Targeting pathological cells with senolytic drugs reduces seizures in neurodevelopmental mTOR-related epilepsy.

Cortical malformations such as focal cortical dysplasia type II (FCDII) are associated with pediatric drug-resistant epilepsy that necessitates neurosurgery. FCDII results from somatic mosaicism due to post-zygotic mutations in genes of the PI3K-AKT-mTOR pathway, which produce a subset of dysmorphic cells clustered within healthy brain tissue. Here we show a correlation between epileptiform activity in acute cortical slices obtained from human surgical FCDII brain tissues and the density of dysmorphic neurons. We uncovered multiple signatures of cellular senescence in these pathological cells, including p53/p16 expression, SASP expression and senescence-associated ß-galactosidase activity. We also show that administration of senolytic drugs (dasatinib/quercetin) decreases the load of senescent cells and reduces seizure frequency in an MtorS2215F FCDII preclinical mouse model, providing proof of concept that senotherapy may be a useful approach to control seizures. These findings pave the way for therapeutic strategies selectively targeting mutated senescent cells in FCDII brain tissue.

Outcome of Epilepsy Surgery in MRI-Negative Patients Without Histopathologic Abnormalities in the Resected Tissue.

BACKGROUND AND OBJECTIVE: Patients with presumed nonlesional focal epilepsy-based on either MRI or histopathologic findings-have a lower success rate of epilepsy surgery compared with lesional patients. In this study, we aimed to characterize a large group of patients with focal epilepsy who underwent epilepsy surgery despite a normal MRI and had no lesion on histopathology. Determinants of their postoperative seizure outcomes were further studied. METHODS: We designed an observational multicenter cohort study of MRI-negative and histopathology-negative patients who were derived from the European Epilepsy Brain Bank and underwent epilepsy surgery between 2000 and 2012 in 34 epilepsy surgery centers within Europe. We collected data on clinical characteristics, presurgical assessment, including genetic testing, surgery characteristics, postoperative outcome, and treatment regimen. RESULTS: Of the 217 included patients, 40% were seizure-free (Engel I) 2 years after surgery and one-third of patients remained seizure-free after 5 years. Temporal lobe surgery (adjusted odds ratio [AOR]: 2.62; 95% CI 1.19-5.76), shorter epilepsy duration (AOR for duration: 0.94; 95% CI 0.89-0.99), and completely normal histopathologic findings-versus nonspecific reactive gliosis-(AOR: 4.69; 95% CI 1.79-11.27) were significantly associated with favorable seizure outcome at 2 years after surgery. Of patients who underwent invasive monitoring, only 35% reached seizure freedom at 2 years. Patients with parietal lobe resections had lowest seizure freedom rates (12.5%). Among temporal lobe surgery patients, there was a trend toward favorable outcome if hippocampectomy was part of the resection strategy (OR: 2.94; 95% CI 0.98-8.80). Genetic testing was only sporadically performed. DISCUSSION: This study shows that seizure freedom can be reached in 40% of nonlesional patients with both normal MRI and histopathology findings. In particular, nonlesional temporal lobe epilepsy should be regarded as a relatively favorable group, with almost half of patients achieving seizure freedom at 2 years after surgery-even more if the hippocampus is resected-compared with only 1 in 5 nonlesional patients who underwent extratemporal surgery. Patients with an electroclinically identified focus, who are nonlesional, will be a promising group for advanced molecular-genetic analysis of brain tissue specimens to identify new brain somatic epilepsy genes or epilepsy-associated molecular pathways.

Detection of brain somatic mutations in focal cortical dysplasia during epilepsy presurgical workup.

