Stereo-electroencephalography evidence of an eccentrically located seizure-onset zone around a polymorphous low-grade neuroepithelial tumor of the young: illustrative case.

Background: Polymorphous low-grade neuroepithelial tumor of the young (PLNTY) is a newly identified low-grade brain tumor with frequent epileptic presentation. Despite the facilitated use of invasive electroencephalography owing to the growing availability of stereo-electroencephalography (SEEG), intracranial features of tumor-related seizures are still scarcely described. This report provides the first description of SEEG-recorded seizures in PLNTY to provide an insight into its surgical strategy.

Observations: Spontaneous clinical seizures were recorded with SEEG in a young adult patient with drug-resistant epilepsy associated with a PLNTY in the left lateral temporal cortex. The seizure onset was characterized by low-voltage fast activity (LVFA) and showed eccentric localization with respect to the tumor: LVFA was localized in the anterior portion of the tumor and spread toward the adjacent polar cortex. The language risks associated with the resection of the posterior temporal cortex could thus be minimized.

Lessons: PLNTY can show a focal and eccentric seizure-onset zone around the tumor. The present findings serve to improve the functional and seizure outcomes using the staged invasive approach in PLNTY.