Focal Cortical Dysplasia Type Research Articles

Phase-amplitude coupling between low- and high-frequency activities as preoperative biomarker of focal cortical dysplasia subtypes

ObjectiveTo evaluate whether ictal phase-amplitude coupling (PAC) between high-frequency activity and low-frequency activity could be used as a preoperative biomarker of Focal Cortical Dysplasia (FCD) subtypes. We hypothesize that FCD seizures present unique PAC characteristics that may be linked to their specific histopathological features. MethodsWe retrospectively examined 12 children with FCD and refractory epilepsy who underwent successful epilepsy surgery. We identified ictal onsets recorded with stereo-EEG. We estimated the strength of PAC between low-frequencies and high-frequencies for each seizure by means of modulation index. Generalized mixed effect models and receiver operating characteristic (ROC) curve analysis were used to test the association between ictal PAC and FCD subtypes. ResultsIctal PAC was significantly higher in patients with FCD type II compared to type I, only on SOZ-electrodes (p < 0.005). No differences in ictal PAC were found on non-SOZ electrodes. Pre-ictal PAC registered on SOZ electrodes predicted FCD histopathology with a classification accuracy > 0.9 (p < 0.05). ConclusionsThe correlations between histopathology and neurophysiology provide evidence for the contribution of ictal PAC as a preoperative biomarker of FCD subtypes. SignificanceDeveloped into a proper clinical application, such a technique may help improve clinical management and facilitate the prediction of surgical outcome in patients with FCD undergoing stereo-EEG monitoring.

Transcriptome analyses of the cortex and white matter of focal cortical dysplasia type II: Insights into pathophysiology and tissue characterization.

Focal cortical dysplasia (FCD) is a common cause of pharmacoresistant epilepsy. According to the 2022 International League Against Epilepsy classification, FCD type II is characterized by dysmorphic neurons (IIa and IIb) and may be associated with balloon cells (IIb). We present a multicentric study to evaluate the transcriptomes of the gray and white matters of surgical FCD type II specimens. We aimed to contribute to pathophysiology and tissue characterization. We investigated FCD II (a and b) and control samples by performing RNA-sequencing followed by immunohistochemical validation employing digital analyses. We found 342 and 399 transcripts differentially expressed in the gray matter of IIa and IIb lesions compared to controls, respectively. Cholesterol biosynthesis was among the main enriched cellular pathways in both IIa and IIb gray matter. Particularly, the genes HMGCS1, HMGCR, and SQLE were upregulated in both type II groups. We also found 12 differentially expressed genes when comparing transcriptomes of IIa and IIb lesions. Only 1 transcript (MTRNR2L12) was significantly upregulated in FCD IIa. The white matter in IIa and IIb lesions showed 2 and 24 transcripts differentially expressed, respectively, compared to controls. No enriched cellular pathways were detected. GPNMB, not previously described in FCD samples, was upregulated in IIb compared to IIa and control groups. Upregulations of cholesterol biosynthesis enzymes and GPNMB genes in FCD groups were immunohistochemically validated. Such enzymes were mainly detected in both dysmorphic and normal neurons, whereas GPNMB was observed only in balloon cells. Overall, our study contributed to identifying cortical enrichment of cholesterol biosynthesis in FCD type II, which may correspond to a neuroprotective response to seizures. Moreover, specific analyses in either the gray or the white matter revealed upregulations of MTRNR2L12 and GPNMB, which might be potential neuropathological biomarkers of a cortex chronically exposed to seizures and of balloon cells, respectively.

