previously been published. Clinical phenotype appears to be more varied than previously assumed and patients with a milder phenotype and normal cognition have probably remained unrecognized.

[Congenital brain malformations]

CLINICAL ISSUE

Malformations of the central nervous system belong to the most common developmental disorders in humans. The clinical presentation of brain malformations is nonspecific including developmental delay, hypotonia, and/or epilepsy. The great heterogeneity concerning etiology, mechanisms of development and morphology is challenging for diagnosis and classification of brain malformations. Thereby recognizing specific malformations is essential for optimal patient management and prognostic evaluation. The aim of this article is to give an overview of several clinically relevant brain malformations occurring from different disrupted developmental processes in brain formation.

STANDARD RADIOLOGICAL METHODS

Several brain malformations are already diagnosed during routine ultrasound in pregnancy. However pre- and postnatal magnetic resonance imaging remains the gold standard in detecting the partially subtle changes and to classify the malformations.

METHODICAL INNOVATIONS

Advances in pre- and postnatal neuroimaging techniques and increasing investigation of genetic mechanisms underlying brain formation and its abnormalities have led to a better understanding of embryologic development and pathogeneses of brain malformations.

CONCLUSION

Besides patient's history and clinical phenotype, neuroimaging plays a key role in diagnosis. Not always a specific diagnosis can be made, but neuroimaging patterns often enable a focused genetic testing and therefore are revolutionary for etiologic and prognostic assignment. Basic knowledge of brain development facilitates understanding and classifying of structural brain abnormalities.

The clinical, imaging, pathological and genetic landscape of bottom-of-sulcus dysplasia

Bottom-of-sulcus dysplasia (BOSD) is increasingly recognized as a cause of drug-resistant, surgically-remediable, focal epilepsy, often in seemingly MRI-negative patients. We describe the clinical manifestations, morphological features, localization patterns and genetics of BOSD, with the aims of improving management and understanding pathogenesis. We studied 85 patients with BOSD diagnosed between 2005-2022. Presenting seizure and EEG characteristics, clinical course, genetic findings and treatment response were obtained from medical records. MRI (3 T) and 18F-FDG-PET scans were reviewed systematically for BOSD morphology and metabolism. Histopathological analysis and tissue genetic testing were performed in 64 operated patients. BOSD locations were transposed to common imaging space to study anatomical location, functional network localization and relationship to normal MTOR gene expression. All patients presented with stereotyped focal seizures with rapidly escalating frequency, prompting hospitalization in 48%. Despite 42% patients having seizure remissions, usually with sodium channel blocking medications, most eventually became drug-resistant and underwent surgery (86% seizure-free). Prior developmental delay was uncommon but intellectual, language and executive dysfunction were present in 24%, 48% and 29% when assessed preoperatively, low intellect being associated with greater epilepsy duration. BOSDs were missed on initial MRI in 68%, being ultimately recognized following repeat MRI, 18F-FDG-PET or image postprocessing. MRI features were grey-white junction blurring (100%), cortical thickening (91%), transmantle band (62%), increased cortical T1 signal (46%) and increased subcortical FLAIR signal (26%). BOSD hypometabolism was present on 18F-FDG-PET in 99%. Additional areas of cortical malformation or grey matter heterotopia were present in eight patients. BOSDs predominated in frontal and pericentral cortex and related functional networks, mostly sparing temporal and occipital cortex, and limbic and visual networks. Genetic testing yielded pathogenic mTOR pathway variants in 63% patients, including somatic MTOR variants in 47% operated patients and germline DEPDC5 or NPRL3 variants in 73% patients with familial focal epilepsy. BOSDs tended to occur in regions where the healthy brain normally shows lower MTOR expression, suggesting these regions may be more vulnerable to upregulation of MTOR activity. Consistent with the existing literature, these results highlight (i) clinical features raising suspicion of BOSD; (ii) the role of somatic and germline mTOR pathway variants in patients with sporadic and familial focal epilepsy associated with BOSD; and (iii) the role of 18F-FDG-PET alongside high-field MRI in detecting subtle BOSD. The anatomical and functional distribution of BOSDs likely explain their seizure, EEG and cognitive manifestations and may relate to relative MTOR expression.

Malformations of cortical development: Fetal imaging and genetics

BACKGROUND

Malformations of cortical development (MCD) are a group of congenital disorders characterized by structural abnormalities in the brain cortex. The clinical manifestations include refractory epilepsy, mental retardation, and cognitive impairment. Genetic factors play a key role in the etiology of MCD. Currently, there is no curative treatment for MCD. Phenotypes such as epilepsy and cerebral palsy cannot be observed in the fetus. Therefore, the diagnosis of MCD is typically based on fetal brain magnetic resonance imaging (MRI), ultrasound, or genetic testing. The recent advances in neuroimaging have enabled the in-utero diagnosis of MCD using fetal ultrasound or MRI.

METHODS

The present study retrospectively reviewed 32 cases of fetal MCD diagnosed by ultrasound or MRI. Then, the chromosome karyotype analysis, single nucleotide polymorphism array or copy number variation sequencing, and whole-exome sequencing (WES) findings were presented.

RESULTS

Pathogenic copy number variants (CNVs) or single-nucleotide variants (SNVs) were detected in 22 fetuses (three pathogenic CNVs [9.4%, 3/32] and 19 SNVs [59.4%, 19/32]), corresponding to a total detection rate of 68.8% (22/32).

CONCLUSION

The results suggest that genetic testing, especially WES, should be performed for fetal MCD, in order to evaluate the outcomes and prognosis, and predict the risk of recurrence in future pregnancies.

Targeting the EGFR pathway: An alternative strategy for the treatment of tuberous sclerosis complex?

INTRODUCTION

Tuberous sclerosis complex (TSC) is caused by variants in TSC1/TSC2, leading to constitutive activation of the mammalian target of rapamycin (mTOR) complex 1. Therapy with everolimus has been approved for TSC, but variations in success are frequent. Recently, caudal late interneuron progenitor (CLIP) cells were identified as a common origin of the TSC brain pathologies such as subependymal giant cell astrocytomas (SEGA) and cortical tubers (CT). Further, targeting the epidermal growth factor receptor (EGFR) with afatinib, which is expressed in CLIP cells, reduces cell growth in cerebral TSC organoids. However, investigation of clinical patient-derived data is lacking.

AIMS

Observation of EGFR expression in SEGA, CT and focal cortical dysplasia (FCD) 2B human brain specimen and investigation of whether its inhibition could be a potential therapeutic intervention for these patients.

METHODS

Brain specimens of 23 SEGAs, 6 CTs, 20 FCD2Bs and 17 controls were analysed via immunohistochemistry to characterise EGFR expression, cell proliferation (via Mib1) and mTOR signalling. In a cell-based assay using primary patient-derived cells (CT n = 1, FCD2B n = 1 and SEGA n = 4), the effects of afatinib and everolimus on cell proliferation and cell viability were observed.

