Electrophysiological intraoperative localization for focal onset refractory epilepsy: Two-dimensional operative video

Epilepsy surgery is a well-established therapeutic option for patients with refractory focal epilepsy. Comprehensive clinical evaluation should encompass documentation of seizure semiology, high spatial resolution magnetic resonance imaging (MRI) sequences, prolonged video electroencephalography, and detailed neuropsychological assessment. Resective surgery remains the cornerstone for medically refractory focal-onset epilepsy. However, even after exhaustive investigation, subtle parenchymal changes on imaging can delay surgical resection, exacerbating the epilepsy burden on quality of life.

A 30-year-old male patient with a long-standing history of seizures was referred to an epilepsy center. The seizures were stereotypical and highly frequent, with unremarkable neurological findings. Multiple trials of anti-seizure medications failed to control the epileptic events. The presurgical evaluation aimed to identify the precise brain regions involved in the primary organization of seizures and to map the eloquent cortex. The extent of epileptic zone resection significantly influences surgical outcomes. Preoperative MRI revealed subtle findings suggestive of a lesion at the bottom of the inferior frontal sulcus, immediately anterior to the precentral sulcus. The patient underwent resection, guided by neuronavigation and intraoperative electrocorticography. Three-dimensional cortical reconstruction facilitated the intraoperative identification of landmarks and electrocorticography-guided resection of pathological brain tissue. Histopathological evaluation revealed neuronal depopulation and irreversible chronic injuries in the remaining neurons. The patient was discharged without neurological deficits or seizures.

In the literature, no specific lesions have been identified or characterized by microscopic inspection in up to 7.7% of cases. Asleep motor mapping identifies eloquent zones and mitigates functional impairment post-resection; direct electrical stimulation remains the gold standard technique for cortical mapping.