Intracranial EEG monitoring

Scalp EEG samples only one third of the cortex, so that discharges arising within sulci, in basal regions, and in interhemispheric regions are not detected. Besides, scalp recordings are subject to muscle and other artifacts, which may obscure the EEG. Patients with lesional epilepsy (not close to the eloquent cortex) or those with hippocampal sclerosis and concordant interictal and ictal foci without other discordant findings can proceed directly to surgery. In other patients, intracranial EEG recordings can more accurately lateralize and localize the epileptic focus and map functional areas before surgery. Modalities for intracranial EEG studies include:  Intraoperative electrocorticography (ECoG)  Extraoperative intracranial EEG through open craniotomy  Stereotactic intracerebral EEG (SEEG)