Brain-restricted somatic variants in genes of the mechanistic target of rapamycin signalling pathway cause focal epilepsies associated with focal cortical dysplasia type II. We hypothesized that somatic variants could be identified from trace tissue adherent to explanted stereoelectroencephalography electrodes used in the presurgical epilepsy workup to localize the epileptogenic zone. We investigated three paediatric patients with drug-resistant focal epilepsy subjected to neurosurgery. In the resected brain tissue, we identified low-level mosaic somatic mutations in AKT3 and DEPDC5 genes. We collected stereoelectroencephalography depth electrodes in the context of a second presurgical evaluation and identified 4/33 mutation-positive electrodes that were either located in the epileptogenic zone or at the border of the dysplasia. We provide the proof-of-concept that somatic mutations with low levels of mosaicism can be detected from individual stereoelectroencephalography electrodes and support a link between the mutation load and the epileptic activity. Our findings emphasize future opportunities for integrating genetic testing from stereoelectroencephalography electrodes into the presurgical evaluation of refractory epilepsy patients with focal cortical dysplasia type II to improve the patients' diagnostic journey and guide towards precision medicine.

Clinical Features, Neuropathology, and Surgical Outcome in Patients With Refractory Epilepsy and Brain Somatic Variants in the SLC35A2 Gene.

BACKGROUND AND OBJECTIVES: The SLC35A2 gene, located at chromosome Xp11.23, encodes for a uridine diphosphate-galactose transporter. We describe clinical, genetic, neuroimaging, EEG, and histopathologic findings and assess possible predictors of postoperative seizure and cognitive outcome in 47 patients with refractory epilepsy and brain somatic SLC35A2 gene variants. METHODS: This is a retrospective multicenter study where we performed a descriptive analysis and classical hypothesis testing. We included the variables of interest significantly associated with the outcomes in the generalized linear models. RESULTS: Two main phenotypes were associated with brain somatic SLC35A2 variants: (1) early epileptic encephalopathy (EE, 39 patients) with epileptic spasms as the predominant seizure type and moderate to severe intellectual disability and (2) drug-resistant focal epilepsy (DR-FE, 8 patients) associated with normal/borderline cognitive function and specific neuropsychological deficits. Brain MRI was abnormal in all patients with EE and in 50% of those with DR-FE. Histopathology review identified mild malformation of cortical development with oligodendroglial hyperplasia in epilepsy in 44/47 patients and was inconclusive in 3. The 47 patients harbored 42 distinct mosaic SLC35A2 variants, including 14 (33.3%) missense, 13 (30.9%) frameshift, 10 (23.8%) nonsense, 4 (9.5%) in-frame deletions/duplications, and 1 (2.4%) splicing variant. Variant allele frequencies (VAFs) ranged from 1.4% to 52.6% (mean VAF: 17.3 ± 13.5). At last follow-up (35.5 ± 21.5 months), 30 patients (63.8%) were in Engel Class I, of which 26 (55.3%) were in Class IA. Cognitive performances remained unchanged in most patients after surgery. Regression analyses showed that the probability of achieving both Engel Class IA and Class I outcomes, adjusted by age at seizure onset, was lower when the duration of epilepsy increased and higher when postoperative EEG was normal or improved. Lower brain VAF was associated with improved postoperative cognitive outcome in the analysis of associations, but this finding was not confirmed in regression analyses. DISCUSSION: Brain somatic SLC35A2 gene variants are associated with 2 main clinical phenotypes, EE and DR-FE, and a histopathologic diagnosis of MOGHE. Additional studies will be needed to delineate any possible correlation between specific genetic variants, mutational load in the epileptogenic tissue, and surgical outcomes.

Complete callosotomy in children with drop attacks; A retrospective monocentric study of 50 patients.

PURPOSE: Corpus callosotomy is a palliative surgical procedure for patients with drug-resistant epilepsy and suffering from drop attacks, which are a source of major deterioration in quality of life and can be responsible for severe traumatic injury. The objective of this study is to identify clinical markers that would predict a better outcome in terms of drop attacks and other types of epileptic seizures. METHODS: We reviewed a retrospective series of children who underwent complete corpus callosotomy at our institution, between January 1998 and February 2019. We analyzed the neurological and cognitive pre- and postoperative status, radiological datas, and electroencephalography (EEG) monitoring data. RESULTS: Fifty children underwent a complete callosotomy at a mean age of 7.5 years. The median postoperative follow-up was 42.5 months. Forty-one patients (82%) had a favorable outcome, 29 (58%) of them becoming totally free of drop attacks. Statistical analysis of correlation between outcome of drop attacks and the characteristics of the patients did not find any trend in terms of age, etiology or developmental level. Regarding seizure types, the probability of being drop attack-free was significantly higher in case of tonic seizures (p = 0.017). Neurological complications occurred in two patients. A transient disconnection syndrome was observed in one child with good preoperative cognitive level. The mean hospital stay was short (5 -10 days). CONCLUSION: The results of this large monocentric case series with a long follow-up indicate that total callosotomy is a safe and effective treatment for children with drug-resistant epileptic drop attacks. Aside from a better surgical outcome for children with tonic seizures causing the falls, the lack of any other significant prognostic factor implies that no patient should a priori be excluded from this palliative surgical indication.