RESULTS

EGFR overexpression was observed in histological sections of SEGA, CT and FCD2B patients. Both everolimus and afatinib decreased the proliferation and viability in primary SEGA, tuber and FCD2B cells.

CONCLUSION

Our study demonstrates that EGFR suppression might be an effective alternative treatment option for SEGAs and tubers, as well as other mTOR-associated malformations of cortical development, including FCD2B.

Somatic mosaicism in focal epilepsies

PURPOSE OF REVIEW

Over the past decade, it has become clear that brain somatic mosaicism is an important contributor to many focal epilepsies. The number of cases and the range of underlying pathologies with somatic mosaicism are rapidly increasing. This growth in somatic variant discovery is revealing dysfunction in distinct molecular pathways in different focal epilepsies.

RECENT FINDINGS

We briefly summarize the current diagnostic yield of pathogenic somatic variants across all types of focal epilepsy where somatic mosaicism has been implicated and outline the specific molecular pathways affected by these variants. We will highlight the recent findings that have increased diagnostic yields such as the discovery of pathogenic somatic variants in novel genes, and new techniques that allow the discovery of somatic variants at much lower variant allele fractions.

SUMMARY

A major focus will be on the emerging evidence that somatic mosaicism may contribute to some of the more common focal epilepsies such as temporal lobe epilepsy with hippocampal sclerosis, which could lead to it being re-conceptualized as a genetic disorder.

RELN gene-related drug-resistant epilepsy with periventricular nodular heterotopia treated with radiofrequency thermocoagulation: a case report

An increasing number of gene mutations associated with epilepsy have been identified, some linked to gray matter heterotopia-a common cause of drug-resistant epilepsy. Current research suggests that gene mutation-associated epilepsy should not be considered a contraindication for surgery in epilepsy patients. At present, stereoelectroencephalography-guided radiofrequency thermocoagulation is an important method to treat periventricular nodular heterotopia-associated drug-resistant epilepsy. We present a case of drug-resistant epilepsy, accompanied by periventricular nodular heterotopia and a heterozygous mutation of the RELN gene, successfully treated with radiofrequency thermocoagulation, resulting in a favorable outcome.

Deep learning-based automated lesion segmentation on pediatric focal cortical dysplasia II preoperative MRI: a reliable approach

OBJECTIVES

Focal cortical dysplasia (FCD) represents one of the most common causes of refractory epilepsy in children. Deep learning demonstrates great power in tissue discrimination by analyzing MRI data. A prediction model was built and verified using 3D full-resolution nnU-Net for automatic lesion detection and segmentation of children with FCD II.

METHODS

High-resolution brain MRI structure data from 65 patients, confirmed with FCD II by pathology, were retrospectively studied. Experienced neuroradiologists segmented and labeled the lesions as the ground truth. Also, we used 3D full-resolution nnU-Net to segment lesions automatically, generating detection maps. The algorithm was trained using fivefold cross-validation, with data partitioned into training (N = 200) and testing (N = 15). To evaluate performance, detection maps were compared to expert manual labels. The Dice-Sørensen coefficient (DSC) and sensitivity were used to assess the algorithm performance.

RESULTS

The 3D nnU-Net showed a good performance for FCD lesion detection at the voxel level, with a sensitivity of 0.73. The best segmentation model achieved a mean DSC score of 0.57 on the testing dataset.

CONCLUSION

This pilot study confirmed that 3D full-resolution nnU-Net can automatically segment FCD lesions with reliable outcomes. This provides a novel approach to FCD lesion detection.

CRITICAL RELEVANCE STATEMENT

Our fully automatic models could process the 3D T1-MPRAGE data and segment FCD II lesions with reliable outcomes.

KEY POINTS

• Simplified image processing promotes the DL model implemented in clinical practice. • The histopathological confirmed lesion masks enhance the clinical credibility of the AI model. • The voxel-level evaluation metrics benefit lesion detection and clinical decisions.

Structural brain abnormalities in Pallister-Killian syndrome: a neuroimaging study of 31 children

BACKGROUND

Pallister-Killian syndrome (PKS) is a rare genetic disorder caused by mosaic tetrasomy of 12p with wide neurological involvement. Intellectual disability, developmental delay, behavioral problems, epilepsy, sleep disturbances, and brain malformations have been described in most individuals, with a broad phenotypic spectrum. This observational study, conducted through brain MRI scan analysis on a cohort of patients with genetically confirmed PKS, aims to systematically investigate the neuroradiological features of this syndrome and identify the possible existence of a typical pattern. Moreover, a literature review differentiating the different types of neuroimaging data was conducted for comparison with our population.

RESULTS

Thirty-one individuals were enrolled (17 females/14 males; age range 0.1-17.5 years old at first MRI). An experienced pediatric neuroradiologist reviewed brain MRIs, blindly to clinical data. Brain abnormalities were observed in all but one individual (compared to the 34% frequency found in the literature review). Corpus callosum abnormalities were found in 20/30 (67%) patients: 6 had callosal hypoplasia; 8 had global hypoplasia with hypoplastic splenium; 4 had only hypoplastic splenium; and 2 had a thin corpus callosum. Cerebral hypoplasia/atrophy was found in 23/31 (74%) and ventriculomegaly in 20/31 (65%). Other frequent features were the enlargement of the cisterna magna in 15/30 (50%) and polymicrogyria in 14/29 (48%). Conversely, the frequency of the latter was found to be 4% from the literature review. Notably, in our population, polymicrogyria was in the perisylvian area in all 14 cases, and it was bilateral in 10/14.

CONCLUSIONS

Brain abnormalities are very common in PKS and occur much more frequently than previously reported. Bilateral perisylvian polymicrogyria was a main aspect of our population. Our findings provide an additional tool for early diagnosis.Further studies to investigate the possible correlations with both genotype and phenotype may help to define the etiopathogenesis of the neurologic phenotype of this syndrome.

Grey matter heterotopia subtypes show specific morpho-electric signatures and network dynamics

Grey matter heterotopia (GMH) are neurodevelopmental disorders associated with abnormal cortical function and epilepsy. Subcortical band heterotopia (SBH) and periventricular nodular heterotopia (PVNH) are two well-recognized GMH subtypes in which neurons are misplaced, either forming nodules lining the ventricles in PVNH, or forming bands in the white matter in SBH. Although both PVNH and SBH are commonly associated with epilepsy, it is unclear whether these two GMH subtypes differ in terms of pathological consequences or, on the contrary, share common altered mechanisms. Here, we studied two robust preclinical models of SBH and PVNH, and performed a systematic comparative assessment of the physiological and morphological diversity of heterotopia neurons, as well as the dynamics of epileptiform activity and input connectivity. We uncovered a complex set of altered properties, including both common and distinct physiological and morphological features across heterotopia subtypes, and associated with specific dynamics of epileptiform activity. Taken together, these results suggest that pro-epileptic circuits in GMH are, at least in part, composed of neurons with distinct, subtype-specific, physiological and morphological properties depending on the heterotopia subtype. Our work supports the notion that GMH represent a complex set of disorders, associating both shared and diverging pathological consequences, and contributing to forming epileptogenic networks with specific properties. A deeper understanding of these properties may help to refine current GMH classification schemes by identifying morpho-electric signatures of GMH subtypes, to potentially inform new treatment strategies.