An integrated genetic analysis of epileptogenic brain malformed lesions

Focal cortical dysplasia is the most common malformation during cortical development, sometimes excised by epilepsy surgery and often caused by somatic variants of the mTOR pathway genes. In this study, we performed a genetic analysis of epileptogenic brain malformed lesions from 64 patients with focal cortical dysplasia, hemimegalencephy, brain tumors, or hippocampal sclerosis. Targeted sequencing, whole-exome sequencing, and single nucleotide polymorphism microarray detected four germline and 35 somatic variants, comprising three copy number variants and 36 single nucleotide variants and indels in 37 patients. One of the somatic variants in focal cortical dysplasia type IIB was an in-frame deletion in MTOR, in which only gain-of-function missense variants have been reported. In focal cortical dysplasia type I, somatic variants of MAP2K1 and PTPN11 involved in the RAS/MAPK pathway were detected. The in-frame deletions of MTOR and MAP2K1 in this study resulted in the activation of the mTOR pathway in transiently transfected cells. In addition, the PTPN11 missense variant tended to elongate activation of the mTOR or RAS/MAPK pathway, depending on culture conditions. We demonstrate that epileptogenic brain malformed lesions except for focal cortical dysplasia type II arose from somatic variants of diverse genes but were eventually linked to the mTOR pathway.

Diagnostic Accuracy of Epilepsy-dedicated MRI with Post-processing

PurposeTo evaluate the diagnostic accuracy of epilepsy-dedicated 3 Tesla MRI including post-processing by correlating MRI, histopathology, and postsurgical seizure outcomes.Methods3 Tesla-MRI including a magnetization-prepared two rapid acquisition gradient echo (MP2RAGE) sequence for post-processing using the morphometric analysis program MAP was acquired in 116 consecutive patients with drug-resistant focal epilepsy undergoing resection surgery. The MRI, histopathology reports and postsurgical seizure outcomes were recorded from the patient’s charts.ResultsThe MRI and histopathology were concordant in 101 and discordant in 15 patients, 3 no hippocampal sclerosis/gliosis only lesions were missed on MRI and 1 of 28 focal cortical dysplasia (FCD) type II associated with a glial scar was considered a glial scar only on MRI. In another five patients, MRI was suggestive of FCD, the histopathology was uneventful but patients were seizure-free following surgery. The MRI and histopathology were concordant in 20 of 21 glioneuronal tumors, 6 cavernomas, and 7 glial scars. Histopathology was negative in 10 patients with temporal lobe epilepsy, 4 of them had anteroinferior meningoencephaloceles. Engel class IA outcome was reached in 71% of patients.ConclusionThe proposed MRI protocol is highly accurate. No hippocampal sclerosis/gliosis only lesions are typically MRI negative. Small MRI positive FCD can be histopathologically missed, most likely due to sampling errors resulting from insufficient harvesting of tissue.

Multimodal mapping of regional brain vulnerability to focal cortical dysplasia.

Focal cortical dysplasia (FCD) type II is a highly epileptogenic developmental malformation and a common cause of surgically treated drug-resistant epilepsy. While clinical observations suggest frequent occurrence in the frontal lobe, mechanisms for such propensity remain unexplored. Here, we hypothesized that cortex-wide spatial associations of FCD distribution with cortical cytoarchitecture, gene expression and organizational axes may offer complementary insights into processes that predispose given cortical regions to harbour FCD. We mapped the cortex-wide MRI distribution of FCDs in 337 patients collected from 13 sites worldwide. We then determined its associations with (i) cytoarchitectural features using histological atlases by Von Economo and Koskinas and BigBrain; (ii) whole-brain gene expression and spatiotemporal dynamics from prenatal to adulthood stages using the Allen Human Brain Atlas and PsychENCODE BrainSpan; and (iii) macroscale developmental axes of cortical organization. FCD lesions were preferentially located in the prefrontal and fronto-limbic cortices typified by low neuron density, large soma and thick grey matter. Transcriptomic associations with FCD distribution uncovered a prenatal component related to neuroglial proliferation and differentiation, likely accounting for the dysplastic makeup, and a postnatal component related to synaptogenesis and circuit organization, possibly contributing to circuit-level hyperexcitability. FCD distribution showed a strong association with the anterior region of the antero-posterior axis derived from heritability analysis of interregional structural covariance of cortical thickness, but not with structural and functional hierarchical axes. Reliability of all results was confirmed through resampling techniques. Multimodal associations with cytoarchitecture, gene expression and axes of cortical organization indicate that prenatal neurogenesis and postnatal synaptogenesis may be key points of developmental vulnerability of the frontal lobe to FCD. Concordant with a causal role of atypical neuroglial proliferation and growth, our results indicate that FCD-vulnerable cortices display properties indicative of earlier termination of neurogenesis and initiation of cell growth. They also suggest a potential contribution of aberrant postnatal synaptogenesis and circuit development to FCD epileptogenicity.