Clinical semiology of temporal lobe seizures in preschool children: contribution of invasive recording to anatomical classification.

Focal seizure semiology is often inadequately studied, specifically in preschool children. Among drug-resistant epilepsies amenable to surgery, temporal lobe seizure semiology has been widely described in this age group. Nevertheless, a systematic anatomo-electroclinical study has never been performed. We retrospectively reviewed the charts of patients younger than six years old at the time of video-EEG recording who were operated on for temporal lobe epilepsy in our centre between 2010 and 2016. In order to describe the electroclinical semiology and establish anatomo-clinical correlations, we reviewed all the recorded seizures on scalp and invasive video-EEG and analysed pre- and postsurgical clinical data, MRI scans, and surgical and pathological data. We classified patients into the following four anatomical groups: mesio-temporal, temporal lateral, polar, and mesio-lateral, and for each group we selected video-EEG samples for educational purposes. Twenty-eight patients fulfilled the selection criteria. Twenty-three patients (82%) were explored with invasive electrodes that consisted of foramen ovale electrodes in 11 (39%) and stereoelectroencephalography in 12 (43%). The majority of the 53% of patients with mesio-temporal epilepsies had specific ictal semiology, as described in adults. The others had subtle seizures or seizures limited to apnoea. The other groups also had some features comparable to adults, although no child reported the classic auras of lateral epilepsies. In total, 11% had infantile spasms (IS); post-ictal examination provided lateralization signs in 28%. With a mean post-surgical follow-up duration of 5.5 years, 89% of the patients were classified as Engel Class I. Preschool children were shown to have non-specific seizures, notably subtle events or IS. However, careful video-EEG analysis can provide arguments for localizing the epileptogenic zone within the temporal lobe in most cases. Seizures with apnoea are characteristic of mesial temporal onset in patients with long-term epilepsy-associated tumours.

Detection of Brain Somatic Mutations in Cerebrospinal Fluid from Refractory Epilepsy Patients.

Brain mosaic mutations are a major cause of refractory focal epilepsies with cortical malformations such as focal cortical dysplasia, hemimegalencephaly, malformation of cortical development with oligodendroglial hyperplasia in epilepsy, and ganglioglioma. Here, we collected cerebrospinal fluid (CSF) during epilepsy surgery to search for somatic variants in cell-free DNA (cfDNA) using targeted droplet digital polymerase chain reaction. In 3 of 12 epileptic patients with known somatic mutations previously identified in brain tissue, we here provide evidence that brain mosaicism can be detected in the CSF-derived cfDNA. These findings suggest future opportunities for detecting the mutant allele driving epilepsy in CSF. ANN NEUROL 2021;89:1248-1252.

18 F-FDG-PET hypometabolic pattern reveals multifocal epileptic foci despite limited unique stereotyped seizures.

PURPOSE: Interictal positron emission tomography (PET) with 18F-FDG has largely proved its utility in presurgical evaluation of drug-resistant epilepsies (DRE) and in the surgical outcomes. Interictal hypometabolism topography is related to the neuronal networks involved in the seizure onset zone (SOZ) and spread pathways. 18F-FDG PET has a good prognostic value for post-surgical outcome, especially in cases with unique focal ictal semiology and a limited extent of hypometabolism. Surprisingly few patients have similar limited ictal features but extended hypometabolism. The objective of this study is to show that stereoelectro encephalography (SEEG) provides an explanation for this large hypometabolism, which impacts the surgical strategy. METHODS: A cohort of 248 patients underwent 18F-FDG PET and SEEG to explore for refractory epilepsy in two close tertiary epilepsy centers between January 2009 and December 2017. From this cohort, a subset of patients was selected with extended PET metabolism despite showing unique and limited ictal features in scalp EEG. The surgical outcome of this subset of patients has been analysed with respect to their FDG-PET and SEEG to understand the relationship between PET/SEEG/ presentation and surgical outcome. RESULTS: We report a series of seven patients with DRE and unique stereotyped ictal semiology but extensive 18F-FDG-PET hypometabolism revealing unexpected multifocal SOZ using SEEG. All SOZ were encompassed by the hypometabolic area. CONCLUSION: Our results demonstrate the necessity of accounting for the discrepancy between limited symptoms and widespread hypometabolism which can reveal multifocal SOZ. In those patients, surgical possibilities should be considered carefully.

