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Brain : a Journal of Neurology Apr 2023Understanding the exact molecular mechanisms involved in the aetiology of epileptogenic pathologies with or without tumour activity is essential for improving treatment...
Understanding the exact molecular mechanisms involved in the aetiology of epileptogenic pathologies with or without tumour activity is essential for improving treatment of drug-resistant focal epilepsy. Here, we characterize the landscape of somatic genetic variants in resected brain specimens from 474 individuals with drug-resistant focal epilepsy using deep whole-exome sequencing (>350×) and whole-genome genotyping. Across the exome, we observe a greater number of somatic single-nucleotide variants in low-grade epilepsy-associated tumours (7.92 ± 5.65 single-nucleotide variants) than in brain tissue from malformations of cortical development (6.11 ± 4 single-nucleotide variants) or hippocampal sclerosis (5.1 ± 3.04 single-nucleotide variants). Tumour tissues also had the largest number of likely pathogenic variant carrying cells. low-grade epilepsy-associated tumours had the highest proportion of samples with one or more somatic copy-number variants (24.7%), followed by malformations of cortical development (5.4%) and hippocampal sclerosis (4.1%). Recurring somatic whole chromosome duplications affecting Chromosome 7 (16.8%), chromosome 5 (10.9%), and chromosome 20 (9.9%) were observed among low-grade epilepsy-associated tumours. For germline variant-associated malformations of cortical development genes such as TSC2, DEPDC5 and PTEN, germline single-nucleotide variants were frequently identified within large loss of heterozygosity regions, supporting the recently proposed 'second hit' disease mechanism in these genes. We detect somatic variants in 12 established lesional epilepsy genes and demonstrate exome-wide statistical support for three of these in the aetiology of low-grade epilepsy-associated tumours (e.g. BRAF) and malformations of cortical development (e.g. SLC35A2 and MTOR). We also identify novel significant associations for PTPN11 with low-grade epilepsy-associated tumours and NRAS Q61 mutated protein with a complex malformation of cortical development characterized by polymicrogyria and nodular heterotopia. The variants identified in NRAS are known from cancer studies to lead to hyperactivation of NRAS, which can be targeted pharmacologically. We identify large recurrent 1q21-q44 duplication including AKT3 in association with focal cortical dysplasia type 2a with hyaline astrocytic inclusions, another rare and possibly under-recognized brain lesion. The clinical-genetic analyses showed that the numbers of somatic single-nucleotide variant across the exome and the fraction of affected cells were positively correlated with the age at seizure onset and surgery in individuals with low-grade epilepsy-associated tumours. In summary, our comprehensive genetic screen sheds light on the genome-scale landscape of genetic variants in epileptic brain lesions, informs the design of gene panels for clinical diagnostic screening and guides future directions for clinical implementation of epilepsy surgery genetics.
Topics: Humans; Epilepsy; Brain; Drug Resistant Epilepsy; Genomics; Malformations of Cortical Development; Epilepsies, Partial; Nucleotides
PubMed: 36226386
DOI: 10.1093/brain/awac376 -
Annals of Indian Academy of Neurology 2022Polymicrogyria (PMG) is a relatively common complex malformation with cortical development, characterized by an exorbitant number of abnormally tiny gyri separated by...
Polymicrogyria (PMG) is a relatively common complex malformation with cortical development, characterized by an exorbitant number of abnormally tiny gyri separated by shallow sulci. It is a neuronal migration disorder. Familial cases of PMG and the manifestation of PMG in patients with chromosomal aberrations and mutations indicate their important role of genetics in this disorder. The highly stereotyped and well-conserved nature of the cortical folding pattern in humans is suggestive of the genetic regulation of the process. The chromosomal abnormalities observed in PMG include deletions, duplications, chromosomal rearrangements, and aneuploidies. Two of the most common deletions in PMG are 22q11.2 deletion and 1p36 deletion. Further, mutations in several genes such as , and are known to be associated with PMG. Intriguingly, these genes are responsible only for a small number of cases of PMG. The protein products of these genes are implicated in diverse molecular and cellular functions. Taken together, PMG could be the result of the disruption of several biological pathways. Different modes of Mendelian inheritance and non-Mendelian inheritance are seen in PMG. We have suggested a gene panel that can be used for the detection of malformations of cortical development.