Usefulness of Intraoperative ultrasound for cortical dysplasia type I treatment - A single-center experience.

Focal cortical dysplasias (FCD) cause a subgroup of malformations of cortical development that has been closely linked to cause drug intractable epilepsy. Attaining adequate and safe resection of the dysplastic lesion has proved to be a viable option to archive meaningful seizure control. Of the three types of FCD (types I, II, and III), type I has the least detectable architectural and radiological abnormalities. This makes it challenging (preoperatively and intraoperatively) to achieve adequate resection. Intraoperatively, ultrasound navigation has proven an effective tool during the resection of these lesions. We evaluate our institutional experience in surgical management of FCD type I using intraoperative ultrasound (IoUS). Our work is a retrospective and descriptive study, where we analyzed patients diagnosed with refractory epilepsy who underwent IoUS-guided epileptogenic tissue resection. The surgical cases analyzed were from January 2015 to June 2020 at the Federal Center of Neurosurgery, Tyumen, only patients with histological confirmation of postoperative CDF type I were included in the study. Of the 11 patients with histologically diagnosed FCD type I, 81.8% of the patients postoperatively had a significant reduction in seizure frequency (Engel outcome I-II). IoUS is a critical tool for detecting and delineating FCD type I lesions, which is necessary for effective post-epilepsy surgery results.

Diffusion tensor imaging discriminates focal cortical dysplasia from normal brain parenchyma and differentiates between focal cortical dysplasia types

ObjectivesAlthough diffusion tensor imaging (DTI) may facilitate the identification of cytoarchitectural changes associated with focal cortical dysplasia (FCD), the predominant aetiology of paediatric structural epilepsy, its potential has thus far remained unexplored in this population. Here, we investigated whether DTI indices can differentiate FCD from contralateral brain parenchyma (CBP) and whether clinical features affect these indices.MethodsIn this single-centre, retrospective study, we considered children and adolescents with FCD-associated epilepsy who underwent brain magnetic resonance (MRI), including DTI. Fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity, and radial diffusivity, were calculated in both FCD and CBP. The DTI indices best discriminating between FCD and CBP were subsequently used to assess the link between DTI and selected clinical and lesion-related parameters.ResultsWe enrolled 32 patients (20 male; median age at MRI 4 years), including 15 with histologically confirmed FCD. FA values were lower (p = 0.03), whereas MD values were higher in FCD than in CBP (p = 0.04). The difference in FA values between FCD and CBP was more pronounced for a positive vs. negative history of status epilepticus (p = 0.004). Among histologically confirmed cases, the difference in FA values between FCD and CBP was more pronounced for type IIb versus type I FCD (p = 0.03).ConclusionsFA and MD discriminate between FCD and CBP, while FA differentiates between FCD types. Status epilepticus increases differences in FA, potentially reflecting changes induced in the brain. Our findings support the potential of DTI to serve as a non-invasive biomarker to characterise FCD in the paediatric population.

Ultra-Low Level Somatic Mutations and Structural Variations in Focal Cortical Dysplasia Type II.