Burden of Rare Copy Number Variants in Microcephaly: A Brazilian Cohort of 185 Microcephalic Patients and Review of the Literature

Microcephaly presents heterogeneous genetic etiology linked to several neurodevelopmental disorders (NDD). Copy number variants (CNVs) are a causal mechanism of microcephaly whose investigation is a crucial step for unraveling its molecular basis. Our purpose was to investigate the burden of rare CNVs in microcephalic individuals and to review genes and CNV syndromes associated with microcephaly. We performed chromosomal microarray analysis (CMA) in 185 Brazilian patients with microcephaly and evaluated microcephalic patients carrying < 200 kb CNVs documented in the DECIPHER database. Additionally, we reviewed known genes and CNV syndromes causally linked to microcephaly through the PubMed, OMIM, DECIPHER, and ClinGen databases. Rare clinically relevant CNVs were detected in 39 out of the 185 Brazilian patients investigated by CMA (21%). In 31 among the 60 DECIPHER patients carrying < 200 kb CNVs, at least one known microcephaly gene was observed. Overall, four gene sets implicated in microcephaly were disclosed: known microcephaly genes; genes with supporting evidence of association with microcephaly; known macrocephaly genes; and novel candidates, including OTUD7A, BBC3, CNTN6, and NAA15. In the review, we compiled 957 known microcephaly genes and 58 genomic CNV loci, comprising 13 duplications and 50 deletions, which have already been associated with clinical findings including microcephaly. We reviewed genes and CNV syndromes previously associated with microcephaly, reinforced the high CMA diagnostic yield for this condition, pinpointed novel candidate loci linked to microcephaly deserving further evaluation, and provided a useful resource for future research on the field of neurodevelopment.

To explore the potential mechanisms of cognitive impairment in children with MRI-negative pharmacoresistant epilepsy due to focal cortical dysplasia: A pilot study from gray matter structure view

Objectives

To investigate the characteristics of brain structure in children with focal cortical dysplasia (FCD)-induced pharmacoresistant epilepsy, and explore the potential mechanisms of cognitive impairment from the view of gray matter alteration.

Methods

25 pharmacoresistant pediatric patients with pathologically confirmed focal cortical dysplasia (FCD), and 25 gender-matched healthy controls were included in this study. 3.0T MRI data and intelligence tests using the Wechsler Intelligence Scale for Children-Forth Edition (WISC-IV) were generated for all subjects. Voxel-based morphometry (VBM)-diffeomorphic anatomical registration through exponentiated lie algebra (DARTEL) and surface-based morphometry (SBM) analyses were performed to analyze gray matter volume and cortical structure. Two-sample t-tests were used to compare the differences in gray matter volume (P＜0.05, FWE) and cortical thickness (P＜0.001, FWE) between the two groups. Also, the Spearman rank correlation analyses were employed to determine the relationship between structural alterations and neuropsychological results.

Results

The WISC-IV scores of the FCD group were significantly lower than those of the HC group in terms of full-scale intelligence quotient (FSIQ), verbal comprehension index (VCI), perceptual reasoning index (PRI), working memory index (WMI), and processing speed index (PSI) (all P＜0.01). Compared with the HC group, in the FCD group, the gray matter volume (GMV) reduced significantly in the left cerebellum_8, cerebellum_Crus2, and bilateral thalamus (P＜0.05, FWE); the GMV increased in the bilateral medial frontal gyrus, right precuneus, and left inferior temporal gyrus (P＜0.05, FWE), and the cortical thickness increased in the bilateral frontal, parietal, and temporal areas (P＜0.001, FWE). Correlation analyses showed that the age of seizure onset had positive correlations with the WISC-IV scores significantly. Meanwhile, the cortex thicknesses of the left pars opercularis gyrus, left middle temporal gyrus, and right inferior temporal gyrus had negative correlations with the WISC-IV scores significantly.

Conclusion

FCD patients showed subtle structural abnormalities in multiple brain regions, with significant involvement of the primary visual cortex and language function cortex. And we also demonstrated a crucial correlation between gray matter structural alteration and cognitive impairment.

Pediatric Intraoperative Neurophysiologic Mapping and Monitoring in Brain Surgery

SUMMARY

Similar to adults, children undergoing brain surgery can significantly benefit from intraoperative neurophysiologic mapping and monitoring. Although young brains present the advantage of increased plasticity, during procedures in close proximity to eloquent regions, the risk of irreversible neurological compromise remains and can be lowered further by these techniques. More so, pathologies specific to the pediatric population, such as neurodevelopmental lesions, often result in medically refractory epilepsy. Thus, their successful surgical treatment also relies on accurate demarcation and resection of the epileptogenic zone, processes in which intraoperative electrocorticography is often employed. However, stemming from the development and maturation of the central and peripheral nervous systems as the child grows, intraoperative neurophysiologic testing in this population poses methodologic and interpretative challenges even to experienced clinical neurophysiologists. For example, it is difficult to perform awake craniotomies and language testing in the majority of pediatric patients. In addition, children may be more prone to intraoperative seizures and exhibit afterdischarges more frequently during functional mapping using electrical cortical stimulation because of high stimulation thresholds needed to depolarize immature cortex. Moreover, choice of anesthetic regimen and doses may be different in pediatric patients, as is the effect of these drugs on immature brain; these factors add additional complexity in terms of interpretation and analysis of neurophysiologic recordings. Below, we are describing the modalities commonly used during intraoperative neurophysiologic testing in pediatric brain surgery, with emphasis on age-specific clinical indications, methodology, and challenges.

Demographic and clinical characteristics, seizure disorders, and antiepileptic drug usage in different types of corpus callosum disorders: a comparative study in children

BACKGROUND

This study aimed to investigate the demographic and clinical characteristics, types of seizure disorders, and antiepileptic drug usage among individuals with different types of corpus callosum disorders.

METHODS

A total of 73 individuals were included in the study and divided into three groups based on the type of corpus callosum abnormality: hypoplasia (H), agenesis (A), and dysgenesis (D). Demographic data, including gender and preterm birth, as well as clinical characteristics such as seizure disorders, attention deficit hyperactivity disorder (ADHD), severe developmental delay/intellectual disability, and other brain malformations, were analyzed. The types of seizure disorders and antiepileptic drugs used were also examined.