Gradient of brain mosaic RHEB variants causes a continuum of cortical dysplasia.

Focal cortical dysplasia (FCD) and hemimegalencephaly (HME) are related malformations with shared etiologies. We report three patients with a spectrum of cortical malformations associated with pathogenic brain-specific somatic Ras homolog enriched in brain (RHEB) variants. The somatic variant load directly correlated with the size of the malformation, with upregulated mTOR activity confirmed in dysplastic tissues. Laser capture microdissection showed enrichment of RHEB variants in dysmorphic neurons and balloon cells. Our findings support the role of RHEB in a spectrum of cortical malformations confirming that FCD and HME represent a disease continuum, with the extent of dysplastic brain directly correlated with the somatic variant load.

Focal polymicrogyria in children: Contribution of invasive explorations and epileptogenicity mapping in the surgical decision.

OBJECTIVE: Report of the contribution of invasive EEG (iEEG) and epileptogenicity mappings (EM) in a pediatric cohort of patients with epilepsy associated with focal polymicrogyria (PMG) and candidates for resective surgery. METHOD: Retrospective pediatric case series of patients presenting focal PMG-related refractory epilepsy undergoing an invasive exploration (iEEG) at Fondation Rothschild Hospital. We reviewed clinical data, structural MRI, and visual analysis of iEEG recordings. Moreover, time-frequency analysis of SEEG signals with a neuroimaging approach (epileptogenicity maps) was used to support visual analysis. RESULTS: Between 2012 and 2019, eight patients were selected. Five patients were explored with stereoelectroencephalography (SEEG) only, one patient with subdural exploration (SDE) only and two patients first underwent SEEG and then SDE. The mean age at seizure onset was 40.3 months (range 3-120), and the mean age for the iEEG 10.8 years (range 7-15). The epileptogenic zone (EZ) appeared concordant to the PMG lesion in only one case, was larger in three cases, smaller in two cases and different in one case. Four cases were selected for tailored resective surgery and one for total callosotomy. Two patients remained seizure-free at their last follow-up (mean 32.6 months, range 7-98). Epileptogenicity mapping (EM) refined the qualitative analysis, showing in four patients an EZ larger than visually defined. CONCLUSION: This study is the first pediatric study to analyze the value of iEEG and EM as well as operability in focal PMG-related refractory epilepsy. The results illustrate the complexity of this pathology with variable concordance between the EZ and the lesion and mixed response to surgery.

Frequent SLC35A2 brain mosaicism in mild malformation of cortical development with oligodendroglial hyperplasia in epilepsy (MOGHE).

Focal malformations of cortical development (MCD) are linked to somatic brain mutations occurring during neurodevelopment. Mild malformation of cortical development with oligodendroglial hyperplasia in epilepsy (MOGHE) is a newly recognized clinico-pathological entity associated with pediatric drug-resistant focal epilepsy, and amenable to neurosurgical treatment. MOGHE is histopathologically characterized by clusters of increased oligodendroglial cell densities, patchy zones of hypomyelination, and heterotopic neurons in the white matter. The molecular etiology of MOGHE remained unknown so far. We hypothesized a contribution of mosaic brain variants and performed deep targeted gene sequencing on 20 surgical MOGHE brain samples from a single-center cohort of pediatric patients. We identified somatic pathogenic SLC35A2 variants in 9/20 (45%) patients with mosaic rates ranging from 7 to 52%. SLC35A2 encodes a UDP-galactose transporter, previously implicated in other malformations of cortical development (MCD) and a rare type of congenital disorder of glycosylation. To further clarify the histological features of SLC35A2-brain tissues, we then collected 17 samples with pathogenic SLC35A2 variants from a multicenter cohort of MCD cases. Histopathological reassessment including anti-Olig2 staining confirmed a MOGHE diagnosis in all cases. Analysis by droplet digital PCR of pools of microdissected cells from one MOGHE tissue revealed a variant enrichment in clustered oligodendroglial cells and heterotopic neurons. Through an international consortium, we assembled an unprecedented series of 26 SLC35A2-MOGHE cases providing evidence that mosaic SLC35A2 variants, likely occurred in a neuroglial progenitor cell during brain development, are a genetic marker for MOGHE.