Brain somatic mutations in mTOR pathway genes are a major genetic etiology of focal cortical dysplasia type II (FCDII). Despite a greater ability to detect low-level somatic mutations in the brain by deep sequencing and analytics, about 40% of cases remain genetically unexplained. We included 2 independent cohorts consisting of 21 patients with mutation-negative FCDII without apparent mutations on conventional deep sequencing of bulk brain. To find ultra-low level somatic variants or structural variants, we isolated cells exhibiting phosphorylation of the S6 ribosomal protein (p-S6) in frozen brain tissues using fluorescence-activated cell sorting (FACS). We then performed deep whole-genome sequencing (WGS; >90×) in p-S6+ cells in a cohort of 11 patients with mutation-negative. Then, we simplified the method to whole-genome amplification and target gene sequencing of p-S6+ cells in independent cohort of 10 patients with mutation-negative followed by low-read depth WGS (10×). We found that 28.6% (6 of 21) of mutation-negative FCDII carries ultra-low level somatic mutations (less than 0.2% of variant allele frequency [VAF]) in mTOR pathway genes. Our method showed ~34 times increase of the average mutational burden in FACS mediated enrichment of p-S6+ cells (average VAF=5.84%) than in bulky brain tissues (average VAF=0.17%). We found that 19% (4 of 21) carried germline structural variations in GATOR1 complex undetectable in whole exome or targeted gene sequencing. Our method facilitates the detection of ultra-low level somatic mutations, in specifically p-S6+ cells, and germline structural variations and increases the genetic diagnostic rate up to ~80% for the entire FCDII cohort. ANN NEUROL 2023;93:1082-1093.

Developing a deep learning model to predict epilepsy recurrence in patients with focal cortical dysplasia type III.

A sizable number of patients with focal cortical dysplasia (FCD) type III-related refractory epilepsy continue to experience seizures postsurgically. Deep learning models can automatically assess complex medical image characteristics and predict prognosis with higher efficiency. This study sought to determine whether T2-weighted fluid attenuated inversion recovery (T2W FLAIR) images could predict prognosis of FCD type III-related refractory epilepsy using a deep learning approach. Magnetic resonance imaging (MRI) images of 266 patients with FCD type III diagnosed between 2015 and 2019 were included in this retrospective analysis. A deep learning algorithm utilizing a convolutional neural network (CNN) was trained to classify T2W FLAIR images according to Engel's classification. The preprocessed original image and the region of interest (ROI) outlined by clinicians were input into our neural network separately and then together. Precision, sensitivity, specificity, receiver operating characteristic (ROC) curves, and areas under the ROC curves (AUCs) were computed as part of the statistical analyses of the network performance with varied inputs of the network model assessed. The overall performance met the following metrics when the original image only was input: AUC of 96.22%, sensitivity of 84.47%, and specificity of 97.21%. The metrics were as follows when the ROI only was input: area under the ROC curve of 94.76%, sensitivity of 84.92%, and specificity of 96.24%. For the combined inputs, the metrics were as follows: AUC of 97.17%, sensitivity of 90.86%, and specificity of 96.63%. Deep learning used with conventional MRI can effectively predict the recurrence conditions of epilepsy. Artificial intelligence may help the design of clinical management and enable more precise and individualized prediction for postsurgical prognosis of FCD type III-related refractory epilepsy.

Editors' Note: Benefits and Risks of Epilepsy Surgery in Patients With Focal Cortical Dysplasia Type 2 in the Central Region.

