Continuous ictal discharges with high frequency oscillations confined to the non-sclerotic hippocampus in an epileptic patient with radiation-induced cavernoma in the lateral temporal lobe

Intraoperative electrocorticography recording is recommended for treating cavernoma-related epilepsy. However, interictal paroxysmal epileptiform activity is generally able to be recorded, but is not always identical to the epileptogenic zone. We surgically treated a 15-year-old girl with drug-resistant epilepsy associated with radiation-induced cavernoma in the right lateral temporal lobe. Electrocorticography revealed paroxysmal activities in the cortex around the cavernoma. Additionally, continuous subclinical “ictal” discharges with high-frequency oscillations confined to the histologically non-sclerotic hippocampus were recorded. Following additional hippocampectomy, a good seizure outcome was obtained. Intraoperative electrocorticography and high-frequency oscillation analysis revealed high epileptogenicity in the non-sclerotic hippocampus of this patient.