Management and results of epilepsy surgery associated with acyclovir prophylaxis in four pediatric patients with drug-resistant epilepsy due to herpetic encephalitis and review of the literature.

PURPOSE: Herpes simplex virus encephalitis (HSE) is the most common cause of sporadic viral encephalitis in children and is responsible for epilepsy in approximately half of patients. In addition to medical treatment, epilepsy surgery may be offered to drug-resistant patients but carries a high risk of relapse of herpetic encephalitis. We are reporting our series of patients operated on between 2000 and 2019 with the systematic administration of acyclovir (ACV). RESULTS: Four pediatric patients aged 4.5-12.8 years with drug-resistant epilepsy post-HSE underwent a tailored focal resection following invasive recordings (three patients) and a complete callosotomy (one patient). The total number of the surgical procedures for the four patients was eight, and a systematic administration of ACV as a prophylactic treatment of herpetic encephalitis relapse was done at each step. No patients had a relapse and the ACV was well-tolerated in all the cases. Following surgery two patients are seizure free, the patient who underwent callosotomy is Engel 3 and the fourth patient, in whom a large epileptic zone has contraindicated a second surgery, is Engel 4. CONCLUSIONS: Our series demonstrated the dramatic efficacy of systematic ACV prophylaxis during all cranial surgeries. Moreover, our results on epilepsy, together with those of the literature, encourage more consideration regarding epilepsy surgery in this specific etiology. All types of surgical procedures (curative or palliative) can be offered to the patients, but in the case of focal surgery, due to the poor anatomical limits, invasive recordings are highly recommended.

Invasive evaluation in children (SEEG vs subdural grids).

Designed from the 60s to the 80s for adults, and despite the development of many new techniques, invasive explorations still have indications in children with focal drug-resistant epilepsy. The main types are stereoelectroencephalography (SEEG) and subdural explorations (SDE). They provide precise information on the localization of the epileptogenic zone (EZ), its relationships with eloquent cortex, and the feasibility of performing a tailored surgical resection. Thermocoagulations, which are a diagnostic and therapeutic tool, can be performed using SEEG electrodes. Both techniques are feasible in children, with an age limitation for SEEG (which requires a bone thickness above 2 mm). The complication rate is higher with SDE. Opposed for a long time and never compared in a systematic study, they should presently be considered complementary. The indications cannot be directly inferred from those for adults, as there are pediatric particularities in the seizures' semiology, functional areas, imaging and urgent situations. We successively discuss the choice in individual cases of SEEG or SDE respectively, the specific problematic in infancy and early childhood, the schema in SEEG for cryptogenic epilepsies (in particular insular), the particularities of polymicrogyria and deeply located lesions, and finally, SEEG designed for thermocoagulations. Future improvements should include more accurate implantation schemas thanks to advanced non-invasive explorations and possibilities to perform SEEG in infants.

Seizure outcome and prognostic factors for surgical management of hypothalamic hamartomas in children.

