Electrocorticography and navigated transcranial magnetic stimulation–tailored supratotal resection for epileptogenic low-grade gliomas

OBJECTIVE Epilepsy is commonly associated with low-grade gliomas (LGGs), impacting patients’ well-being. While resection is the primary treatment, seizures can persist postoperatively in 27%–55% of cases. The authors aimed to evaluate an electrocorticography (ECoG) and navigated transcranial magnetic stimulation (nTMS)–tailored supratotal resection (ETT-SpTR) for LGG in controlling seizures, preserving neurological function, and enhancing treatment effectiveness. METHODS The authors retrospectively analyzed a prospectively enrolled cohort of patients with LGG presenting with epileptic seizures with ictal/interictal activity on electroencephalography (EEG) who underwent resective surgery. The authors performed preoperative nTMS to identify functional cortical areas. ECoG was used to guide the removal of the high-risk epilepsy cortical areas (HREAs). Patients were divided into two groups: group I, the control group, underwent gross-total resection alone, whereas group II patients underwent removal of HREAs identified by ECoG (ETT-SpTR). Resection avoided functionally eloquent areas as identified on nTMS, checked with cortical mapping. Postoperative seizure outcome was assessed using the Engel classification. RESULTS Fifteen patients who underwent LGG resection between January and July 2023 were included. Among 24 identified nTMS-positive points, none were included in the resection. Overall, 73.3% of patients (11/15) showed positive intraoperative ECoG, with better outcomes in group II (85.7% Engel class IA) than in group I (25% Engel class IA) at the follow-up (p = 0.02, OR 0.5 [95% CI 0.035–7.10], RR 0.19 [95% CI 0.03–1.2]). Seizure control was significantly better in group II, with no notable differences in postoperative transient neurological deficits between the two groups (p = 0.45). No permanent neurological deficits were observed during follow-up. Statistical analysis revealed significant differences between the two groups (p < 0.05). CONCLUSIONS This preliminary study affirms the predictive value of TMS for postoperative neurological status and safety in epileptic patients. Intraoperative ECoG effectively identified peritumoral HREAs. ETT-SpTR significantly improved epileptic outcomes, preserving functions without permanent neurological worsening. Additional resection targets the HREAs in the temporal, frontal, and parietal lobes.