RESULTS

The H group had the highest number of participants (n = 47), followed by the A group (n = 11) and the D group (n = 15). The A group had the highest percentage of males and preterm births, while the D group had the highest percentage of seizure disorders, other brain malformations, and severe developmental delay/intellectual disability. The A group also had the highest percentage of ADHD. Focal seizures were observed in all three groups, with the highest proportion in the A group. Focal impaired awareness seizures (FIAS) were present in all groups, with the highest proportion in the D group. Generalized tonic-clonic seizures (GTCS) were observed in all groups, with the highest proportion in the H group. Different types of antiepileptic drugs were used among the groups, with variations in usage rates for each drug.

CONCLUSION

This study provided insights into the demographic and clinical characteristics, seizure disorders, and antiepileptic drug usage among individuals with different types of corpus callosum disorders. Significant differences were found between the groups, indicating the need for tailored management approaches. However, the study has limitations, including a small sample size and a cross-sectional design. Further research with larger sample sizes and longitudinal designs is warranted to validate these findings and explore the relationship between corpus callosum abnormality severity and clinical outcomes.

Cortical surface analysis for focal cortical dysplasia diagnosis by using PET images

Focal cortical dysplasia (FCD) is a neurological disorder distinguished by faulty brain cell structure and development. Repetitive and uncontrollable seizures may be linked to FCD's aberrant cortical thickness, gyrification, and sulcal depth. Quantitative cortical surface analysis is a crucial alternative to ineffective visual inspection. This study recruited 42 subjects including 22 FCD patients who underwent surgery and 20 healthy controls (HC). For the FCD patients, T1-weighted and PET images were obtained by a PET-MRI scanner, and the confirmed epileptogenic zone (EZ) was collected from postsurgical follow-up. For the HCs, CT and PET images were obtained by a PET-CT scanner. Cortical thickness, gyrification index, and sulcal depth were calculated using a computational anatomical toolbox (CAT12). A cluster-based analysis is carried out to determine each FCD patient's aberrant cortical surface. After parcellating the cerebral cortex into 68 regions by the Desikan-Killiany atlas, a region of interest (ROI) analysis was conducted to know whether the feature in the FCD group is significantly different from that in the HC group. Finally, the features of all ROIs were utilised to train a support vector machine classifier (SVM). The classification performance is evaluated by the leave-one-out cross-validation. The cluster-based analysis can localize the EZ cluster with the highest accuracy of 54.5 % (12/22) for cortical thickness, 40.9 % (9/22) and 13.6 % (3/22) for sulcal depth and gyrification, respectively. Moderate concordance (Kappa, 0.6) is observed between the confirmed EZs and identified clusters by using the cortical thickness. Fair concordance (Kappa, 0.3) and no concordance (Kappa, 0.1) is found by using sulcal depth and gyrification. Significant differences are found in 46 of 68 regions (67.7 %) for the three measures. The trained SVM classifier achieved a prediction accuracy of 95.5 % for the cortical thickness, while the sulcal depth and the gyrification obtained 86.0 % and 81.5 %. Cortical thickness, as determined by quantitative cortical surface analysis of PET data, has a greater ability than sulcal depth and gyrification to locate aberrant EZ clusters in FCD. Surface measures might be different in many regions for FCD and HC. By integrating machine learning and cortical morphologies features, individual prediction of FCD seems to be feasible.

MRI Data Analysis in Malformations of Cortical Development

Brain magnetic resonance imaging (MRI) is a noninvasive imaging modality that utilizes powerful magnets and radio waves to generate detailed images of the brain, making it a valuable tool for investigating malformations of cortical development (MCD). Various MRI techniques, including 3D T1-weighted, multiplanar thin-sliced T2-weighted, and 3D fluid-attenuated inversion recovery (FLAIR) sequences, can provide high-resolution images with excellent spatial and contrast resolution, allowing for a detailed visualization of cortical anatomy and abnormalities. Almost all MCD can be detected and characterized using MRI. Advanced techniques, such as arterial spin labeling MR perfusion, diffusion tensor imaging (DTI), and functional MRI (fMRI), may be used to improve the detection rate of these malformations and to plan surgery in case of drug-resistant epilepsy. However, there are also limitations related to high cost, relatively low availability, need for sedation or anesthesia, and limited sensitivity for detecting subtle focal cortical malformations. Despite these limitations, brain MRI plays a crucial role in the investigation of MCD, providing valuable information for diagnosis, treatment planning, and patient management.

Long-term seizure and developmental outcomes of epilepsy surgery in children under 3 years old: A single-center study of 113 patients

AIMS

To investigate the clinical characteristics, surgical strategy, developmental and seizure outcomes, and predictors of surgical outcome in children with drug-resistant epilepsy (DRE) under 3 years old.

METHODS

One hundred thirteen consecutive children younger than 3 years of age with DRE underwent curative surgical treatment after multidisciplinary preoperative evaluation using the strategy developed in the pediatric epilepsy center of Peking University First Hospital (PKFHPEC) between 2014 and 2018. These patients were selected for retrospective study. The relevant clinical data were collected and analyzed. The surgical prognoses were classified using the Engel classification, and the developmental assessment results were collected. Statistical analysis of the clinical data was performed to analyze the predictors of seizure outcomes and their correlation with developmental outcomes.

RESULTS

All the patients were followed up for more than 3 years, and 98 (86.7%) patients had no seizure recurrence. One year after surgery, the seizure-free rate was 86.7%, which was as high as that at the last follow-up. Cortical dysplasia was the most frequent etiology of DRE in this cohort, accounting for 77.0%. According to the Engel classification, acute postoperative seizure (APOS; p < 0.001) was a predictor of seizure recurrence. No deaths occurred. No unpredicted long-term severe complications occurred except for one ventricular peritoneal shunt. The patients' neurodevelopmental statuses were improved after successful surgery, while the scores of the pre- and postoperative developmental assessments were closely correlated.

CONCLUSIONS

For children who are younger than 3 years old and have DRE and structural abnormalities, early curative treatment can lead to long-term good seizure outcomes and a low complication rate. The development of appropriate strategies for both presurgical evaluation and resection is crucial for the success of surgery.

Live Imaging of Migrating Neurons and Glial Progenitors Visualized by in Utero Electroporation

During cortical development, both neurons and glial cells are generated in the germinal zone near the lateral ventricle, migrate in the correct direction, and settle in their appropriate locations. This developmental process can be clearly visualized by introducing fluorescent protein-expression vectors via in utero electroporation. In this chapter, we describe labeling methods for migrating neurons and glial progenitors, as well as methods for slice culture, and time-lapse imaging.

