152 Use of Stereotactic EEG (sEEG) Investigation in Patients Who Are Hemispherectomy Candidates

INTRODUCTION: Hemispherectomy is an important surgical technique for seizure control. METHODS: Between 2019 to 2023, 65 sEEGs, 11 functional hemispherectomy surgeries were carried out in the authors’ institution. All patients had at least a one-year follow up. Four patients who fulfilled the standard criteria for hemispherectomy underwent sEEG investigation. All four patients also underwent vEEG, MRI, functional MRI, PET, and neuropsychological studies. One patient underwent a MEG study. RESULTS: Patients’ age ranged from 10 to 16 years and epilepsy etiologies were related to neonatal middle cerebral artery (MCA) stroke secondary to prematurity (n=2), abusive head trauma (n=1), and unknown etiology (n=1). Two cases involved the left hemisphere. All patients presented with various degrees of hemiparesis with corresponding cerebral atrophy. Functional MRI was determined language dominance in one patient; another was indeterminate, and two patients failed. vEEG showed fast, diffuse hemispheric involvement and hinted at seizure onset zone (SOZ) in central and frontal regions, diffuse midline, and posterior quadrant. vEEG findings were the main indications for sEEG investigation. Intracranial sEEG monitoring was used to identify focal seizure onset zones in the retrosplenial cortex, frontal pole, mesial temporal, and perisylvian regions and for functional mapping of eloquent cortex. Based on results, patients underwent posterior quadrant disconnection, All 4 patients were seizure-free at one year with documented functional improvement. All patients were without focal neurological loss. CONCLUSIONS: In patients with large MCA stroke, determining the degree of residual function in the affected hemisphere and SOZ can be difficult. sEEG can be used to guide a targeted surgical approach instead of hemispherectomy.