PubMed: 36211152
DOI: 10.4103/aian.aian_97_22 -
Neurobiology of Disease Nov 2022Malformations of cortical development (MCDs) are common causes of drug-resistant epilepsy. The mechanisms underlying the associated epileptogenesis and ictogenesis... (Review)
Review
OBJECTIVES
Malformations of cortical development (MCDs) are common causes of drug-resistant epilepsy. The mechanisms underlying the associated epileptogenesis and ictogenesis remain poorly elucidated. EEG can help in understanding these mechanisms. We systematically reviewed studies reporting scalp or intracranial EEG features of MCDs to characterise interictal and seizure-onset EEG patterns across different MCD types.
METHODS
We conducted a systematic review in accordance with PRISMA guidelines. MEDLINE, PubMed, and Cochrane databases were searched for studies describing interictal and seizure-onset EEG patterns in MCD patients. A classification framework was implemented to group EEG features into 20 predefined patterns, comprising nine interictal (five, scalp EEG; four, intracranial EEG) and 11 seizure-onset (five, scalp EEG; six, intracranial EEG) patterns. Logistic regression was used to estimate the odds ratios (OR) of each seizure-onset pattern being associated with specific MCD types.
RESULTS
Our search yielded 1682 studies, of which 27 comprising 936 MCD patients were included. Of the nine interictal EEG patterns, five (three, scalp EEG; two, intracranial EEG) were detected in ≥2 MCD types, while four (rhythmic epileptiform discharges type 1 and type 2 on scalp EEG; repetitive bursting spikes and sporadic spikes on intracranial EEG) were seen only in focal cortical dysplasia (FCD). Of the 11 seizure-onset patterns, eight (three, scalp EEG; five, intracranial EEG) were found in ≥2 MCD types, whereas three were observed only in FCD (suppression on scalp EEG; delta brush on intracranial EEG) or tuberous sclerosis complex (TSC; focal fast wave on scalp EEG). Among scalp EEG seizure-onset patterns, paroxysmal fast activity (OR = 0.13; 95% CI: 0.03-0.53; p = 0.024) and repetitive epileptiform discharges (OR = 0.18; 95% CI: 0.05-0.61; p = 0.036) were less likely to occur in TSC than FCD. Among intracranial EEG seizure-onset patterns, low-voltage fast activity was more likely to be detected in heterotopia (OR = 19.3; 95% CI: 6.22-60.1; p < 0.001), polymicrogyria (OR = 6.70; 95% CI: 2.25-20.0; p = 0.004) and TSC (OR = 4.27; 95% CI: 1.88-9.70; p = 0.005) than FCD.
SIGNIFICANCE
Different MCD types can share similar interictal or seizure-onset EEG patterns, reflecting common underlying biological mechanisms. However, selected EEG patterns appear to point to distinct MCD types, suggesting certain differences in their neuronal networks.
Topics: Humans; Electrocorticography; Electroencephalography; Magnetic Resonance Imaging; Malformations of Cortical Development; Seizures; Tuberous Sclerosis
PubMed: 36165814
DOI: 10.1016/j.nbd.2022.105863 -
Seizure Oct 2022
Topics: Electroencephalography; Epilepsy; Humans; Magnetic Resonance Imaging; Malformations of Cortical Development; Polymicrogyria
PubMed: 36103786
DOI: 10.1016/j.seizure.2022.09.005 -
Human Molecular Genetics Jan 2023DEPDC5 (DEP Domain-Containing Protein 5) encodes an inhibitory component of the mammalian target of rapamycin (mTOR) pathway and is commonly implicated in sporadic and...