CT Scan Data Analysis in Malformations of Cortical Development

Malformations of cortical development (MCDs) are a diverse group of disorders that result from abnormal neuronal migration, proliferation, and differentiation during brain development. Head computed tomography (CT) has limited use in the diagnosis of MCDs and should be reserved for selected cases with specific indications or when magnetic resonance imaging is not available or contraindicated. CT can detect brain calcifications associated with MCDs, thus helping in the differential diagnosis between acquired and genetic MCDs or in the identification of different genetic patterns. Moreover, CT can provide high-resolution images of the skull and bones, thus identifying associated malformations, such as craniosynostosis, inner and middle ear malformations, and vertebral anomalies. In this chapter, we review the CT scan technique, data analysis, and indications in the investigation of MCDs.

Sonographic demonstration of the sulci and gyri on the convex surface in normal fetuses using 3D-ICRV rendering technology

PURPOSE

To demonstrate morphological alteration of the sulci and gyri on the convex surface in normal fetuses using innovative three-dimensional inversion and Crystalvue and Realisticvue (3D-ICRV) rendering technology.

MATERIALS AND METHODS

3D fetal brain volumes were collected from low-risk singleton pregnancies between 15+0 and 35+6 gestational weeks. Volumes were acquired from the transthalamic axial plane by transabdominal ultrasonography and were then post-processed with Crystalvue, Realisticvue rendering software and inversion mode. Volume quality was assessed. The anatomic definition of the sulci and gyri was determined according to location and orientation. The morphology alteration and sulcus display rates were recorded in sequential order of gestational weeks. Follow-up data were collected in all cases.

RESULTS

294 of 300 fetuses (294 brain volumes) (98%) with qualified fetal brain volumes were included (n=294, median 27 gestational weeks). 6 fetuses with unsatisfactory 3D-ICRV image quality were excluded. The morphology of the sulci and gyri on the brain convex surface could be demonstrated clearly on 3D-ICRV images. The Sylvian fissure was the first structure to be recognized. From 25 to 30 weeks, other sulci and gyri became visible. An ascending trend in the display rate of the sulci was found in this period. Follow-up showed no detectable anomalies.

CONCLUSION

3D-ICRV rendering technology is different from traditional 3D ultrasound. It can provide vivid and intuitive prenatal visualization of the sulci and gyri on the brain surface. Moreover, it may offer new ideas for neurodevelopment exploration.

The "cortical invagination sign": a midtrimester sonographic marker of unilateral cortical focal dysgyria in fetuses with complete agenesis of the corpus callosum

BACKGROUND

Agenesis of the corpus callosum is associated with several malformations of cortical development. Recently, features of focal cortical dysgyria have been described in fetuses with agenesis of the corpus callosum.

OBJECTIVE

This study aimed to describe the "cortical invagination sign," a specific sonographic feature of focal cortical dysgyria, which is consistently seen at midtrimester axial brain ultrasound in fetuses with complete agenesis of the corpus callosum.

STUDY DESIGN

This was a retrospective analysis of prospectively collected data from 2018 to 2021, including patients referred to 5 fetal medicine centers in the second trimester of pregnancy (19 0/7 to 22 0/7 weeks of gestation) with suspected complete agenesis of the corpus callosum. All cases with the diagnosis of complete agenesis of the corpus callosum were submitted to an axial sonographic assessment of the fetal brain on the transventricular plane. In this scanning section, the mesial profile of both cerebral hemispheres at the level of the frontal-parietal cortex was investigated. In this area, the operator looked for an abnormal invagination of the cortical surface along the widened interhemispheric fissure, which was referred to as the "cortical invagination sign." All fetuses were submitted to dedicated antenatal magnetic resonance imaging to reassess the ultrasound findings. Cases with additional brain anomalies, which did not involve the cortex, were excluded. The final diagnosis was confirmed at postnatal brain magnetic resonance imaging or postmortem examination, for cases undergoing termination of pregnancy. The primary outcome of this study was to evaluate the presence and laterality of the "cortical invagination sign" in fetuses with complete agenesis of the corpus callosum at antenatal ultrasound and magnetic resonance imaging.

RESULTS

During the study period, 64 cases of complete agenesis of the corpus callosum were included; of those cases, 50 (78.1%) resulted in termination of pregnancy, and 14 (21.9%) resulted in a live birth. The "cortical invagination sign" was detected at ultrasound in 13 of 64 cases (20.3%) and at targeted brain magnetic resonance imaging in 2 additional cases (23.4%), all of which were electively terminated. Moreover, the "cortical invagination sign" was found to be exclusively unilateral and on the left cerebral hemisphere in all the cases. There was a predominant number, although nonsignificant, of male fetuses (80.0% of cases; P=.06) in the group of complete agenesis of the corpus callosum with the "cortical invagination sign."

CONCLUSION

The "cortical invagination sign" is a specific marker of focal cortical dysgyria, which seems to characterize at midtrimester of pregnancy in a large group of fetuses with complete agenesis of the corpus callosum. The etiology, pathophysiology, and prognostic significance of this finding remain to be elucidated.

Brain Pathways in LIS1-Associated Lissencephaly Revealed by Diffusion MRI Tractography

Lissencephaly (LIS) is a rare neurodevelopmental disorder with severe symptoms caused by abnormal neuronal migration during cortical development. It is caused by both genetic and non-genetic factors. Despite frequent studies about the cortex, comprehensive elucidation of structural abnormalities and their effects on the white matter is limited. The main objective of this study is to analyze abnormal neuronal migration pathways and white matter fiber organization in LIS1-associated LIS using diffusion MRI (dMRI) tractography. For this purpose, slabs of brain specimens with LIS (n = 3) and age and sex-matched controls (n = 4) were scanned with 3T dMRI. Our high-resolution ex vivo dMRI successfully identified common abnormalities across the samples. The results revealed an abnormal increase in radially oriented subcortical fibers likely associated with radial migration pathways and u-fibers and a decrease in association fibers in all LIS specimens.

Recommendations for neuroradiological examinations in children living with achondroplasia: a European Society of Pediatric Radiology and European Society of Neuroradiology opinion paper

Children living with achondroplasia are at an increased risk of developing neurological complications, which may be associated with acute and life-altering events. To remediate this risk, the timely acquisition of effective neuroimaging that can help to guide clinical management is essential. We propose imaging protocols and follow-up strategies for evaluating the neuroanatomy of these children and to effectively identify potential neurological complications, including compression at the cervicomedullary junction secondary to foramen magnum stenosis, spinal deformity and spinal canal stenosis. When compiling these recommendations, emphasis has been placed on reducing scan times and avoiding unnecessary radiation exposure. Standardized imaging protocols are important to ensure that clinically useful neuroimaging is performed in children living with achondroplasia and to ensure reproducibility in future clinical trials. The members of the European Society of Pediatric Radiology (ESPR) Neuroradiology Taskforce and European Society of Neuroradiology pediatric subcommittee, together with clinicians and surgeons with specific expertise in achondroplasia, wrote this opinion paper. The research committee of the ESPR also endorsed the final draft. The rationale for these recommendations is based on currently available literature, supplemented by best practice opinion from radiologists and clinicians with subject-specific expertise.

