Epilepsy surgery for refractory focal epilepsy based on the analysis of high frequency oscillations with intracranial electroencephalography: A case report

Intracranial electroencephalography (IEEG) is useful as an evaluation component of resective surgery when the results of noninvasive tests are incongruent in patients with refractory neocortical epilepsy. High-frequency oscillations (HFOs>80 Hz) have recently been recognized as having a strong relationship to the epileptogenic zone, and the complete resection of HFOs has been considered a favorable prognostic indicator for surgical outcome. It is sometimes difficult, however, to comprehend dynamic changes in ictal HFOs recorded via subdural electrodes. We performed surgical treatment on a medically intractable patient diagnosed with occipital lobe epilepsy after analyzing the patient's HFOs with IEEG using the original program. The patient has achieved seizure-free status one year after surgery. Our method of creating a brain surface topographic map of interictal HFOs and a topographic movie of ictal HFOs was useful for easy understanding of seizure onset zone and epileptic HFOs propagation. It may also be helpful for determining the necessary extent of surgical resection to include the epileptogenic zone, thus promoting better postsurgical seizure outcomes.