DEPDC5 (DEP Domain-Containing Protein 5) encodes an inhibitory component of the mammalian target of rapamycin (mTOR) pathway and is commonly implicated in sporadic and familial focal epilepsies, both non-lesional and in association with focal cortical dysplasia. Germline pathogenic variants are typically heterozygous and inactivating. We describe a novel phenotype caused by germline biallelic missense variants in DEPDC5. Cases were identified clinically. Available records, including magnetic resonance imaging and electroencephalography, were reviewed. Genetic testing was performed by whole exome and whole-genome sequencing and cascade screening. In addition, immunohistochemistry was performed on skin biopsy. The phenotype was identified in nine children, eight of which are described in detail herein. Six of the children were of Irish Traveller, two of Tunisian and one of Lebanese origin. The Irish Traveller children shared the same DEPDC5 germline homozygous missense variant (p.Thr337Arg), whereas the Lebanese and Tunisian children shared a different germline homozygous variant (p.Arg806Cys). Consistent phenotypic features included extensive bilateral polymicrogyria, congenital macrocephaly and early-onset refractory epilepsy, in keeping with other mTOR-opathies. Eye and cardiac involvement and severe neutropenia were also observed in one or more patients. Five of the children died in infancy or childhood; the other four are currently aged between 5 months and 6 years. Skin biopsy immunohistochemistry was supportive of hyperactivation of the mTOR pathway. The clinical, histopathological and genetic evidence supports a causal role for the homozygous DEPDC5 variants, expanding our understanding of the biology of this gene.
Topics: Humans; Mutation; Polymicrogyria; GTPase-Activating Proteins; TOR Serine-Threonine Kinases; Epilepsies, Partial; Megalencephaly; Epileptic Syndromes
PubMed: 36067010
DOI: 10.1093/hmg/ddac225 -
BMC Neurology Aug 2022Polymicrogyria refers to the disruption of normal cerebral cortical development late in neuronal migration or in early cortical organization. Although patients with...
BACKGROUND
Polymicrogyria refers to the disruption of normal cerebral cortical development late in neuronal migration or in early cortical organization. Although patients with polymicrogyria feature relatively favorable motor outcomes, polymicrogyric lesions accompanied by extensive unilateral hemispheric atrophy and ipsilateral brainstem atrophy may induce poorer motor outcomes. This study is the first to employ transcranial magnetic stimulation (TMS) and diffusion tensor imaging (DTI) to characterize changes to motor organization and white matter tracts induced by polymicrogyria.
CASE PRESENTATION
We document a case of a 16-year-old female with left hemiplegic unilateral polymicrogyria associated with ipsilateral brainstem atrophy. Magnetic resonance imaging (MRI) of the brain revealed unilateral polymicrogyria to have affected anterior cortical areas, including the perisylvian region on the right side. The right halves of the brain and brainstem were significantly smaller than the left halves. Although our patient was found to exhibit cortical dysplasia of the right frontoparietal and sylvian fissure areas and a decreased number of fibers in the corticospinal tract (CST) of the affected side on DTI, the connectivity of the CST was preserved up to the motor cortex. We also measured the cross-sectional area of the CST at the level of the pons. In TMS, contralateral motor evoked potentials (MEPs) were evoked from both hands, but the ipsilateral MEPs were evoked only from the left hand. The left hand featured a long duration, polyphasic pattern of contralateral MEPs.
DISCUSSION AND CONCLUSION
TMS revealed that the concurrent bilateral projections to the paretic hand from the affected and unaffected hemispheres and contralateral MEPs in the paretic hand were polyphasic, indicating delayed electrophysiological maturation or a pathologic condition of the corticospinal motor pathways. In DTI, the cross-sectional area of the CST at the level of the pons on the affected side was smaller than that on the unaffected side. These DTI findings reveal an inadequate CST volume. Despite extensive brain malformation and ipsilateral brainstem atrophy, our patient had less severe motor dysfunction and presented with involuntary mirror movements. Mirror movements in the paretic hand are considered to indicate ipsilateral corticospinal projections from the unaffected hemisphere and may suggest favorable motor outcomes in early brain injury.