In the research article entitled “Benefits and Risks of Epilepsy Surgery in Patients With Focal Cortical Dysplasia Type 2 in the Central Region,” Chassoux et al. described their findings from a retrospective review of preoperative and postoperative data for 60 patients with focal cortical dysplasia type 2 (FCD2) in the central region who underwent surgical resection. They reported that surgical resection led to seizure freedom in 88% of patients, and although 87% had early transitory postoperative deficits, 40% of these patients had total recovery. Abe noted that patients with FCD2 can experience neurologic deficits due to the location of the dysplasia and asked the authors to describe preoperative neurologic deficits for patients included in this study. Chassoux reported that 18% of patients experienced a preoperative deficit that was either permanent or fluctuating and they all experienced transitory worsening of this deficit postoperatively, but 36% subsequently had functional improvement. Chassoux also noted that 84% of patients with a normal neurologic examination preoperatively experienced a postoperative deficit. In the research article entitled “Benefits and Risks of Epilepsy Surgery in Patients With Focal Cortical Dysplasia Type 2 in the Central Region,” Chassoux et al. described their findings from a retrospective review of preoperative and postoperative data for 60 patients with focal cortical dysplasia type 2 (FCD2) in the central region who underwent surgical resection. They reported that surgical resection led to seizure freedom in 88% of patients, and although 87% had early transitory postoperative deficits, 40% of these patients had total recovery. Abe noted that patients with FCD2 can experience neurologic deficits due to the location of the dysplasia and asked the authors to describe preoperative neurologic deficits for patients included in this study. Chassoux reported that 18% of patients experienced a preoperative deficit that was either permanent or fluctuating and they all experienced transitory worsening of this deficit postoperatively, but 36% subsequently had functional improvement. Chassoux also noted that 84% of patients with a normal neurologic examination preoperatively experienced a postoperative deficit.

Reader Response: Benefits and Risks of Epilepsy Surgery in Patients With Focal Cortical Dysplasia Type 2 in the Central Region.

I read the article by Chassoux et al.1 with interest, and I have some questions that may be outside the focus of their study. The authors described that resections were associated with minor/moderate deficits and total recovery was observed in 40% of patients. Did any of these patients have neurologic deficits before resections? For example, the patient demonstrated in the MRI images showed focal cortical dysplasia near the precentral knob. Injury to this area has been reported to show isolated motor palsy in the hand, mimicking a peripheral nerve palsy.2,3 Can the authors please comment on the neurologic findings of these patients?

Author Response: Benefits and Risks of Epilepsy Surgery in Patients With Focal Cortical Dysplasia Type 2 in the Central Region.

We are grateful for the opportunity to respond to the comments by Dr. Abe on our research.1 As described in the Results section of the article, 11 patients had a preoperative deficit that was either permanent (including a spastic component in 2 and arm atrophy in 1) or fluctuating, according to the seizure frequency (clumsiness or hemineglect). Postoperatively, all of them had a transitory worsening (which was major in 5 patients), and then, a recovery included functional improvement in 4. Among the 49 patients with normal preoperative examination, 41 had a postoperative deficit (which was major in 14).

The clinico-pathological characterization of Focal Cortical Dysplasia type IIb genetically defined by MTOR mosaicism.

Focal Cortical Dysplasia (FCD) is a major cause of drug-resistant paediatric epilepsy and is amenable to successful neurosurgical resection. FCD ILAE Type IIb is the most common FCD subtype, and brain somatic mutations affecting the mTOR pathway play a major pathogenic role. The aim of this study was to comprehensively describe the genotype-phenotype association of twenty patients with histopathologically confirmed FCDIIb using Next Generation Sequencing (NGS) of paired blood-brain samples METHODS: Clinical and neuropathological data were retrospectively reviewed from the hospital archive. The NGS panel included 11 mTOR-pathway-related genes with maximum coverage of 2000x. The detected variants were validated by digital droplet PCR. Pathogenic MTOR variants were identified in 10 patients (50%). Further comparison with MTOR-wildtype FCDIIb suggested a profound genotype-phenotype association characterized by (1) a non-temporal lobe lesion on MRI, (2) a larger lesion volume occupying grey and white matter (3.032±1.859cm3 vs. 1.110±0.856cm3 , p=0.014), (3) more balloon cells (50.20±14.40BC/mm2 vs. 31.64±30.56BC/mm2 , p=0.099) and dysmorphic neurons (48.72±19.47DN/mm2 vs. 15.28±13.95DN/mm2 , p=0.000), as well as (4) a positive correlation between VAF and the lesion volume (r=0.802, p=0.017). Our study identified frequent MTOR mutations in the cell-rich FCDIIb phenotype, clinically characterized by a non-temporal location and large lesion volume. Comprehensive genotype-phenotype associations will help us further explore and define the broad spectrum of FCD lesions to make more targeted therapies available in the realm of epileptology.

