Ultraslow and high-frequency recordings in MRI-negative refractory focal epilepsy

Scalp EEG and intracranial EEG (icEEG) are critical technologies for localization of epileptogenic brain and guiding epilepsy surgery in patients with drug-resistant focal epilepsy and negative MRI. Scalp EEG is universally used to confirm the diagnosis of epilepsy and for developing a hypothesis for the localization of epileptogenic brain tissue. In order to localize the brain region(s) generating seizures, patients with negative MRI often have intracranial electrodes implanted based on the localization hypothesis developed using noninvasive studies (semiology, scalp EEG, and functional imaging). It can be argued that icEEG is the gold standard for localizing the seizure onset zone (SOZ) [1], but whether there is an electrophysiological biomarker for the epileptogenic zone (EZ) remains unanswered [2,3].