Topics: Adolescent; Atrophy; Brain Stem; Diffusion Tensor Imaging; Evoked Potentials, Motor; Female; Functional Laterality; Humans; Motor Cortex; Movement Disorders; Nervous System Malformations; Polymicrogyria; Pyramidal Tracts; Transcranial Magnetic Stimulation
PubMed: 35982397
DOI: 10.1186/s12883-022-02795-y -
Congenital Anomalies Nov 2022Congenital cytomegalovirus (CMV) infection can cause severe neurological sequelae or even fetal death. We present a 17-year-old pregnant woman with fetal CMV infection,...
Congenital cytomegalovirus (CMV) infection can cause severe neurological sequelae or even fetal death. We present a 17-year-old pregnant woman with fetal CMV infection, leading to voluntary termination of pregnancy. Fetopsy demonstrated a brainstem hemorrhage and focal polymicrogyria. CMV inclusions were observed in the lung, liver, thyroid, pancreas, kidneys, adrenal, placenta, and central nervous system. Intracranial hemorrhage is a rare finding in the context of congenital CMV infection, with isolated brainstem hemorrhage being an exceptional form of presentation. Polymicrogyria appears to be a more frequent finding, although its actual incidence is unknown. Future studies are needed to determine the causal association.
Topics: Pregnancy; Female; Humans; Adolescent; Polymicrogyria; Cytomegalovirus Infections; Pregnancy Complications, Infectious; Brain Stem; Hemorrhage
PubMed: 35941838
DOI: 10.1111/cga.12488 -
British Journal of Clinical Pharmacology Dec 2022To evaluate the number and nature of reported congenital malformations (CMs) after intrauterine exposure to non-tumour necrosis factor inhibitor biologics (non-TNFi...
AIMS
To evaluate the number and nature of reported congenital malformations (CMs) after intrauterine exposure to non-tumour necrosis factor inhibitor biologics (non-TNFi biologics) compared to certolizumab pegol (CZP).
METHODS
A retrospective comparative study was conducted in the EudraVigilance (EV) database. A safe biologic (CZP) was considered as the reference group. Odds ratios (ORs) for CMs were calculated for each non-TNFi biologic (including abatacept, anakinra, belimumab, ixekizumab, rituximab, secukinumab, tocilizumab, ustekinumab and vedolizumab), versus CZP (quantitative assessment). Then, CM patterns were reviewed in consultation with a clinical geneticist (qualitative assessment).
RESULTS
ORs were not statistically significant except for belimumab and vedolizumab (similar in magnitude). Except for vedolizumab, no specific CM patterns were observed for the included non-TNFi biologics. Three cases of corpus callosum agenesis (CCA) were identified for vedolizumab (versus none in CZP and other investigated non-TNFi biologics). Two of the CCA cases were associated with other neurological CMs (one cerebral ventriculomegaly with microcephaly and one polymicrogyria). This may indicate that these CCAs are related to undiagnosed genetic alterations or are associated with the underlying maternal disease, although a definite relationship with vedolizumab exposure cannot be ruled out.
CONCLUSION
No special safety signal was identified regarding the occurrence of CMs after exposure to abatacept (n = 64), anakinra (n = 20), belimumab (n = 93), ixekizumab (n = 29), rituximab (n = 57), secukinumab (n = 128), tocilizumab (n = 124) and ustekinumab (n = 215). Regarding observed CCAs in the vedolizumab group (n = 113), no firm conclusions can be made based on available information.
Topics: Humans; Abatacept; Antirheumatic Agents; Arthritis, Rheumatoid; Biological Products; Certolizumab Pegol; Interleukin 1 Receptor Antagonist Protein; Necrosis; Retrospective Studies; Rituximab; Tumor Necrosis Factor-alpha; Ustekinumab
PubMed: 35894810
DOI: 10.1111/bcp.15471