Hippocampal and neocortical BRAF mutant non-expansive lesions in focal epilepsies

OBJECTIVE

Mesial Temporal Lobe Epilepsy-associated Hippocampal Sclerosis (MTLE-HS) is a syndrome associated with various aetiologies. We previously identified CD34-positive extravascular stellate cells (CD34+ cells) possibly related to BRAFV600E oncogenic variant in a subset of MTLE-HS. We aimed to identify the BRAFV600E oncogenic variants and characterise the CD34+ cells.

METHODS

We analysed BRAFV600E oncogenic variant by digital droplet Polymerase Chain Reaction in 53 MTLE-HS samples (25 with CD34+ cells) and nine non-expansive neocortical lesions resected during epilepsy surgery (five with CD34+ cells). Ex vivo multi-electrode array recording, immunolabelling, methylation microarray and single nuclei RNAseq were performed on BRAFwildtype MTLE-HS and BRAFV600E mutant non-expansive lesion of hippocampus and/or neocortex.

RESULTS

We identified a BRAFV600E oncogenic variant in five MTLE-HS samples with CD34+ cells (19%) and in five neocortical samples with CD34+ cells (100%). Single nuclei RNAseq of resected samples revealed two unique clusters of abnormal cells (including CD34+ cells) associated with senescence and oligodendrocyte development in both hippocampal and neocortical BRAFV600E mutant samples. The co-expression of the oncogene-induced senescence marker p16INK4A and the outer subventricular zone radial glia progenitor marker HOPX in CD34+ cells was confirmed by multiplex immunostaining. Pseudotime analysis showed that abnormal cells share a common lineage from progenitors to myelinating oligodendrocytes. Epilepsy surgery led to seizure freedom in eight of the 10 patients with BRAF mutant lesions.

INTERPRETATION

BRAFV600E underlies a subset of MTLE-HS and epileptogenic non-expansive neocortical focal lesions. Detection of the oncogenic variant may help diagnosis and open perspectives for targeted therapies.

Double inversion recovery MRI of subcortical band heterotopia and its variations

BACKGROUND AND PURPOSE

Subcortical band heterotopia (SBH) is a malformation of cortical development diagnosed via MRI. Currently, patients with SBH are classified according to Di Donato's classification. We aimed to show a variation of SBH and the usefulness of double inversion recovery (DIR) images.

METHODS

We retrospectively reviewed the MRI findings of 28 patients with SBH. The patients were classified according to Donato's classification by using conventional MR images, and their DIR findings were reviewed.

RESULTS

Of 28 patients, 20 were grade 1 and 8 were grade 2 according to Di Donato's classification. In 15 of 28 patients, the following four types of atypical MRI findings were detected: asymmetry distribution (four cases), coexistence of thin and thick SBH (five cases), and DIR faint abnormal signal intensity in subcortical white matter (five cases) and in deep white matter (five cases). The latter two types were detected on DIR alone and have not been reported. Additionally, these were identified only in the mild group (Di Donato's classification 1-1 or 1-2).

CONCLUSION

DIR is a useful MRI sequence for detecting faint white matter signal abnormalities, and it can aid in the accurate classification of SBH and identification of its variations, which may reflect the pathology of SBH.

Normal and abnormal appearance of fetal ganglionic eminence on second-trimester three-dimensional ultrasound

OBJECTIVES

To describe the appearance and size of the ganglionic eminence (GE) in normal fetuses on midtrimester three-dimensional (3D) neurosonography and to report on the association between GE alterations (cavitation or enlargement) and malformation of cortical development (MCD).

METHODS

This was a prospective multicenter cohort study of normal fetuses and a retrospective analysis of pathological cases with MCD. From January 2022 to June 2022, patients attending our tertiary centers for an expert fetal brain scan were recruited for the purpose of the study. A 3D volume of the fetal head, starting from the sagittal plane, was acquired in apparently normal fetuses using a transabdominal or transvaginal approach. Stored volume datasets were then evaluated independently by two expert operators. Two measurements (longitudinal diameter and transverse diameter) of the GE in the coronal view were obtained twice by each operator. Intra- and interobserver measurement variation was calculated. Reference ranges for GE measurements were calculated in the normal population. A previously stored volume dataset of 60 cases with MCD was also analyzed independently by the two operators using the same method in order to assess if GE abnormalities (cavitation or enlargement) were present. Postnatal follow-up was obtained in all cases.

RESULTS

In the study period, 160 normal fetuses between 19 and 22 weeks of gestation were included in the study. The GE was visible in the coronal plane on 3D neurosonography in 144 (90%) cases and was not clearly visible in the remaining 16 (10%) cases. The intra- and interobserver agreement was almost perfect for the longitudinal diameter, with an intraclass correlation coefficient (ICC) of 0.90 (95% CI, 0.83-0.93) and 0.90 (95% CI, 0.86-0.92), respectively, and substantial for the transverse diameter, with an ICC of 0.80 (95% CI, 0.70-0.87) and 0.64 (95% CI, 0.53-0.72), respectively. A retrospective analysis of 50 cases with MCD in the second trimester showed that GE enlargement was present in 12 cases and GE cavitation was present in four cases.

CONCLUSIONS

Systematic assessment of the GE in fetuses at 19-22 weeks of gestation is feasible on 3D neurosonography, with good reproducibility in normal cases. Cavitation or enlargement of the GE can be demonstrated in fetuses with MCD. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Exome Sequencing and the Identification of New Genes and Shared Mechanisms in Polymicrogyria

Importance

Polymicrogyria is the most commonly diagnosed cortical malformation and is associated with neurodevelopmental sequelae including epilepsy, motor abnormalities, and cognitive deficits. Polymicrogyria frequently co-occurs with other brain malformations or as part of syndromic diseases. Past studies of polymicrogyria have defined heterogeneous genetic and nongenetic causes but have explained only a small fraction of cases.

Objective

To survey germline genetic causes of polymicrogyria in a large cohort and to consider novel polymicrogyria gene associations.

Design, Setting, and Participants

This genetic association study analyzed panel sequencing and exome sequencing of accrued DNA samples from a retrospective cohort of families with members with polymicrogyria. Samples were accrued over more than 20 years (1994 to 2020), and sequencing occurred in 2 stages: panel sequencing (June 2015 to January 2016) and whole-exome sequencing (September 2019 to March 2020). Individuals seen at multiple clinical sites for neurological complaints found to have polymicrogyria on neuroimaging, then referred to the research team by evaluating clinicians, were included in the study. Targeted next-generation sequencing and/or exome sequencing were performed on probands (and available parents and siblings) from 284 families with individuals who had isolated polymicrogyria or polymicrogyria as part of a clinical syndrome and no genetic diagnosis at time of referral from clinic, with sequencing from 275 families passing quality control.