Lesion Detection Through MRI Postprocessing in Pathology-Proven Focal Cortical Dysplasia: Experience at a Single Institution in the Republic of Korea.

Focal cortical dysplasia (FCD) is one of the most common causes of drug-resistant epilepsy, and necessitates a multimodal evaluation to ensure optimal surgical treatment. This study aimed to determine the supportive value of the morphometric analysis program (MAP) in detecting FCD using data from a single institution in Korea. To develop a standard reference for the MAP, normal-looking MRIs by two scanners that are frequently used in this center were chosen. Patients with drug-resistant epilepsy and FCD after surgery were candidates for the analysis. The three-dimensional T1-weighted MRI scans of the patients were analyzed as test cases using the MAP. The MRI scans of 87 patients were included in the analysis. The radiologist detected abnormal findings correlated with FCD (RAD positive [RAD(+)]) in 34 cases (39.1%), while the MAP could detect FCD in 25.3% of cases. A combination of the MAP (MAP[+] cases) with interpretations by the radiologist increased the detection to 42.5% (37 cases). The lesion detection rate was not different according to the type of reference scanners except in one case. MAP(+)/RAD(-) presented in three cases, all of which had FCD type IIa. The detection rate was slightly higher using the same kind of scanner as a reference, but not significantly (35.0% vs. 22.4% p=0.26). The results of postprocessing in the MAP for detecting FCD did not depend on the type of reference scanner, and the MAP was the strongest in detecting FCD IIa. We suggested that the MAP could be widely utilized without developing institutional standards and could become an effective tool for detecting FCD lesions.

Intrinsic and secondary epileptogenicity in focal cortical dysplasia type II.

Favorable seizure outcome is reported following resection of bottom-of-sulcus dysplasia (BOSD). We assessed the distribution of epileptogenicity and dysplasia in and around BOSD to better understand this clinical outcome and the optimal surgical approach. We studied 27 children and adolescents with magnetic resonance imaging (MRI)-positive BOSD who underwent epilepsy surgery; 85% became seizure-free postresection (median=5.0 years follow-up). All patients had resection of the dysplastic sulcus, and 11 had additional resection of the gyral crown (GC) or adjacent gyri (AG). Markers of epileptogenicity were relative cortical hypometabolism on preoperative 18 F-fluorodeoxyglucose (FDG) positron emission tomography (PET), and spiking, ripples, fast ripples, spike-high-frequency oscillation cross-rate, and phase amplitude coupling (PAC) on preresection and postresection electrocorticography (ECoG), all analyzed at the bottom-of-sulcus (BOS), top-of-sulcus (TOS), GC, and AG. Markers of dysplasia were increased cortical thickness on preoperative MRI, and dysmorphic neuron density and variant allele frequency of somatic MTOR mutations in resected tissue, analyzed at similar locations. Relative cortical metabolism was significantly reduced and ECoG markers were significantly increased at the BOS compared to other regions. Apart from spiking and PAC, which were greater at the TOS compared to the GC, there were no significant differences in PET and other ECoG markers between the TOS, GC, and AG, suggesting a cutoff of epileptogenicity at the TOS rather than a tapering gradient on the cortical surface. MRI and tissue markers of dysplasia were all maximal in the BOS, reduced in the TOS, and mostly absent in the GC. Spiking and PAC reduced significantly over the GC after resection of the dysplastic sulcus. These findings support the concept that dysplasia and intrinsic epileptogenicity are mostly limited to the dysplastic sulcus in BOSD and support resection or ablation confined to the MRI-visible lesion as a first-line surgical approach. 18 F-FDG PET and ECoG abnormalities in surrounding cortex seem to be secondary phenomena.

