The role of scalp EEG in the presurgical evaluation of patients with medically refractory frontal lobe epilepsy

The availability of modern structural and functional imaging technologies has not diminished the impact of scalp EEG in the presurgical evaluation of patients with frontal lobe epilepsy (FLE). A lesion detected by magnetic resonance imaging (MRI) alone does not guarantee a postoperative seizure-free outcome in patients with FLE. Interictal and ictal scalp EEG findings might provide information useful in the localization of a frontal epileptogenic focus. The yield of scalp EEG is dependent upon the anatomical site of the epileptogenic focus in the frontal lobe. While a dorsolateral convexity focus is associated with a high EEG positivity, medial frontal and orbitofrontal lesions more often exhibit absent or false localizing EEG features. Coregistration of digitized scalp EEG data with MRI and magnetoencephalography may improve the localization of the epileptogenic focus in FLE. Since the epileptogenic zone cannot be reliably defined by any of the currently available investigative techniques, selection of ideal surgical candidates for frontal resection requires a careful correlation between clinical, electrophysiological, and neuroimaging data.