Main Outcomes and Measures

The number of families in whom genetic sequencing yielded a molecular diagnosis that explained the polymicrogyria in the family. Secondarily, the relative frequency of different genetic causes of polymicrogyria and whether specific genetic causes were associated with co-occurring head size changes were also analyzed.

Results

In 32.7% (90 of 275) of polymicrogyria-affected families, genetic variants were identified that provided satisfactory molecular explanations. Known genes most frequently implicated by polymicrogyria-associated variants in this cohort were PIK3R2, TUBB2B, COL4A1, and SCN3A. Six candidate novel polymicrogyria genes were identified or confirmed: de novo missense variants in PANX1, QRICH1, and SCN2A and compound heterozygous variants in TMEM161B, KIF26A, and MAN2C1, each with consistent genotype-phenotype relationships in multiple families.

Conclusions and Relevance

This study's findings reveal a higher than previously recognized rate of identifiable genetic causes, specifically of channelopathies, in individuals with polymicrogyria and support the utility of exome sequencing for families affected with polymicrogyria.

Polymicrogyria: epidemiology, imaging, and clinical aspects in a population-based cohort

Polymicrogyria is estimated to be one of the most common brain malformations, accounting for ∼16% of malformations of cortical development. However, the prevalence and incidence of polymicrogyria is unknown. Our aim was to estimate the prevalence, incidence rate, neuroimaging diversity, aetiology, and clinical phenotype of polymicrogyria in a population-based paediatric cohort. We performed a systematic search of MRI scans at neuroradiology department databases in Stockholm using the keyword polymicrogyria. The study population included all children living in the Stockholm region born from January 2004 to June 2021 with polymicrogyria. Information on the number of children living in the region during 2004-21 was collected from records from Statistics Sweden, whereas the number of births for each year during the study period was collected from the Swedish Medical Birth Register. All MRI scans were re-evaluated, and malformations were classified by a senior paediatric neuroradiologist. The prevalence and yearly incidence were estimated. Clinical data were collected from medical records. A total of 109 patients with polymicrogyria were included in the study. The overall polymicrogyria prevalence in Stockholm was 2.3 per 10 000 children, and the overall estimated yearly incidence between 2004 and 2020 was 1.9 per 10 000 person-years. The most common polymicrogyria distribution was in the frontal lobe (71%), followed by the parietal lobe (37%). Polymicrogyria in the peri-sylvian region was observed in 53%. Genetic testing was performed in 90 patients revealing pathogenic variants in 32%. Additionally, 12% had variants of uncertain significance. Five patients had a confirmed congenital infection, and in six individuals, the cause of polymicrogyria was assumed to be vascular. Epilepsy was diagnosed in 54%. Seizure onset during the first year of life was observed in 44%. The most common seizure types were focal seizures with impaired awareness, followed by epileptic spasms. Thirty-three of 59 patients with epilepsy (56%) were treated with more than two anti-seizure medications, indicating that pharmacoresistant epilepsy is common in polymicrogyria patients. Neurodevelopmental symptoms were observed in 94% of the individuals. This is the first population-based study on polymicrogyria prevalence and incidence. Confirmed genetic aetiology was present in one-third of individuals with polymicrogyria. Epilepsy was common in this patient group, and the majority had pharmacoresistant epilepsy. These findings increase our knowledge about polymicrogyria and will help in counselling patients and their families.

TUBB3 and KIF21A in neurodevelopment and disease

Neuronal migration and axon growth and guidance require precise control of microtubule dynamics and microtubule-based cargo transport. TUBB3 encodes the neuronal-specific β-tubulin isotype III, TUBB3, a component of neuronal microtubules expressed throughout the life of central and peripheral neurons. Human pathogenic TUBB3 missense variants result in altered TUBB3 function and cause errors either in the growth and guidance of cranial and, to a lesser extent, central axons, or in cortical neuronal migration and organization, and rarely in both. Moreover, human pathogenic missense variants in KIF21A, which encodes an anterograde kinesin motor protein that interacts directly with microtubules, alter KIF21A function and cause errors in cranial axon growth and guidance that can phenocopy TUBB3 variants. Here, we review reported TUBB3 and KIF21A variants, resulting phenotypes, and corresponding functional studies of both wildtype and mutant proteins. We summarize the evidence that, in vitro and in mouse models, loss-of-function and missense variants can alter microtubule dynamics and microtubule-kinesin interactions. Lastly, we highlight additional studies that might contribute to our understanding of the relationship between specific tubulin isotypes and specific kinesin motor proteins in health and disease.

Impact of Etiology on Seizure and Quantitative Functional Outcomes in Children with Cerebral Palsy and Medically Intractable Epilepsy Undergoing Hemispherotomy/Hemispherectomy

OBJECTIVE

To compare functional and seizure outcomes in children with vascular and dysplastic etiologies of cerebral palsy and medically intractable epilepsy following functional hemispherotomy or anatomic hemispherectomy.

METHODS

Consecutive patients satisfying inclusion criteria from 07/01/2015 to 12/01/2019 were reviewed for demographic data and seizure (Engel classification) and functional (Functional Independence Measure for Children) outcomes.

RESULTS

After a mean follow-up of 2 years 8 months (1 year 2 months), 11 of 18 patients achieved post-operative seizure freedom without significant difference between vascular (5/7) and dysplastic (6/11) etiologies (P = 0.64). Functional assessments were completed for 15 of 18 of subjects, split comparably between groups. Mean change in the Functional Independence Measure for Children from pre-operative baseline to inpatient rehabilitation admission (vascular, -35.3 [13.2]; malformation of cortical development{MCD}, -34.5 [25.0]; P = 0.69), inpatient rehabilitation admission to discharge (vascular, 18.7 [9.0]; MCD, 20.8 [11.4]; P = 0.60), and pre-operative evaluation to clinic follow-up (vascular, -7.6 [9.7]; MCD, -3.6 [19.3]; P = 0.61) did not differ between groups.

CONCLUSION

Quantitative functional and seizure outcomes following functional hemispherotomy or anatomic hemispherectomy did not differ significantly between vascular and dysplastic etiologies of cerebral palsy and medically intractable epilepsy in this study. Hemispheric surgery resulted in minor functional declines from baseline following comprehensive multidisciplinary therapy.

Cat-Ear-Line: A Sonographic Sign of Cortical Development?