Dendritic spine loss in epileptogenic Type II focal cortical dysplasia: Role of enhanced classical complement pathway activation.

Dendritic spines are the postsynaptic sites for most excitatory glutamatergic synapses. We previously demonstrated a severe spine loss and synaptic reorganization in human neocortices presenting Type II focal cortical dysplasia (FCD), a developmental malformation and frequent cause of drug-resistant focal epilepsy. We extend the findings, investigating the potential role of complement components C1q and C3 in synaptic pruning imbalance. Data from Type II FCD were compared with those obtained in focal epilepsies with different etiologies. Neocortical tissues were collected from 20 subjects, mainly adults with a mean age at surgery of 31 years, admitted to epilepsy surgery with a neuropathological diagnosis of: cryptogenic, temporal lobe epilepsy with hippocampal sclerosis, and Type IIa/b FCD. Dendritic spine density quantitation, evaluated in a previous paper using Golgi impregnation, was available in a subgroup. Immunohistochemistry, in situ hybridization, electron microscopy, and organotypic cultures were utilized to study complement/microglial activation patterns. FCD Type II samples presenting dendritic spine loss were characterized by an activation of the classical complement pathway and microglial reactivity. In the same samples, a close relationship between microglial cells and dendritic segments/synapses was found. These features were consistently observed in Type IIb FCD and in 1 of 3 Type IIa cases. In other patient groups and in perilesional areas outside the dysplasia, not presenting spine loss, these features were not observed. In vitro treatment with complement proteins of organotypic slices of cortical tissue with no sign of FCD induced a reduction in dendritic spine density. These data suggest that dysregulation of the complement system plays a role in microglia-mediated spine loss. This mechanism, known to be involved in the removal of redundant synapses during development, is likely reactivated in Type II FCD, particularly in Type IIb; local treatment with anticomplement drugs could in principle modify the course of disease in these patients.

Basal ganglia dysplasia and mTORopathy: A potential cause of postoperative seizures in focal cortical dysplasia.

Pathogenic somatic MTOR variants in the cerebral cortex are a frequent cause of focal cortical dysplasia (FCD). We describe a child with drug and surgery-resistant focal epilepsy due to FCD type II who developed progressive enlargement and T2 signal hyperintensity in the ipsilateral caudate and lentiform nuclei. Histopathology of caudate nucleus biopsies showed dysmorphic neurons, similar to those in resected cortex. Genetic analysis of frontal and temporal cortex and caudate nucleus identified a pathogenic somatic MTOR variant [NM_004958.4:c.4375G > C (p.Ala1459Pro)] that was not present in blood-derived gDNA. The mean variant allele frequency ranged from 0.4% to 3.2% in cerebral cortex and up to 5.4% in the caudate nucleus. The basal ganglia abnormalities suggest more widespread, potentially hemispheric dysplasia in this patient, consistent with the pathogenic variant occurring in early cerebral development. This finding provides a potential explanation for persistent seizures in some patients with seemingly complete resection of FCD or disconnection of a dysplastic hemisphere.

Hemimegalencephaly associated with drug-resistant epilepsy and a rare molecular genetic alteration in the CPA6 gene: a clinical case

Hemimegalencephaly (HME) is one of the extremely rare congenital malformations of cortical development (MCD). It belongs to the MCD group of mTOR-related pathologies and can be the result of various genetic disorders. One of the main clinical manifestations of HME is drug-resistant epilepsy requiring surgical treatment.Case report. This article describes a clinical case of HME in a 4-year-old boy with frequent generalized tonic-clonic seizures and drug-resistant epilepsy; also, he had speech development delay. MRI revealed a HME of the right frontal lobe. Stereotaxic laser disconnection of the large cortical dysplasia in the right frontal lobe of the brain was performed. Morphological features of focal cortical dysplasia type IIb (FCD IIb) were reported. No seizures were observed in the hospital follow up after the operation for 14 days. The whole exome DNA sequencing showed the presence of a heterozygous state _000008.10^G 68419028del / 633del, pGlu212LysfsTers of the CPA6 gene.Discussion. A feature of the case is the identified association of HME, morphologically represented by FCD IIb, with a previously unknown heterozygous state in the 6th exon of the CPA6 gene. This association allows to expand our understanding of changes in the activation of PI3K/AKT/mTOR pathway as a key link in the pathogenesis of congenital anomaly of cortical development.

