Abstract
Introduction Direct cortical stimulation (CS) is commonly used to outline eloquent cortex where induced seizures are an undesirable side effect. Direct CS can also be used to induce habitual aura and seizures to confirm epileptogenic network (EZ) that is mapped to stereo EEG investigation. Evoked seizures can induce seizures that may or may not be similar to patient’s habitual seizure. The accuracy of CS-induced seizures in localizing EZ has not been studied systematically. Here we compare the CS-induced seizures with spontaneous seizures recorded during a stereo-EEG investigation at a level-IV epilepsy center. Methods We performed a retrospective review of all patients who underwent direct CS at our center during the years 2016–2017. Among these we identified and collected data on 13 patients who underwent direct CS for mapping EZ. Results 9 (69%) patients of the 13 were male, 4 (31%) were female, with a mean age of 33 years. Anatomical targets included mesial temporal lobe (hippocampus, amygdala, temporal pole), lateral and basal temporal regions, insula, anterior cingulate, and orbitofrontal regions. 54% (N = 7) had abnormal brain MRI. Spontaneous seizures were localized to - hippocampus, amygdala hippocampus, hippocampus-temporal pole, ant. Cingulum, superior temporal gyrus, and frontal operculum. With direct CS, 7 (54%) had typical seizures (aura followed by seizures with impaired awareness), 4 (31%) had atypical seizures (aura and clonic activity), and 2 (15%) had both types. Localization of CS-induced seizures overlapped with spontaneous seizures in 9/13 (70%) patients. Overlapping was 100% with mesial temporal structures. 7 (54%) patients underwent surgery, and 3 had RNS placement. Conclusion Direct CS induced seizures complemented localization of spontaneous seizures in two-thirds of the patients who underwent stereo EEG investigation. The accuracy of direct CS in the localization of EZ is higher with infrasylvian structures.
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