PURPOSE: Hypothalamic hamartomas (HH) are rare benign lesions frequently associated with gelastic seizures early in life. Epilepsy can progress to multiple seizure types with cognitive impairment and behavioural disturbance, leading in some cases to epileptic encephalopathy. METHODS: We reviewed a retrospective series of 112 children treated in a single center, between 1998 and 2017. RESULTS: According to Delalande's HH classification, type1 was found in 2 patients, type 2 in 67, type 3 in 31, and type 4 in 12 patients. Stereotactic endoscopic disconnection was performed in 92 % of the procedures. Median age at diagnosis was 40 months and 7.6 years at surgery. Median time between diagnosis and surgery was 31 months and median follow up 4.1 years. For all HH types, 77.6 % of the patients had a favourable outcome (Engel I + II outcome score) with 57.1 % seizure-free (Engel I). The best outcome was obtained in patients with type 2 HH, (68.7 % Engel I and 85.1 % Engel I + II). The overall complication rate was 8.3 %, which is in line with previous series. Patients with isolated gelastic seizures had a better outcome (Engel I + II in 90 %), as compared to those with other seizure types (p = 0.07). A short delay between hamartoma diagnosis and surgery was a statistically significant factor for a good outcome (p = 0.03). CONCLUSION: Patients with HH and drug-resistant epilepsy should be early identified in order to propose surgical treatment without delay. Endoscopic disconnection is a safe and efficacious surgical option with good seizure outcome and immediate treatment results.

Parasagittal hemispherotomy in hemispheric polymicrogyria with electrical status epilepticus during slow sleep: Indications, results and follow-up.

PURPOSE: Polymicrogyria (PMG), although the most common brain malformation, represents a low percentage among patients operated on for epilepsy. In cases of hemispheric PMG, electrical status epilepticus during slow sleep (ESESS) may occur leading to an aggravation of the neurological condition and a risk of drug resistance. In such cases, surgical treatment can be offered. METHODS: From a population of 230 children who underwent hemispherotomy for epilepsy, we retrospectively reviewed the patients with unilateral PMG and drug-resistant ESESS focusing on clinical charts, electrophysiological data and post-surgical outcome. RESULTS: Eighteen patients were operated on at a mean age of 7.2 years. The average age was 2 years at seizure onset and 4.4 years at diagnosis of ESESS. All the patients preoperatively had some degree of developmental delay associated with a hemiparesis. During ESESS all of them evidenced a cognitive decline and eight experienced a worsening of the hemiparesis; ESESS was resistant to at least three antiepileptic drugs. The outcome of epilepsy, with a mean follow-up of 12.8 years showed that ESESS disappeared in all patients while 16 of 18 became seizure-free. An improvement of behavior and cognitive condition was observed in all. CONCLUSION: Hemispherotomy can be helpful in patients with drug-resistant ESESS and hemispheric PMG while keeping in mind that more often an accurate medical treatment can be sufficient. The main benefit of surgery is to definitively stop the seizures and to withdraw the medical treatment while keeping in mind the risk of motor aggravation.

Dissecting the genetic basis of focal cortical dysplasia: a large cohort study.

Genetic malformations of cortical development (MCDs), such as mild MCDs (mMCD), focal cortical dysplasia (FCD), and hemimegalencephaly (HME), are major causes of severe pediatric refractory epilepsies subjected to neurosurgery. FCD2 are characterized by neuropathological hallmarks that include enlarged dysmorphic neurons (DNs) and balloon cells (BCs). Here, we provide a comprehensive assessment of the contribution of germline and somatic variants in a large cohort of surgical MCD cases. We enrolled in a monocentric study 80 children with drug-resistant epilepsy and a postsurgical neuropathological diagnosis of mMCD, FCD1, FCD2, or HME. We performed targeted gene sequencing ( ≥ 2000X read depth) on matched blood-brain samples to search for low-allele frequency variants in mTOR pathway and FCD genes. We were able to elucidate 29% of mMCD/FCD1 patients and 63% of FCD2/HME patients. Somatic loss-of-function variants in the N-glycosylation pathway-associated SLC35A2 gene were found in mMCD/FCD1 cases. Somatic gain-of-function variants in MTOR and its activators (AKT3, PIK3CA, RHEB), as well as germline, somatic and two-hit loss-of-function variants in its repressors (DEPDC5, TSC1, TSC2) were found exclusively in FCD2/HME cases. We show that panel-negative FCD2 cases display strong pS6-immunostaining, stressing that all FCD2 are mTORopathies. Analysis of microdissected cells demonstrated that DNs and BCs carry the pathogenic variants. We further observed a correlation between the density of pathological cells and the variant-detection likelihood. Single-cell microdissection followed by sequencing of enriched pools of DNs unveiled a somatic second-hit loss-of-heterozygosity in a DEPDC5 germline case. In conclusion, this study indicates that mMCD/FCD1 and FCD2/HME are two distinct genetic entities: while all FCD2/HME are mosaic mTORopathies, mMCD/FCD1 are not caused by mTOR-pathway-hyperactivating variants, and ~ 30% of the cases are related to glycosylation defects. We provide a framework for efficient genetic testing in FCD/HME, linking neuropathology to genetic findings and emphasizing the usefulness of molecular evaluation in the pediatric epileptic neurosurgical population.

