Use of scalp-sphenoidal EEG for seizure localization in temporal lobe epilepsy

We determined the accuracy and sensitivity of scalp-sphenoidal EEG for seizure focus localization in 50 patients who became seizure-free or had rare seizures following temporal lobectomy. EEG localization was based on concordant interpretations of scalp-sphenoidal ictal EEG by three independent interpreters. All patients became seizure-free or had rare seizures following temporal lobectomy. Localization from EEG disagreed with the side of surgery in only 1 (2%) of 50 patients. We identified 3 distinct patient groups with a low, moderate, and high likelihood of having a focal ictal EEG pattern during a seizure. These groups comprised 31% (low likelihood), 44% (moderate likelihood), and 25% (high likelihood) of patients. A model based on these results suggests that with multiple ictal EEG recordings, accurate localization from scalp-sphenoidal EEG is possible in approximately up to 65-70% of patients with temporal lobe epilepsy.