Surgical planning, histopathology findings and postoperative outcome in MR-negative extra-temporal epilepsy using intracranial EEG, functional imaging, magnetoencephalography, neuronavigation and intraoperative MRI

Resective epilepsy surgery in pediatric patients with normal MRI: outcomes, challenges, and cost-effectiveness in low-resource settings

BACKGROUND

Pediatric patients with drug-resistant epilepsy and normal preoperative MRIs present significant challenges in surgical planning. Advanced diagnostic techniques, including PET, SPECT, and intraoperative ECOG, are used to localize seizure foci, but their high cost and limited availability pose challenges, especially in low-resource settings. This study aims to evaluate the outcomes of resective epilepsy surgery in these cases and assess the role of advanced imaging in a middle-income country.

METHODS

This retrospective cohort study included 12 pediatric patients (mean age 10.21 years) with normal preoperative 3 T MRI who underwent resective epilepsy surgery or functional hemispherectomy between 2007 and 2021 at two centers in Medellín, Colombia. Demographic, clinical, and surgical data were collected, including the use of advanced imaging techniques (PET, SPECT) and intraoperative ECOG. Seizure outcomes were assessed using the Engel Epilepsy Surgery Outcome Scale.

RESULTS

Of the 12 patients, 10 underwent extratemporal resections, and 2 underwent temporal lobe surgery. Seven patients had advanced imaging, and 5 were evaluated with intraoperative ECOG. At 2-year follow-up, 83.3% of patients who underwent resective surgery achieved favorable outcomes (Engel Classes I and II). Temporal lobe resections had a higher rate of seizure freedom (50%) compared to extratemporal resections (30%), although the difference was not statistically significant (p = 0.47). Reoperations due to seizure recurrence were required in 30% of extratemporal resections (p = 0.02). Complications were minimal, with three superficial wound infections. Histopathology revealed cortical dysplasia in 33.3% of cases.

CONCLUSION

Epilepsy surgery in pediatric patients with normal MRIs can yield favorable outcomes, especially with temporal lobe resections. Advanced imaging improves localization but remains costly, highlighting the need for cost-effective surgical strategies in resource-limited settings.

Augmented Reality in Extratemporal Lobe Epilepsy Surgery

Background: Epilepsy surgery for extratemporal lobe epilepsy (ETLE) is challenging, particularly when MRI findings are non-lesional and seizure patterns are complex. Invasive diagnostic techniques are crucial for accurately identifying the epileptogenic zone and its relationship with surrounding functional tissue. Microscope-based augmented reality (AR) support, combined with navigation, may enhance intraoperative orientation, particularly in cases involving subtle or indistinct lesions, thereby improving patient outcomes and safety (e.g., seizure freedom and preservation of neuronal integrity). Therefore, this study was conducted to prove the clinical advantages of microscope-based AR support in ETLE surgery. Methods: We retrospectively analyzed data from ten patients with pharmacoresistant ETLE who underwent invasive diagnostics with depth and/or subdural grid electrodes, followed by resective surgery. AR support was provided via the head-up displays of the operative microscope, with navigation based on automatic intraoperative computed tomography (iCT)-based registration. The surgical plan included the suspected epileptogenic lesion, electrode positions, and relevant surrounding functional structures, all of which were visualized intraoperatively. Results: Six patients reported complete seizure freedom following surgery (ILAE 1), one patient was seizure-free at the 2-year follow-up, and one patient experienced only auras (ILAE 2). Two patients developed transient neurological deficits that resolved shortly after surgery. Conclusions: Microscope-based AR support enhanced intraoperative orientation in all cases, contributing to improved patient outcomes and safety. It was highly valued by experienced surgeons and as a training tool for less experienced practitioners.

From bench to bedside: Overview of magnetoencephalography in basic principle, signal processing, source localization and clinical applications

Magnetoencephalography (MEG) is a non-invasive technique that can precisely capture the dynamic spatiotemporal patterns of the brain by measuring the magnetic fields arising from neuronal activity along the order of milliseconds. Observations of brain dynamics have been used in cognitive neuroscience, the diagnosis of neurological diseases, and the brain-computer interface (BCI). In this study, we outline the basic principle, signal processing, and source localization of MEG, and describe its clinical applications for cognitive assessment, the diagnoses of neurological diseases and mental disorders, preoperative evaluation, and the BCI. This review not only provides an overall perspective of MEG, ranging from practical techniques to clinical applications, but also enhances the prevalent understanding of neural mechanisms. The use of MEG is expected to lead to significant breakthroughs in neuroscience.