We sought institutional approval (Federal Center of Neurosurgery, Tyumen, Russia) for the use of IoUS as our neuronavigational tool during epilepsy surgery. The study model was to retrospectively analyze and descriptively report the patients who had been diagnosed with refractive epilepsy and underwent IoUS-guided epileptogenic tissue resection from January 2015 to June 31, 2020 with subsequent postoperative histological confirmation of FCD type I. In instances where histological results were inconclusive, specimens were sent to an independent histology laboratory for confirmation.