SEEG-guided radiofrequency thermocoagulation of epileptic foci in the paediatric population: Feasibility, safety and efficacy.

PURPOSE: Focal epilepsy in children may be refractory to pharmacological treatment and surgical resection may be an appropriate option. When invasive electroencephalogram is required in the presurgical evaluation, depth electrodes can be used to create focal lesions in the epileptogenic zone using radiofrequency thermocoagulation (RFTC), to disrupt the epileptogenic zone. METHODS: This study aimed to assess the efficacy and safety of RFTC in a paediatric population of 46 patients. RESULTS: The mean age of onset was 3.3 years and the mean age at SEEG was 8.2 years. MRI lesions were identified in 71.7% of the series, among them 60% of malformation of cortical development. 43.5% of the patients were seizure free at 1 month, 26.1% were responders. The mean duration of improvement was 6.8 months. 8 children were seizure free for >8 months and among them, 6 are currently seizure free for 8-24 months. 5 patients had functional deficits post-procedures, transient in 4 patients and prolonged in one of whom. 3/5 were anticipated following the results of cortical stimulation. Multivariate analysis found 3 independent criteria linked to RFTC efficiency one month after RFTC: frequency of the seizures before RFTC, age and number of contacts used. CONCLUSION: RFTC is a safe method for the paediatric population providing important predictive information for surgical resection. An improvement in seizure frequency, often transient, is seen in 2/3 of our patients. RTFC could be useful as a palliative technique for children with an epileptogenic zone overlapping with eloquent areas, with minimal risk of sequelae.

Correction to: The landscape of epilepsy-related GATOR1 variants.

The original version of this Article contained an error in the author list where the corresponding author Stéphanie Baulac was repeated twice. This has now been corrected in the HTML, the PDF was correct at the time of publication.

The landscape of epilepsy-related GATOR1 variants.

PURPOSE: To define the phenotypic and mutational spectrum of epilepsies related to DEPDC5, NPRL2 and NPRL3 genes encoding the GATOR1 complex, a negative regulator of the mTORC1 pathway METHODS: We analyzed clinical and genetic data of 73 novel probands (familial and sporadic) with epilepsy-related variants in GATOR1-encoding genes and proposed new guidelines for clinical interpretation of GATOR1 variants. RESULTS: The GATOR1 seizure phenotype consisted mostly in focal seizures (e.g., hypermotor or frontal lobe seizures in 50%), with a mean age at onset of 4.4 years, often sleep-related and drug-resistant (54%), and associated with focal cortical dysplasia (20%). Infantile spasms were reported in 10% of the probands. Sudden unexpected death in epilepsy (SUDEP) occurred in 10% of the families. Novel classification framework of all 140 epilepsy-related GATOR1 variants (including the variants of this study) revealed that 68% are loss-of-function pathogenic, 14% are likely pathogenic, 15% are variants of uncertain significance and 3% are likely benign. CONCLUSION: Our data emphasize the increasingly important role of GATOR1 genes in the pathogenesis of focal epilepsies (>180 probands to date). The GATOR1 phenotypic spectrum ranges from sporadic early-onset epilepsies with cognitive impairment comorbidities to familial focal epilepsies, and SUDEP.

Correction: The landscape of epilepsy-related GATOR1 variants.

The original version of this article contained an error in the spelling of the author Erik H. Niks, which was incorrectly given as Erik Niks. This has now been corrected in both the PDF and HTML versions of the article.