Barba, Carmen

Abstract Objective Invasive presurgical evaluation plays a key role in pediatric epilepsy surgery, particularly in magnetic resonance imaging (MRI)‐negative cases, by guiding resective, disconnective, or ablative procedures. This International League Against Epilepsy (ILAE) Pediatric Epilepsy Surgery Taskforce study provides an updated global overview of current invasive evaluation practices. Methods Group‐level data were collected from 61 epilepsy surgery programs (49 pediatric‐only) in 29 countries across six continents. Included were children and adolescents who underwent presurgical evaluation and epilepsy surgery in 2023. The study was designed to enable comparison with the similar ILAE survey conducted in 2004. Results A total of 2427 patients were included. Invasive evaluations were performed in 21.1% of cases, most frequently in North America (33.7%, higher than Europe: 18.0%, p = .003). Among invasive cases, 32.3% had no detectable MRI abnormalities. The main indication for invasive evaluation was seizure onset localization (88.1%), followed by motor or sensory mapping (17.2%) and language mapping (14.2%). Stereoelectroencephalography (SEEG) was the predominant technique (19.8% overall, 93.6% of invasive cases), more common in North America (30.0%, p = .021) and less common in South America (7.4%, p < .001). Subdural electrodes were used in only 3.2% of invasive cases, and combined depth and subdural approaches in 3.2%. SEEG‐guided radiofrequency thermocoagulation (RF‐TC) was performed in 40.9% of SEEG cases, most commonly in Asia (63.8%). In 16.2% of invasive evaluations, patients did not proceed to resection, disconnection, or ablation, with the highest rate in Europe (28.5%). Significance This global survey provides the first broad overview of invasive evaluation practices in pediatric epilepsy surgery across participating centers worldwide. It highlights the widespread adoption of SEEG, declining use of subdural electrodes, and increasing application of SEEG‐guided RF‐TC. The high proportion of MRI‐negative cases and the considerable proportion of patients not proceeding to resection, disconnection, or ablation underscore the complexity of contemporary surgical candidates and the need for further refinement of selection strategies.

Abstract Objective Pediatric epilepsy surgery is well established, but contemporary global data on referral and presurgical evaluation practices are lacking. This International League Against Epilepsy (ILAE) Pediatric Epilepsy Surgery Task Force study provides an updated overview of current trends and regional differences. Methods Group‐level data were collected from 61 epilepsy surgery programs (49 pediatric‐only) across 29 countries and six continents, identified through ILAE networks, and included all children and adolescents treated in 2023 who underwent presurgical evaluation/epilepsy surgery. Results Group‐level data were available for 2427 patients. Mean age at surgery was 9.1 ± 4.9 years; mean epilepsy duration was 5.3. At surgery, 3.2% were <1 year old (highest in Oceania: 5.1%), and 6.1% were nonpharmacoresistant (highest in Europe: 15.0%). Prior neurosurgery was reported in 14.2% (highest in North America: 28.8%), including 8.0% resections (6.1% for epilepsy, 1.5% for tumors; highest in Oceania: 16.5%), 2.3% disconnections (1.3% corpus callosotomy; highest in South America: 4.7%), and 4.2% neuromodulation (3.7% vagal nerve stimulation, .2% responsive neurostimulation, one deep brain stimulation; highest in North America: 12.2%). Developmental and epileptic encephalopathies (DEEs) at surgery included Lennox–Gastaut syndrome (7.4%), infantile epileptic spasms syndrome (5.1%), and DEE with spike–wave activation in sleep (1.5%). Presurgical investigations included fluorodeoxyglucose positron emission tomography (52.6%; highest in Oceania: 79.7%), genetic testing (46.8%; highest in Asia: 54.3%), magnetic resonance imaging (MRI) postprocessing (32.4%; highest in South America: 53.0%), functional MRI (fMRI; 15.2%; highest in North America: 40.3%), magnetoencephalography (11.9%; highest in North America: 39.3%), single photon emission computed tomography (9.6%; highest in North America: 22.2%), high‐density electroencephalography (EEG; 1.9%; highest in Europe: 4.7%), source localization (1.6%; highest in Oceania: 7.6%), Wada test (1.2%; highest in North America: 3.5%), and EEG‐fMRI (.5%; highest in Europe: 1.1%). Significance Despite some early surgeries, including in infancy and before pharmacoresistance, mean epilepsy duration before surgery remains >5 years. Reoperations are common, with resection more frequent than neuromodulation. Genetic testing in nearly half of patients reflects its growing relevance, and the high rate of DEEs underscores the complexity of surgical candidates.

AbstractFocal 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.