OBJECTIVES

Diagonal echogenic lines outside the lateral ventricle have often been observed in the anterior coronal planes of the normal fetal brain by neurosonography. We have observed abnormal shapes of these echogenic lines in cases of malformation of cortical development (MCD). We named the ultrasound finding "cat-ear-line" (CEL). This study aimed to examine how and when CEL develops in normal cases compared with MCD cases.

METHODS

We retrospectively examined the fetal brain volume dataset acquired through transvaginal 3D neurosonography of 575 control cases and 39 MCD cases from 2014 to 2020. We defined CEL as the hyperechogenic continuous lines through subplate (SP) and intermediate zone (IZ), pre-CEL as the lines that existed only within the SP, and abnormal CEL as a mass-like or mosaic shadow-like structure that existed across the SP and IZ. All fetuses in the MCD group had some neurosonographic abnormalities and were ultimately diagnosed with MCD.

RESULTS

The CEL was detected in 97.9% (369/377) of the control group from 19 to 30 weeks. The CEL visualization rate of the MCD group in the same period was 40.0% (14/35) which was significantly lower than that of the control group (P < .001).

CONCLUSIONS

From this study, it appears that the CEL is an ultrasound finding observed at and beyond 19 weeks in a normally developing fetus. In some MCD cases, pre-CEL at and beyond 19 weeks or abnormal CEL was observed. Maldeveloped CEL at mid-trimester may help identify cases at-risk of subsequent MCD.

Shaping the cerebral cortex by cellular crosstalk

The cerebral cortex is the brain's outermost layer. It is responsible for processing motor and sensory information that support high-level cognitive abilities and shape personality. Its development and functional organization strongly rely on cell communication that is established via an intricate system of diffusible signals and physical contacts during development. Interfering with this cellular crosstalk can cause neurodevelopmental disorders. Here, we review how crosstalk between migrating cells and their environment influences cerebral cortex development, ranging from neurogenesis to synaptogenesis and assembly of cortical circuits.

Heterogeneous growth of the insula shapes the human brain

The human cerebrum consists of a precise and stereotyped arrangement of lobes, primary gyri, and connectivity that underlies human cognition [P. Rakic, Nat. Rev. Neurosci. 10, 724-735 (2009)]. The development of this arrangement is less clear. Current models explain individual primary gyrification but largely do not account for the global configuration of the cerebral lobes [T. Tallinen, J. Y. Chung, J. S. Biggins, L. Mahadevan, Proc. Natl. Acad. Sci. U.S.A. 111, 12667-12672 (2014) and D. C. Van Essen, Nature 385, 313-318 (1997)]. The insula, buried in the depths of the Sylvian fissure, is unique in terms of gyral anatomy and size. Here, we quantitatively show that the insula has unique morphology and location in the cerebrum and that these key differences emerge during fetal development. Finally, we identify quantitative differences in developmental migration patterns to the insula that may underlie these differences. We calculated morphologic data in the insula and other lobes in adults (N = 107) and in an in utero fetal brain atlas (N = 81 healthy fetuses). In utero, the insula grows an order of magnitude slower than the other lobes and demonstrates shallower sulci, less curvature, and less surface complexity both in adults and progressively throughout fetal development. Spherical projection analysis demonstrates that the lenticular nuclei obstruct 60 to 70% of radial pathways from the ventricular zone (VZ) to the insula, forcing a curved migration to the insula in contrast to a direct radial pathway. Using fetal diffusion tractography, we identify radial glial fascicles that originate from the VZ and curve around the lenticular nuclei to form the insula. These results confirm existing models of radial migration to the cortex and illustrate findings that suggest differential insular and cerebral development, laying the groundwork to understand cerebral malformations and insular function and pathologies.

Excitatory somatostatin interneurons in the dentate gyrus drive a widespread seizure network in cortical dysplasia

Seizures due to cortical dysplasia are notorious for their poor prognosis even with medications and surgery, likely due to the widespread seizure network. Previous studies have primarily focused on the disruption of dysplastic lesions, rather than remote regions such as the hippocampus. Here, we first quantified the epileptogenicity of the hippocampus in patients with late-stage cortical dysplasia. We further investigated the cellular substrates leading to the epileptic hippocampus, using multiscale tools including calcium imaging, optogenetics, immunohistochemistry and electrophysiology. For the first time, we revealed the role of hippocampal somatostatin-positive interneurons in cortical dysplasia-related seizures. Somatostatin-positive were recruited during cortical dysplasia-related seizures. Interestingly, optogenetic studies suggested that somatostatin-positive interneurons paradoxically facilitated seizure generalization. By contrast, parvalbumin-positive interneurons retained an inhibitory role as in controls. Electrophysiological recordings and immunohistochemical studies revealed glutamate-mediated excitatory transmission from somatostatin-positive interneurons in the dentate gyrus. Taken together, our study reveals a novel role of excitatory somatostatin-positive neurons in the seizure network and brings new insights into the cellular basis of cortical dysplasia.

Case report: Genotype and phenotype of DYNC1H1-related malformations of cortical development: a case report and literature review

Background

Mutations in the dynein cytoplasmic 1 heavy chain 1 (DYNC1H1) gene are linked to malformations of cortical development (MCD), which may be accompanied by central nervous system (CNS) manifestations. Here, we present the case of a patient with MCD harboring a variant of DYNC1H1 and review the relevant literature to explore genotype-phenotype relationships.

Case presentation

A girl having infantile spasms, was unsuccessfully administered multiple antiseizure medications and developed drug-resistant epilepsy. Brain magnetic resonance imaging (MRI) at 14 months-of-age revealed pachygyria. At 4 years-of-age, the patient exhibited severe developmental delay and mental retardation. A de novo heterozygous mutation (p.Arg292Trp) in the DYNC1H1 gene was identified. A search of multiple databases, including PubMed and Embase, using the search strategy DYNC1H1 AND [malformations of cortical development OR seizure OR intellectual OR clinical symptoms] up to June 2022, identified 129 patients from 43 studies (including the case presented herein). A review of these cases showed that patients with DYNC1H1-related MCD had higher risks of epilepsy (odds ratio [OR] = 33.67, 95% confidence interval [CI] = 11.59, 97.84) and intellectual disability/developmental delay (OR = 52.64, 95% CI = 16.27, 170.38). Patients with the variants in the regions encoding the protein stalk or microtubule-binding domain had the most prevalence of MCD (95%).

Conclusion

MCD, particularly pachygyria, is a common neurodevelopmental disorder in patients with DYNC1H1 mutations. Literature searches reveales that most (95%) patients who carried mutations in the protein stalk or microtubule binding domains exhibited DYNC1H1-related MCD, whereas almost two-thirds of patients (63%) who carried mutations in the tail domain did not display MCD. Patients with DYNC1H1 mutations may experience central nervous system (CNS) manifestations due to MCD.