GABAergic Neurotransmission in Human Tissues Is Modulated by Cannabidiol.

Recently, the potential use of phytocannabinoids (pCBs) to treat different pathological conditions has attracted great attention in the scientific community. Among the different pCBs, cannabidiol (CBD) has showed interesting biological properties, making it a promising molecule with a high security profile that has been approved for treatment as an add-on therapy in patients afflicted by severe pharmaco-resistant epilepsy, including Dravet syndrome (DS), Lennox-Gastaut syndrome (LGS) and tuberous sclerosis complex (TSC). CBD is pharmacologically considered a "dirty drug", since it has the capacity to bind different targets and to activate several cellular pathways. GABAergic impairment is one of the key processes during the epileptogenesis period able to induce a generalized hyperexcitability of the central nervous system (CNS), leading to epileptic seizures. Here, by using the microtransplantation of human brain membranes approach in Xenopus oocytes and electrophysiological recordings, we confirm the ability of CBD to modulate GABAergic neurotransmission in human cerebral tissues obtained from patients afflicted by different forms of pharmaco-resistant epilepsies, such as DS, TSC, focal cortical dysplasia (FCD) type IIb and temporal lobe epilepsy (TLE). Furthermore, using cDNAs encoding for human GABAA receptor subunits, we found that α1β2 receptors are still affected by CBD, while classical benzodiazepine lost its efficacy as expected.

Expression of cation chloride cotransporter (NKCC1/KCC2) in brain tissue of children with focal cortical dysplasia type Ⅱ

Objective: To investigate the expression of cation chloride cotransporter (NKCC1/KCC2) in the neurons from cerebral lesions of children with focal cortical dysplasia (FCD) type Ⅱ, to provide a morphological basis for revealing the possible mechanism of epilepsy. Methods: Eight cases of FCD type Ⅱ diagnosed at Beijing Haidian Hospital, Beijing, China and 12 cases diagnosed at Xuanwu Hospital, Capital Medical University, Beijing, China from February 2017 to December 2019 were included. The expression of NKCC1 and KCC2 in FCD type Ⅱa and FCD type Ⅱb was detected using immunohistochemistry and double immunohistochemical stains. The average optical density of NKCC1 in dysmorphic neurons and normal neurons was also determined using immunohistochemical staining in FCD type Ⅱa (10 cases). Results: The patients were all younger than 14 years of age. Ten cases were classified as FCD type IIa, and 10 cases as FCD type Ⅱb. NKCC1 was expressed in the cytoplasm of normal cerebral cortex neurons and KCC2 expressed on cell membranes. In dysmorphic neurons of FCD type Ⅱa, expression of NKCC1 increased, which was statistically higher than that of normal neurons (P<0.01). Aberrant expression of KCC2 in dysmorphic neurons was also noted in the cytoplasm. In the FCD Ⅱb type, the expression pattern of NKCC1/KCC2 in dysmorphic neurons was the same as that of FCD type Ⅱa. The aberrant expression of NKCC1 in balloon cells was negative or weakly positive on the cell membrane, while the aberrant expression of KCC2 was absent. Conclusions: The expression pattern of NKCC1/KCC2 in dysmorphic neurons and balloon cells is completely different from that of normal neurons. The NKCC1/KCC2 protein-expression changes may affect the transmembrane chloride flow of neurons, modify the effect of inhibitory neurotransmitters γ-aminobutyric acid and increase neuronal excitability. These effects may be related to the occurrence of clinical epileptic symptoms.